Abstract:
A fluid control system for use with toxic or corrosive gases (for example) has been provided that includes a fluid pressure regulator comprising a fluid inlet; a fluid outlet; a first fluid flow path between the fluid inlet and the fluid outlet; a valve seat positioned in the first fluid flow path and dividing the fluid inlet and the fluid outlet; a valve element regulating flow through the valve seat; a generally cylindrical membrane defining an inflatable fluid cavity that moves axially, responsive to inflation; a wall portion of the cavity that moves responsive to inflation and deflation of the cavity; a second fluid flow path communicating between the cavity and a source of pressure outside the cavity; and a link transmitting the movement of the wall portion to the valve element, thereby moving the valve element with respect to the valve seat responsive to inflation and deflation of the cavity.

Description:
RELATED APPLICATIONS 
   This application is a division of U.S. application Ser. No. 10/439,565, entitled “Intra-Cylinder Tubular Pressure Regulator,” filed May 16, 2003, which claims priority benefits of United Kingdom Patent Application No. 0211410.6, filed May 17, 2002, entitled “Intra-Cylinder Tubular Pressure Regulator,” both of which are hereby expressly incorporated herein in their entireties including the specification, claims, drawings and abstract. 

   BACKGROUND OF THE INVENTION 
   The present invention generally relates to improvements in a fluid pressure regulator, and more particularly relates to an improved fluid pressure regulator used within a fluid control system. 
   Pressurized fluid containers, such as gas containers or cylinders, have been used for many applications. For example, cylinders storing high-pressure hydrides have been used in semiconductor manufacturing processes. Typically, the high-pressure fluid, such as a gas, stored in fluid cylinders is not dispensed at high pressure. Rather, a pressure regulator or other flow restriction device used in conjunction with a cylinder typically delivers, or dispenses, the fluid from the cylinder at a pressure substantially lower than that inside the cylinder. Typically, a self-regulating mechanical device, or pressure regulator, is used to reduce the pressure of a dispensed gas. Most, if not all, pressure regulators incorporate a diaphragm or a piston connected to a valve as a way of reducing the pressure of the dispensed gas. 
   Typically, a pressure regulator is discrete from the fluid cylinder and from the valve that selectively controls the dispensing of the gas from the cylinder. Gas under high pressure, however, may escape at a dangerously high rate from a fluid cylinder if the cylinder valve is inadvertently opened. To minimize the risks associated with gas leaks, some gas dispensing systems have included pressure reduction devices, such as a restrictive flow orifice or an integrated valve, as part of the cylinder assembly. An integrated valve typically includes a low-pressure shut-off valve and a pressure regulator within the same fluid dispensing assembly. 
   A pressure regulator may be set to reduce the pressure of a gas to subatmospheric pressure, i.e., less than 1 bar absolute pressure. A fluid dispensing, or fluid control, system utilizing a subatmospheric pressure regulator offers a safety advantage. That is, gas is not dispensed from the system, even if the cylinder valve is opened, unless the pressure on the downstream side of the pressure regulator is lower than atmospheric pressure. In other words, gas is dispensed from the system only when a downstream device or condition draws the gas from a fluid outlet of the dispensing assembly, i.e., by drawing a vacuum. The method of actively extracting gas from a dispensing assembly of a gas dispensing system is used in, for example, self-contained underwater breathing apparatus (“SCUBA”) and in systems designed to supply hazardous toxic gases to semiconductor manufacturing systems. 
   Positioning an integrated valve substantially or entirely within a fluid cylinder protects the pressure regulator of the integrated valve from external forces and damage associated with moving the cylinder. Further, installing an integrated valve within a fluid cylinder makes the gas dispensing system more compact and easier to handle. 
   U.S. Pat. No. 6,101,816 issued to Wang et al. (“Wang I”) (assigned to Advanced Technology Materials, Inc), granted Aug. 15, 2000, teaches a fluid pressure regulator positioned within a fluid cylinder. The invention described in Wang I, however, includes a pressure regulator located upstream from any valves included within the system. Fluid contained in the fluid cylinder or vessel flows through the pressure regulator before flowing through any valve or through any other flow control element within the system. Wang I, however, does not disclose the size of the opening of the cylinder or vessel used with the invention. Pressure regulators conventionally used with toxic gases, however, do not easily fit inside standard fluid cylinders. Typically, standard fluid cylinders include an opening of ¾ inch NGT (National Gas Taper), which is approximately 23 mm in diameter. However, the smallest gas pressure regulators commercially available for use with such applications are approximately 40 mm in diameter. 
   U.S. Pat. No. 6,089,027, also issued to Wang et al, (“Wang II”) (also assigned to Advanced Technology Materials, Inc.) and granted Jul. 18, 2000, also teaches a fluid pressure regulator disposed within a fluid cylinder or vessel. Wang II states at column 4, lines 55–59, “In order to usefully exploit the Wang et al. system of the parent application [Wang I], embodying a ‘regulator in a bottle’ approach, larger cylinder inlets are required than are conventionally available.” Further, at column 5, lines 3–11, Wang II states, “In order to commercially enable the Wang et al. ‘regulator in a bottle’ approach of the parent patent application, it is necessary to provide a cylinder that satisfies United States Department of Transportation (USDOT) packaging standards, has a larger inlet opening than is conventionally available, and can withstand pressures in the range of from about 1000 to about 5000 pounds per square inch (psi). No such vessel has been proposed or fabricated by the prior art, and none is commercially available.” Thus, while Wang I does not specify the size of the opening of the cylinder or vessel, Wang II clarifies that the invention described in Wang I cannot be used with standard fluid cylinders. Further, Wang II teaches a cylinder having an inlet opening of greater than 1 inch NGT. 
   As compared to standard fluid cylinders having a ¾ inch NGT opening, fluid cylinders having an opening greater than the standard ¾ inch NGT, such as those used with Wang I and Wang II, are more prone to leaks, are heavier, and are more expensive to manufacture. The cylinder openings of standard fluid cylinders are, for reasons of weight, containment integrity and manufacturing cost, made as small as possible. Further, a large number of standard fluid cylinders already exist. The regulators described in Wang I and Wang II, however, cannot be used with these standard cylinders. 
   European Patent Application 0 512 553 A1 (“MEVA application”), published Nov. 11, 1992 is directed to a superatmospheric pressure controlled reducing valve. The MEVA application, at column 2, lines 56 to Col. 3, lines 1–2 states, “The valve designed for being used in respirators adapted to operate exclusively in the superatmospheric pressure breathing regime is controlled by a straight stay or stays immediately confining a space or cavity.” The MEVA application shows a valve that is pulled against a fluid inlet through the bending of stays. However, the MEVA application does not teach or suggest the use of the superatmospheric pressure controlled reducing valve with a semiconductor manufacturing system, or with toxic gases. Rather, as discussed in the MEVA abstract and at Col. 2, lines 56 to Col. 3, lines 1–2, the reducing valve described in the MEVA application is used “exclusively in the superatmospheric pressure breathing regime.” Further the MEVA application does not teach or suggest positioning, or interiorly disposing, the superatmospheric pressure controlled reducing valve within a fluid cylinder. 
   Thus a need exists for a system and method of efficiently and inexpensively protecting a fluid pressure regulator that is used with a standard fluid cylinder having an opening of ¾ inch NGT. Further, a need exists for a system and method of protecting a fluid pressure regulator that is used with a standard fluid cylinder that stores toxic gases, such as hydrides used in the semiconductor manufacturing industry. 
   SUMMARY OF THE INVENTION 
   In accordance with at least one embodiment of the present invention, a fluid pressure regulator has been developed that includes a fluid inlet, a fluid outlet, a first fluid flow path between the fluid inlet and the fluid outlet, a valve seat positioned in the first fluid flow path and dividing the fluid inlet and the fluid outlet, a valve element regulating flow through the valve seat, and a generally cylindrical membrane defining an inflatable fluid cavity that includes a wall portion that moves responsive to inflation and deflation of the cavity, a second fluid flow path communicating between the cavity and a source of pressure outside the cavity, and a link transmitting the movement of the wall portion to the valve element, thereby moving the valve element with respect to the valve seat responsive to inflation and deflation of the cavity. The valve element regulating flow between the fluid inlet and the fluid outlet may be a poppet comprising a valve disk and a valve stem, in which case, the valve stem can define the link. 
   In certain embodiments of the present invention, the fluid pressure regulator further comprises at least one radially flexible stiffening member extending generally axially along the membrane and having a first portion, a second portion spaced axially from the first portion, and a third portion between the first and second portions. The third portion is positioned to contact and be flexed by the membrane when the membrane moves radially. The first portion of the stiffening member is secured with respect to a first end cap and the second portion of the stiffening member is secured with respect to a second end cap. 
   Certain embodiments of the present invention utilize the fluid pressure regulator within a fluid control system for dispensing high-pressure fluid at reduced pressure. The fluid control system comprises a container for storage and dispensing of a fluid and a fluid flow control device connected to the outlet of the container. The fluid flow control device comprises at least a first fluid flow path having a main fluid inlet in fluid communication with the container and a main fluid outlet, and a high-pressure shut-off valve in the first fluid flow path to selectively open or close the fluid flow path. The fluid pressure regulator is positioned in the first fluid flow path for providing fluid at the main fluid outlet at a selected pressure. The fluid pressure regulator is downstream of the high-pressure shut-off valve and located inside the container. 

   
     BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS 
     The foregoing summary, as well as the following detailed description of certain embodiments of the present invention, will be better understood when read in conjunction with the appended drawings. For the purpose of illustrating the invention, there are shown in the drawings certain embodiments that illustrate the invention. It should be understood, however, that the present invention is not limited to the arrangements and instrumentalities shown in the attached drawings. 
       FIG. 1  is a partial axial section of a fluid control system according to an embodiment of the present invention. 
       FIG. 2  is an axial section showing the tubular pressure regulator of  FIG. 1  in isolation. 
       FIG. 3  is an axial section similar to  FIG. 2 , but showing the regulator chamber inflated. 
       FIG. 4  is an axial section of an absolute pressure regulator according to another embodiment of the present invention. 
       FIG. 5  is a cross-sectional view of the corrugated tube of the absolute pressure regulator of  FIG. 4 . 
       FIG. 6  is a perspective view of the corrugated tube of the absolute pressure regulator of  FIG. 4 . 
       FIG. 7  is a schematic representation of a fluid control system according to an embodiment of the present invention. 
       FIG. 8  is a graph showing the relationship between inlet pressure and outlet pressure of the pressure regulator. 
     Like reference characters on the several drawing figures indicate like or similar parts. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1  shows a fluid control system  10  according to an embodiment of the present invention. The system  10  includes a pressurized fluid container or cylinder  12  having an outlet port  14  and a fluid flow control device, such as an integrated valve assembly  16 . The integrated valve assembly  16  includes a main body  18 , a main fluid inlet  20 , a high-pressure shut-off valve  22 , a pressure regulator  24 , a low-pressure shut-off valve  26 , a main fluid outlet  28 , a bursting disc safety member  30  and a vent  32 . 
   A fluid flow path  34  progresses from the main fluid inlet  20  to the high-pressure shut-off valve  22 , then from the valve  22  to the pressure regulator  24 . The fluid flow path  34  continues from the pressure regulator  24  to the low-pressure shut-off valve  26  and through the main fluid outlet  28 . The high-pressure shut-off valve  22  regulates flow of the fluid in the fluid flow path  34  between the inlet  20  and the regulator  24 . The pressure regulator  24  regulates flow of the fluid in the fluid flow path  34  between the high-pressure shut-off valve  22  and the low-pressure shut-off valve  26 . The low-pressure shut-off valve  26 , in turn, regulates flow and delivers the fluid at a predetermined pressure through the fluid flow path  34  between the regulator  24  and the main fluid outlet  28 . 
   The integrated valve assembly  16  is affixed to the outlet port  14  of the cylinder  12  in a conventional manner, such as by providing mating threads on the exterior of the integrated valve assembly  16  and on the interior of the outlet port  14 . Alternatively, the integrated valve assembly  16  may be welded into the outlet port  14 . 
   In operation, fluid flows from the interior of the cylinder  12  and enters the fluid flow path  34  through the main fluid inlet  20 . The fluid then travels from the main fluid inlet  20  through the fluid flow path  34  to the high-pressure shut-off valve  22 . After flowing through the high-pressure shut-off valve  22  (when the high-pressure shut-off valve  22  is opened), the fluid travels along the fluid flow path  34  to the pressure regulator  24 . The fluid then travels through the pressure regulator  24 . After passing through the pressure regulator  24 , the fluid travels along the fluid flow path  34  and encounters the low-pressure shut-off valve  26 . When the low-pressure shut-off valve  26  is opened, the fluid then passes from the system  10  at the main fluid outlet  28 . 
   Referring now to  FIGS. 1–3 , the pressure regulator  24  includes a regulator inlet  44 , a valve seat  46  dividing the regulator  24  into a high pressure side in the inlet  44  and a low-pressure side downstream of the valve seat  46 , a poppet  48  movably positioned to seat on the valve seat  46 , and a regulator outlet  50  communicating with the low-pressure side of the valve seat  46 . The poppet  48  includes a valve stem  52  and a valve head or disk  54  located at one end of the valve stem  52 , adjacent to the seat  46 . 
   A cylindrical expandable membrane  56  is an inflatable tubular diaphragm secured by a fixed inlet end  58  to the main body  18  of the integrated valve assembly  16 , and capped at the other end by a movable plate  60 . The cylindrical expandable membrane  56  separates an inner fluid cavity  62  from an outer fluid cavity  64 . The membrane  56  is radially inflatable or deflatable responsive to pressure differences between the inner fluid cavity  62  and the outer fluid cavity  64 . (shown inflated in  FIG. 3 , and otherwise shown deflated). The inner fluid cavity  62  communicates with the low-pressure outlet  50  of the regulator  24  via a second fluid flow path  65 . The outer fluid cavity  64  is further defined by a substantially rigid housing  66  connected to and supported by the main body  18  of the integrated valve  16 . The housing  66  isolates the interior of the regulator  24  from the pressure inside the cylinder  12 . In this embodiment, the outer fluid cavity  64  is vented to the atmosphere through the vent  32  to define a reference pressure. 
   The expandable membrane  56  may be fabricated from any of a variety of materials, such as elastomeric film. In this embodiment, the membrane  56  is stiffened by radially flexible, axially relatively inflexible stiffening members  68  extending axially between and connected at their respective ends to the main body  18  of the integrated valve assembly  16  and the movable plate  60 . 
   The regulator  24  regulates pressure at its outlet  50  as follows. The cylindrical expandable membrane  56  moves the valve stem  48  responsive to the pressure on the low-pressure side of the valve seat  46  to maintain the low-pressure side at a desired setpoint pressure. 
   A pressure increase in the inner fluid cavity  62  (and thus at the regulator outlet  50 ) approaching its setpoint, relative to the atmospheric reference provided by the outer fluid cavity  64 , inflates the membrane  56  radially outward, particularly between its end plates  58  and  60 , as shown in  FIG. 3 . Outward inflation flexes the centers of the stiffening members  68  radially outward. Bending the stiffening members  68  outward at the center draws their ends toward each other and lifts the movable plate  60 . Upward motion of the plate  60  is transmitted by the valve stem  52  to the valve disk  54 , which moves toward and (if the inflation pressure is at its setpoint) bears against the seat  46 . Seating the valve disk  54  stops the flow of high-pressure fluid from the regulator inlet into the inner fluid cavity  62 , responsive to elevated pressure in the low-pressure side of the regulator  24 . The pressure at which inflation of the membrane  56  seats the valve disk  54  on the valve seat  46  is the setpoint of the regulator, and defines the highest pressure the regulator will allow at the low-pressure outlet  50 . The setpoint may be adjustable by a set point adjusting member  67 , such as a screw or other such adjustment means, which moves the valve stem  52 , thereby changing the distance between the valve disk  54  and the valve seat  46 . Such an adjustment means is preferably lockable at any desired position. 
   When the pressure in the inner fluid cavity  62  drops below the setpoint, due to flow through the outlet  50  with the valve disk  54  seated, the membrane  56  deflates to a degree, causing the stiffening members  68  to straighten, the movable plate  60  to drop (in the orientation of the Figures), the stem  52  to move downward, and thus the valve disk  54  to unseat. Unseating the valve allows the membrane  56  to inflate once again, until its setpoint is again reached and the valve closes again. This continual inflation and deflation of the membrane  56 , as the pressure in the inner fluid cavity  62  varies, maintains the pressure delivered to the outlet  50  substantially at the setpoint value, providing a higher pressure is delivered to the regulator inlet  44 . 
   The membrane  56  optionally is generally cylindrical, as in the illustrated embodiments, and can be elongated as necessary to increase its valve seating force, generated in response to a given pressure difference between the inner and outer cavities  62  and  64 , without increasing its radial dimensions. Thus, one advantage of this configuration is that the pressure regulator  24  can be slender enough to be positioned inside the cylinder  12 . The tubular, slender shape of the pressure regulator  24  allows it to safely pass through the outlet port  14  of the cylinder  12 . For example, the cylinder  12  can be a standard fluid cylinder wherein the outlet port  14  is ¾ inch NGT (National Gas Taper). The placement of the pressure regulator  24  inside the cylinder  12  protects the pressure regulator  24  from damage by external forces, stresses and strains. Alternatively, however, the outlet port  14  of the cylinder  12  may be any size that is suitable for passage of the pressure regulator  24  into the cylinder  12 . 
   The bursting disc safety member  30  is a thin, circular diaphragm made of corrosion-proof metal. The bursting disc safety member  30  is intended to break at a defined pressure. The main body  18  supports the high-pressure shut-off valve  22 , the low-pressure shut-off valve  26  and the pressure regulator  24 . 
   The fluid flow path  34  may provide a fill path for the cylinder  12 . For example, liquefied gas at a low pressure, which may be below the setpoint of the regulator, may be filled via fluid flow path  34 . Alternatively, a separate fluid fill inlet and fluid fill path may be formed within the cylinder  12 . A fluid fill valve may also be positioned within the fluid fill path. 
   Alternatively, the pressure regulator  24 , the high-pressure shut-off valve  22  and the low-pressure shut-off valve  26  may be discrete devices not included in a common integrated valve assembly  16 . Also, the system  10  does not require the bursting disc safety member  30 . Additionally, the system  10  does not necessarily require the stiffening members  68 . Also, the system  10  does not require the rigid housing  66 . The present invention can include an expandable membrane  56  that can expand without a rigid housing  66  limiting the degree of expansion. 
   The stiffening members  68  may be flexible metal or plastic strips or plates. Alternatively, the stiffening members  68  may comprise a diaphragm that is stiffer than the expandable membrane  56 , and which encompasses the more expandable membrane  56 . The stiffening members  68  and the expandable membrane  56 , both of which are connected to the movable plate  60 , pull the movable plate  60  toward the main body  18  as the stiffening members  68  bow out and the membrane  56  inflates. 
     FIG. 4  shows an absolute pressure regulator  70  according to another embodiment of the present invention. The absolute pressure regulator  70  includes an expandable membrane that is an expandable longitudinally corrugated tube  72  formed of metal (although other material can instead be used). Instead of using the expandable membrane  56  (a flexible diaphragm) and the stiffening members  68 , as shown in  FIGS. 1 and 2 , the absolute pressure regulator  70  of this embodiment utilizes the corrugated tube  72  to perform a similar function. One end of the corrugated tube  72  is connected to the main body  18 , while another end of the corrugated tube  72  is connected to the movable plate  60 . The corrugated tube  72  expands radially and contracts axially when fluid exerts pressure on the interior walls of the corrugated tube  72 , and contracts radially and expands axially when fluid exerts a greater pressure on the exterior of the corrugated tube  72  as compared to the pressure within the corrugated tube  72 . Thus, the axial expansion of the corrugated tube  72  causes the poppet  48  to contact the valve seat  46  in a similar fashion as the expandable membrane  56  and the stiffening members  68  (as shown in  FIG. 1–3 ) act to cause the poppet  48  to contact the valve seat  46 . Also, similar to the expandable membrane  56  and the stiffening members  68  of  FIGS. 1–3 , the contraction of the corrugated tube  72  causes the poppet  48  to recede from the valve seat  46 . 
   Because in this embodiment the pressure regulator  70  is an absolute pressure regulator, no vent to atmosphere is used. Instead, a getter  74  is used to maintain a vacuum condition within the outer cavity  64  by removing traces of gas within the outer cavity  64 . The getter  74  is a reactive substance, such as zirconium or calcium, which is incorporated into the absolute pressure regulator  70  to absorb residual gases and moisture. A sealed off vacuum space, such as the interior of the absolute pressure regulator  70 , may have a small amount of getter  74  to maintain a low-pressure within that space. Without the getter  74 , the interior of the absolute pressure regulator  70  would increase in pressure as absorbed moisture and other gases are released from the interior walls of the absolute pressure regulator  70 . 
     FIG. 7  is a schematic representation of a fluid control system  78  according to an embodiment of the present invention. The fluid control system  78  includes a fluid cylinder  12  having an outlet port  14  and a tubular pressure regulator  24  positioned inside the cylinder  12 . The pressure regulator  24  includes a poppet  48 . The system  78  also includes a residual pressure valve  80 , a fluid flow path  34 , a high-pressure relief valve  82 , a high-pressure shut off valve  22 , a filter  84 , a low-pressure shut-off valve  26 , a low-pressure relief valve  86  and a fluid outlet  28 . The system  78  also includes a vent  32 . If, however, the pressure regulator  24  is an absolute pressure regulator, the vent  32  is not included within the system  78 . Additionally, this embodiment includes a fluid fill path  88 , a fluid fill port  90  and fluid fill valve  92 . The valve body  18  plugs the outlet port  14  of the cylinder  12 . 
   In operation, fluid is supplied to the cylinder  12  through the fluid fill path  88 . That is, an external fluid supply is connected to the fluid fill port  90 , so fluid passes from the supply into the fluid fill path  88 . The fluid fill valve  92  selectively opens and closes the fluid fill path  88 . 
   Fluid to be dispensed from the cylinder  12  enters the residual pressure valve  80  and passes to the high-pressure shut-off valve  22  via the fluid flow path  34 . When the high-pressure shut-off valve  22  is open, fluid then travels downstream from the high-pressure shut-off valve  22  through the filter  84  and to the poppet  48  of the pressure regulator  24 . The pressure of the fluid passing through the poppet  48  is reduced by operation of the pressure regulator  24 , as described with respect to  FIG. 1 . Most of the fluid passed by the poppet  48  passes through the fluid flow path  34  to the low-pressure shut-off valve  26 . When the low-pressure shut-off valve  26  is opened, the fluid is dispensed through the fluid outlet  28 . 
   The tubular pressure regulator  24  may be set to deliver fluid at a subatmospheric, atmospheric, or superatmospheric pressure, depending on the set point of the pressure regulator  24 . If the pressure regulator  24  is set to deliver fluid at subatmospheric pressure, the ambient pressure of the atmosphere ensures that fluid does not pass through the fluid outlet  28  when the outlet is not connected to an external device. That is, the pressure of the atmosphere may exert enough pressure on the fluid to keep it within the system  78 . 
   It will be understood that the present invention lends itself to many alternative embodiments within the scope of one or more claims. For example, inflation pressure could be communicated between the outlet  50  and the outer fluid cavity  64 , and the inner fluid cavity  62  could be vented to the atmosphere. This would reverse the action of the poppet  48  responsive to pressure changes. The orientation of the valve disk  54  and seat  46  could also be reversed so the disk  54  would seat by moving downward on the seat  46 . These modifications would provide a regulator  24  that works in essentially the same way as the illustrated embodiments. 
   As another example of a contemplated modification, the stiffening members  56  could be normally bowed inward, so inflation of the inner fluid cavity  62  straightens the stiffening members  56  and moves the end plate  60  axially downward. This modification would again reverse the influence of pressure changes on the poppet  48 . Either of the two compensating changes described in the previous example could be employed as well, so the valve disk  54  would still close on the seat  46  responsive to pressure in the regulator outlet  50  reaching the setpoint pressure. 
   As yet another example of a contemplated modification, movement of the side walls of the cylindrical expandable membrane  56  could be directly transmitted to the poppet  48  by a mechanical linkage within the inner fluid cavity  62 . One example of such a mechanical linkage would be a parallelogram linkage having one pair of opposed pivots pulled apart by inflation of the cylindrical expandable membrane  56 , thus pushing together the remaining two, axially spaced pivots of the parallelogram. One of the two axially spaced pivots could be linked to the poppet  48  and the other of the two axially spaced pivots could be free floating, or linked to the movable plate  60 , or linked to the fixed inlet end  58 . Instead of a free floating link, the floating pivot and the two adjacent links could be omitted, leaving a pair of links that function as described above in this paragraph. By selecting one or the other of the axially spaced links to connect to the poppet  48 , the poppet  48  would either be raised or lowered by inflation of the inner fluid cavity  62 . A compound lever linkage could also be employed to provide a mechanical advantage. 
   Still another example of a contemplated modification would be to fix the movable plate  60  relative to the housing  66 , fix the poppet  48  relative to the inlet end  58 , and mount the inlet end  58  to be axially movable. One of the previously described expedients, such as reversing the valve and valve seat, or arranging the mechanism so inflation would straighten the stiffening members  56  instead of bending them, could again be used to complete the modification. 
   Additionally, pressure gauges may be added within the system. An active high pressure gauge, which may communicate directly with the cylinder, may be used within the system. A passive high pressure gauge, which may communicate with the fluid flow path  34  between the high pressure shut-off valve  22  and the regulator  24 , may also be used. Also, a low pressure gauge may be included within the fluid flow path  34 , downstream of the regulator  24 . The gauges may be mechanical display gauges, such as Bourdon tube gauges, or may be electronic gauges, which provide an electrical output. 
   Many other modifications and combinations of the above modifications will readily occur to those skilled in the art, upon further contemplation of this specification. 
     FIG. 8  is a graph showing the relationship between inlet pressure and outlet pressure of the pressure regulator. The flow rate is approximately 20 liters per minute. The plot  100  shows the relationship between inlet pressure (measured in Barg—Bars, gauge pressure), shown on the X-axis, and outlet pressure (measured in Barg), shown on the Y-axis. The plot  100  shows that the pressure regulator yields a relatively constant pressure outlet for varying inlet pressure at a relatively high flow rate. As shown by reference line  102 , at approximately 3 Barg of inlet pressure, the pressure regulator begins to close. Also, as shown by graph  100 , even at 14 Barg of inlet pressure, the outlet pressure is less than 4.5 Barg. 
   Thus, embodiments of the present invention provide a pressure regulator having a small radial dimension. The regulator can be made small enough to fit within a standard fluid cylinder having an opening of ¾ inch NGT. In one embodiment of the invention, the regulator can be placed within a standard fluid cylinder to protect the regulator from damage. The embodiments shown and described offer increased safety for users of gases, such as hydrides used in semiconductor manufacturing processes, stored at high pressures within fluid cylinders. Embodiments of the present invention offer a compact and robust package for use in, for example, semiconductor manufacturing. Also, the embodiments of the present invention may also be used with welding gases and oxygen dispensing devices used in the medical field, with scuba-diving gas cylinders, or with any gas dispensing apparatus for any use. 
   While particular elements, embodiments and applications of the present invention have been shown and described, it will be understood, of course, that the invention is not limited thereto since modifications may be made by those skilled in the art, particularly in light of the foregoing teachings.