Patent Publication Number: US-6901962-B2

Title: Surge prevention device

Description:
This is a continuation-in-part of U.S. patent application Ser. No. 09/374,130, filed Aug. 9, 1999, the entire disclosure of which is incorporated by reference herein. 

   BACKGROUND OF THE INVENTION 
   The present invention relates generally to a device for handling a gas, such as oxygen and nitrous oxide, under high pressure. The present invention also relates to a valve for controlling the flow of gas and to a system for reducing or preventing high pressure surge. 
   Known high pressure oxygen delivery systems are provided with an oxygen cylinder, a cylinder valve and a pressure regulator. The oxygen cylinder may be charged with pure oxygen at a pressure of two thousand two hundred pounds per square inch (psi) or more in the United States and over three thousand psi in other countries. The valve is attached to the cylinder to stop the flow of oxygen to the regulator. The pressure regulator is designed to reduce the tank pressure to under two hundred psi. Most pressure regulators in the United States reduce tank pressure to approximately fifty psi. Typical pressure regulators in Europe reduce tank pressure to approximately sixty psi. 
   When the valves in the known oxygen systems are opened rapidly, undesirable high pressure surges may be applied to the pressure regulator. There is a need in the art for preventing such high pressure surges, as well as increases in the temperature of the gas which may result in ignition. A similar problem may occur with respect to nitrous oxide supplied, for example, for dental procedures. 
   The risk of oxygen regulator failure may be higher for portable oxygen systems that are used in adverse environments and/or by untrained personnel. Portable oxygen systems are used for emergency oxygen delivery at accident sites; for other medical emergencies, such as heart attacks; and for transporting patients. Homecare patients who use oxygen concentrators as the main source of oxygen for oxygen therapy are required to have standby oxygen cylinders in case of power failures. Oxygen cylinders are also used to provide homecare patients with mobility outside the house. There is a need in the art for a valve that can be used easily in such portable systems and that reduces or eliminates the occurrence of high pressure surges. Other uses include hospitals, where oxygen cylinders are used to transport patients. They are also used as emergency backup systems. 
   Known surge suppression devices are illustrated in U.S. Pat. No. 3,841,353 (Acomb), U.S. Pat. No. 2,367,662 (Baxter et al.), and U.S. Pat. No. 4,172,468 (Ruus). These devices all suffer from one or more of the following drawbacks: relatively massive pistons resulting in slower response times, relatively elongated bodies, complicated construction resulting in increased cost, or construction preventing positioning of the devices in different locations in existing systems. 
   Acomb discloses an anti-surge oxygen cylinder valve in which the surge-suppression device is integrated with the cylinder valve. The device referred to by Acomb requires a force opposed to a spring force to function. In the Acomb device, the opposing force is provided by a stem connected to the valve handle. Additionally, if the bleeder orifice becomes plugged, the valve does not allow flow, and the gas supply is not available for use. In that case, the user may interpret the tank to be empty when it is full, with the danger that such a misunderstanding brings. 
   Baxter discloses a pressure shock absorber for a welding system. Baxter refers to a piston that is elongated with a bore through the center. The elongated piston results in an increased moment of inertia that increases the time in which the piston reacts to a pressure surge. The long bore results in necessarily tighter tolerances for controlling the gas flow rate through the bore. In addition, the placement of the spring abutting the elongated piston results in a relatively large device. 
   Ruus discloses a pressure shock absorber for an oxygen-regulator supply system with an elongated, two-part piston. The elongate construction of the piston results in an increased moment of inertia that increases the time required for the piston to react to a pressure surge. The two-part piston results in increased complexity and manufacturing cost. Also in this device, if the restricted passageway becomes plugged, no flow is allowed and the device suffers from the same potential for user misinterpretation as the Acomb device. 
   SUMMARY OF INVENTION 
   The present invention overcomes to a great extent the deficiencies of the prior art by providing a device that has a first flow path for flowing gas at a first flow rate, a second flow path for flowing gas at a greater flow rate, and a handle that moves in a first direction to open the first flow path and enable opening of the second flow path, and in a second direction to open the second flow path. In a preferred embodiment of the invention, the device may be a surge prevention valve. 
   According to one aspect of the invention, the handle moves in an axial direction to open the first flow path, and in a rotational direction to open the second flow path. In a preferred embodiment of the invention, the axial motion of the handle may be required to enable opening of the second flow path. The present invention should not be limited, however, to the preferred embodiments shown and described in detail herein. 
   According to another aspect of the invention, a spring may be used to bias the handle member in a direction opposite to the first direction. In addition, an engageable torque unit may be employed to transmit torque from the handle to open the second flow path. In a preferred embodiment of the invention, the spring is compressed to engage the torque unit. 
   The present invention also relates to a surge prevention valve, such as a valve for use with a high pressure gas cylinder. The surge prevention valve may have a housing with an inlet and an outlet. A seal unit may be used to close the flow path from the inlet to the outlet, and a bleed passageway may be provided in the seal unit. The valve also may have an actuator for opening the bleed pathway and for moving the seal unit to open the main flow path. 
   If desired, the seal unit may be threaded into the housing. With this construction, the actuator may be used to threadedly move the seal unit toward and away from the valve seat to close and open the main flow path. In addition, a valve rod may be provided for closing the bleed passageway. The valve rod may be slidably located within the seal unit. 
   The present invention also relates to a method of operating a high pressure valve. The method includes the steps of: (1) moving a handle in an enabling direction to cause gas to flow through a first path at a first flow rate; and then (2) moving the handle in a second direction to cause gas to flow through a second path at a much greater flow rate. The method also may include the step of closing the valve. According to a preferred embodiment of the invention, the method may involve flowing gas, such as oxygen or nitrous oxide, through a pressure regulator to a user or to an intended device (such as a respirator). The method may be used to gradually increase the flow rate into the regulator and to prevent the formation of a high pressure surge in the system. 
   According to another preferred embodiment of the present invention, a method of opening a valve includes the steps of: (1) moving a handle button, within the handle, in an enabling direction to cause gas to flow through a first path at a first flow rate; and then (2) moving the entire handle in a second direction to cause gas to flow through a second path at a much greater flow rate. According to one aspect of the invention, the enabling direction may be an axial direction, and the second direction may be a rotational direction. 
   The present invention further relates to a surge prevention dual-port (or dual-path) valve, which is provided with first and second valves located within a housing and integrating a pressurization orifice. The initial opening of the dual-port (or dual-path) valve in an axial direction enables a first flow of gas to flow through the pressurization orifice at a first flow rate. The fill opening of the dual-port (or dual-path) valve enables a second flow of gas to flow through the second valve at a second flow rate which is higher than the first flow rate. The controlled pressurization of the gas through the pressurization control orifice delays the time in which the gas reaches full recompression. This, in turn, allows the heat generated by the near adiabatic process of the recompression of the gas to be dispersed. This way, high pressure surges are prevented, the heat during gas recompression is dispersed and excessive heating is avoided. The present invention also relates to a method of operating the dual-port (or dual-path) valve. 
   In a preferred embodiment of the invention, the device has two separate ports or seats, to define at two respective flow paths. The first port/seat is a bleed port that is sized to pressurize an attached oxygen regulator in greater than 0.250 seconds. The first port/seat is opened during the initial actuation of the valve. The second (main) port/seat is opened during the continuing actuation of the valve. If desired, the device may be constructed to require enough motion so that, without the use of a mechanical drive system, the valve cannot be opened fast enough to override the bleed function. 
   According to another aspect of the invention, the main port may be held in place by a spring (such as a coil compression spring) surrounding the actuator) that is sized to overcome the source of pressure and to maintain a gas-tight seal on the main port. According to this aspect of the invention, during the bleed portion of the valve actuation process, the main port is not influenced by the actuating stem. 
   According to yet another aspect of the invention, the main port is opened as the actuating stem re-engages the main seat carrier by means of a stop which then allows the seat carrier to be driven open against the force of the spring (by further rotation of the actuator). In a preferred embodiment of the invention, the spring is compressed as the seat carrier is driven open. 
   These and other objects and advantages of the invention may be best understood with reference to the following detailed description of preferred embodiments of the invention, the appended claims and the several drawings attached hereto. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a side view of an oxygen supply system constructed in accordance with a preferred embodiment of the invention. 
       FIG. 2  is a cross-sectional view of a surge prevention valve for the system of  FIG. 1 , taken along the line  2 — 2  of FIG.  1 . 
       FIG. 3  is another cross-sectional view of the surge prevention valve of  FIG. 2 , at a subsequent stage of operation. 
       FIG. 4  is yet another cross-sectional view of the surge prevention valve of  FIG. 2 , at yet another stage of operation. 
       FIG. 5  is a cross sectional view of a surge prevention valve constructed in accordance with another preferred embodiment of the invention. 
       FIG. 6  is an expanded view of a lower section of the surge prevention valve of FIG.  5 . 
       FIG. 7  is another cross sectional view of the surge prevention valve of  FIG. 5 , at a subsequent stage of operation. 
       FIG. 8  is yet another cross sectional view of the surge prevention valve of  FIG. 5 , at yet another stage of operation. 
       FIG. 9  is a cross sectional view of a dual-port surge prevention valve constructed in accordance with another embodiment of the present invention. 
   

   DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
   Referring now to the drawings, where like elements are designated by like reference numerals, there is shown in  FIG. 1  an oxygen supply system  10  constructed in accordance with a preferred embodiment of the present invention. A detailed description of the illustrated system  10  is provided below. The present invention should not be limited, however, to the specific features of the illustrated system  10 . 
   Referring now to  FIG. 1 , the oxygen supply system  10  includes a pressure regulator  12 , a conduit  14  for flowing oxygen from the pressure regulator  12  to a patient (not illustrated), a source of oxygen  16 , and a post valve  20  for preventing oxygen from flowing out of the source  16 . The source  16  may be an oxygen cylinder, for example. As discussed in more detail below, the valve  20  may be arranged to prevent a high pressure surge from occurring in the pressure regulator  12  when the valve  20  is opened. In addition to oxygen, the present invention may be also used to handle nitrous oxide and other concentrated oxidizing agents, as well as other gas combinations used in the industry. The present invention may also be used in systems other than medical systems. For example, the present invention may be applicable to oxygen welding equipment. 
   Referring now to  FIG. 2 , the valve  20  includes a housing  22  having an inlet  24  and an outlet  26 . The inlet  24  may be connected to the oxygen source  16 . The outlet  26  may be connected to the pressure regulator  12 . In addition, the valve  20  includes a seal unit  28 , a valve rod  30 , and an actuator unit  32 . The seal unit  28  may have an annular elastomeric seal pad  34  for sealing against a valve seat  36 . A passageway  37  may be provided to allow oxygen to flow through the pad  34  and into a first bypass space  38  within the seal unit  28 . The seal unit  28  also has a second bypass space  40  and a bleed passageway  42 . 
   The upper end  44  of the valve rod  30  is fixed within the actuator unit  32 . The lower portion of the valve rod  30  is slidably located within the second bypass space  40 . The valve rod  30  may have a reduced diameter portion  46  and a conical lower end  48 . Except for the reduced diameter portion  46  and the lower end  48 , the remainder of the valve rod  30  may have a circular cross-section with a substantially constant diameter. The cross-sectional configuration of the valve rod  30  is such that an upper opening  50  of the first bypass space  38  is sealed by the lower end  48  of the rod  30  in the position shown in FIG.  2 . 
   As discussed in more detail below, the valve rod  30  may be moved down and through the seal unit  28  to the position shown in FIG.  3 . In the  FIG. 3  position, the reduced diameter portion  46  is located in the upper opening  50  of the first bypass space  38 . The cross-sectional area of the reduced diameter portion  46  is less than that of the upper opening  50 . Consequently, oxygen may flow through the upper opening  50  when the valve rod  30  is in the  FIG. 3  position. 
   The seal unit  28  is connected to the housing  22  by suitable threads  62 . The threads  62  are arranged such that rotating the seal unit  28  with respect to the housing  22  in a first direction moves the seal pad  34  into sealing engagement with the valve seat  36 . Rotating the seal unit  28  in the opposite direction causes the seal pad  34  to move away from the valve seat  36  to the open position shown in FIG.  4 . In the open position, oxygen is allowed to flow through the valve seat  36 , around the seal unit  28  in the direction of arrow  64  and into the outlet  26 . An o-ring  66  or other suitable seal may be provided between the seal unit  28  and the housing  22  for preventing oxygen from flowing around the seal unit  28  above the outlet  26 . 
   The actuator unit  32  has a piston unit  70 , a handle  72  fixed to the piston unit  70 , and a cover  74 . The piston unit  70  is slidably located in the cover  74 . The piston unit  70  is also allowed to rotate within the cover  74  as described in more detail below. The piston unit  70  is biased upwardly (away from the seal unit  28 ) by a coil spring  76 . The cover  74  may be threaded into the housing  22 , if desired. 
   A torque unit is formed by openings  78 ,  80  formed in the piston unit  70  and pins  82 ,  84  fixed with respect to the seal unit  28 . As shown in  FIG. 3 , the pins  82 ,  84  may be received within the openings  78 ,  80  when the piston unit  70  is pushed downwardly against the bias of the spring  76 . When the pins  82 ,  84  are received within the openings  78 ,  80 , a torque applied to the handle  72  may be transmitted to the seal unit  28 . Thus, a torque may be manually applied to the handle  72  in a first direction to cause the seal unit  28  to move further down into the housing  22  to press the seal pad  34  into the sealed position shown in FIG.  2 . In addition, a torque may be applied in the opposite direction to threadedly move the seal pad  34  away from the valve seat  36  to the open position shown in FIG.  4 . 
   The present invention should not be limited to the specific features and instrumentalities of the surge prevention valve  20  described and shown herein. Thus, for example, the torque unit may be formed by openings in the seal unit  28  and pins fixed to the piston unit  70 , and a variety of other devices and mechanisms may be used to practice the present invention. 
   Thus, the valve  20  is closed in the position shown in FIG.  2 . In the closed position, oxygen cannot flow between the seal pad  34  and the valve seat  36 . In addition, in the closed position, the valve rod  30  seals the upper opening  50  of the first bypass space  38 , such that oxygen cannot flow into the second bypass space  40 . A suitable o-ring  88  may be provided to form a gas-tight seal against the valve rod  30  in the upper opening  50 , if desired. 
   The valve  20  is open in the position shown in FIG.  4 . In the open position, as mentioned above, oxygen can flow through the valve seat  36 , around the seal unit  28  in the direction of arrow  64 , and through the valve outlet  26 . To move the valve  20  from the closed position to the open position, the user first pushes down manually on the handle  72 , against the bias of the spring  76 , until the pins  82 ,  84  are located in the openings  78 ,  80 . Pushing down on the handle  72  causes the piston unit  72  to move axially toward the seal unit  28 . Then the user applies torque to the handle  72  in an opening rotational direction to threadedly rotate the seal unit  28  away from the valve seat  36 . The torque is transmitted through the piston unit  70  and through the torque unit  78 - 84  to rotate the threaded seal unit  28 . In the illustrated arrangement, the seal unit  28  cannot be rotated by the handle  72  unless the torque unit  78 - 84  is engaged, with the spring  76  in the compressed position shown in FIG.  3 . The torque unit  78 - 84  is engaged to enable rotation of the seal unit  28 . 
   Pushing down on the handle  72  to engage the torque unit  78 - 84  causes the reduced diameter portion  46  of the valve rod  30  to move into the upper opening  50  of the first bypass space  38 . When the reduced diameter portion  46  is in the upper opening  50 , oxygen may flow into the second bypass space  40  and through the bleed passageway  42 . Oxygen can start to flow through the upper opening  50  while the handle  72  is moving downwardly, before the torque unit  78 - 84  is fully engaged. In the illustrated arrangement, the handle  72  must be moved to the intermediate  FIG. 3  position before the seal unit  28  can be threadedly lifted from the valve seat  36 . Opening the valve  20  requires a two-step sequential push-then-twist operation much like the two-step operation required to open safety caps on medicine bottles. If the user does not push down on the handle  72 , the piston unit  70  merely rotates within the cover  74  without engaging the seal unit  28 . However, this invention is not limited to the preferred embodiment discussed herein. 
   Consequently, the illustrated valve  20  allows oxygen to bleed into the outlet  26  through the bleed passageway  42  before the seal pad  34  is moved away from the valve seat  36 . The small amount of oxygen that bleeds through the restricted passageway  42  during the short time required to engage the torque unit  78 - 84  may be sufficient to prevent a high pressure surge from developing in the system  10  when the valve  20  is subsequently opened. Thus, the regulator  12  ( FIG. 1 ) may be filled at a relatively slow, controlled rate before a full flow of high pressure oxygen is allowed through the valve  20 . The oxygen flow rate through the valve seat  36  in the valve open position ( FIG. 4 ) may be much greater than the flow rate through the bleed passageway  42  in the intermediate position shown in FIG.  3 . 
   In the preferred method of operation, the user will first push handle  72  until the pressure stabilizes in the valve  20 . This will open the first flow path  38  and allow oxygen to flow at a reduced rate. The time it takes to push the handle  72  down to enable opening of the valve  20  may be sufficient for the desired gradual pressurization of the regulator  12 . The ability of the valve  20  to bleed sufficient oxygen into the outlet  26  in the available time may be controlled, for example, by selecting a suitable cross-sectional area for the bleed passageway  42 . The bleed passageway  42  may be formed by drilling the desired opening into the seal unit  28 , if desired. Larger or smaller drills may form larger or smaller bleed passageways. 
   If the user intends to bypass the preferred method of operation or if the first bypass space  38  or bleed passageway  42  should become clogged, there will still be an added safety factor as long as the user slowly twists the handle  72 . Consequently, if desired, the user may be instructed to twist the handle  72  slowly. If such instructions regarding the twisting of the handle  72  are properly followed, the valve  20  may still prevent a high pressure surge in the regulator  12  even without the assistance of the first bypass space  38  or bleed passageway  42 . The present invention should not be limited, however, to the specific valve  34 ,  36  and bleed passageway  42  arrangement shown and described in detail herein. 
   In the open position shown in  FIG. 4 , substantially all of the oxygen flowing through the valve  20  travels in the direction of arrow  64  and not through the bleed passageway  42 . Consequently, the bleed passageway  42  does not tend to become occluded by small contaminant particles entrained in the gas flow. If the bleed passageway  42  becomes plugged, the valve  20  will still be operable so that oxygen is still supplied to the intended operative device. 
   To close the valve  20 , the user pushes down on the handle  72 , against the bias of the spring  76 , to engage the torque unit  78 - 84 . Then, while the spring  76  is compressed, the user manually twists the handle  72  to threadedly move the seal unit  28  back into sealing contact with the valve seat  36 . Then the downward pressure on the handle  72  is released, such that the spring  76  draws the end  48  of the valve rod  30  back into a sealed position within the upper opening  50  of the first bypass space  38 . 
     FIG. 5  illustrates a valve  100  constructed in accordance with another embodiment of the present invention which includes a housing  130  having an inlet  140  and an outlet  114 . The inlet  140  may be connected to the oxygen source  16 . The outlet  114  may be connected to a pressure regulator  12 . In addition, the valve  100  includes a seal unit  124 , a valve rod  106 , and an actuator unit  142 . The seal unit  124  may have an annular elastomeric seal pad  144  for sealing against a valve seat  146 . A first bypass  138  is provided to allow oxygen to flow through the pad  144  to the seal unit  124 . The seal unit  124  also has a bleed passageway  118 . 
   The upper end  160  of the valve rod  106  is fixed within a handle button  104 . The lower portion of the valve rod  106  is slidably located within a second bypass space  116  and a valve space  162 . The valve rod  106  may have a reduced diameter portion  110  and a conical lower end  132 . Except for the reduced diameter portion  110  and the lower end  132 , the remainder of the valve rod  106  may have a circular cross-section with a substantially constant diameter. The cross-sectional configuration of the valve rod  106  is such that the o-ring  136  of the first bypass space  138  seals the second bypass  116  from the first bypass  138  by the lower end  132  of the rod  106  in the position shown in FIG.  5 . As shown in  FIG. 6 , the o-ring  136  combined with the lower end  132  of the valve rod  106  may be the only components forming the seal  204  between the first bypass space  138  and the second bypass space  116 . Moreover, a continuous passageway  202  is provided between the first bypass space  138  and the exposed lower surface of the o-ring  136  regardless of the location of the valve rod  106 . Thus, gas may pass through the upper opening  164 . In the illustrated system, the upper opening  164  serves as a backup plate which keeps o-ring  136  from being blown into opening  128  in the event that someone tries to fill the gas source  16 , without first opening valve  100 . 
   As discussed in more detail below, the valve rod  106  may be moved down and through the seal unit  124  to the position shown in FIG.  7 . In the  FIG. 7  position, the reduced diameter portion  110  is located in the first and second bypass spaces  138 ,  116 . The cross-sectional area of the reduced diameter portion  110  is less than that of the first and second bypasses  138 ,  116 . Consequently, oxygen may flow through the first and second bypass openings  138 ,  116  when the valve rod  106  is in the  FIG. 7  position. 
   The seal unit  124  is connected to the housing  130  by suitable threads  126 . The threads  126  are arranged such that rotating the seal unit  124  with respect to the housing  130  in a first direction moves the seal pad  144  into sealing engagement with the valve seat  146 . Rotating the seal unit  124  in the opposite direction causes the seal pad  144  to move away from the valve seat  146  to the open position shown in FIG.  8 . In the open position, oxygen is allowed to flow through the valve seat  146 , around the seal unit  124  in the direction of arrow  170  and into the outlet  114 . 
   The actuator unit  142  has a handle button  104 , a handle  102  surrounding the handle button  104 , a socket structure  112 , and a handle cover  154 . The handle button  104  and the socket structure  112  are biased upwardly (away from the seal unit  124 ) by a coil spring  108 . The cover  154  may be threaded into the housing  130 , if desired. 
   A torque unit is formed by pins  120 ,  156  formed in the handle  152  and pins  122 ,  158  fixed with respect to the seal unit  124  together with socket structure  112 . As shown in  FIG. 7 , the four pins  122 ,  158 ,  120 ,  156  may be received by the socket structure  112  when the handle button  104  is pushed downwardly against the bias of the spring  108 . In the  FIG. 7  position, the socket structure  112  causes the pins  122 ,  158 ,  120 ,  156  to move as one unit. Therefore, a torque applied to the handle  102  may be transmitted to the seal unit  124 . Thus, a torque may be manually applied to the handle  102  in a first direction to cause the seal unit  124  to move further down into the housing  130  to press the seal pad  144  into the sealed position shown in FIG.  7 . In addition, a torque may be applied in the opposite direction to threadedly move the seal pad  144  away from the valve seat  146  to the open position shown in FIG.  8 . 
   The valve  100  is closed in the position shown in FIG.  5 . In the closed position, oxygen cannot flow between the seal pad  144  and the valve seat  146 . In addition, in the closed position, the o-ring  136  and the valve rod  106  seal the first bypass space  138 , such that oxygen cannot flow into the second bypass space  116 . As noted above, a suitable o-ring  136  may be provided to form a gas-tight seal against the valve rod  106  in the upper opening  164 , if desired. 
   The valve  100  is open in the position shown in FIG.  8 . In the open position, as mentioned above, oxygen can flow through the valve seat  146 , around the seal unit  124  in the direction of arrow  170 , and through the valve outlet  114 . To move the valve  100  from the closed position to the open position, the user first pushes down manually on the handle button  104 , against the bias of the spring  108 . Since the socket structure  112  is integrated with the valve rod  106 , the socket structure  112  also moves down to the enclosing position against the bias of the spring  108 . The socket structure  112  may be fixed with respect to the valve rod  106  by a force fit or by adhesive, for example. 
   Pushing down on the handle button  104  causes the valve rod  106  to move axially toward the seal unit  124  and causes the pins  122 ,  158 ,  120 ,  156  to become engaged within the socket structure  112 . Then the user applies torque to the handle  102  in an opening rotational direction to threadedly rotate the seal unit  124  away from the valve seat  146 . The torque is transmitted through the handle  102  and through the torque unit  112 ,  120 ,  122 ,  156 ,  158 , to rotate the threaded seal unit  124 . In the illustrated arrangement, the seal unit  124  cannot be rotated by the handle  102  unless the torque unit  112 ,  120 ,  122 ,  156 ,  158  is engaged, with the spring  108  in the compressed position shown in FIG.  7 . The torque unit  112 ,  120 ,  122 ,  156 ,  158  is engaged to enable rotation of the seal unit  124 . As shown in the drawings, the handle button  104  may be formed as part of the handle  102 , and the button  104  may be located conveniently to be operated by the thumb of the hand that grips the handle  102 . 
   Pushing down on the handle button  104  to engage the torque unit  112 ,  120 ,  122 ,  156 ,  158  causes the reduced diameter portion  110  of the valve rod  106  to move into the upper opening  164  of the first bypass space  138 . When the reduced diameter portion  110  is in the upper opening  164 , oxygen may flow into the second bypass space  116  and through the bleed passageway  118 . Oxygen can start to flow through the upper opening  164  while the handle button  104  is moving downwardly, before the torque unit  112 ,  120 ,  122 ,  156 ,  158  is fully engaged. In the illustrated arrangement, the handle button  104  must be moved to the intermediate  FIG. 7  position before the seal unit  124  can be threadedly lifted from the valve seat  138 . Opening the valve  100  requires a two-step sequential push-then-twist operation. If the user does not push down on the handle button  104 , the handle  102  merely rotates within the cover  154  without engaging the seal unit  124 . 
   Consequently, the illustrated valve  100  allows oxygen to bleed into the outlet  114  through the bleed passageway  118  before the seal pad  144  is moved away from the valve seat  146 . The small amount of oxygen that bleeds through the restricted passageway  118  during the short time required to engage the torque unit  112 ,  120 ,  122 ,  156 ,  158  may be sufficient to prevent a high pressure surge from developing in the system  10  when the valve  100  is subsequently opened. Thus, the regulator  12  ( FIG. 1 ) may be filled at a relatively slow, controlled rate before a full flow of high pressure oxygen is allowed through the valve  100 . The oxygen flow rate through the valve seat  146  in the valve open position ( FIG. 8 ) may be much greater than the flow rate through the bleed passageway  118  in the intermediate position shown in FIG.  7 . 
   In the preferred method of operation, the user will first push handle button  104  until the pressure stabilizes in the valve  100 . The time it takes to push the handle button  104  down to enable opening of the valve  100  may be sufficient for the desired gradual pressurization of the regulator  12 . The ability of the valve  100  to bleed sufficient oxygen into the outlet  114  in the available time may be controlled, for example, by selecting a suitable cross-sectional area for the bleed passageway  118 . 
   In the open position shown in  FIG. 8 , substantially all of the oxygen flowing through the valve  100  travels in the direction of arrow  170  and not through the bleed passageway  118 . Consequently, the bleed passageway  118  does not tend to become occluded by small contaminant particles entrained in the gas flow. If the bleed passageway  118  becomes plugged, the valve  100  will still be operable so that oxygen is still supplied to the intended operative device. 
   To close the valve  100 , the user may grip the handle  102  and simultaneously depress the handle button  104 , against the bias of the spring  108 , to engage the torque unit  112 ,  120 ,  122 ,  156 ,  158 . Then, while the spring  108  is compressed, the user manually twists the handle  102  to threadedly move the seal unit  124  back into sealing contact with the valve seat  146 . Then the downward pressure on the handle button  104  is released, such that the spring  108  draws the end  132  of the valve rod  106  back into a sealed position with o-ring  136  within the upper opening  164  of the first bypass space  138 . 
     FIG. 9  illustrates a dual-port (or dual-path) valve  300  constructed in accordance with another embodiment of the present invention. As illustrated in  FIG. 9 , the dual-port (or dual-path) valve  300  includes a housing  322  having an inlet  324  and an outlet  326 . The inlet  324  may be connected to the oxygen source  16  (FIG.  1 ). The outlet  326  may be connected to the pressure regulator  12  (FIG.  1 ). The housing  322  is preferably provided with wrench flats (not shown). The dual-port (or dual-path) valve  300  further includes an actuator unit  332 , which in turn is provided with a cover  374  and an actuator body  333 . The actuator body  333  has an inner surface  335  which is provided with threads  336 . The actuator body  333  is connected to the housing  332  by suitable threads  334 . The lower end surface of the actuator body  333  provides an upper limit for a coil compression spring  391 . 
   As also illustrated in  FIG. 9 , the actuator unit  332  has a piston unit  370  which is rotatably and threadedly located in the cover  374 . A threaded center section  371  of the piston unit  370  is connected to the actuator body  333  by suitable threads  372  corresponding to the threads  336  of the inner surface  335 . As described in more detail below, the piston unit  370  is rotatable within the actuator body  333 . 
   A lower portion  377  of the piston unit  370  is slidably located within a space  340  of a lower cup-shaped valve element  360 , which in turn is located within the housing  322 . The lower portion  377  of the piston unit  370  is provided with an elastomeric upper seat  350  which rests on a first valve seat  351  of a first (upper) valve  355 . A washer  341  is located on the upper surface of the lower portion  377  of the piston unit  370 . Except for the lower portion  377  of the piston unit  370 , the remainder of the piston unit  370  may have a cross-section with a substantially constant diameter. (The terms “upper” and “lower” are relative terms used herein for convenience in connection with FIG.  9 . The device of  FIG. 9  will operate in a horizontal position as well as in other orientations besides that shown in  FIG. 9. ) 
   The lower cup-shaped valve element  360  is further provided with a second (lower) valve  366  comprising a lower elastomeric, annular seat  395  which rests on a second annular valve seat  376 . The first (upper) valve  355  and the second (lower) valve  366  integrate a pressurization control orifice  380 . The lower cup-shaped valve element  360  is further provided with a lower stem seat  390  which is biased downwardly by the coil compression spring  391 . Annular elastomeric seal pads  381  and  382  may be provided for sealing against the first valve seat  351  and the second valve seat  376 , respectively. 
   The valve  300  is closed in the position shown in FIG.  9 . In the closed position, oxygen cannot flow between the seal pad  381  and the second valve seat  376 . In addition, in the closed position, the first valve seat  351  seals the upper portion of the pressurization control orifice  380 . In the closed position, oxygen cannot bleed upwardly through the small control orifice  380 . 
   In operation, the valve  300  is initially opened by rotating the threaded center post  371  of the piston unit  370  upward. A suitable handle  370 A for rotating the piston unit  370  may be attached to the top end of the piston unit  370 . When the user first rotates the threaded center section  371 , the upper seat  350  moves upwardly, in an axial direction. As a result, the first (upper) valve  355  opens and allows the pressurization control orifice  380  to be in fluid communication with the outlet  326 . This, in turn, will open a first flow path in the direction of arrow  393  and allow oxygen to flow at a reduced rate. 
   As the user further rotates the threaded center section  371 , the lower portion  377  of the piston unit  370  continues to move upwardly in an axial direction, and travels a distance “D” which is the height of the space  340  of the lower cup-shaped valve element  360 . This way, the upper surface of the washer  341  contacts retaining clip  342  of the lower cup-shaped valve element  360  so that the lower portion  377  of the piston unit  370  interlocks with the retaining clip  342  in a first axial position. 
   The time it takes the lower portion  377  of the piston unit  370  to travel the distance D within the space  340  to the first axial position may be sufficient for the slow and gradual pressurization of the regulator  12  (FIG.  1 ). The time it takes the lower portion  377  of the piston unit  370  to travel the distance D to the first axial position, and thus to completely open the first (upper) valve  355  and to start opening the second (lower) valve  366 , is preferably in the range of about 0.25 seconds to about 1.5 seconds, and more preferably in the range of about 0.5 seconds to about 1.25 seconds. The above range of time required for the complete opening of the first (upper) valve  355  can, if desired, be correlated to the amount of handle rotation required to start the opening of the second valve  366 , by controlling the spacing (pitch) of the engaged threads  372 ,  336  of the actuator body  333  and inner surface  335 . 
   For example, the spacing (pitch) of the threads  372 ,  336  may be set such that the piston unit  370  has to be rotated in the range of at least about 270 degrees to about 450 degrees, more preferably at least about 270 degrees to about 360 degrees, to allow the second (lower) valve  366  to start opening. To rotate the piston unit  370  through at least 270 degrees, a typical user is required to remove his/her hand from the oxygen tank valve handle  370 A and to re-grip the handle  370 A to complete the opening process. It would be awkward and unusual for the typical user to rotate the handle  370 A through 270 degrees without removing his or her hand from the handle  370 A at least once. The time it takes the typical operator to release and re-grip the handle  370 A, to accomplish rotation of the handle through 270 degrees or more, is at least about 0.25 seconds. Accordingly, in the preferred embodiment of the invention, the time it takes the piston unit  370  to rotate through at least about 270 degrees, to start the opening of the second (lower) valve  366  is at least 0.25 seconds. 
   The ability of the first (upper) valve  355  to bleed sufficient oxygen into the outlet  326  may be further controlled, for example, by selecting a suitable cross-sectional area for the pressurization control orifice  380 . In any event, the regulator  12  ( FIG. 1 ) may be filled at a relatively slow and controlled rate before a full flow of high pressure oxygen is allowed through the valve  300 . 
   While the piston unit  370  travels distance D within the space  340  to the first axial position, the coil compression spring  391  holds the lower stem seat  390  of the lower cup-shaped valve element  360  in a closed position (biased downwardly against the second valve seat  376 ). As a result, the second valve seat  376  of the second (lower) valve  366  remains closed and oxygen cannot flow between the seal pad  381  and the second valve seat  376 . 
   As the user subsequently rotates the threaded center section  371 , the lower cup-shaped valve element  360 , which becomes interlocked with the lower portion of the piston unit  370  through retaining clip  342 , is retracted from the first axial position (i.e., the illustrated position) to a second axial position. Consequently, the lower seat  395  lifts off the second valve seat  376  and the second (lower) valve  366  is open. This way, in the full open position, substantially all of the oxygen is allowed to flow through the second (lower) valve  366  of the dual-port valve  300  in the direction of arrow  399 . 
   The multi-path valve  300  of  FIG. 9  provides a controlled pressurization of gases and prevents a high pressure surge from occurring in the pressure regulator  12  ( FIG. 1 ) when the valve  300  is initially opened. The controlled initial bleeding of the gas through the pressurization control orifice  380  ( FIG. 9 ) delays the time in which the gas (e.g. oxygen) reaches full recompression. This, in turn, provides time for the heat generated by the recompression of the gas to be dispersed. By preventing high pressure surges and by dispersing heat during gas recompression, the occurrence of excessive heat is avoided and, consequently, the possibility of ignition of the valve and/or regulator is substantially eliminated. 
   Although the embodiments of the present invention have been described above with reference to a supply system for oxygen, the invention is not limited to oxygen or to an oxygen supply system. Thus, the invention is also applicable to other gases, compositions of gases or gas systems, including but not limited to nitrous oxide and other gases mentioned in CGA V-1 Standards (October 1994, revised January 1996). 
   The above description and drawings are only illustrative of preferred embodiments which can achieve and provide the objects, features and advantages of the present invention. It is not intended that the invention be limited to the embodiments shown and described in detail herein. Modifications coming within the spirit and scope of the following claims are to be considered part of the invention.