Patent Publication Number: US-2010108068-A1

Title: Hybrid electro-pneumatic conserver for oxygen conserving regulator

Description:
RELATED APPLICATION(S) 
     This application is a continuation of U.S. application Ser. No. 10/772,220, filed Feb. 4, 2004, which claims the benefit of U.S. Provisional Application No. 60/444,995, filed Feb. 4, 2003. The entire teachings of the above applications are incorporated herein by reference. 
    
    
     BACKGROUND 
     Gas-conserving regulators include oxygen regulators, which are used to supply a patient with a regulated flow of oxygen. The oxygen is supplied by a source of compressed oxygen, such as from a supply tank, which has its pressure reduced to a low pressure for delivery to the patient. Typical oxygen regulators employ a back-pressure piston to supply a continuous flow of that low pressure oxygen to the patient. Much of that oxygen is wasted because it is not inhaled by the patient. 
     To reduce the amount of wasted oxygen, oxygen-conserving regulators have been developed which tend to limit the oxygen flow to periods of inhalation. One way of controlling the oxygen flow is by electronic means. In a typical electronic conserver, a solenoid valve controls the flow of oxygen to the patient. The solenoid valve can accurately open to provide the flow of oxygen to the patient when the patient inhales, and close between breaths. Typically, the solenoid valve requires large energy requirements so that a C or D sized battery powering the solenoid valve might last only one month. 
     SUMMARY 
     Embodiments of the present invention include a gas conserving regulator which can deliver gas to a patient with the accuracy of an electronic conserver, but with significantly reduced energy consumption so that batteries can last much longer or can be smaller. 
     One embodiment includes a gas regulator including a slave valve assembly for receiving and controlling the flow of gas to a desired destination. A timing chamber can be positioned adjacent to the slave valve assembly. The timing chamber has an inlet for also receiving the gas. An electronically operated pilot valve assembly can be in communication with the timing chamber for operating the slave valve assembly. When the pilot valve assembly is closed, gas pressure within the timing chamber acting on the slave valve assembly closes the slave valve assembly. When the pilot valve assembly is open, gas exits the timing chamber and reduces the gas pressure in the timing chamber, thereby allowing the slave valve assembly to open and deliver the gas to the desired destination. 
     In particular embodiments, the gas is oxygen which is delivered to a patient. A sensing circuit can sense inhalation by the patient for controlling the electronically operated pilot valve assembly. 
     The slave valve assembly can include a slave valve nozzle and a slave valve member for engaging the slave valve nozzle. The gas pressure within the timing chamber acting on the slave valve member can control the operation of the slave valve member, which can be a diaphragm. 
     In one embodiment, the electronically operated pilot valve assembly can include a piezoelectric device. In another embodiment, the electronically operated pilot valve assembly can be a solenoid operated pilot valve assembly. 
     The solenoid operated pilot valve assembly can include a pilot valve nozzle and a pilot valve member for engaging the pilot valve nozzle. A solenoid operates the pilot valve member. A spring can be used to bias the pilot valve member towards the pilot valve nozzle to be normally closed. The pilot valve nozzle and the pilot valve member can be aligned along a common axis whereby the pilot valve member moves along the axis for engaging and disengaging from the pilot valve nozzle. 
     The timing chamber and the solenoid operated pilot valve assembly can be positioned within a common housing with the timing chamber and the pilot valve nozzle being connected by a passage therebetween. The slave and pilot valve nozzles each have an opening where the pilot valve nozzle opening can be smaller than the slave valve nozzle opening for minimizing the solenoid size and energy expended by the solenoid. The slave and pilot valve nozzle openings can be sized to provide at least about a 45:1 area and solenoid energy efficiency ratio. For such a ratio, the slave valve nozzle opening can be at least about 0.048 inches in diameter and the pilot valve nozzle opening can be about 0.007 inches in diameter. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing and other objects, features and advantages of the invention will be apparent from the following more particular description of particular embodiments of the invention, as illustrated in the accompanying drawings in which like reference characters refer to the same parts throughout the different views. The drawings are not necessarily to scale, emphasis instead being placed upon illustrating the principles of the invention. 
         FIG. 1  is a schematic sectional drawing of a prior art electronic conserver for a regulator. 
         FIG. 2  is a schematic sectional drawing of an embodiment of a hybrid electro-pneumatic conserver regulator in the closed position. 
         FIG. 3  is a schematic sectional drawings of the conserver regulator of  FIG. 2  with only the solenoid operated pilot valve assembly being in the open position. 
         FIG. 4  is a schematic sectional drawing of the conserver regulator of  FIG. 2  with both the solenoid operated pilot valve assembly and the pneumatic operated slave valve assembly being in the open position. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  is a schematic cross-section of a typical prior art electronic conserver  10 . A solenoid  14  of a solenoid valve  18  controls a sealing member  12 , such as a stopper made of rubber or similar material, relative to a nozzle  16 . When the solenoid valve  18  is in the open position, oxygen flows through the nozzle  16  to the patient. At rest, the valve  18  is closed by the solenoid  14  thereby preventing the flow of oxygen to the patient. The solenoid  14  is actuated by a sensor (not shown) that senses a vacuum caused by the patient&#39;s inhalation, which results in the solenoid valve  18  opening. After a specific amount of time, the solenoid  14  is returned to its rest position, halting the flow of oxygen, and the system waits for the next inhalation trigger. A benefit of electronic conservers is that an electronic timing mechanism can provide accurate delivery of the gas to the patient. In addition, most electronic conservers can operate with a single-lumen cannula. 
     In electronic conservers, the opening of the nozzle  16  must be large enough to deliver the required amount of oxygen to the patient during the actuation period. For a system operating at a normal pressure of 15-25 PSI, the nozzle  16  typically has an opening that is about 3/64 inches in diameter. The solenoid valve  18  must therefore be able to seal the nozzle  16  against the gas pressure. At 22 PSI, for example, the solenoid  14  must provide at least about 0.04 pounds of resistance to seal the nozzle  16 . That requires a fairly large solenoid unit, which has significant energy requirements. To meet those energy requirements, typical prior art conservers use a C or D-size battery. That battery is the largest single component of prior art conservers. Such batteries may only last for about one month. 
       FIG. 2  is a schematic cross-section of a particular hybrid oxygen conserver regulator  20 . Examples of the core pneumatic architecture are described in U.S. Provisional Application No. 60/412,056, filed on Sep. 19, 2002, by LeNoir E. Zaiser, and U.S. application Ser. No. 10/666,115, filed on Sep. 19, 2003, by LeNoir E. Zaiser, the teachings of which are incorporated herein by reference. 
     Conserver  20  includes a housing  20   a  having a slave valve assembly  40  which receives low pressure oxygen from a pressure regulating portion  19 . The pressure regulating portion  19  is in communication with a pressurized source of oxygen, such as from a supply tank which is often at about 2200 psi. The pressure regulating portion  19  typically includes a back pressure piston assembly, as is common in the art, which reduces the pressure of oxygen received from the pressurized source to between about 15-25 psi, typically about 22 psi. The slave valve assembly  40  controls the flow of the low pressure oxygen to the patient through a passage  50  and, in turn, is controlled by a solenoid operated pilot valve assembly  30 . The slave valve assembly  40  is sized to deliver a sufficient amount of oxygen to the patient while the solenoid operated pilot valve assembly  30  is designed to use a minimal amount of energy while at the same time being capable of controlling the slave valve assembly  40 . Typically, tubing is connected in communication with passage  50  and connected to the patient for delivering the oxygen through a mask or cannula. 
     The slave valve assembly  40  includes a slave valve nozzle  42  with a nozzle opening  46  and a filter  48  which receives oxygen from the pressure regulating portion  19 . A slave valve member  44 , typically a diaphragm, is engageable with the slave valve nozzle  42  for opening and closing the slave valve assembly  40 . The operation of the slave valve member  44  is determined by the pressure within a timing chamber  54  adjacent to or against the slave valve member  44  which receives low pressure oxygen through an inlet passage  52 . The timing chamber  54  is in communication with the solenoid operated pilot valve assembly  30  through a passage  38  in the housing  20   a.  The opening and closing of the pilot valve assembly  30  controls the pressure within timing chamber  54  and, therefore, the operation of the slave valve assembly  40 . 
     The solenoid operated pilot valve assembly  30  has a pilot valve nozzle  32  and a pilot valve member  26  for engaging the pilot valve nozzle  32 . The pilot valve member  26  is biased by a spring  24  against the pilot valve nozzle  32  to be normally closed and is opened by the activation of a solenoid  28 . The pilot valve member  26  has a sealing surface or member  22  for sealing the pilot valve nozzle  32 . The pilot valve assembly  30  is positioned in a cavity  34  within the housing  20   a  with the pilot valve nozzle  32  and the pilot valve member  26  extending into the cavity  34  from opposite sides. The cavity  34  is in communication with the atmosphere through a passage  36 . The solenoid  28  is controlled by a sensing circuit  64  which senses inhalation of the patient. The sensing circuit  64  includes a controller  58  that is connected to the solenoid  28  via line  56 , and a sensor  62  which is in communication with controller  58  via line  60 . The sensor  60  is positioned in a location to sense inhalation of the patient, such as in communication with the tubing connected to the patient. 
     In operation, referring to  FIG. 2 , at rest, the pilot valve assembly  30  and the slave valve assembly  40  of conserver  20  are both in the closed position so that low pressure oxygen provided by the pressure regulating portion  19  of conserver  20  is prevented from reaching the patient. In the solenoid operated pilot valve assembly  30 , the solenoid  28  is deactivated so that the spring  24  biases the pilot valve member  26  against pilot valve nozzle  32  where the sealing member  22  seals the pilot valve nozzle  32  closed to prevent gas from passing through the opening  32   a . The biasing force exerted by the spring  24  for closing the pilot valve member  26  is greater than the force exerted on the valve member  26  in the opposite direction by the gas or oxygen pressure within the pilot valve nozzle  32  over the small surface area provided by the diameter of the opening  32   a  of the nozzle  32 . Since the pilot valve assembly  30  is closed, oxygen within the timing chamber cannot escape. As a result, the gas or oxygen pressure within the timing chamber  54  keeps the slave valve member  44  pressed against the slave valve nozzle  42  due to a force differential, because the closing force exerted by the gas pressure of the timing chamber  54  over the large surface area of the diaphragm of the slave valve member  44  is greater than the force exerted on the opposite side of the diaphragm by the gas pressure within the nozzle opening  46  of the slave valve nozzle  42  over the small surface area provided by the diameter of the nozzle opening  46 . 
     Referring to  FIG. 3 , when the patient takes a breath, the sensor  62  of sensing circuit  64  detects the vacuum caused by the patient&#39;s inhalation. The controller  58  then energizes and activates solenoid  28 . The energized solenoid  28  overcomes the biasing force of the spring  24  and retracts the pilot valve member  26  away from the pilot valve nozzle  32 . This opens the pilot valve assembly  30 , which allows gas to exit the pilot valve nozzle  32 . Once the pilot valve assembly  30  is opened, oxygen within the timing chamber  54  begins to exit the timing chamber  54  to the atmosphere via passage  38 , pilot valve nozzle  32 , cavity  34  and passage  36 . 
     Referring to  FIG. 4 , as the oxygen within timing chamber  54  is vented to the atmosphere, the gas or oxygen pressure within the timing chamber  54  drops causing a reversed force differential on the slave valve member  44 . The force exerted on the slave valve member  44  by the gas pressure within the nozzle opening  46  of the slave nozzle  42  becomes greater than the force exerted on the slave valve member  44  by the reduced gas pressure within the timing chamber  54 . As a result, the gas pressure within the nozzle opening  46  pushes the slave valve member  44  off the slave valve nozzle  42  causing the slave valve member  44  to flex into the timing chamber  54 , thereby opening the slave valve assembly  40 . Once the slave valve assembly  40  is opened, low pressure oxygen provided by the pressure regulator portion  19  of conserver  20  can pass through slave valve nozzle  42  and passage  50  for delivery to the patient. After a timer in the controller  58  determines that a specific amount of time has passed, the controller  58  deactivates the solenoid  28  thereby allowing the spring  24  to bias the pilot valve member  26  back against the pilot valve nozzle  32  to close the pilot valve assembly  30 . With the flow of oxygen through the pilot valve nozzle  32  terminated, the pressure within the timing chamber  54  repressurizes or rises back to the original or starting operating level. Consequently, this pressure forces the slave valve member  44  back against the slave valve nozzle  42  to block the flow through nozzle opening  46 , thereby closing slave valve assembly  40  and terminating the flow of oxygen to the patient, such as shown in  FIG. 2 . The conserver  20  is then ready for the next breath by the patient. 
     A more detailed discussion of embodiments of conserver  20  now follows. The conserver  20  is typically operated with a single-lumen cannula, but alternatively can be operated with a dual-lumen cannula. The diaphragm of the slave valve member  44  forms one of the boundaries of the timing chamber  54  as well as operates as a valve member. The slave valve member  44  typically requires gas pressure in order to be closed. When there is no gas pressure, the slave valve member  44  can be apart from the slave valve nozzle  42 . The sealing member  22  on the pilot valve member  26  is typically made of polymeric material suitable for sealing pilot valve nozzle  32 , such as silicone rubber, or similar materials. In the embodiment shown in  FIGS. 2-4 , the pilot valve member  26  and the opening  32   a  of the pilot valve nozzle  32  are positioned along a longitudinal axis A where the pilot valve member  26  is a plunger that is reciprocated longitudinally along axis A towards and away from pilot valve nozzle  32  for opening and closing pilot valve assembly  30 . The pilot valve nozzle  32  can have an opening  32   a  that is approximately 0.007 inches in diameter, so when the timing chamber  54  has a gas pressure of about 22 psi, the spring  24  only needs to overcome about 0.00085 lbs. of force against pilot valve member  26  exerted by the gas in the opening  32   a  of the pilot valve nozzle  32 . The slave valve nozzle  42  can have an opening  46  that is about 0.048 inches in diameter so that the ratio of areas and gas pressure forces in the openings  46  and  32  is about 45:1, and is closer to about 47:1. In other embodiments, the pilot valve nozzle  32  can have an opening  32   a  that is about 0.007 inches in diameter and the slave valve nozzle  42  can have an opening  46  that is larger than 0.048 inches in diameter, for example, about 0.250 inches in diameter. In such an embodiment, the ratio of areas and gas pressure forces in the openings  46  and  32  is about 1290:1. 
     In comparison to the pilot valve nozzle  32 , the nozzle opening in a conventional electronic conserver is typically about 3/64 inches in diameter for providing sufficient oxygen flow to the patient so that the force exerted by the gas at a pressure of 22 psi within such an opening against a valve member is about 0.04 lbs. and is over 45 times greater than in the opening  32   a  that is about 0.007 inches in diameter, because the ratio of the area of the nozzle openings is about 45:1. As a result, it can be seen that the solenoid  28  in conserver  20  can be sized many times smaller than the solenoid in a conventional electronic conserver. With the solenoid  28  being sized smaller than those in conventional electronic conservers, less energy is required for operation. 
     The solenoid energy efficiency can be directly proportional to the ratio of forces entered through the opening  32   a  in the pilot valve nozzle  32  relative to the opening in a standard electronic conserver. In embodiments having a pilot valve nozzle  32  with an opening  32   a  about 0.007 inches in diameter, the conserver  20  can have about a 45:1 solenoid efficiency ratio relative to a standard electronic conserver. That is, the solenoid  28  in the conserver  20  is about 45 times more energy efficient than a solenoid in a standard electronic conserver. 
     This means that a battery, that may only operate for one month in a conventional electronic conserver, can operate the conserver  20  for nearly four years. It also follows that a smaller battery, such as a camera battery, can be used to power the conserver  20  for an adequate period of time. Such advantages permit the conserver  20  to be both smaller and lighter than the conventional electronic conservers. 
     The conserver  20  allows for a variety of conserving ratios, defined as the ratio of the volume of oxygen delivered to the patient in comparison with the volume delivered by a standard, non-conserving regulator operating at the same flow rate. The conserver  20  can also be operated with a continuous, non-conserving flow at all flow settings, unlike conventional single-lumen conservers, most of which have only one continuous flow setting. 
     There are a number of variations that can be made to the mechanism with regard to the deactivation of the solenoid  28 . In one such variation, the pilot valve member  26  can remain open for a fixed amount of time. To vary the amount of oxygen delivered to the patient, the flow rate of the oxygen can be adjusted. In another variation, the conserver  20  can deliver oxygen at a fixed flow rate, while the pilot valve member  26  remains open for a variable amount of time. This also allows the user to vary the amount of oxygen delivered to the patient. In yet another variation, the pilot valve member  26  can be opened using electronic means, and a pneumatic timer can be used to close the pilot valve member  26 . 
     In another embodiment, the solenoid-controlled pilot valve member  26  can be replaced by a piezoelectric device. Circuitry can excite the piezo device, causing the piezo device to open the pilot valve nozzle, such as by expanding. 
     While this invention has been particularly shown and described with references to preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the scope of the invention encompassed by the appended claims. 
     For example, although conserver  20  has been described for delivering oxygen to a patient, it is understood that conserver  20  can be used to deliver other gases, and to other desired destinations. Other therapeutic gases can be delivered such as nitrous oxide, or non-therapeutic gas can be delivered, such as lethal gases or gases for industrial uses. Although the components of the slave valve assembly  40  and the solenoid operated pilot valve assembly  30  have been shown in the figures to be aligned along axis A, alternatively, these components do not have to be in alignment with each other. In addition, it is understood that the slave valve assembly  40  and the solenoid operated pilot valve assembly  30  can have configurations other than those shown and described. For example, in some embodiments, the slave valve member can be a rigid member such as a piston having a large surface area acted on by gas pressure in the timing chamber  54  and a small surface area acted on by gas pressure in the nozzle opening  46 . Also, gate valve configurations are possible. Other embodiments of the conserver  20  can have a solenoid operated pilot valve assembly including a spool that is shifted laterally relative to the gas flow for opening and closing the pilot valve assembly. Also, the solenoid operated pilot valve assembly can be located in a different housing than the slave valve assembly  40 . Furthermore, it is understood that the diameter of the opening  32   a  of the pilot valve nozzle  32  can be varied to obtain the desired combination of energy efficiency and venting speed of timing chamber  55 . Finally, it is understood that features of the present invention can be omitted or combined.