Abstract:
A first stage pressure regulator is provided. A valve body has an inlet and an outlet that define a pressure chamber therebetween. The valve body defines a pressure compensation chamber having an opening fluidly communicating the pressure compensation chamber with the surrounding water. The first stage pressure regulator comprises an inlet tubular union removably received into the inlet. A removable high pressure orifice body defines an orifice therethrough. The orifice body is carried by the valve body proximate the inlet. A valve seat is within the valve body.

Description:
FIELD OF THE INVENTION 
       [0001]    This invention generally relates to a first stage regulatory valve for use in a self-contained underwater breathing apparatus. 
       BACKGROUND OF THE INVENTION 
       [0002]    First stage pressure regulators for underwater breathing convert high pressure gas to a lower pressure at or near a pressure that can be breathed by a diver. The high pressure gas is generally supplied to the first stage pressure regulator from an outlet of a cylinder of compressed air at a pressure that may be in excess of 4,000 psi. 
         [0003]    The high pressure gas is received by the first stage pressure regulator through an orifice of the first stage pressure regulator into a high pressure chamber of the valve body of the first stage pressure regulator. Orifice sizes, hardness, and sealing surfaces contribute to the efficiency and amount of high pressure air passing into the high pressure chamber of the valve body. Heretofore, the high pressure gas has been received into the high pressure chamber of the valve body through an orifice formed into and of the valve body. 
         [0004]    Such high pressure receiving orifices that are integral with the valve body have resulted in complex and time consuming machining of the first stage pressure regulating valve body. Additionally, because the orifice is integral with the valve body the hardness of the outer sealing edges of the orifice is limited to the same material and hence the same hardness of the valve body itself. Accordingly, the sealing edge of the orifice has proven difficult to protect from wear. Further, it has been difficult to protect such an integral orifice from corrosion because its location within the valve body makes it difficult to coat with anti-corrosion materials. Still further, quality control of the integral valve body orifice must be done with the valve body itself as opposed to being able to do quality control of the orifice independent of the valve body. Moreover, maintenance of such orifices has proven difficult since its wear is wear of the valve body itself. 
         [0005]    The present invention seeks to provide improvements over the current state of the art of first stage pressure regulators for underwater breathing devices. These and other advantages of the invention, as well as additional inventive features, will be apparent from the description of the invention provided herein. 
       BRIEF SUMMARY OF THE INVENTION 
       [0006]    In one aspect, the invention provides a first stage pressure regulator comprising a valve body having an inlet and an outlet that define a pressure chamber between the inlet and an outlet. The valve body defines a pressure compensation chamber having an opening fluidly communicating the pressure compensation chamber with the surrounding water. The first stage pressure regulator comprises an inlet tubular union removably received into the inlet. A removable high pressure orifice body defines an orifice therethrough. The orifice body is carried by the valve body proximate the inlet. A valve seat is within the valve body. 
         [0007]    A valve member is slidably carried within the valve body pressure chamber. The valve member has a valve end. The valve seat is carried by the valve end. The valve member is slidable between an open state and a closed state. In the open state the valve end carrying the valve seat is spaced from the removable high pressure orifice permitting fluid flow through the orifice between the inlet and outlet. In the closed state the valve end carrying the valve seat is sealingly seated against the removable high pressure orifice body preventing fluid flow between the inlet and outlet. 
         [0008]    In an embodiment, the removable high pressure orifice body may include an upstream end in the form of a T-shaped head having a larger diameter than a downstream end. The orifice body may extend downstream of the T-shaped head into the inlet. 
         [0009]    In another embodiment, a bottom surface of the T-shaped head is seated upon an outward facing surface of the inlet of the valve body. A top surface of the T-shaped head is in contact with the inlet tubular union such that the tubular union secures the orifice body in the inlet. 
         [0010]    In an embodiment, the T-shaped head may fit inside a cavity at a distal end of the inlet tubular union. The T-shaped head may include a slot that fluidly communicates a high pressure passage surrounding the T-shaped head with a center passage of the inlet tubular union. The high pressure passage is in fluid communication with a high pressure exit port of the valve body. 
         [0011]    In an embodiment, a head of the removable high pressure orifice body is inside a cavity formed in a distal end of the inlet tubular union. 
         [0012]    In another embodiment, a T-shaped head of the high pressure orifice body is dimensioned to fit within a cavity of the inlet tubular union. 
         [0013]    In yet another embodiment, the orifice body is axially movable and the inlet tubular union limits axial motion of the orifice body. 
         [0014]    In another embodiment, an end of the removable high pressure orifice body is in sealing contact with the valve seat in the closed state. 
         [0015]    In yet another embodiment, the valve body comprises a material of a first hardness and the removable high pressure orifice is comprised of a material of a second hardness greater than the first hardness. 
         [0016]    In still another embodiment, the removable high pressure orifice body generally includes a T-shaped head at an upstream end; a conical protrusion at a downstream end; a slot formed into a top surface of the T-shaped head; an annular groove formed into the valve body proximate an axial center of the orifice body. The annular groove receives an O-ring; the O-ring is in sealing contact with walls of the inlet of the valve body. The conical protrusion terminates at a tip; the tip is in sealing contact with the valve seat in the closed state. 
         [0017]    In another embodiment the removable high pressure orifice is free of fastening threads. 
         [0018]    In yet another embodiment the compensation chamber includes an insulated bushing; an insulating ring an insulating sleeve and an insulating biasing member. 
         [0019]    In another aspect, the invention provides a method of assembly of a first stage pressure regulator. The method includes seating a removable high pressure orifice that defines an orifice in an inlet of a valve body. The method includes securing an inlet tubular union to the valve body to limit axial motion of the orifice body within the inlet between the inlet tubular union and the valve body. 
         [0020]    In an embodiment, the valve body has an inlet and an outlet and that define a pressure chamber between the inlet and an outlet. The valve body defines a pressure compensation chamber having an opening fluidly communicating the pressure compensation chamber with the surrounding water. 
         [0021]    The valve body includes a valve seat within the valve body. A valve member is slidably carried within the valve body pressure chamber and has a valve end and an expansion head connected to the valve end. The valve member is slidable between an open state and a closed state. In the open state the valve end carrying the valve seat is spaced from a downstream end of the removable high pressure orifice permitting fluid flow between the inlet and outlet. In a closed state the valve end carrying the valve seat is sealingly seated against the downstream end of the removable high pressure orifice preventing fluid flow between the inlet and outlet. The expansion head is exposed to the pressure compensation chamber and is operably acted upon by the surrounding water within the pressure compensation chamber to bias the valve member toward the open state. A biasing member is carried within the compensation chamber to bias the valve member towards the open state. 
         [0022]    The removable high pressure orifice body of the method may include a T-shaped head at an upstream end, a conical protrusion at a downstream end, a slot formed into a top surface of the T-shaped head, a central passage through the valve body and an annular groove formed into the valve body at approximate a longitudinal center of the orifice body. 
         [0023]    In an embodiment, the step of securing is threading. 
         [0024]    In another embodiment, the step of securing includes receiving a head of the removable high pressure orifice body in a cavity in a distal end of the inlet tubular union. 
         [0025]    In yet another aspect, the invention provides a method of servicing a first stage pressure regulator. The method comprises removing a removable high pressure orifice body from an inlet of a valve body. The method includes modifying the removable high pressure orifice body and includes the step of reinserting the repaired orifice body into and on the inlet of the valve body. 
         [0026]    In an embodiment, the step of modifying the removable high pressure orifice body may include machining a new diameter of a flow restriction orifice of the removable high pressure orifice body that is of greater diameter than an original diameter of the flow restriction orifice. 
         [0027]    In yet another embodiment, the step of securing fixes the orifice body within the inlet between the inlet tubular union and the valve body. 
         [0028]    In yet another embodiment, the step of modifying may include replacing the removable high pressure orifice body with a second removable high pressure orifice body. 
         [0029]    Other aspects, objectives and advantages of the invention will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0030]    The accompanying drawings incorporated in and forming a part of the specification illustrate several aspects of the present invention and, together with the description, serve to explain the principles of the invention. In the drawings: 
           [0031]      FIG. 1  illustrates an axial section of an embodiment of the pressure regulator valve according to the present invention with the valve member in a closed position. 
           [0032]      FIG. 2  illustrates an enlarged view of a downstream portion of an inlet tubular union of the pressure regulator of  FIG. 1 . 
           [0033]      FIG. 3  illustrates an elevated perspective view of a removable high pressure orifice body of the pressure regulator of  FIG. 1 . 
       
    
    
       [0034]    While the invention will be described in connection with certain preferred embodiments, there is no intent to limit it to those embodiments. On the contrary, the intent is to cover all alternatives, modifications and equivalents as included within the spirit and scope of the invention as defined by the appended claims. 
       DETAILED DESCRIPTION OF THE INVENTION 
       [0035]      FIG. 1  illustrates a first stage air pressure reduction valve  10  of a two stage system. The first stage air pressure reduction valve  10  may also be referred to as first stage pressure regulator  10  or even more simply as pressure regulator  10 . The first stage pressure regulator  10  is used to reduce the pressure of high pressure gas stored, typically, in a tank carried by a diver to a more manageable pressure that is used by a second stage regulator that supplies breathing gas to the diver. Typically, the high pressure gas source approximates 4000 psi. The high pressure air is compressed air that may be a mixture of oxygen and other suitable gases for diving. For simplicity, hereinafter, the air or gas mixture will be referred to as gas. 
         [0036]    The pressure regulator  10  generally includes a valve body  12 . In the illustrated embodiment, the valve body  12  is generally a two piece valve body having two components  13  and  15  attached to one another. In this embodiment, the components  13  and  15  are threadedly connected to one another. The valve body  12  may be constructed of brass and coated in an anti-corrosion material such as chrome. 
         [0037]    The valve body  12  is joined to a supply of compressed air (not shown), such as a cylinder of compressed air, by an inlet tubular union  14  attached to a high pressure inlet  16  of the valve body  12 . As with the valve body  12 , the inlet tubular union  14  may be made of brass and coated in an anti-corrosion material such as chrome. In this embodiment, the inlet tubular union  14  is threadedly connected to the high pressure inlet  16  of the valve body  12 . The inlet tubular union  14  is a conduit having a center passage  18  surrounding a center axis  20  of the inlet tubular union  14 . High pressure air flows from the cylinder through the center passage  18  and selectively into and through an orifice  22  of a removable high pressure orifice body  23 . With additional reference to  FIG. 2 , the center passage  18  of the inlet tubular union  14  has a central portion of a first diameter  26  and a downstream portion  32  that includes an annular cavity  44  having a second diameter  34  that is greater than first diameter  26  formed by a stepped portion of the inner surface of inlet tubular union  14 . The center passage  18  may be coaxial and concentric with a center axis  36  of the orifice  22  of the removable high pressure orifice body  23 . 
         [0038]      FIG. 2  illustrates an enlarged view of the downstream portion  32  of the inlet tubular union  14 . The downstream portion  32  has an outermost surface  40  that forms a distal end of the tubular union  14  that may contact or simply come very near without contacting an axially outward facing surface  42  of the high pressure inlet  16  of the valve body  12 . The annular cavity  44  is formed into the outermost surface  40  of the downstream portion  32  of the inlet tubular union  14 . The annular cavity  44  is in the form of a cylindrical cavity having diameter  34  and having a smooth planer surface  46  and a sidewall  47  extending axially between surfaces  40  and  46 . The depth  48  of the annular cavity  44  is defined as the distance from the surface  40  of the downstream portion  32  of the inlet tubular union  14  to the upstream surface  46  of the cavity  44  and corresponds to sidewall  47 . In an embodiment, the depth  48  of the cavity  44  may be configured to seat orifice body  23  against component  13  of the valve body  12  and thereby fix the orifice body  23  between the inlet tubular union  14  and the valve body  12 . In another embodiment, the cavity  44  is spaced upstream of surface  42  far enough to permits the orifice body  23  to move axially within the cavity  44  with surface  40  and  46  acting as stops to limit the axial movement of the orifice body  23 . 
         [0039]    Thus, the depth  48  of the cavity  44  of the inlet tubular union is such that a T-shaped head  52  of the removable high pressure orifice body  23  is received into the cavity  44  and is sandwiched between the planar surface  46  of the cavity  44  of the inlet tubular union  14  and the valve body  12 . More specifically, a top surface  55  ( FIG. 3 ) of the T-shaped head  52  may be in contact with the bottom surface  46  of the inlet tubular union  14  while the orifice body  23  is in axial contact with and thus seated upon valve body  12 . A slot  53  ( FIG. 3 ) is formed into the top surface  55  of the T-shaped head  52 . 
         [0040]    The slot  53  provides a means by which high pressure air in the center passage  18  of the inlet tubular union  14  fluidly communicates with a high pressure passage  116  when the planar surface  46  of the inlet tubular union is in contact with the top surface  55  of the T-shaped head  52 . The fluid communication is possible because the diameter  120  of the T-shaped head is less than the diameter  34  of the cavity  44  and thus an annular high pressure passage  116  is formed that surrounds the T-shaped head and fluidly communicates with a high pressure exit port  118  of the valve body  12 . The high pressure exit port  118  may permit a high pressure gauge to attach to the valve body  12  via the exit port  118  to enable a diver to read the pressure of the tank (not shown) containing the high pressure air. 
         [0041]    In another embodiment, as shown in  FIG. 2  planar surface  46  of the cavity is not in contact with the top surface  55  of the T-shaped head and thus the orifice body  23  is free to move in an axial direction and is thus held in place against the valve body by the high pressure air in contact with the top surface  55  of the T-shaped head. It can be readily appreciated that the axial movement of the orifice body  23  is not without limits, that is, the planar surface  46  acts as a stop for limiting the axial movement of the orifice body  23 . In this embodiment it is the high pressure gas acting against the orifice body  23  that seats the orifice body  23  against the valve body  12 . In this embodiment a gap  122  is created between planar surface  46  and top surface  55 . The gap  122  is in fluid communication with the annular high pressure passage  116  which in turn, as previously discussed is in fluid communication with the high pressure exit port  118  of the valve body  12 . 
         [0042]    The inlet tubular union  14  may be threadily received into the high pressure inlet  16  of the valve body  12  and over the top surface  55  of the T-shaped head  52 . Although, threading is shown, it is not the intent to limit reception by threading as other fastening means may be used. Thus, it can be readily appreciated that insertion of the removable high pressure orifice body  23  takes place prior to threading the inlet tubular union  14  into the high pressure inlet  16  of the valve body  12 . The fastening of the inlet tubular union  14  to the high pressure inlet  16  of the valve body  12  easily secures the removable high pressure orifice body  23  between the inlet tubular union  16  and the valve body  12  during assembly. More specifically, the T-shaped head  52  of the high pressure orifice body  23  is received into the cavity  44  of the inlet tubular union  14  as the inlet tubular union  14  is threaded, as shown in this embodiment, into the high pressure inlet  16  of the valve body  12 . Further, during disassembly of the regulator  10  one need only to unthread the inlet tubular union  14  from the high pressure inlet  16  of the valve body  12  in order to access the removable high pressure orifice  22 . Once the inlet tubular union  14  is removed from the inlet  16 , the removable high pressure orifice body  23  can be easily removed from the inlet  16 . The removal may be done, for example, by a simple grasp and light pull of the T-shaped head  52  and/or simply allowing gravity to let the removable high pressure orifice body  23  to fall from the inlet  16 . 
         [0043]    The removable high pressure orifice body  23  provides for less complex machining processes with respect to forming the valve body  12  (or the inlet tubular union  14 ). Heretofore, a high pressure orifice was machined as part of the valve body  12  (or inlet tubular union  14 ). Such machining can be readily understood to be more complex and time consuming than a valve body  12  (or inlet tubular union  14 ) that does not have an integral high pressure orifice. 
         [0044]    Because the orifice  22  is no long machined into the valve body  12  an embodiment of the removable high pressure orifice  22  may provide for a removable high pressure orifice body  23  made of a material of a first hardness while the valve body  12  may be made of material of a second hardness. In a preferred embodiment, the first hardness may be greater than the second hardness. For a non-limiting example, the high pressure orifice  22  may be made of stainless steel while the valve body  12  may be made of nickel-brass. Because the removable high pressure orifice body  23  may be of a greater hardness than the valve body  12 , sealing edges  28  of the removable high pressure orifice body  23  will wear more slowly than mating surfaces of the valve body  12 . 
         [0045]    The removable high pressure orifice body  23  defines orifice  22  that receives high pressure air from the center passage  18  of the inlet tubular union  14 . The central orifice  22  of the removable high pressure orifice body  23  has a diameter  74  that is less than the diameter  26  of the center passage  18  of the inlet tubular  14  and thus acts as a flow restriction. In an embodiment the diameter  74  of the orifice  22  of the removable high pressure orifice body  23  may be between 1 and 4 mm. In a preferred embodiment the diameter of the orifice may be between 1.5 mm and 3 mm and in a more preferred embodiment the diameter  74  may be between 1.9 mm and 2.1 mm. 
         [0046]    The replaceable high pressure orifice body  23  as heretofore described has shown the unexpected result of as much as 15% increased airflow through the pressure regulator valve  10  as compared to similar pressure regulator valves having a high pressure orifice integral with the valve body  12 . 
         [0047]    Further, by providing a removable high pressure orifice body  23  the valve body  12  and the inlet tubular union  14  can more easily be protected from corrosion. In a preferred embodiment, the high pressure inlet  16  of the valve body  12  and the inner surface of the inlet tubular union  14  are smooth as opposed to inner surfaces having threads or other internal grooves. This presents an advantage because smooth continuous surfaces are more easily protected from corrosion with anti-corrosion coatings than are those with threads or grooves that are difficult to coat. 
         [0048]    Still further, with such a readily removable high pressure orifice body  23  quality control of the removable high pressure orifice  22  may be done independently of the valve body itself  12  and thus results in more precise and timely quality control as opposed to an orifice integral with the valve body  12 . Such a removable high pressure orifice body  23  saves repair costs where, for example, the entire valve body  12  (or inlet tubular union  14 ) has to be re-machined upon a machining error or upon wear of a high pressure orifice integral thereto. The ease of removing the replaceable high pressure orifice body  23  allows for simply replacing the high pressure orifice body  23  when worn or re-machining the high pressure orifice body  23  or simply replacing an annular radial seal  54  of the high pressure orifice body  23 . 
         [0049]    Turning now to  FIG. 3 , the removable high pressure orifice body  23  as was discussed above, has a T-shaped head  52  having a slot  53  at an upstream end  56 . The T-shaped head  52  provides the means by which the removable high pressure orifice body  23  mates with the valve body  12  and is received into the cavity  44  of the inlet tubular union  14 . (See  FIGS. 1 and 2 ) At a downstream end  58  of the removable high pressure orifice body  23  there is an annular planar flange  60  and a conical protrusion  64  that mates with and is received by corresponding surfaces  67  of valve seat  66  ( FIG. 1 ). An annular groove  68  is provided in approximately the axial center of removable high pressure orifice body  23 . Axial is to be understood in this context as between the upstream end  56  of the removable high pressure orifice body  23  and the downstream end  58  of the removable high pressure orifice body  23  and corresponds to central axis  36 . The annular groove  68  provides sealing and bearing surfaces  70  for the annular radial seal  54  carried therein. The annular radial seal  54  also bears against and seals with an annular interior wall  72  ( FIG. 2 ) of the high pressure inlet  16  of the valve body  12  so as to prevent any gas or liquid from bypassing orifice  22 . 
         [0050]    Turning again to  FIG. 1 , the valve body  12  provides a pressure chamber  76  and a compensation chamber  78 . The pressure chamber  76  and compensation chamber  78  may be concentric and coaxial. The pressure chamber  76  and compensation chamber  78  are separated from one another by a partition wall  80  and a valve member  82  that is movable. 
         [0051]    The pressure chamber  76  communicates via the inlet tubular union  14  and orifice  22  of the removable high pressure orifice body  23  with the pressurized gas supplied into the pressure regulator  10  from the cylinder of compressed gas. The compensation chamber  78  communicates with the outside ambient water through openings  84  in the valve body  12 . During a dive, the compensation chamber  78  fills with water at a pressure corresponding to the dive depth. 
         [0052]    The valve member  82  is slidingly carried within the valve body  12 . The valve member  82  has an expansion head  86  that is connected to a valve end  88  by a tubular stem  90 . The tubular stem  90  and expansion head  86  are both sealed to the valve body  12  to prevent ingress of ambient water or egress of the gas within the regulator. The tubular stem  90  and expansion head  86  are also allowed to slide axially within the valve body  12  as illustrated by arrow  92  so as to allow the pressure regulator  10  to reduce the pressure of the gas from its inlet pressure. 
         [0053]    The tubular stem  90  is preferably a metal material such as stainless steel to ensure a better resistance both mechanically and chemically (saline, etc.). In this embodiment, the tubular stem  90  defines the valve end  88 . 
         [0054]    The valve end  88  is shaped to carry valve seat  66 . The valve end  88  carrying valve seat  66  selectively seats against the distal end of the tapered protrusion  64  of the removable high pressure orifice body  23 . When the valve end  88  is spaced away from valve seat  66 , the pressure regulator  10  is in an open state and gas is allowed to flow through the orifice  22  to outlet  94  of the valve body  12  and into the tubular stem  90  through passage  83 . This configuration is illustrated in  FIG. 1 . When the valve end  88  is biased against the distal end of the tapered protrusion  64 , the fluid flow path from the inlet tubular union  14  through the orifice  23  of the removable high pressure orifice body  23  is closed preventing fluid flow. 
         [0055]    The valve seat  66  is preferably of a non-metallic material so as to provide a good sealing engagement with the valve end  88  and the distal end of the tapered protrusion  64  of the removable high pressure orifice body  23  when the valve member  22  is in a closed state. 
         [0056]    The expansion head  86  is at an end opposite valve end  88  of the valve member  82  and has an enlarged conical shape. Gas passes from the pressure chamber  76  into passage  83 , through the tubular stem  90  and into the enlarged area provided by the conical shape of the expansion head  86 . This conical shape provides an enlarged area in which the gas is allowed to expand. The exterior surfaces of the expansion head are acted on by the water within the compensation chamber  78  to bias the valve member  82  toward the open state (e.g. in the direction of arrow  96 ). The interior surfaces of the expansion head  86  are acted on by the gas sealed within the pressure regulator  10  to bias the valve member  82  towards the closed state (e.g. in the direction of arrow  98 ). 
         [0057]    A coil spring  100  is located within the compensation chamber  78  to bias the valve member  82  toward the open state (e.g. in the direction of arrow  96 ) with a minimum predetermined amount of force. The coil spring  100  is interposed between the expansion head  86  and the valve body  12 , and particularly a portion of the partition wall  80 . The coils of the spring  100 , in this embodiment, are formed by a stainless steel core  102  covered by a thermal insulating material layer  104 . 
         [0058]    As gas flows from orifice  22  to the outlet  94  and through the valve member  82 , the gas is allowed to expand and drop in pressure. This expansion and pressure drop is an endothermic process that draws heat energy out of the components of the pressure regulator  10  that surround the pressure chamber  76 , such as the valve body  12  and the valve member  82 . 
         [0059]    Because of the endothermic gas expansion, the compensation chamber  78  is subjected to a temperature drop which can cause freezing of the water within the compensation chamber  78 . Ice formation within the compensation chamber  78  can affect the operation of coil spring  100 , valve member  82  or the openings  84  and inhibit the pressure compensation feature of the pressure regulator  10 . 
         [0060]    One particular location where freezing occurs is proximate the end of the coil spring  100  that is pressed against the valve body  12 . To address the freezing problems within the compensation chamber  78 , the illustrated embodiment includes a thermally insulated bushing  106  that covers the outer surfaces of the valve body  12  proximate the location where the coil spring  100  is supported. 
         [0061]    The thermally insulated bushing  106  is preferably made of thermal insulating plastic material, which can also include a suitable filling material, such as for instance empty microspheres embedded in the plastic to improve the thermal insulation and inhibit heat transfer from the water within the compensation chamber to the valve body  12  and pressure regulator  10 , generally. 
         [0062]    Additional insulation may be provided by thermally insulating with an insulating sleeve  112  the expansion head  86  surfaces acted upon by the water. Still more insulation may be provided by insulating the external surfaces exposed to water of the valve stem  90  with both the sleeve  112  and an insulating ring  114  that surrounds a portion of tubular stem  90 . The insulating sleeve  112  and insulating ring  114  in a non-limiting embodiment are of the same material as that discussed above with respect to insulated bushing  106 . An annular part  108  of the expansion head  86  carries on its outer radial periphery a watertight ring (O-ring)  110 . 
         [0063]    The surfaces exposed to the ambient water (also referred to as the “wet area”) of compensation chamber  78  are substantially insulated, e.g. formed from an insulating material. In some embodiments, more than 80% of the surfaces in compensation chamber  78  are insulated and in yet other embodiments at least 90% of the surfaces in compensation chamber  18  are insulated. Because of the thermally insulated means heretofore discussed, heat transfer from the water within the compensation chamber  78  is reduced which inhibits freezing of the water within the pressure compensation chamber  78  during cold water dives, at least for the length of time of a normal diving, thus avoiding the inefficiency or the eventual valve blocking and the associated risks for the user. 
         [0064]    The invention provides a method of servicing the first stage pressure regulator  10 . The method includes removing a removable high pressure orifice body  23  from an inlet  16  of the valve body  12 . The removal may be, as a non-limiting example unthreading the inlet tubular union  14  from the valve body  12  and allowing gravity to let the removable high pressure orifice body  23  to drop from valve body  12 . The removable high pressure orifice may then be modified by machining or simply replacing the entire removable high pressure orifice body  23  with a new orifice body. 
         [0065]    As can be readily appreciated, the orifice diameter  74  of the original orifice body  23  that has worn may be machined to a greater diameter or simply cleaned so as to retain the original orifice diameter  74 . The sealing surfaces of the orifice body may be machined or cleaned as well and as previously discussed the annular seal  54  may be replaced. 
         [0066]    On the other hand, as discussed, modifying may mean the orifice body  23  is replaced with a second orifice body, that is, a new orifice body. In that case, the orifice diameter may equal the diameter  74  of the original orifice  22  or the orifice diameter may have a smaller diameter or greater diameter and thereby provide for an orifice diameter of a flow restriction different than the original orifice  22 . 
         [0067]    All references, including publications, patent applications, and patents cited herein are hereby incorporated by reference to the same extent as if each reference were individually and specifically indicated to be incorporated by reference and were set forth in its entirety herein. 
         [0068]    The use of the terms “a” and “an” and “the” and similar referents in the context of describing the invention (especially in the context of the following claims) is to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The terms “comprising,” “having,” “including,” and “containing” are to be construed as open-ended terms (i.e., meaning “including, but not limited to,”) unless otherwise noted. Recitation of ranges of values herein are merely intended to serve as a shorthand method of referring individually to each separate value falling within the range, unless otherwise indicated herein, and each separate value is incorporated into the specification as if it were individually recited herein. All methods described herein can be performed in any suitable order unless otherwise indicated herein or otherwise clearly contradicted by context. The use of any and all examples, or exemplary language (e.g., “such as”) provided herein, is intended merely to better illuminate the invention and does not pose a limitation on the scope of the invention unless otherwise claimed. No language in the specification should be construed as indicating any non-claimed element as essential to the practice of the invention. 
         [0069]    Preferred embodiments of this invention are described herein, including the best mode known to the inventors for carrying out the invention. Variations of those preferred embodiments may become apparent to those of ordinary skill in the art upon reading the foregoing description. The inventors expect skilled artisans to employ such variations as appropriate, and the inventors intend for the invention to be practiced otherwise than as specifically described herein. Accordingly, this invention includes all modifications and equivalents of the subject matter recited in the claims appended hereto as permitted by applicable law. Moreover, any combination of the above-described elements in all possible variations thereof is encompassed by the invention unless otherwise indicated herein or otherwise clearly contradicted by context.