Abstract:
A backup metal O-ring seal is retained around the outer diameter of a seal retainer of an undersea hydraulic coupling member to seal a leak path around the seal retainer. The metal O-ring seal may be seated on a shoulder on the seal retainer. The backup metal seal is effective for high temperature and high pressure applications.

Description:
BACKGROUND 
   1. Field of the Invention 
   This invention relates, in general, to hydraulic couplings, and specifically to hydraulic couplings used in undersea drilling and production applications. More particularly, the invention involves seals between male and the female coupling members in undersea hydraulic couplings. 
   2. Description of Related Art 
   Subsea hydraulic couplings are old in the art. The couplings generally consist of a male member and a female member with seals to seal the junction between the male and female members. The female member generally has a cylindrical body with a relatively large diameter bore at one end and a relatively small diameter bore at the other. The small bore facilitates connections to hydraulic lines, while the large bore contains the seals and receives the male portion of the coupling. The male member includes a probe section insertable into the large bore of the female member. According to various embodiments of the device, the seals either abut the end, or face, of the male member or engage the male member about its outer circumference. Hydraulic fluid is then free to flow through the female and male portions of the coupling and seals prevent that flow from escaping about the joints of the coupling. 
   Optionally, a check valve may be installed in the female member and also in the male member. Each check valve is open when the coupling is made up; however, each check valve closes when the coupling is broken so as to prevent fluid from leaking out of the system of which the coupling is part. 
   In U.S. Pat. Nos. 4,694,859 and 5,762,106 to Robert E. Smith III, an undersea hydraulic coupling and metal seal is disclosed. A reusable metal seal engages the circumference of the probe when it is positioned within the female member body. The seal is held in place by a cylindrical seal retainer. When the male and female portions of the coupling are parted under pressure, the seal retainer prevents the metal seal from blowing out through the bore of the female member. 
   In U.S. Pat. No. 5,339,861, a hydraulic coupling with a hollow metal O-ring seal is disclosed. The hollow metal O-ring is held captive between an internal shoulder and a retainer inserted into the internal bore of the female member. The metal O-ring also may be pressure-energized to expand the seal cavity in response to fluid pressure in the coupling. 
   To retain the metal seal in the female member of an undersea hydraulic coupling, a seal retainer may be connected to the female member. The seal retainer may be a generally sleeve-shaped cylindrical body that is inserted into the bore of the female member until the seal retainer abuts a shoulder in the bore of female member. To secure the seal retainer against the shoulder, a retainer locking member may also be attached to the female member using threads or snap rings, for example. 
   Although metal seals that are used in undersea hydraulic couplings are generally reliable, a leak path may exist between the seal retainer and the female coupling member. In the past, elastomeric O-rings have been used to provide a seal between the outer circumference of the seal retainer and the inner circumference of the bore of the female coupling member. However, the elastomeric O-rings may not be reliable enough to block this leak path at the extreme temperatures and pressures that may be encountered at subsea depths. A more reliable seal is needed between the seal retainer and female coupling member to withstand the temperatures and pressures in the subsea environment. An undersea hydraulic coupling is needed having a more reliable seal around the outer circumference of the seal retainer that may be removed and replaced. 
   SUMMARY OF THE INVENTION 
   A metal back-up seal for an undersea hydraulic coupling seals a leak path between the female coupling member and the seal retainer. The metal back-up seal is held by the seal retainer in the receiving chamber of the female coupling member. The metal back-up seal may be a metal O-ring seal that fits around the outer diameter of the seal retainer and may be pressure energized by hydraulic fluid acting on a cavity of the seal. The seal may be press fitted around the seal retainer so that the seal may be removed from the receiving chamber together with the seal retainer. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The following drawings form part of the present specification and are included to further demonstrate certain aspects of the present invention. The invention may be better understood by reference to one or more of these drawings in combination with the detailed description of specific embodiments presented herein. 
       FIG. 1  is a section view of a metal back-up seal retained in a female coupling member of an undersea hydraulic coupling according to a first embodiment. 
       FIG. 2  is a section view of a metal back-up seal in a female coupling member of an undersea hydraulic coupling according to a second embodiment. 
   

   DETAILED DESCRIPTION 
   As shown in  FIG. 1 , in a first embodiment, seal retainer  60  retains primary metal seal  70  and back-up metal seal  80  in the receiving chamber  91  of female coupling member  90 . In this embodiment, the primary metal seal is a hollow pressure energized metal seal with a C-shaped cross section that is retained on internal shoulder  71  of the receiving chamber. The primary metal seal may be axially compressed slightly by the seal retainer to pre-load the seal, and may be pressure energized by hydraulic fluid in the seal cavity to urge the inner diameter radially inwardly further than the internal diameter of receiving chamber wall  74  to seal with the male coupling member, and the outer diameter radially outwardly to seal against the female coupling member. 
   In one embodiment of the invention, the back-up metal seal is a hollow metal O-ring that is seated on shoulder  79  of the seal retainer. The back-up metal seal may be press fitted against the seal retainer so that it may be removed from the receiving chamber together with the seal retainer. The back-up metal seal may be slightly compressed when the seal retainer is fully inserted into the receiving chamber to approach or abut shoulder  73 . The compression urges the inner diameter radially inwardly against the seal retainer and the outer diameter radially outwardly against the receiving chamber of the female coupling member. In one embodiment, the back-up metal seal may have one or more holes therein to allow hydraulic fluid to enter the seal and pressure energize the seal. 
   In one embodiment of the invention, the seal retainer may include shell  61  and seal carrier  75 . The shell may be a generally ring-shaped body with an outer diameter  66  that may be threaded to engage with the female coupling member. The shell has first end  68 , second end  64 , first larger inner diameter  63 , second smaller inner diameter  62 , and internal shoulder  76  between the first and second inner diameters. The shell also may include negative or reverse angle shoulder  84  that extends radially inwardly from internal shoulder  76 . Holes  65  may be included in the first end of the shell, and a spanner or other tool may be inserted into the holes to rotate the shell to engage or disengage it from the female member. 
   In the first embodiment, the seal carrier is a generally ring shaped sleeve, part of which engages or fits at least partially into the shell. The seal carrier has first end  77  which fits into the shell, second end  78 , first larger outer diameter  99 , second smaller outer diameter  69 , first larger inner diameter  86 , and second smaller inner diameter  67 . In one embodiment, the seal carrier may have negative or reverse angle shoulder  83  between the first larger inner diameter and second smaller inner diameter. The seal carrier also may include outer shoulder  87  between the first larger outer diameter and the second smaller outer diameter. 
   In one embodiment, the first end of the seal carrier slides into the first larger inner diameter of  63  of the shell. There may be little or no clearance between the second smaller outer diameter of the seal carrier and the inner diameter of the shell, or there may be a slight interference fit. When the first end of the seal carrier is fully inserted into the shell, the first end  77  may abut internal step  76  of the shell, and second end  64  of the shell may abut outer shoulder  31  of the seal carrier. 
   In the embodiment of  FIG. 1 , seal  72  is an elastomeric O-ring in a groove in shoulder  73  of the receiving chamber. Additionally, the seal retainer holds elastomeric seal  81  between reverse angled shoulders  83  and  84  that restrain the seal from implosion into the central bore. Seal  81  may have a dovetail cross section, and has a dovetail interfit between the reverse angled shoulders. The inner diameter of seal  81  may have one or more projections  85 ,  88  that extend farther into the central bore than the smaller inner diameters of the shell or seal carrier, to seal radially with the male member when the male member is in the receiving chamber. O-rings  82 ,  89  may be positioned around the outer diameter of seal  81 . 
   In another embodiment, as shown in  FIG. 2 , the back-up metal seal may be integral with the seal carrier. For example, metal sealing surfaces  48 ,  49  on the seal carrier may be angled or beveled to form metal to metal seals with surfaces  108  and  109  of female coupling member  100  when the seal retainer is fully engaged to the female coupling member. 
   As shown in  FIG. 2 , seal retainer  10  holds primary metal seal  50  on or adjacent shoulder  122  in the female coupling member. The seal retainer may include shell  21  and seal carrier  30 , with elastomeric seal  40  between the shell and seal carrier. The shell may be threaded or otherwise removably attached to the wall  124  of the receiving chamber  112  of the female coupling member, and the seal carrier may abut internal shoulder  126  in the receiving chamber. 
   In the embodiment of  FIG. 2 , the female coupling member has body section  111  with first end  116  and second end  117 . Poppet valve  114  slides within bore  113  to control fluid flow through the female coupling member. The poppet valve may be biased by spring  118  to a closed position against valve seat  115 . The valve spring may be held between the poppet valve and spring collar  119 , which is held in the bore by snap ring or collar clip  120 . Valve actuator  125  may extend from the face of the valve. When a male coupling member probe is inserted into receiving chamber  112 , the probe may have a sliding interfit with the second section  121  of the receiving chamber until the male member approaches or abuts shoulder  123 . The valve actuator of the male member may engage the valve actuator of the female member to open the poppet valves for fluid flow between the coupling members. 
   While the present invention has been described with respect to a limited number of embodiments, those skilled in the art will appreciate numerous modifications and variations therefrom. It is intended that the appended claims cover all such modifications and variations as fall within the true spirit and scope of this present invention.