Abstract:
A choke valve comprising: a body having an axial through hole and a radial entry port; a valve seat coaxially housed in the body axial through hole on a first side of the radial entry port; a pressure balanced valving member axially reciprocable within the body axial through hole between a first sealing position bearing against the valve seat and a second position spaced away from the seat; an actuator housing operably connected to the valving member; and a detachably connected reinforcement member detachably connected to the actuator housing and increasing the axial load that the actuator housing can take before failure of the actuator housing.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This is a continuation of U.S. patent application Ser. No. 14/071,015, filed Nov. 4, 2013 (now U.S. Pat. No. 9,297,458, issuing on Mar. 29, 2016), which claims benefit of U.S. Provisional Patent Application Ser. No. 61/752,168, filed on Jan. 14, 2013, which applications are incorporated herein by reference and priority to/of such applications are hereby claimed. 
    
    
     STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
     Not applicable 
     REFERENCE TO A “MICROFICHE APPENDIX” 
     Not applicable 
     BACKGROUND 
     One embodiment relates to an apparatus and method for providing relief and/or reinforcement to a hydraulic choke valve from exposure to excessive backpressure. More particularly, one embodiment relates to pressure reducing valves and valve openings having secondary reinforcing members. 
     One embodiment can be applicable to hydraulic choke valves, which are a subclass of pressure reducing valves. Choke type pressure reducing valves generally function by causing a portion of the potential energy of a pressurized fluid to be dissipated through turbulence when the pressurized fluid is passed through a restrictive orifice. Typically, the orifice of a choke valve is selectably variable through reciprocation of its valving member toward and away from the valve seat, so that a desired combination of flow and exit pressure may be obtained. 
     A choke valve is normally open and is designed for one-way flow. This construction differs from that of a relief valve, which is another type of one-way flow valve that is normally closed. The present invention is applicable to a choke valve that differs in construction from the most common arrangement of such valves in having its flow gate pressure-balanced. Because of the pressure balancing of the sealing plug, the actuating loads on the stem of the flow gate are considerably reduced compared to those of most choke valves of comparable capacity. However, the stem of the flow gate, which connects to the reciprocable control screw of the actuator used to reciprocate the flow gate for this type of choke, is not pressure balanced causing possibly substantially increased loading on such stems and the housings supporting such stems. 
     In one embodiment excessive axial loading is reinforced and/or assumed by a detachably connectable reinforcing member which is attached to the primary housing of the valve body. 
     Excessive axial loading on valve plugs has been addressed using shearable relief means of opening a relief valves on single time basis using a shearing member which must be repaired after a shearing event. Schmidt et al. U.S. Pat. No. 7,124,770 discloses a mechanism for preventing damage to the actuator of a hydraulic choke valve in the event of excessive backpressure on the outlet of the choke which uses a shearable means to connect the reciprocable control shank of the actuator to the throttling valve member of the choke valve where in the event of excessive pressure on the exit channel of the choke valve, the shearable means will shear, thereby fully opening the valve and permitting the excessive pressure to escape. However, each time the shearing means is used, the valve must be taken out of commission so that the shearing means can be replaced. 
     The above prior art solution require modifications to the stems and actuators, along with rebuilding same after failure necessitating taking the valves with such solutions out of service in the event of a failure. 
     SUMMARY 
     The invention contemplates a simple, easy means to increase the maximum pressure that a particular choke valve actuator can address before the actual body overloads and fails. 
     One embodiment provides a choke valve comprising: 
     a body having an axial through hole and a radial entry port; 
     a valve seat coaxially housed in the body axial through hole on a first side of the radial entry port; 
     a pressure balanced valving member axially reciprocable within the body axial through hole between a first sealing position bearing against the valve seat and a second position spaced away from the seat; 
     a detachably connected reinforcement member detachably connected to the valve body and increasing the axial load that the valve valving member can take before failure of the valve body. 
     One embodiment provides a choke valve comprising: 
     a body having an axial through hole passing from a first side of the body to a second side of the body, an outlet passageway coaxially aligned with the through hole and positioned at the first side of the body, and a radial inlet port intersecting the through hole between the first and second sides of the body; 
     a valve seat coaxially housed in the through hole between the inlet port and the outlet passageway; a pressure balanced valving member axially reciprocable within the through hole between a first position bearing against the valve seat and a second open position spaced away from the valve seat; 
     an actuator attached to the second side of the body, the actuator having an axially reciprocating actuator shank for reciprocably moving the valving member between the first position and the second position; 
     an actuator reinforcing member detachably connected to the actuator housing, the reinforcing member comprising a plate section with an opening allowing the actual housing to partially extend therethrough; and 
     a first end of the stem positioned in a socket in one end of the actuator shank; whereby whenever the actuator shank is subjected to a fluid pressure in excess of a predetermined value from the outlet passageway the actuator reinforcing member will reinforce the body of the actuator. 
     While certain novel features of this invention shown and described below are pointed out in the annexed claims, the invention is not intended to be limited to the details specified, since a person of ordinary skill in the relevant art will understand that various omissions, modifications, substitutions and changes in the forms and details of the device illustrated and in its operation may be made without departing in any way from the spirit of the present invention. No feature of the invention is critical or essential unless it is expressly stated as being “critical” or “essential.” 
     The drawings constitute a part of this specification and include exemplary embodiments to the invention, which may be embodied in various forms. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       For a further understanding of the nature, objects, and advantages of the present invention, reference should be had to the following detailed description, read in conjunction with the following drawings, wherein like reference numerals denote like elements and wherein: 
         FIG. 1  is a perspective view of an actuator detachably connected to a choke valve body. 
         FIG. 2  is a cutaway perspective view of a plug drive system which operatively connects the primary actuator shank drive to the choke plug. 
         FIG. 3  is an exploded view of the plug drive system of  FIG. 2 . 
         FIG. 3A  is an enlarged exploded perspective view of the axial shaft and driver gear. 
         FIG. 4  is a sectional view of the plug drive system of  FIG. 1  taken through the lines  4 - 4 . 
         FIG. 5  shows the view of  FIG. 4  where the bonnet of the plug drive system has failed with respect to the body of the plug drive system. 
         FIGS. 6 through 11  are various views of the plug drive reinforcement plate to minimize the type of failures shown in  FIG. 5 . 
         FIG. 12  is an exploded perspective view of a reinforcement plate being detachably connected to the plug drive system of  FIGS. 1 and 2 . 
         FIG. 13  is an upper perspective view of the connected reinforcement plate now detachably connected to the plug drive system of  FIGS. 1 and 2 , and with the plug drive system connected to a choke valve. 
         FIG. 14  is a lower perspective view of the connected reinforcement plate now detachably connected to the plug drive system of  FIGS. 1 and 2 , and with the plug drive system connected to a choke valve. 
         FIG. 15  is a close up upper perspective view of the connected reinforcement plate now detachably connected to the plug drive system of  FIGS. 1 and 2 . 
         FIG. 16  is another close up upper perspective view of the connected reinforcement plate now detachably connected to the plug drive system of  FIGS. 1 and 2 . 
         FIG. 17  is an upper perspective view of the connected reinforcement plate now detachably connected to the plug drive system of  FIGS. 1 and 2 . 
         FIG. 18  is a sectional view of the plug drive system of  FIG. 17  taken through lines  18 - 18  of  FIG. 17 . 
         FIG. 19  is a sectional view of the plug drive of  FIG. 13  attached to a choke valve and taken through lines  19 - 19  of  FIG. 13 . 
         FIG. 20  is an upper perspective view of the connected reinforcement plate now detachably connected to the plug drive system of  FIGS. 1 and 2 , and with the primary actuator drive removed. 
         FIG. 21  is a bottom view of the plug drive system of  FIG. 20 . 
         FIG. 22  is a perspective view of the plug drive system of  FIGS. 1 and 2 , and with the plug drive system connected to a choke valve. 
         FIG. 23  is perspective view of the connected reinforcement plate now detachably connected to the plug drive system of  FIGS. 1 and 2 , and with the plug drive system being connected to a choke valve. 
     
    
    
     DETAILED DESCRIPTION 
     Detailed descriptions of one or more preferred embodiments are provided herein. It is to be understood, however, that the present invention may be embodied in various forms. Therefore, specific details disclosed herein are not to be interpreted as limiting, but rather as a basis for the claims and as a representative basis for teaching one skilled in the art to employ the present invention in any appropriate system, structure or manner. 
     The present invention provides a mechanism absorbing excessive backpressure acting on the plug  400  of a choke valve  100  before overloading either the body  710  of the plug drive system  700  and/or its bonnet  900 . 
     Shown in the Figures is an assembled hydraulic choke valve system  10  consisting of a hydraulic choke valve  100  and an electrically or manually powered actuator  1300 . Herein, the term “hydraulic choke” is taken to refer to the fact that the device is used with a variety of fluids, such as drilling mud, salt water, oil, gas, and other chemicals which may be injected into a well. “Hydraulic” does not herein refer to the choke actuation means. Although the materials of construction of choke valve  100 , plug drive system  700 , and actuator  1300  may vary, typically they are constructed of a high strength low alloy steel, mild steel, or, in the case of O-rings and other elastomeric seals, Viton™ or nitrile rubber. 
       FIG. 1  is a perspective view of an actuator  1300  detachably connected to plug primary drive  700  which itself is connected to a choke valve body  200 .  FIG. 2  is a cutaway perspective view of a plug drive system  700  which operatively connects the primary actuator drive  700  to the choke plug  400 .  FIG. 3  is an exploded view of the plug drive system  700 . 
       FIGS. 4 and 5  schematically illustrate a catastrophic failure based on excessive axial loading  2000 .  FIG. 4  is a sectional view of the plug drive system  700  taken through the lines  4 - 4 . Here force  2000  travels up through axial shaft  1000  which is transferred to driven gear  820  which is transferred to upper bearing  850  which is transferred to bonnet  900  (vial enlarged area  909 ) which is transferred to body  710  through the interaction of threads  740  and  912 . The transfer of force to body will tend to cause upper portion  720  of body to extend vertically (schematically indicated by arrow  2010 ) along with expanding outwardly (schematically indicated by arrows  2040 ) which expansion decreases the strength of the connection between threads  740  and  912 .  FIG. 5  shows the view of  FIG. 4  where the bonnet  900  of the plug drive system  700  has failed with respect to the body  710  of the plug drive system  710 . This type of failure would be a catastrophic failure as bonnet  900  and shaft  1000  can continue to move in the direction of arrow  2010 ′ leaving open the interior of the choke valve and allowing fluid to freely flow outside of the valve. 
       FIGS. 6 through 11  are various views of the plug drive reinforcement plate  1500 , which as described below can be used to reinforce and absorb excessive backpressure acting on the plug  400  of a choke valve  100  before overloading either the body  710  of the plug drive system  700  and/or its bonnet  900 . Plate  1500  can comprise first end  1510 , second end  1520 , plurality of openings  1530 , and first  1550 , second  1560 , and third  1570  bores. Plurality of bolts  1540  with plurality of nuts  1532  can be used to detachably connect reinforcement plate  1500  to body  710  of plug drive system  700 . In various embodiments each of the plurality of bolts  1540  can include first  1542  and second  1544  threaded areas. In various embodiments a second plurality of nuts  1536  can be used to lock plurality of bolts  1540  to flange  750  of plug drive system  700 . 
     The body  200  of the hydraulic choke valve  100  can be heavy walled steel with an axial passage extending from inlet  110  to outlet  120 . Both the inlet  110  and outlet  120  flow passages can be provided with concentric mounting grooves for metal ring gasket seals (not shown) and concentric hole circles for the mounting of the choke to connecting piping by means of threaded studs and nuts (not shown). The outlet flow passage has a terminal flange. The bolted and ring gasketed inlet and outlet connections are mateable with standard American Petroleum Institute (API) flange connections typically used for high pressures in the oilfield. 
       FIG. 18  illustrates the internal arrangements of the choke  10 . Inlet flow passage  110  into body  200  is radial to the axis of the through axial passage  150  which extends from actuator end to outlet  120  end of body  200 . 
     The flow passage from the cavity  150  to outlet  120  is restricted by choke plug  400 . Choke plug  400 . Choke plug  400  can seal against seat  160 . Choke plug  400  can have one or more internal flow passages parallel to but offset from its longitudinal axis and connecting from one side to the other in order that it will not fluid lock and will be exposed to balanced opening forces when it is fully or nearly closed. 
     Choke plug  400  is located on shaft  1200 , which can be a cylindrical rod extending upwardly towards driven axial shaft  1000 . The portions of the choke valve  100  exposed to high velocity flow (such as the plug  40  and seat  160 ) will typically be constructed of sintered tungsten carbide, a ceramic material, or will be hardfaced with a suitable wear resistant material, such as Stellite 3™ 
     Primary actuator drive  1300  is not described in detail, since such actuators are in very broad use and are well known to those skilled in the art. Only a general description of one type of actuator is given here. Actuator drive  1300  may be manual or either electrically, hydraulically, or pneumatically operated. In most cases, actuator  1300  will be powered and also provided with a separate manual override. Actuator drive  1300  can be rotary device powered by an electric power line or hydraulic or pneumatic hoses (not shown). 
     Although not shown, coaxial with and on the opposed side of primary actuator drive  1300  can a selectably manually engageable handwheel which is normally declutched, but can be used to operate the internal worm gear drive  810  of plug drive system  700  if primary actuator drive  1300  malfunctions. The handwheel shaft can be supported in a bearing (not shown) in the external boss projecting from plug drive system  700  on the handwheel side. Internal to plug drive system  700  body  710  is the worm gear set mount in which are a mounted a driven gear  820  and a screw drive worm gear  810  driven by shaft  800  which shaft  800  can be operably connected to both primary actuator drive  1300  and alternative manual/handwheel drive. 
     Driven axial shaft  1000  provides a linear/axial output of plug  400  from rotation of primary actuator drive  1300 . Driven axial shaft  1000  can have a male acme threaded area  1100 . 
     Shaft  800  is directly attached to screw drive worm gear  810 . Both gears  810  and  820  can be supported on bearings in plug drive body  710  and prevented from shifting axially by their mountings therein. Driven gear  820  is driven on its outer periphery by driving worm gear  810 . Driven gear  820  can include female acme drive thread  830  which can be threadably connected to driven axial shaft  100  (which includes threaded area  1100 ). Plug drive system  700  can provide a torque multiplication and speed reduction between primary actuator drive  1300  and driven axial shaft  1000  (via the gear reduction between driving worm gear  810 , driven gear  820 , and threadably connected driven axial shaft  1000 ). Such gear reduction can also resist backdriving of actuator  1300  by thrusts on the actuator shaft  1200  from plug  400 . To resist axial rotation of driven axial shaft  1000 , an anti-rotation system can be used. 
     Operation 
     Choke valve  100  is operated by non-rotating linear up and down stroking of plug  400  driven by primary drive actuator  1300 . Plug  400  can be pressure balanced through communication of fluid pressure from one end of plug  400  to the other through the internal flow passages of the plug. This pressure balancing of the plug permits the pressure on plug shaft  1200  to be reduced and, accordingly, the pressure loads typically expected on plug drive system  700  will be correspondingly reduced. This is because the pressure in the outlet  120  of the choke acts only on the cross-sectional area of the shaft  1200 ; the pressure load on the actuator is the product of the outlet pressure and the shaft  1200  area. The consequence of this is that smaller actuators can be used to control a given flow condition, when compared to the conventional unbalanced chokes. 
     Normally, pressures in the outlet  120  of choke  100  are much lower than in the inlet  110 . When choke  100  is in good condition, it will reliably seal when the sealing face of plug  400  is pressed against the seat  160 . Since the outlet  120  of the choke is typically vented, the pressure on the outlet line would thus be very low in such a case. Even when the choke  100  is opened and exposed to a high inlet  110  pressure, it is typically operated in a manner such that a very, high pressure drop is taken across the flow orifice opened between the plug  400  and seat  160 , with the result that the outlet pressure still would be low. Thus, in the normal situation, the axial loads transmitted to shaft  1200  and hence to primary drive actuator  1300  through the connection of the shaft  1200  to the actuator screw  130  are low. 
     In the event of a stoppage in the outlet  120  or some other flow upset, such as a downstream water hammer or the opening of a valve at the wrong time, very high pressures can be produced in the outlet  120  of the choke valve  100 . In such an instance, a high pressure induced axial compression load is translated to shaft  1200 , driven gear  820 , and ultimate to bonnet  900  of choke valve  100 . This high load has the potential to damage bonnet  900  and/or plug drive body  710 . 
     In  FIGS. 1 and 2  such high axial load is schematically indicated by arrows  2000  and  2010 . The response to such axial load is schematically indicated by arrow  2020 . In this embodiment bonnet  900  and body  710  of plug drive system  700  muss absorb and counteract the entire axial loading schematically indicated by arrow  2000 . With such axial loading there is a risk that body  710  and/or the threaded connection between body  710  and bonnet  900  will fail. 
     However, it is apparent that the compressive reaction load path from shaft  1200  to bonnet  900  and/or plug drive body  710 , can be at least partially absorbed by detachably connected reinforcement plate  1500  to plug drive system  700 . Such reinforcement will increase the thrust load bearing capacity of housing  710  and/or bonnet  900  of plug drive system  700 . 
     Various embodiments permit the use of a smaller, less expensive plug drive bodies  710  and/or bonnets  900  for plug drive system  700  while at the same time greatly reducing the likelihood of failure of these bodies  710  and/or bonnets  900  due to an incident of high back-pressure on the choke  1000  outlet  120 . This and other advantages will be readily apparent to those familiar with the art. 
       FIG. 10  is an exploded perspective view of a reinforcement plate  1500  being detachably connected to the plug drive system  700 . 
       FIG. 13  is an upper perspective view of the connected reinforcement plate now detachably connected to the plug drive system  700 , and with the plug drive system  700  being connected to a choke valve  100 .  FIG. 14  is a lower perspective view of the connected reinforcement plate  1500  now detachably connected to the plug drive system  700 , and with the plug drive system  700  being connected to a choke valve  100 .  FIG. 15  is a close up upper perspective view of the connected reinforcement plate  1500  now detachably connected to the plug drive system  700 , and with the plug drive system  700  being connected to a choke valve  100 .  FIG. 16  is another close up upper perspective view of the connected reinforcement plate  1500  now detachably connected to the plug drive system  700 , and with the plug drive system  700  being connected to a choke valve  100 .  FIG. 15  is an upper perspective view of the connected reinforcement plate  1500  detachably connected to the plug drive  700 , and with the plug drive system  700  not being connected to a choke valve.  FIG. 17  is a side view of the connected reinforcement plate  1500  detachably connected to the plug drive system  700 .  FIG. 18  is a sectional view of the plug drive  700  taken through lines  18 - 18  of  FIG. 17 .  FIG. 18  is a sectional view of the plug drive  700  attached to choke valve  100  taken through lines  18 - 18  of  FIG. 17 . 
       FIG. 20  is an upper perspective view of the connected reinforcement plate  1500  now detachably connected to the plug drive system  700 , and with the primary actuator drive  1300  removed.  FIG. 21  is a bottom view of the plug drive system  700 .  FIG. 22  is a sectional view of the of the connected reinforcement plate  1500  now detachably connected to the plug drive system  700  taken through lines  22 - 22  of  FIG. 21 . 
     Instead of body  710  and/or bonnet  900  absorbing the entire axial loading from plug  400 , reinforcement plate  1500  will absorb most and transfer such absorbed loading to plurality of bolts  1540  which in turn transfer such loading to second end  730  of plug drive system  700  and/or flange  750 . 
       FIGS. 22 and 23  are perspective views of the connected reinforcement plate  1500  now detachably connected to the plug drive  700 , and with the plug drive system  700  being connected to a choke valve  100 , along with the same system  10 ′ but omitting the reinforcement plate  1500 . 
     As schematically shown in  FIG. 1 , prior art systems have arrow  2000  indicating axial force from plug  400  transmitted to plug shaft  1200 , then to driven axial shaft  1000 , and bonnet  900 , and ultimately absorbed by plug drive body  710  and bonnet  900 . In these prior art systems body  710 , bonnet  900 , and/or the threaded connection between body  710  and bonnet  900  can fail. In one embodiment (shown in  FIGS. 10, 17, 18, and 21 ), a bonnet  950  can be threadably attached to a threaded locking ring  950  which locking ring is axially reinforced by reinforcement plate  1500 . In this embodiment bonnet  900  can also be threadably connected to body  710  of plug drive system  700 . As shown in  FIG. 21  locking rind  950  can sit in first bore  1550  of plate  1500  and enlarged area  909  of bonnet  900  can sit in second bore  1560  of plate  1500 , while bonnet  900  extends through third bore  1570  of plate  1500 . 
     In this embodiment a gap between shoulder  1562  of second bore  1560  and shoulder of enlarged area  909  of bonnet  900  such that a secondary protection is provided if the threaded connection between bonnet  900  and body  710 /locking ring  950  fails. If such failure occurs, shoulder  1562  of second bore  1560  will contact shoulder of enlarged area  909  of bonnet preventing a catastrophic failure of plug driving system  700 . 
     As schematically shown in  FIG. 18 , reinforcement plate  1500  can reduce the amount of reaction force from plug  400  transmitted to plug shaft  1200 , then to driven axial shaft  1000 , and bonnet  900 , and ultimately absorbed by plug drive body  710  and bonnet  900 . With reinforcement plate  1500 , instead of the full reaction force being ultimately absorbed by plug drive body  710  and  900 , arrow  2010  schematically indicates that plate  1500  absorbs a large part of this force and arrow  2020  schematically indicates that the absorbed reaction force is transmitted back down plurality of bolts  1540  and into second end  730  of plug drive system  700  and/or flange  750  with such amount of transmitted force reducing the amount of reaction force ultimately absorbed by plug drive body  710 , bonnet  900 , and the connection between plug drive body  710  and bonnet  900 . 
     The following is a list of reference numerals: 
     
       
         
               
             
               
               
             
               
               
             
           
               
                   
               
               
                 LIST FOR REFERENCE NUMERALS 
               
             
          
           
               
                 (Reference No.) 
                 (Description) 
               
               
                   
               
             
          
           
               
                 10 
                 hydraulic choke valve system 
               
               
                 100 
                 hydraulic choke valve 
               
               
                 110 
                 inlet 
               
               
                 120 
                 outlet 
               
               
                 150 
                 axial passage 
               
               
                 160 
                 seat 
               
               
                 200 
                 body 
               
               
                 300 
                 central cylindrical neck outlet 
               
               
                 400 
                 choke plug 
               
               
                 700 
                 plug drive system 
               
               
                 710 
                 plug drive body 
               
               
                 720 
                 first end 
               
               
                 730 
                 second end 
               
               
                 740 
                 threaded attachment collar 
               
               
                 750 
                 flange 
               
               
                 752 
                 threaded openings 
               
               
                 760 
                 plug shaft 
               
               
                 800 
                 input shaft 
               
               
                 802 
                 first end 
               
               
                 804 
                 second end 
               
               
                 810 
                 driving worm gear 
               
               
                 820 
                 driven gear 
               
               
                 830 
                 interior threads 
               
               
                 850 
                 thrust bearings 
               
               
                 900 
                 bonnet 
               
               
                 904 
                 first end 
               
               
                 908 
                 second end 
               
               
                 909 
                 enlarged area 
               
               
                 912 
                 threaded area 
               
               
                 918 
                 shoulder 
               
               
                 950 
                 locking ring 
               
               
                 952 
                 first end 
               
               
                 954 
                 second end 
               
               
                 956 
                 threaded area 
               
               
                 1000 
                 driven axial shaft 
               
               
                 1100 
                 threaded area 
               
               
                 1200 
                 plug shaft 
               
               
                 1300 
                 primary actuator drive 
               
               
                 1350 
                 secondary actuator drive 
               
               
                 1500 
                 detachably connectable reinforcing plate 
               
               
                 1510 
                 first end 
               
               
                 1520 
                 second end 
               
               
                 1530 
                 plurality of openings 
               
               
                 1532 
                 plurality of nuts 
               
               
                 1536 
                 second plurality of nuts 
               
               
                 1540 
                 plurality of bolts 
               
               
                 1542 
                 first threaded area for bolts 
               
               
                 1544 
                 second threaded area for bolts 
               
               
                 1550 
                 first bore 
               
               
                 1560 
                 second bore 
               
               
                 1562 
                 shoulder 
               
               
                 1570 
                 third bore 
               
               
                 1572 
                 shoulder 
               
               
                 2000 
                 arrow 
               
               
                 2005 
                 arrow 
               
               
                 2010 
                 arrow 
               
               
                 2020 
                 arrow 
               
               
                 2030 
                 arrow 
               
               
                   
               
             
          
         
       
     
     All measurements disclosed herein are at standard temperature and pressure, at sea level on Earth, unless indicated otherwise. All materials used or intended to be used in a human being are biocompatible, unless indicated otherwise. 
     It will be understood that each of the elements described above, or two or more together may also find a useful application in other types of methods differing from the type described above. Without further analysis, the foregoing will so fully reveal the gist of the present invention that others can, by applying current knowledge, readily adapt it for various applications without omitting features that, from the standpoint of prior art, fairly constitute essential characteristics of the generic or specific aspects of this invention set forth in the appended claims. The foregoing embodiments are presented by way of example only; the scope of the present invention is to be limited only by the following claims.