Patent Publication Number: US-7584764-B2

Title: Coaxial quick disconnect coupling

Description:
CROSS-REFERENCE TO RELATED CASES 
   The present application is a divisional of application Ser. No. 10/795,599, filed Mar. 8, 2004 now U.S. Pat. No. 7,147,003, and claims the benefit of the filing date of U.S. Provisional Application Ser. No. 60/475,289 filed Jun. 3, 2003, and U.S. Provisional Application Ser. No. 60/491,657 filed Jul. 29, 2003, all of which are expressly incorporated herein by reference in their entirety. 

   FIELD OF THE INVENTION 
   The present invention relates to quick disconnect, concentric coaxial couplings and their attachment with mating hose assemblies. 
   BACKGROUND OF THE INVENTION 
   Coaxial couplings, particularly those which conduct high and low pressure fluids, are well known in the art. An example of such a coupling is shown in U.S. Pat. No. 6,179,001 B1 to Schutz. This type of coupling assembly permits a rapid-action connection of a male and female coupling that sealingly closes when the male and female halves are disconnected. Typically, these concentric, coaxial coupling are attached with coaxial hose assemblies. 
   Coaxial hose assemblies are generally used to conduct hydraulic fluid, for example, from a driving element such as a pump, to a hydraulically driven apparatus such as a tool and then return the hydraulic fluid back to a reservoir that supplies the pump with fluid. Typically, the concentric inner passage of both the hose assembly and coaxial coupling is filled with high pressure working fluid, while the outer concentric passage of both the hose assembly and coupling is filled with the low pressure return fluid. 
   Trapped pressurized fluid or flow impediments are harmful to the coaxial coupling assembly. Connection of the two halves is difficult if the pressure in either half has escalated due to trapped fluid. Sudden pressure surges within the hose assemblies can cause harm to all of the components. Therefore, it is desirable to control the fluid flow through the coupling halves and ensure that trapped pressurized fluid is properly dissipated without harming the assembly. 
   Coaxial couplings are comprised of a multitude of components. It is necessary to properly seal the areas where connections are made between the components to ensure that pressurized fluid does not escape. In addition, sudden pressure spikes within the assembly can extrude the seals that reside in and between the components. 
   At some point, due to age, misuse, etc., the conduit that provides the connection to the coaxial coupling halves will have to be replaced. It is cost prohibitive to replace both the conduit and its mating coaxial coupling. Some prior art patent structures combine the coaxial coupling and conduit into an integral assembly. The end fitting that attaches to the conduit is also a primary component of the coupling. Therefore, replacement of the hose assembly, which is comprised of the conduit and attached end fitting, is impractical without replacing the coupling. 
   Valving componentry is needed for the interconnection of fluid paths. It is desirable to provide an unimpeded connection so that a smooth fluid connection is achieved. Small passageways restrict the fluid flow and interrupt the smooth continuous passage of fluid. It is desirable to have a full passage at the mating halves of the male and female couplings immediately upon the connection. Passageways through the valving components can restrict the fluid flow and provide a hindrance to a smooth continuous flow. 
   The connector, or port, at the driving component, e.g. the pump, and the driven component, e.g. the tool, can have various configurations. Both twin-line and concentric coaxial connectors are commonly used at the port. Therefore, both mating twin line or concentric coaxial conduits are used. Since it is costly and inconvenient to carry both styles of mating coaxial couplings, it is desirable to have but one coaxial coupling that can mate with both the twin line and coaxial styled conduits. 
   Coaxial couplings are commonly used in unclean environments, with properly sealed components within the coaxial coupling, preventing outside contaminants from entering. If contaminants do enter, the joints and seals of the mating componentry can be adversely affected. The locking collar assembly of a quick disconnect, coaxial coupling functions with internal springs and locking componentry that are housed within a cavity isolated from outside contaminants. Thus, it is essential that seals between the mating and moving components not only prevent contaminants from entering, but also not hinder necessary movements between the components. 
   Since both of the male and female halves of the coaxial coupling are concentric, proper mating can only occur if they both remain concentric. Soft connecting joints between the components can allow one component to move radially relative to another, thus causing this coupling half to be eccentric. Strong, secure joints between the components ensure that one coupling half remains concentric and sealingly mates with the other half. 
   Prior art coaxial coupling have integrated the end fitting of the connecting hose assembly into the componentry of the coaxial coupling. Therefore the same component that is used as a functioning part of the male and/or female coaxial coupling connects with the conduit. Although this design reduces the number of components for the entire coaxial coupling assembly, i.e. the coaxial coupler with the hose assembly, it also eliminates any reusability of the coaxial coupling. For example, if one of the conduits fails during use of the coaxial coupling assembly, it is desirable to change only the failed conduit. This can not be done if the conduit is permanently attached with a component of the coaxial coupling. The entire coaxial coupling assembly has to be replaced in such a case, which adds cost for the enduser. 
   SUMMARY OF THE INVENTION 
   The present invention provides a method of fluidly connecting a first coaxial coupling and a second coaxial coupling, both having concentric inner and outer passages. The method initially fluidly connects the first coaxial coupling inner and outer passages with each other while isolating both of the inner and outer passages of the second coaxial coupling. The process then fluidly connects one of the second coaxial coupling inner and outer passages with one of the first coaxial coupling inner and outer passages. The process finally fluidly connects the first coaxial coupling inner passage with the second coaxial coupling inner passage and the first coaxial coupling outer passage with the second coaxial coupling outer passage. The noted method can also include the steps of conducting high pressure fluid via the first and second inner coupling passages and then conducting low pressure fluid via the first and second coupling outer passages. 
   Another feature of the present invention includes providing a method of fluidly connecting coaxially aligned first and second couplings wherein the first coupling has an inner high pressure passage and a coaxial outer lower pressure passage. The second coupling has an inner high pressure passage and a coaxial outer lower pressure passage. The method initially fluidly connects the first coupling inner high pressure passage with the first outer lower pressure passage while isolating the second coupling inner high pressure passage and the coaxial outer lower pressure passage. The method then fluidly connects the first coupling inner high pressure passage and one of the second coupling inner high pressure and outer lower pressure passages with the first coupling coaxial outer lower pressure passage while still isolating the other of the second coupling inner high pressure and low pressure passages. The method then finally fluidly connects the first coupling inner high pressure passage with the second coupling inner high pressure passage and the first coupling outer lower pressure passage with the second coupling outer lower pressure passage. Another feature of the present invention includes the noted method of connecting coaxially aligned first and second couplings while providing a continuous flow of high pressure fluid through the first coaxial coupling. 
   A further feature of the present invention includes providing a method of fluidly connecting coaxially aligned first and second couplings wherein both couplings have inner high pressure passages and coaxially outer lower pressure passages. The method initially connects the first coupling inner high pressure passage with the first coupling coaxial outer lower pressure passage while isolating the second coupling inner high pressure passage and the second coupling coaxial outer lower pressure passage. The method then fluidly connects both of the second coaxial coupling high and coaxial lower pressure passages with the first coaxial coupling outer lower pressure passage. The method then finally fluidly connects the first coupling inner high pressure passage with the second coaxial coupling inner high pressure passage and the first coaxial coupling outer low pressure passage wit the second coaxial coupling outer low pressure passage. 
   Still another feature of the present invention includes providing a method of operatively, fluidly and concentrically interconnecting adjoining proximate ends of self-contained subassemblies comprised of first and second coaxial coupling halves, with the distal end of each of said coupling halves being operatively, fluidly interconnected with a separate hose assembly. The hose assembly includes a flexible hose assembly having multiple conduits, each of said conduits being, in turn, connected with an individual hose fitting. The coupling halves, together with their respective hose assemblies form a coupling assembly between a driving member and a driven member. The noted method initially maintains an operative fluid connection between the concentric inner and outer passages of the first coupling half, which are connected via separate conduits and hose fittings to the driving member, while concurrently isolating concentric inner and outer passages of the second coupling half, which are connected via further separate conduits and hose fittings to the driven member. The method then fluidly connects one of the second coaxial coupling member inner and outer passages with one of the first coaxial coupling member inner and outer passages in order to relieve any residual pressure buildup in the second coaxial coupling member. The method finally fluidly interconnects the first and second coaxial coupling member inner passages and the first and second coaxial coupling member outer passages, thereby empowering the driven member. 
   Another feature of the present invention includes a quick disconnect coupler, having a male half for connection with a female half. The male half includes an inner passage, a concentric outer passage, an outer cylindrical plug having a plurality of flow passages longitudinally extending therethrough, a cylindrical outer sleeve, received within and axially moveable relative to the cylindrical plug, a cylindrical valve body positioned within and axially moveable relative to the cylindrical outer sleeve from a first position in which the outer surface of the valve body is sealed against the inner surface of the sleeve to a second position in which the outer surface of the valve body is out of contact with the inner surface of the sleeve, and an inner valve element positioned within and axially moveable relative to the valve body. The inner valve is moveable from a first position in which the outer surface of the inner valve element is sealed against the inner surface of the valve body to a second position in which the outer surface of the inner valve element is out of contact with the inner surface of the valve body. The female half includes an inner passage, a concentric outer passage, a cylindrical body having a locking mechanism, a face sleeve, received within and axially moveable relative to the cylindrical body, engageable with the cylindrical plug when the male half is inserted into the female half. The female half also includes a cylindrical sealing sleeve received within and axially moveable relative to the face sleeve, engageable with the cylindrical outer sleeve when the male half is inserted into the female half. The female half further includes a cylindrical valve body, positioned within and axially moveable relative to the cylindrical sealing sleeve from a first position in which the outer surface of the cylindrical valve body is sealed against the inner surface of the cylindrical sealing sleeve to a second position in which the outer surface of the cylindrical valve body is free of being sealed against the inner surface of the sealing sleeve, engageable with the valve body when the male half is inserted into the female half. The female half also includes an inner valve, positioned within and axially moveable relative to the cylindrical valve body, having a forward end, with a front face engageable with the valve element when the male half is inserted into the female half, and a plurality of side passages. The inner valve is moveable from a first position, in which the outer surface of the forward end is sealed against the inner surface of the valve body, to a second position, in which the outer surface of the forward end is out of contact with the valve body ( 86 ). In the first position, the male half inner passage and the male half concentric outer passage are each isolated from all other passages, and the female inner passage is fluidly connected with the female half concentric outer passage. In a position between the first and second positions, the female half inner passage and at least one of the male half inner passage and male half concentric outer passage are fluidly connected with the female half concentric outer passage. In the second position, the female half inner passage is fluidly connected with the male half inner passage, and the female half concentric outer passage is fluidly connected with the male half concentric outer passage. 
   Still another feature of the noted quick disconnect coupler includes having the female half inner passage as a high pressure passage, the female half concentric outer passage is a low pressure passage, the male half inner passage is a high pressure passage, and the male half concentric outer passage is a low pressure passage. Still another feature of the noted quick disconnect coupler has the male half inner valve element being substantially cup-shaped and having a continuous, uninterrupted outer surface. A further feature of the noted quick disconnect coupler has the male valve body attached to the male cylindrical body via press-fitting, the female cylindrical sealing sleeve attached to the cylindrical body via press-fitting, and the female inner valve attached to the cylindrical sealing sleeve via press-fitting. 
   Still another feature of the present invention has the noted quick disconnect coupler being part of a quick disconnect assembly and attached with a series of hose assemblies. The female half is attached to a first high pressure hose assembly, including a first hose fitting having a first end sealingly attachable to the female inner valve, a longitudinal passage extending therethrough which is axially aligned with the inner valve inner passage when the first hose fitting is attached to the female coupler half, and a second end. The first high pressure hose assembly also includes a first conduit having a first end sealingly attachable to the second end of the first hose fitting and a second end. The female coupler half is also attached to a first low pressure hose assembly that includes a second hose fitting having a first end sealingly attachable to the cylindrical body, a longitudinal passage extending therethrough which is axially aligned with the female half outer passage when the second hose fitting is attached to the female half and a second end. The first low pressure hose assembly also includes a second conduit having a first end sealingly attachable to the second end of the second hose fitting and a second end. The male coupler half is attached to a second high pressure hose assembly that includes a third hose fitting having a first end sealingly attachable to the male inner valve body, a longitudinal passage extending therethrough and axially aligned with inner passage when the third hose fitting is attached to the male half and a second end. The second high pressure hose assembly also includes a third conduit having a first end, sealingly attachable to the second end of the third hose fitting and a second end. The male coupler half is also attached to a second low pressure hose assembly that includes a fourth hose fitting having a first end sealingly attachable to the male cylindrical plug, a longitudinal passage extending therethrough that is aligned with passage when the fourth hose fitting is attached to the male half and a second end. The second low pressure hose assembly also includes a fourth conduit having a first end sealingly attachable to the second end of the fourth hose fitting and a second end. 
   Still another feature of the noted quick disconnect assembly has the first, second, third and fourth fittings being capable of repeated assembly and disassembly relative to respective ones of the female and male halves. Yet another feature of the noted quick disconnect assembly has the third hose fitting attached to the male inner valve body via a press-fit arrangement. Further features and advantages of the present invention will become apparent to those skilled in the art upon review of the following specification in conjunction with the accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a longitudinal sectional view of a first embodiment of a connected coaxial coupling, with attached end fittings, according to the present invention. 
       FIG. 2  is a longitudinal sectional view of the coaxial coupling shown in  FIG. 1 , with separated male and female halves. 
       FIG. 3  is a partial sectional view of the female half of the coaxial coupling with an unattached high pressure hose assembly. 
       FIG. 4  is a partial sectional view of both the female and male halves of the coaxial coupling with an unattached low pressure hose assembly. 
       FIG. 5  is a partial sectional view of the female half of the coaxial coupling with attached high and low pressure hose assemblies. 
       FIG. 6  is a partial sectional view similar to  FIG. 5 , but also showing the male half of the coaxial coupling attached with the high pressure hose assembly. 
       FIG. 7  is a partial sectional view of both the male and female halves of the coaxial coupling fully attached to the high and low pressure hose assemblies. 
       FIG. 8  is a longitudinal sectional view of a further embodiment of the present invention shown with separated male and female halves. 
       FIG. 9  is a longitudinal sectional view of the further embodiment shown in  FIG. 8  shown as a connected coupling. 
       FIG. 10  is a longitudinal sectional view of the first embodiment half of the male and female couplings, with attached end fittings, shown at an initial stage of connection. 
       FIGS. 11-14  are longitudinal sectional views of half of the male and female couplings, similar to  FIG. 10 , showing the male coupling at respective incremental connection stages with the female coupling. 
       FIG. 15  is a longitudinal sectional view of half of the male and female couplings, similar to  FIG. 14 , shown with the male coupling half fully connected with the female half. 
       FIG. 16  is a longitudinal sectional view of half of male and female couplings, with enlarged sections detailing the connection of components. 
       FIGS. 17 and 18  are longitudinal sectional views of half of the male and female couplings, similar to  FIG. 14 , showing alternative placements of seals within the male coupling. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Referring to  FIG. 1 , the present invention relates to a first embodiment  10  of a coaxial coupling that is utilized for quickly connecting and disconnecting coaxial hoses or twin line hose assemblies. Coaxial coupling  10 , when connected with hose assemblies, can be particularly useful for connecting a piece of construction or industrial equipment (e.g. pump) to a remote implement (e.g. a piece of rescue equipment), however, it should be appreciated that such couplings could be used for a variety of applications that require quick connection and disconnection. Coaxial coupling  10  enables the system to have just one coupling and one coaxial hose instead of two separate hoses and couplings. The present invention is more compact, lightweight and easier for an end user to connect and use. Other applications include any system that utilizes two hoses which can be combined into one hose for the noted reasons. 
   Referring to  FIGS. 1 ,  2  and  4 , coaxial coupling  10  is comprised of a male half  130  and a female half  50 .  FIG. 4  shows male  130  and female  50  halves prior to attachment with respective end fittings.  FIG. 2  shows male  130  and female halves  50  uncoupled, but united with respective end fittings. Specifically, male coupling  130  is attached to both a first high pressure hose fitting  138  and a first low pressure hose fitting  143 , coaxial with each other. Female coupling  50  is attached to both a second high pressure hose fitting  58  and a second low pressure hose fitting  63 , again coaxial with each other. As shown in  FIG. 1 , the inner flow passage (indicated by flow arrow  47 ) through coupling  10  and high pressure hose fittings  138 ,  58  serves as the high pressure fluid supply line. The coaxial outer flow passage (indicated by flow arrow  96 ) through coupling  10  and low pressure hose fittings  143 ,  63  serves as the low pressure fluid return line. 
   Referring to  FIG. 2 , female half  50  includes a cylindrical body  54  which is fixedly connected to second low pressure hose fitting  63 . Fitting  63  can have any desired outer geometry (e.g. hexagonal configuration) appropriate for being engaged by a conventional tool, and an inner geometry defining an internal cavity or passage  64  having a first end that is fluidly connected with an internal low pressure coupler passage  53  within female half  50 . The second end of passage  64  is likewise fluidly connected with a passage  93  (shown in  FIG. 5 ) within a low pressure conduit  90 , or otherwise can be connected, as appropriate, within the fluid system. Body  54  has a front end with a plurality of circular openings  56 , evenly spaced around its circumference, for receiving a plurality of locking balls  82 . Body  54  also has a rear end that attaches (e.g. threadingly) with the front end of second low pressure hose fitting  63 . 
   A cylindrical locking collar  70  is received on the front end of body  54  and peripherally envelopes a portion thereof. Locking collar  70  includes a known, outer, knurled surface  72  (shown in  FIG. 4 ) for easy grip by the user. A spring  74  is located internally of collar  70  (housed within a cavity located between the outer surface of body  54  and inner surface of collar  70 ) for urging locking collar  70  forwardly along body  54 . Locking collar  70  further includes an inner circumferential groove or channel  56  which is dimensioned to receive locking balls  82  in order to retain locking collar  70  on body  54  when coupling  10  is disconnected (as shown in  FIG. 2 ). A retaining ring  78  is provided forwardly of channel  56  to retain locking collar  70  in the position shown in  FIG. 2 . If locking ball  82  is dislodged from its abutment with a locking sleeve  81 , retaining ring  78  will prevent locking sleeve  81  (and collar  70 ) from moving forwardly. Locking sleeve  81  is securely situated inside locking collar  70  since its outer frontal edge contacts an inner shoulder of locking collar  70  and its outer rear edge contacts spring  74 . Locking collar  70  thereby has limited axial movement along body  54 . As best seen in  FIG. 1 , a washer seal  61  is located inside the rearward end of locking collar  70  and abuts the forward annular end of second low pressure hose fitting  63 . Washer seal  61  is shaped to match the inner surface contour of locking collar  70 , and is free to rotate with same. 
   Female coupling half  50  includes two valve assemblies. A first valve assembly  68  is affiliated with high pressure hose fitting  58  and will be discussed below. A second valve assembly includes an axially-moveable and spring-biased cylindrical face sleeve  80 ; a coaxial cylindrical sealing sleeve  84  received within face sleeve  80 ; and a cylindrical valve body  86  located within sealing sleeve  84 . Cylindrical face sleeve  80  is axially moveable relative to cylindrical body  54  and is unidirectionally biased by a spring  66 . Cylindrical sealing sleeve  84  has a rear, outwardly extending annular shoulder  85  which is fixed in a groove  88  formed at the intersection of low pressure hose fitting  63  and cylindrical body  54 . An O-ring  99 , located within groove  88 , is compressively sealed by annular shoulder  85  and hose fitting  63 . Annular shoulder  85  is press-fitted into sealing relationship with cylindrical body  54  at a location indicated by element  75 , best shown in  FIG. 16 . O-ring  99  prevents fluid traveling along a flow passage (represented by arrow  96 ) from egressing outwardly. Outer flow passage  96  is located between sealing sleeve  84  and cylindrical valve body  86  and continues on, through coupling  10 , when male  130  and female  50  halves are connected (as shown in  FIG. 1 ). 
   Cylindrical face sleeve  80  is dimensioned so as to be closely received within cylindrical body  54  and moves axially with respect thereto. Face sleeve  80  includes an annular, radially-inwardly directed annular flange  91  at its front end, and a radially-outwardly directed annular flange  92  at its rear end. Rear flange  92  is designed to engage a radially-inwardly projecting annular shoulder on cylindrical body  54  to limit the forward movement of face sleeve  80  with respect to body  54 . Spring  66  urges face sleeve  80  forwardly on body  54  and is disposed between the inner surface of annular flange  91  and an outer surface of annular shoulder  85  of sealing sleeve  84 . 
   Valve body  86  is axially moveable within cylindrical sealing sleeve  84  and is biased forwardly by a spring  98 . Valve body  86  includes an enlarged forward valve head  87  with a flat front face and a rearward portion  89  having longitudinal channels for allowing fluid flow. Valve head  87  has an inner surface with a groove that houses an inner O-ring  95  and an outer surface with a groove that house an outer O-ring  94 . Inner O-ring  95  provides a fluid tight seal between cylindrical valve body  86  and a female high pressure inner valve  68 . Outer O-ring  94  provides a fluid tight seal between cylindrical valve body  86  and an inwardly extending front shoulder of cylindrical sealing sleeve  84 . 
   Female high pressure inner valve  68  includes a forward end  24  with a flat front face and an outer surface that sealingly abuts the inner surface of valve head  87 , via inner O-ring  95 , when female half is in the uncoupled position shown in  FIG. 2 . An entire outer circumferential portion of forward end  24  contacts seal  95  ensuring that fluid inside passage  53  doesn&#39;t extend beyond this junction. Inner valve  68  has an inner passage  26  that is in fluid communication and coaxial with an inner passage  59  inside second high pressure hose fitting  58  when same is physically attached to high pressure inner valve  68 . High pressure inner valve  68  has a series of lateral radial passages  27  near forward end  24  that fluidly connect valve inner passage  26  with coupler passage  53  when female half  50  is in the uncoupled position, or is separated from male half  130 , as shown in  FIG. 2 . Referring to  FIGS. 1 and 2 , high pressure inner valve  68  has a rearward end flange  31  having longitudinal passages  32  that fluidly connect coupler passage  53  with low pressure hose fitting passage  64 . Rearward end flange  31  further has a radial extension  33  that is fixedly attached, e.g.—in a press-fit manner, with outwardly extending sealing sleeve annular shoulder  85  at a location indicated by element  71 , best seen in  FIG. 16 . 
   Referring to  FIGS. 1 ,  2 , and  10 , male coupling half  130  includes a generally cylindrical plug  146  defining an inner fluid passage  151 . Plug  146  has a flat annular front surface  148 , which, when coupled, as illustrated in  FIGS. 2 and 10 , can be located flush against face sleeve inwardly-directed flange  91  of female half  50  and can be received within female cylindrical body  54 . Plug  146  further includes a circumferential locking groove  153  in its outer surface and an inwardly facing groove  155  in its inner surface. A seal, or O-ring  157  is housed within groove  155  and prevents fluid within inner fluid passage  151  from escaping between plug  146  and an outer sealing sleeve  161  received on the inner peripheral surface of plug  146 . The other end of plug  146  is fixedly interconnected, such as via cooperating threads, to an adjoining end of low pressure fitting  143 . A seal, or O-ring  189  is positioned between plug  146  and low pressure fitting  143  to prevent any fluid, within an internal passage  174  of low pressure hose fitting  143 , from escaping. A plurality of longitudinal flow passages  167  are integrated within a rear section  172  of cylindrical plug  146  in order to fluidly connect low pressure hose fitting internal passage  174  with inner fluid passage  151  of cylindrical plug  146 . A spring  163  is positioned within passage  151  and biases outer sleeve  161  towards the front end of male half  130 . Specifically, spring  163  is disposed between an inner shoulder of cylindrical plug  146  and an outer shoulder of outer sealing sleeve  161 . Outer sealing sleeve  161  is movable relative to cylindrical plug  146  and has a front face which abuts the annular frontal face of female cylindrical sealing sleeve  84  when coupled (as in  FIG. 1 ). 
   An inner valve cylindrical body  170  is interposed between cylindrical plug  146  and outer sealing sleeve  161 . Inner valve body  170  has a front portion or head  177  that has a flat frontal annular surface that abuts the front face of female valve head  87  when coupled (as shown in  FIG. 1 ). Head  177  has an outer peripheral surface with a groove that houses a seal or O-ring  194  and an inner peripheral surface with a groove that houses another seal or O-ring  196 . In the closed or uncoupled position shown in  FIG. 2 , O-ring  194  prevents fluid within fluid passage  151  from escaping between outer sleeve  161  and valve body  170 , and O-ring  196  prevents fluid within an inner passage  166  from escaping between valve body  170  and an inner valve sealing element  182 . Inner valve body  170  has a tail portion  179  with an inner surface which is interconnected, e.g., by press-fitting or via threads, to cylindrical plug  146  at a position indicated by element number  176 , best seen in  FIG. 16 . When tail portion  179  is interconnected with a plug rear section  172  (e.g., at press-fit location  176 ), all previous clearances between valve body tail portion  179  and plug rear section  172  are totally eliminated. Between head  177  and tail portion  179 , inner valve body  170  has an inner annular shoulder  181  that has a smaller inner diameter than that of tail portion  179 . 
   Inner valve sealing element  182  has a flat frontal face that abuts the face of female high pressure inner valve forward end  24  when male half  130  is coupled with female half  50  (as in  FIG. 1 ). A spring  198  biases valve element  182  forward such that a rear outer annular shoulder  184  thereof contacts an outer shoulder of valve body head  177 . Specifically, spring  198  is disposed between the inner surface portion of valve element  182  and the inner stepped surface portion of high pressure hose fitting  138 . Hose fitting  138  is preferably affixed to inner valve body  170  with threads at tail portion  179 . The leading portion of fitting  138  has an O-ring seal  186 , housed within a groove  185 , which is press-fitted against the inner surface of inner valve body  170  near valve body inner shoulder  181  to eliminate any clearance between fitting  138  and valve body  170 . This press-fit connection is indicated by element number  192 , best shown in  FIG. 16 . This allows extremely high pressurized fluid, within passage  166 , to be sealed with only a standard seal, such as O-ring  186 , when flowing through male coupler  130  towards a high pressure passage  159  within fitting  138  and eliminates the necessity for a backup washer in groove  185  as well as forming a reliable seal at high pressure operating conditions. 
     FIGS. 3-7  illustrate the sequence for connecting coaxial hoses  65  and  90  to male  130  and female  50  coaxial coupling halves. It should be noted that  FIGS. 3-7  show one coaxial hose assembly being coupled with both an unattached female coupler  50  and an unattached male coupler  130 . It is common for only one end of the hose assembly to be connected to one of the male  130  and female  50  halves of coaxial coupling  10  with the other one of the male and female halves being attached to something other than coupling  10 , e.g. a tool.  FIGS. 3-7  show but one hose assembly for sake of simplicity. As is well known in the art, the inner hose assembly conducts higher pressure fluid than the outer hose assembly. 
   It should also be noted that both male  130  and female  50  halves are fully contained sub-assemblies without hose fittings  138 ,  143 ,  58 ,  63  being installed thereon. This simplifies the assembly procedure for an installer. High pressure end fittings  138  and  58  can separately be attached to a conduit  65  (as will be explained below), forming a high pressure hose assembly, and that assembly can simply be attached to coupling halves  130  and  50 . Likewise, low pressure end fittings  143  and  63  can be attached to a conduit  90 , forming a low pressure hose assembly, and that low pressure hose assembly can also be attached to coupling halves  130  and  50 . It is common in the industry for an installer to have a prefabricated hose assembly that needs to be attached to either of the coupler halves (which are typically attached to, e.g., the portable tool implement or the piece of industrial equipment). Since male and female halves  130 ,  50  are fully contained sub-assemblies, end fittings  138 ,  143 ,  58  and  63  can be installed in the field. Without the self-contained subassembly, the hose end fittings would have to be integrated into the male and female coupling halves. Upon assembly with the hose assemblies, both male and female halves  130 ,  50  have internal components that have been press-fitted so that leak paths are minimized. 
   Referring to  FIG. 16 , male half  130  has press-fitted components, namely the abutting relationship of valve body inner shoulder  181  and the leading portion of fitting  138 , specifically O-ring  186 , at location  192 . Inner shoulder  181  of male half inner valve body  170  is press-fit with plug rear section  172  at location  176 . Female half  50  has press-fitted components, namely the abutting relationship of inner valve rearward end  31  and cylindrical sealing sleeve  84 , at location  71 , and the abutting relationship of cylindrical body  54  with sealing sleeve annular shoulder  85  at location  75 . As is well known in the art, press-fitting (also known as compression-fitting and interference-fitting) is just one method of producing the sub-assembly. Other methods such as threading could be used. Press-fitting does provide a reliable sealing connection without the need for extra sealing elements. In high pressure applications this is useful since sealing elements, e.g. washers, may be extruded by the high pressure thus providing an unwanted leakpath. Press-fit metal components will not be adversely affected by these high pressures. Press-fitting also ensures that the eccentricity of male and female halves,  130 ,  50 , remains at a minimum (preferably zero). This is important in this application since the coaxial passages have to be aligned in order to ensure leak free fluid communication between the same. If both halves  130 ,  50  do not remain concentric, they will not properly mate and high pressurized fluid will easily escape. 
   Referring to  FIG. 5 , second high pressure hose fitting  58 , which is attached to a high pressure conduit  65 , is threaded into female coupling half high pressure inner valve  68 . Low pressure conduit  90  along with attached second low pressure fitting  63  is slid over high pressure conduit  65  while fitting  63  is threaded to female coupling half cylindrical body  54 . Referring to  FIG. 6 , male coupling half inner valve body  170  is threaded to first high pressure hose fitting  138 . Referring to  FIG. 7 , then first low pressure hose fitting  143  is moved towards male coupling half  130  and is threaded onto cylindrical plug  146 . A metal sleeve  34 , positioned around the outside of low pressure conduit  90  is moved to the right and secures conduit  90  around a nipple portion  144  of low pressure hose fitting  143 . 
     FIGS. 10-15  illustrate the connection or coupling of male half  130  with female half  50 . Referring to  FIG. 10 , male half  130  (left half) and female half  50  (right half) are shown aligned and having their flat annular frontal faces abutting prior to connection. The interior of female cylindrical body  54  receives male half  130 , specifically cylindrical plug  146  thereof, and functions as a pilot for insertion of the latter. As noted above, passage  151  conducts low pressure fluid within male coupler half  130 ; passage  166  conducts high pressure fluid within male coupler half  130 ; passage  53  conducts low pressure fluid within female coupler half  50 ; and passage  26  conducts high pressure fluid within female coupler half  50 . As shown in  FIG. 10 , passages  26  and  53  are connected via side passages  27  in inner valve  68 . This interconnection of coaxial paths within female coupler half  50  prevents any pressure build-up therein since any high pressure fluid within passage  26  travels directly to passage  53 . Although described in greater detail below and shown in  FIG. 1 , it should be noted that high pressure fluid (referenced by flow arrow  47 ) is supplied (e.g. by an external pump) within passage  26  and low pressure fluid (referenced by flow arrow  96 ) is returned through passage  64  which is connected to the hydraulic fluid reservoir and is at atmospheric pressure. Likewise, within male coupler half  130 , high pressure fluid is conducted within passage  166  and low pressure fluid is conducted within passage  151 . 
     FIGS. 11-12  show the two halves  50 ,  130  in successive progressing stages of connecting. The flat annular frontal surface of cylindrical plug  146  engages flush with abutting face of face sleeve  80  and moves face sleeve  80  rearwardly in female half  50 . At the same time, cylindrical sealing sleeve  84  of female half  50  engages male half outer sealing sleeve  161  and drives same rearward against the force of spring  163 . Outer sleeve  161  is thus moved off seals  157 ,  194 , and the outer surface of cylindrical sealing sleeve  84  begins to abut seals  157 ,  194 . Further, the front face of inner valve body  170  abuttingly moves cylindrical valve body  86  rearwardly against the force of spring  98 . Seal  94  remains in contact with the inner surface of cylindrical sealing sleeve  84 . O-ring  95  remains in contact with the outer surface of high pressure inner valve  68 . O-ring  196  remains in contact with valve element  182 . The flat front face of high pressure inner valve  68  abuttingly contacts the flat front face of valve element  182  and pushes same rearward against the force of spring  198 . It should be noted that during this movement, inner passage  26  continues to be fluidly connected with outer passage  53  via lateral side passages  27 . 
   Referring to  FIG. 13 , cylindrical plug  146  and inner valve body  170  have moved face sleeve  80  and cylindrical valve body  86  further into female half  50 . Similarly, cylindrical sealing sleeve  84  and high pressure inner valve  68  have pushed outer sealing sleeve  161  and valve element  182  further into male half  130 . Seal  157  is still in contact with the outer surface of cylindrical sealing sleeve  84 . Seals  94  and  194  have moved out of contact with sealing sleeve  84 . Seal  95  has moved out of contact with inner valve  68  at passages  27  but seal  196  remains in contact with the surface of inner valve  68 . Thus, inner passage  26  is still partially open to passage  53  while inner fluid passage  151  just begins opening to passages  26  and  53 . Therefore both passages  26  and  151  can dump their pressurized fluid into passage  53 , which leads to the reservoir (and is under atmospheric pressure) before inner high pressure passage  166  opens. This prevents any trapped pressurized fluid within passage  166  from entering low pressure passage  53  and results from the positioning of seals  196  and  194 . Since seal  194  is positioned more forward on valve body head  177  it discontinues its sealing relationship with cylindrical sealing sleeve  84  before seal  196  moves off the front portion of inner valve  68 . 
   Alternatively and shown in  FIG. 18 , seals  194  and  196  can be axially aligned so that both passages  151 ,  166  dump fluid to passage  53  simultaneously. This will ensure that any trapped pressurized fluid within male half  130  is routed through passage  53  to the reservoir. This assists with pressure relief in systems where either the inner or outer fluid passage conducts high pressurized fluid. Still alternatively and shown in  FIG. 17 , seal  196  can be positioned more forwardly on valve body head  177  than seal  194 . In this position, as inner valve body  170  travels forwardly, relative to female coupling half  50 , seal  196  is no longer in sealing abutment with either male coupler inner valve element  182  or female coupler high pressure inner valve  68 . Rather, seal  196  is in axial alignment with inner valve side passages  27 , thus allowing pressurized fluid to escape from passage  166  and travel to the path of lowest pressure resistance, which is passage  53 . This opens high pressure passage  166  to passage  53  before opening low pressure passage  151  to passage  53 . Once seal  196  of inner valve body  170  travels past side passages  27 , it sealingly abuts the outer surface of inner valve  68  and closes passage  166  to passage  53 , and only allows fluid communication between passage  166  and passage  26 . 
   Referring to  FIG. 14 , passage  26  is now the flow path that receives pressurized fluid from an external component, e.g. a pump. The external component can be supplying pressurized fluid while female coupler  50  is closed off from male coupler  130 . The pressurized fluid will flow from passage  26  to passage  53 . Between  FIGS. 13 and 14 , cylindrical valve body  86 , and specifically seal  95 , passes over side passages  27  which are receiving pressurized fluid from inner passage  26 . The fluid flow chokes off and pushes valve body  86  back against the pressure of spring  98 . This ensures that passage  53  remains open to pressurized passage  26  and allows full flow during the balance of the connect cycle. Seal  196  remains in contact with the outer surface of inner valve  68  on the front side of passages  27  so fluid flow from passage  26  cannot enter inner passage  166  of male half  130 . 
     FIG. 15  shows coupling  10  fully connected. Locking balls  82  have dropped into locked position within locking groove  153  in the male half  130 . Locking collar  70  has moved to the left, positioning locking sleeve  81  over locking balls  82  which are securely seated within groove  153 . Seal  196  passes over radial side passages  27  and abuts the outer surface of inner valve  68  on the rear side of passages  27  so flow from passage  26  can no longer directly enter passage  53 . Flow passages  26  and  166  are now connected via passages  27 . Flow passages  53  and  151  are connected. 
   Referring to FIGS.  1  and  10 - 15 , the fluid flow through male half  130 , female half  50 , and connected coupling  10  will be detailed.  FIG. 1  illustrates two flow paths  47 ,  96  through connected coaxial coupling  10 . High pressure fluid from the pump (not shown) flows from right to left (indicated by arrows  47 ), through the coupling and to the hydraulic tool (not shown). Return, low pressure fluid flows from the tool, to the right (indicated by arrows  96 ), and to the hydraulic reservoir. Referring to  FIG. 10 , flow from the pump passes through fitting  58 , through coupler inner valve  68 , through side passages  27 , through passage  53 ; and out coupler  63  back to the reservoir. Fluid within passages  166  and  151  are isolated from other passages. This flow pattern continues until  FIG. 13  wherein fluid within passage  151  can start to enter passage  53 . This is the first time that fluid from male half  130  communicates with fluid from female half  50 . At this time of the coupling sequence, all fluid flow is traveling to the reservoir (not shown) which is the location of least pressure. 
     FIG. 14  shows how pressurized fluid can still continue to flow within female coupler  50  while male half  130  is being coupled with female half  50 , even as the pump is supplying pressurized fluid to passage  26 . The pressurized fluid can continue to flow back to the reservoir (through passage  53 ) during the coupling sequence. This enables a connection of male and female halves,  130 ,  50 , when the pump is operating while ensuring that the pressure within female coupler  50  does not suddenly spike from impeded flow. If the fluid flowing through passage  26  is impeded or stopped, the pressure within passage  26  will increase which can provide an obstacle during assembly. In  FIG. 15 , full high pressure flow is achieved through inner passages  26  and  166 . Full low pressure fluid flow is seen in passage  151  and  53 . The high pressure flow path at the connection of inner valve  68  and valve element  182  is “around” the outer peripheral surface of valve element  182  and not “through” the valve, e.g. via radial apertures. Flow around valve element  182  creates less restriction and less pressure drop compared with the fluid flow if it passes directly through same. 
   Referring again to  FIG. 1 , during the connection and disconnection of coupling halves  130 ,  50 , locking collar  70  is moved right and left against spring  74  in cavity  41 . If cavity  41  sifts full of dirt or debris, which is typical for hydraulic tool applications and their environment, locking collar  70  cannot be moved right and left. Obviously, if this happens, one cannot connect and disconnect coupling  10 . Thus, in order to prevent dirt from sifting into cavity  41 , washer seal  61  is placed within locking collar  70  so that cavity  41  is completely surrounded by cylindrical body  54 , locking sleeve  81 , locking collar  70  and washer  61 . The front face of washer  61  abuts an outer shoulder  55  of cylindrical body  54  and the rear face abuts the annular frontal face of low pressure fitting  63 . As mentioned above, washer seal  61  has an outer surface that matches the inner contour of locking collar  70 , and is free to rotate with same. During connection, use, and disconnection of coupler  10 , washer  61  remains in contact with the front annular edge of second low pressure hose fitting  63 , the inner surface of locking collar  70  and the outer surface of body  54 , and sealingly isolates a cavity  41  within locking collar  70 . 
     FIGS. 8 and 9  show a further embodiment  210  of a coupling in which male half  130 ′ and connected female half  50 ′ are mated with “Y” configuration fittings instead of coaxial end fittings  138 ,  143 ,  58 ,  63 . Embodiment  210  provides for a connection of male  130 ′ and female  50 ′ halves to two conventional hoses (rather than the coaxial version detailed above). For example, a user may have a coaxial power unit and a conventional two hose hydraulic tool. Embodiment  210  enables the user to connect the two systems by using the coaxial fittings on one coupling half and the “Y” fitting on the other coupling half.  FIGS. 8 and 9  show both the “Y” fitting on both halves since the coaxial fittings were already described above. The majority of the componentry of male  130 ′ and female  50 ′ halves is identical to that of the description above, with reference to male  130  and female  50  halves, so, for the sake of brevity, it will not be totally re-addressed here. 
     FIG. 8  shows male  130 ′ and female  50 ′ halves prior to connection. Male half  130 ′ is connected to a high pressure male adapter  238  that is substantially similar to high pressure hose fitting  138  discussed above, except that adapter  238  does not have a barbed nipple  139  as does fitting  138 . Rather, adapter  238  has a truncated nose  241  with an external groove that houses an O-ring  243 . A twin line coupling  218  is attached to male half  130 ′ and adapter  238  similar to the attachment of second low pressure hose fitting  63  in the embodiment of  FIG. 1 . Twin line coupling  218  has internal threads  264  at its front end which mate with external threads on cylindrical plug  146 . Upon threading twin line coupling  218  onto male half  130 , truncated nose portion  241  is sealingly received within a bore  274  in the center of twin line coupling  218 . O-ring  243  provides a seal for the connection between adapter  238  and twin line coupling  218 . Unlike coaxial coupling  10  which is connected with a coaxial conduit and has aligned passages between the coupling and conduit, high pressure internal passage  166  is routed to fluidly connect with a twin line high pressure passage  280 . Similarly, low pressure fluid passage  151  is connected with a twin line low pressure passage  290 . 
   Female half  50 ′ has essentially the same componentry as described with coaxial coupling  10 , except that high pressure inner valve  268  has a nose portion  286  with an external groove that houses a seal, or O-ring  293 . As with the connection to male half  130 ′, twin line coupling  218  is threaded onto external threads on cylindrical body  54 . When attached, nose portion  286  is sealingly received within bore  274 . O-ring  293  prevents any fluid from escaping the high and low pressure passages. High pressure internal passage  26  is routed to fluidly connect with twin line high pressure passage  250 . Low pressure fluid passage  53  is connected with twin line low pressure passage  295 . 
   High pressure fluid (e.g. from an external pump) enters high pressure passage  250  in coupling  218  and takes the path indicated by flow arrow  247 . Specifically, fluid flows through passage  26  within female half  50 , around valve element  182  (indicated by flow arrow  249 ), through inside passage  166 ; and out through twin line coupling passage  280 . Similar to the fluid flow paths in coaxial coupling  10 , flow  247  would travel to the hydraulic tool and would return (as low pressure return flow  298 ) from the hydraulic tool through low pressure passage  290 . Again, specifically, flow  298  continues through fluid passage  151  within cylindrical plug  146 ; through passage  53  within cylindrical sealing sleeve  84 ; out low pressure passage  295 ; and back to the reservoir. 
   It should be noted that the present invention is not limited to the specified preferred embodiments and principles. Those skilled in the art to which this invention pertains may formulate modifications and alterations to the present invention. These changes which rely upon the teachings by which this disclosure has advanced are properly considered within the scope of this invention as defined by the appended claims.