Abstract:
A tube nut includes a first member and a second member. The first member is threaded and defines a first hole. The second member is selectively rotatable with respect to the first member and defines a second hole. A tube or pipe extends through the first and second holes. The rotation of the first member in a threaded hole causes an axial load on the second member and the tube to urge the tube against a seat to provide a seal between the tube and a fluid passage. Relative rotation between the first and second members reduces or eliminates torsional strain on the tube.

Description:
TECHNICAL FIELD 
     This invention relates to tube nut assemblies for connecting fluid passageways. 
     BACKGROUND OF THE INVENTION 
     Fluid couplings are configured to provide fluid communication between two fluid passages. Some fluid coupling configurations include a nut and a body. Such fluid coupling configurations are often used in automotive brake line applications, and include those defined by SAE J533 and JASO F402 standards. The body defines a threaded bore. At the terminal end of the bore, a first fluid passage terminates at a protuberant seat. The nut includes threads that are engageable with the threads of the bore so that rotation of the nut inside the bore causes axial movement of the nut. The nut also defines a hole that extends therethrough. 
     A tube defines a second fluid passage and extends through the hole of the nut. The tube is positioned with respect to the nut such that, as torque is applied to the nut, the nut applies an axial load to the tube, which urges the end of the tube into contact with the seat, thereby establishing fluid communication between the first and second fluid passageways. The nut also transfers some of the torque to the tube. 
     SUMMARY OF THE INVENTION 
     A tube nut assembly includes a tube nut having a first member and a second member. The first member has a threaded shank, and defines a first hole that extends through the threaded shank. The second member defines a second hole and is selectively rotatable with respect to the first member. A tube extends through the first hole and the second hole. 
     The second member is positioned with respect to the first member such that, when the first member is rotated about an axis with the threaded shank engaged with a threaded hole, the first member rotates with respect to the second member and transmits an axial force to the second member. The tube is positioned with respect to the second member such that the second member transmits the axial force to the tube. 
     The axial force urges the tube against a seat when the tube nut assembly is engaged with a corresponding coupling, and thereby establishes a sealed connection between a first passageway defined by the tube and a second passageway extending through the seat. The interface between the first and second members supports little or no torque transfer from the first member to the second member and the tube, and thus the tube experiences reduced torsional strain compared to the prior art. The reduced torsional strain contributes to an improved seal between the tube and the seat. 
     A corresponding fluid coupling system is also provided. The fluid coupling system includes a body defining a threaded hole. The body includes a terminal surface that defines a terminal end of the threaded hole, a seat that protrudes from the terminal surface, and a first fluid passage that extends through the seat. 
     The fluid coupling system further includes a tube nut having a first member and a second member. The first member has a threaded shank, and defines a first hole that extends through the threaded shank. The second member defines a second hole and is selectively rotatable with respect to the first member. A tube defines a second fluid passage and extends through the first hole and the second hole. 
     The threaded shank is engageable with the threaded hole. The second member is positioned with respect to the first member such that, when the first member is rotated about an axis during engagement of the threaded shank with the threaded hole, the first member rotates with respect to the second member and transmits an axial force to the second member. The tube is sufficiently positioned with respect to the second member such that the second member transmits the axial force to the tube. 
     A corresponding method is also provided. The method includes providing a body defining a threaded hole. The body has a terminal surface that defines a terminal end of the threaded hole, a seat that protrudes from the terminal surface and defines at least part of a first fluid passage. The method also includes providing a tube nut assembly having a first member, a second member, and a tube. The first member has a threaded shank, and defines a first hole that extends through the threaded shank. The second member defines a second hole and is selectively rotatable with respect to the first member. The tube defines a second fluid passage, and extends through the first hole and the second hole. 
     The method further includes inserting the shank into the threaded hole, and rotating the first member such that the first member rotates with respect to the second member and applies an axial load to the second member. 
     The above features and advantages and other features and advantages of the present invention are readily apparent from the following detailed description of the best modes for carrying out the invention when taken in connection with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic, cross-sectional side view of a tube nut assembly in accordance with the claimed invention; and 
         FIG. 2  is a schematic, cross-sectional side view of a portion of an alternative tube nut in accordance with the claimed invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring to  FIG. 1 , a fluid coupling system  10  includes a tube nut  14 . The tube nut  14  includes a first member  18  and a second member  22 . The first member  18  includes a polygonal (e.g., hexagonal) head  26 . The first member  18  also includes a cylindrical shank  30 . The shank  30  is threaded, i.e., the shank  30  has threads  34  on its outer surface. The first member  18  also defines a cylindrical hole  38  that extends through the polygonal head  26  and the threaded shank  30 . In the embodiment depicted, the hole  38  and the shank  30  have a common centerline. The end of the first member  18  opposite the head  26  is formed by annular surface  40 . 
     The second member  22  is generally cylindrical and defines a cylindrical hole  42  and an annular surface  46 . The second member  22  is disposed with respect to the first member  18  such that the centerline of hole  42  is coextensive with the centerline of hole  38 , and such that annular surface  46  is parallel to, and contacts, annular surface  40 . The first member  18  is selectively rotatable with respect to the second member  22 . During rotation of the first member  18  with respect to the second member  22 , surface  40  slides along surface  46 . Surfaces  40 ,  46  in the embodiment depicted are generally flat and are oriented perpendicularly to the centerlines of the holes  38 ,  42 . Surfaces  40 ,  46  are characterized by a low roughness, and one or both of surfaces  40 ,  46  includes a lubricant or friction modifier coating, as understood by those skilled in the art, to reduce friction between surfaces  40 ,  46 . 
     The first member  18  defines an annular concavity  50 . Concavity  50  is disposed between the surface  40  and the opening of hole  38 . The second member  22  defines an annular protuberance  54 . The protuberance  54  is disposed between an opening of hole  42  and surface  46 . The protuberance  54  extends into the concavity  50  to maintain radial alignment of the second member  22  with respect to the first member  18 . Surfaces  40 ,  46 , protuberance  54 , and concavity  50  form the interface between members  18 ,  22  in the embodiment depicted. The second member  22  includes a frusto-conical surface  58  that defines a frusto-conical portion of hole  42 . Surface  58  is positioned such that the opening of the hole  42  (formed in surface  62  of the second member  18 ) is flared. Surface  62  is parallel to surface  46 . 
     A tube  66  extends through the holes  38  and  42 . The tube defines a fluid passage  70  that extends from a frustoconical, flared portion  74  of the tube  66 , adjacent surface  62  of the second member  22 , through the head  26  of the first member  18 . The tube  66  includes a frusto-conical surface  78 , which defines the outer surface of the flared portion  74  of tube  66 . The tube  66  also includes a frusto-conical surface  82 , which defines the inner surface of the flared portion  74  of tube  66 . More specifically, surface  82  defines a flared opening of the fluid passage  70 . 
     In the embodiment depicted, the tube  66 , including the flared portion  74 , is metal and is formed from a single piece of material. However, and within the scope of the claimed invention, the tube  66  may be formed from multiple pieces comprising different materials. For example, the flared portion  74  may be metal and the remainder of the tube  66  may be plastic or elastomeric. 
     The fluid coupling system  10  also includes a body  86  that defines a fluid passage  90 . The body also defines a generally cylindrical bore or hole  94 . The hole  94  is threaded, i.e., the body  86  includes threads  98  along the surface of the hole  94 . The hole  94  is characterized by an opening  102  through which the tube nut  14  is insertable for engagement between the threads  98  of the hole  94  and the threads  34  of the shank  30  of the first member  18 . 
     The body  86  also includes a seat  106  and a terminal surface  110 . The terminal surface  110  defines the terminal end of the hole  94 . The seat  106  is frusto-conical and is protuberant from the terminal surface  110 . The seat  106  includes a frusto-conical outer surface  114 . The fluid passage  90  extends through the seat  106  to an opening  118  formed in the seat  106 . The portion of the fluid passage  90  that extends through the seat  106  has a common centerline with the seat  106 . 
     The fluid coupling system  10  is operative to provide sealed fluid communication between fluid passage  70  and fluid passage  90 . To provide sealed communication between the fluid passages  70 ,  90 , the tube nut  14  is inserted into the hole  94  of the body  86  through opening  102  so that the second member  22  is positioned between the first member  18  and the terminal surface  110  of the hole  94 , and so that the threaded shank  30  engages the threaded hole  94 , i.e., threads  34  engage threads  98 . The centerlines of the holes  38 ,  42  and passages  70 ,  90  are coextensive, i.e., aligned with one another. 
     Torque T is applied to the polygonal head  26 , which causes the first member  18  to rotate about axis A. In the embodiment depicted, axis A is coextensive with the centerlines of holes  38 ,  42  and passages  70 ,  90 . As understood by those skilled in the art, interaction between threads  34  and threads  98  causes the rotation of the first member  18  to result in axial movement of the first member  18  toward the terminal surface  110 . The axial movement of the first member  18  causes the first member  18  to exert an axial force F on the second member  22 . More specifically, surface  40  exerts axial force F on surface  46 , which urges the second member  22  toward the terminal surface  110 . The low friction between surfaces  40  and  46  permits the rotation of the first member  18  with respect to the second member  22 , such that little or no torque is transmitted from the first member  18  to the second member  22 . 
     The tube  66  is sufficiently positioned with respect to the second member  22  such that the second member  22  transmits the axial force F to the tube  66 . More specifically, in the embodiment depicted, surface  58  of the second member  22  transmits the axial force to surface  78  of the tube  66 , urging surface  82  of the tube  66  into sealing engagement with surface  114  of the seat  106 , and thereby establishing sealed fluid communication between passages  70 ,  90 . 
     It should be noted that, in the embodiment depicted, the axial force F is transmitted directly from the first member  18  to the second member  22 , and from the second member  22  to the tube  66 . However, and within the scope of the claimed invention, the axial force F may be translated between the members  18 ,  22  and the tube  66  indirectly. For example, an intermediate member, such as a bearing (not shown) may be disposed between the first and second members  18 ,  22  and transmit the axial force F from the first member  18  to the second member  22  within the scope of the claimed invention. 
     Referring to  FIG. 2 , wherein like reference numbers refer to like components from  FIG. 1 , a portion of an alternative tube nut  14 A is schematically depicted. The tube nut  14 A is substantially identical to the tube nut shown at  14  in  FIG. 1  except that the interface between the first member  18 A and the second member  22 A includes a retention feature that rotatably retains the second member  22 A to the first member  18 A independent of the body (shown at  86  in  FIG. 1 ). 
     More specifically, the first member  18 A defines an annular groove  120  that is open in the direction of hole  38 . A leg  124  extends axially from surface  46 A of the second member  22 A. An annular flange  128  extends radially from the leg  124  into the groove  120 . Interference between the flange  128  and the surfaces of the first member  18 A that define the groove  120  prevents axial or radial movement of the second member  22 A with respect to the first member  18 A, while permitting rotation of the first member  18 A with respect to the second member  22 A. The groove  120  and the flange  128  thus cooperate to form the retention feature. Surface  40 A of member  18 A and surface  46 A of member  22 A have the same relationship and orientation as surfaces  40  and  46  in  FIG. 1 . At least one of surfaces  40 A,  46 A includes a lubricant or a friction modifier coating. 
     While the best modes for carrying out the invention have been described in detail, those familiar with the art to which this invention relates will recognize various alternative designs and embodiments for practicing the invention within the scope of the appended claims.