Abstract:
A tubular connection for centering a tube within a female connecting block that has a throughbore with a chamfer, wherein a transition surface is defined between the chamfer and the throughbore. The tube has an upset bead, a tapered portion narrowing from the upset bead, and an end-form extending from the tapered portion, the end-form having an annular groove with an O-ring therein. The connection further includes a device for securing the tube within the female connecting block whereby the upset bead of the tube is caused to abut the female connecting block. The tube locates inside the female connecting block such that the end-form seals via the O-ring inside the throughbore of the female connecting block and the tapered portion of the tube sealingly engages against the transition surface of the female connecting block to keep the tube centered within the female connecting block and to form a secondary fluid-tight seal.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates to a tubular connection, and more particularly to a tube to block connection incorporating novel self-centering features for more reliability and better fluid-tight sealing in the service life of the connection. 
   2. Description of the Prior Art 
   In assembling certain air-conditioning units, such as those used in automobiles, it is common practice to secure a tube to a female connecting block. In order to effect a fluid-tight seal between the tube and the female connecting block, an O-ring is situated in an annular groove in an end-form on the tube. Typically, the end-form of the tube is initially secured in a male connecting block and then is attached to the female connecting block by a bolt that extends through an aperture in the male connecting block and threadingly engages the female connecting block. The bolt is located adjacent but spaced away from the tube that in turn engages the female connecting block via a throughbore therein. 
   The bolt is caused to threadingly engage the female connecting block by applying a torque in the clockwise direction to the head of the bolt. In turn, the clockwise torque on the bolt imparts a clockwise torque on the male connecting block causing it to rotate relative to the threads of the female connecting block in the clockwise direction. Since the tube is secured within the male connecting block, the tube likewise pivots relative to the threads of the female connecting block in the clockwise direction. Because the tube is also loosely located within the female connecting block when the torque is applied to the bolt, the tube undergoes a side-loading phenomenon within the throughbore. That is, the tube and associated O-ring translate within the female connecting block and become over-compressed on one side and under-compressed on an opposite side. The resultant uneven compression on the O-ring can result in premature failure of the O-ring at the over-compressed side and leakage of fluid past the O-ring seal at the under-compressed side over the life of the tubular connection. 
   Accordingly, there are many examples in the prior art of apparatus to assure proper alignment of tubular connections embodying similar male and female members. One such example is disclosed in U.S. Pat. No. 4,659,116 to Cameron. The Cameron patent discloses a fitting including a male part having a contoured lead end that engages a female end having a complementary contour. The male and female parts self align as they are joined together and create a fluid-tight seal. However, the contoured surfaces of the male and female parts do not prevent off-center compression of the O-ring once the fitting is clamped together by a threaded collar. 
   Further, the Cameron patent is representative of the prior art, which essentially focuses on alignment of male and female members during the joining process. However, the special problem of aligning a tube within a male-female connecting block connection as described hereinabove is not addressed in the prior art. The special problem applies to the present invention where torque is applied indirectly to the tube during the joining process. None of the prior art teaches or suggests apparatus for centering a tube within a female connecting block and maintaining the centering during the application of a torque imparted to the tube. 
   Accordingly, what is needed is a tube to block connection that provides a tube that supports an O-ring, wherein a male connecting block encircles part of the tube, and the tube can be centered in a bore within the female connecting block. The tube remains centered during the application of a torque to a fastener in the male connecting block. The resultant centering maintains even compression of the O-ring seal. Moreover, the mating tube and female connecting block can each accommodate a greater degree of variation in size and/or shape in either or both the tube and female connecting block. 
   SUMMARY OF THE INVENTION 
   In accordance with the present invention, the tubular connection includes a female connecting block having an end surface, an opposite end surface, and a throughbore therebetween. The throughbore has a chamfer in the end surface such that a transition surface is defined between the chamfer and the throughbore. The connection further includes a tube mounted in the throughbore of the female connecting block. The tube has a tapered portion that engages the transition surface of the female connecting block. The tapered portion of the tube terminates in an end-form that has an annular groove with an O-ring therein that forms a primary fluid-tight seal between the tube and the throughbore of the female connecting block. A secondary fluid-tight seal is defined by the engagement of the transition surface with the tapered portion of the tube. 
   According to an alternative configuration, a tapered ring may be used where it is not possible to form the tapered portion on the tube. Here, the tapered ring would encircle the end-form of the tube and replace the tapered portion described above. The tapered ring would function to provide the requisite interference fit with the transition surface of the female connecting block, thereby centering the tube in the throughbore. 
   Accordingly, it is an object of the present invention to provide a self-piloting O-ring seal for a tube to block connection that results in no damage to the O-ring during assembly. 
   It is a further object of this invention to center and constrain the tube within the block so as to prevent lateral movement of the tube within the block. 
   It is yet a further object of this invention to prevent uneven side loading of the O-ring within the female connecting block due to torquing of the fastener attached to the male connecting block. 
   These objects and other features, aspects, and advantages of this invention will be more apparent after a reading of the following detailed description, appended claims, and accompanying drawings. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a partial cross-sectional exploded view showing the components of the tubular connection of the present invention before complete assembly; 
       FIG. 2  is a partial cross-sectional view of the tubular connection having the male connecting block and the tube secured to the female connecting block; 
       FIG. 3  is a partial cross-sectional view taken on the plane indicted by line  3 — 3  in  FIG. 2 ; 
       FIG. 4  is a partial cross-sectional exploded view of an alternative embodiment of the tube shown in  FIG. 1 ; and 
       FIG. 5  is a partial cross-sectional view similar to  FIG. 4  but shows the male connecting block and tube secured to the female connecting block. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
   In describing the preferred embodiment of the present invention, reference is made to the drawings, wherein there is seen in  FIG. 1  the unassembled components of a tubular connection  10 . The tubular connection  10  includes a tube  20 , a female connecting block  40 , a male connecting block  60 , and a bolt  80 . 
   The tube  20  is best seen in FIG.  1  and includes an upset bead  22  and a pair of annular grooves  24  on the outside diameter thereof. A pair of O-rings  26  are seated in the annular grooves  24 . The tube  20  includes a tapered portion  28  that narrows from the upset bead  22 , terminating in an end-form  30  of the tube  20 . Details of the tapered portion  28  are further discussed herein below. 
   The second component of the tubular connection  10  is the female connecting block  40  that includes an end or top surface  42 , an opposite end, or bottom surface  44 , and a throughbore  46  therebetween. The throughbore  46  includes a chamfer  48  in the top surface  42 . An annular edge or transition surface  50  is defined at the intersection of the chamfer  48  and the throughbore  46 . The female connecting block  40  also includes a threaded hole  52  adjacent but spaced from the throughbore  46 . Details of the chamfer  48  are further discussed hereinbelow. 
   The third component of the tubular connection  10  is the male connecting block  60  that includes a throughbore  62  and a counterbore  64  in a mating surface  63  that intersect and are coaxial. The diameter of the counterbore  64  is greater than the diameter of the throughbore  62 . The different size diameters of the throughbore  62  and counterbore  64  define a shoulder  66 . As best seen in  FIGS. 1 and 2 , the diameter of the throughbore  62  is slightly greater than an outer diameter “e” of the tube  20 . Similarly, the counterbore  64  is slightly greater in diameter than the diameter of the upset bead  22 . The male connecting block  60  additionally includes a bolthole  68 . 
   The fourth and final component of the tubular connection  10  is the bolt  80 , which is conventional and includes a threaded shank  82  and a hexagonal head  84 . The threaded shank  82  is smaller in diameter than the bolthole  68  of the male connecting block  60 . 
   As best seen in  FIG. 1 , the chamfer  48  of the female connecting block is oriented at an acute angle “a” to the axis of the throughbore  46  of the female connecting block  40 . Likewise, the tapered portion  28  of the tube  20  is oriented at an acute angle “b” to the axis of the end-form  30  of the tube  20 . The acute angles “a” and “b” can vary, but it is preferable that angle “a” be greater than angle “b”. However, should angle “a” be less than angle “b”, the invention would still work. Instead, the tapered portion  28  would engage the female connecting block  40  where the chamfer  48  intersects the top surface  42 . Also, the tapered portion  28  of the tube  20  has an axial length “x” and the chamfer  48  has an axial length “y”. Preferably, the length “x” should always be at least equal to the length “y” and more preferably, the length “x” should exceed the length “y”. As above, however, should length “x” be less than length “y”, the invention will still work. Further, the throughbore  46  of the female connecting block  40  has a diameter “d” that is intermediate a diameter “f” of the tapered portion  28  and the outer diameter “e” of the end-form  30 . 
   The key objective in aligning the tube  20  in the female connecting block  40  is to avoid uneven compression of the O-rings  26  during the assembly process. The first stage of the assembly process includes placing the tube  20  within the female connecting block  40 . In so doing, the chamfer  48  acts as a guide in order that the tube  20  may be centered within the throughbore  46 . The upset bead  22  is caused to mount flush against the top surface  42  of the female connecting block  40  and the tapered portion  28  of the tube  20  is caused to pilot and center about the transition surface  50  of the female connecting block  40 . 
   As seen in  FIG. 2 , the guiding action of the chamfer  48  allows the O-rings  26  to attain the positions without the O-rings  26  undergoing uneven compression due to side-loading from torquing of the bolt  80 . Therefore, the O-rings  26  circumferentially engage the throughbore  46  to define a primary fluid-tight seal. Additionally, the transition surface  50  sealingly engages the tapered portion  28  by circumferentially penetrating its surface to define a secondary fluid-tight seal. 
   Referring again to  FIG. 1 , assembly of the tubular connection  10  further involves placing the male connecting block  60  over a free end  32  of the tube  20  before the upset bead  22  is formed on the tube. Then the upset bead  22  is formed on the tube and within the counterbore  64  of the male connecting block  60 , by an axial upsetting process, as is well known in the art. The male connecting block  60  and the tube  20  are then advanced toward the top surface  42  of the female connecting block  40 . The end-form  30  of the tube  20  is inserted into the throughbore  46  of the female connecting block  40 . The upset bead  22  locates flat against the top surface  42  of the female connecting block  40 , and the tapered portion  28  of the tube  20  engages the transition surface  50  of the female connecting block  40 . Ultimately, the O-rings  26  form a primary fluid-tight seal between the tube  20  and the throughbore  46  of the female connecting block  40 . 
   Referring now to  FIG. 2 , the final stage of assembly of the tubular connection  10  includes placing the threaded shank  82  of the bolt  80  through the bolt hole  68  of the male connecting block  60  and into the threaded hole  52  of the female connecting block  40 . A clockwise torque is then applied to the hexagonal head  84  of the bolt  80  that causes the bolt  80  to threadingly engage the threaded hole  52  of the female connecting block  40 . The engagement of the threaded hole  52  by the bolt  80  effects a locking arrangement between the male connecting block  60  and the female connecting block  40 . 
   Consequently, the application of the clockwise torque to the bolt  80  ordinarily would cause the male connecting block  60  to rotate a very slight amount about the throughbore  46  in the clockwise direction, as indicated by the arrows in FIG.  3 . However, such rotation is resisted using the present invention because the tapered portion  28  pilots and thereby maintains the tube  20  centered within the throughbore  46  of the female connecting block  40 . This resistance to rotation amounts to an absence of lateral movement of the tube  20  within the female connecting block  40  and prevents uneven compression of the O-rings  26 . The absence of uneven compression of the O-rings  26  substantially reduces the incidence of premature failure in the O-rings  26  and resultant leakage of fluid past the O-rings  26 . 
   In the foregoing preferred embodiment illustrated in  FIGS. 1 through 3 , the tube  20  was formed to include the tapered portion  28  in order to prevent movement of the tube  20  after being inserted into the female connecting block  40 . The same result can be achieved without the tube  20  being formed to include the tapered portion  28  as shown in FIG.  4 . There, a tubular connection  10 ′ is an alternative embodiment of the tubular connection  10  seen in  FIGS. 1 through 3 . The only difference in the alternative connection  10 ′ is that a tube  20 ′ lacks the tapered portion  28  of  FIGS. 1 through 3 . The functionality of the tapered portion  28  in the tube  20  of  FIGS. 1 through 3  is attained here by the use of a plastic or soft metal tapered ring  21 ′ that initially is placed on the tube  20 ′ encircling an end-form  30 ′ and adjacent an upset bead  22 ′. The end-form  30 ′ has a pair of annular grooves  24 ′ that hold the pair of O-rings  26 . 
   Referring now to both  FIGS. 4 and 5 , the tapered ring  21 ′ includes a tapered portion  28 ′ that is analogous to the tapered portion  28  of the tube  20  of  FIGS. 1 through 3 . The tapered portion  28 ′ bears the same relationship in terms of angles and distances to the female connecting block  40  of  FIGS. 4 and 5 , as does the tapered portion  28  of the tube  20  with respect to the female connecting block  40  of  FIGS. 1 through 3 . When the tube  20 ′ is located within the female connecting block  40 , the tapered ring  21 ′ seats against the transition surface  50  of the female connecting block  40  to keep the tube  20 ′ centered therein. 
   Accordingly, an advantage of the present invention is that the tube self-aligns to the female connecting block during assembly, thereby reducing the risk of damaging the O-rings. This self-aligning action also constrains and centers the tube within the female connecting block such that the tube is prevented from moving laterally within the female connecting block from the torque that is applied to the mounting bolt. Preventing lateral movement of the tube prevents side loading the O-rings and leads to more equally distributed compressive loads upon the O-rings within the throughbore of the female connecting block. Tests conducted by the applicant reveal that this technology may result in 35% more squeeze at minimum material condition and may lead to a reduction in the tolerance stack-up for the tubular connection of 4%. 
   An additional advantage is that the sealing potential of the connection is improved. The transition surface of the female connecting block circumferentially penetrates into the tapered portion of the tube so as to form a secondary fluid-tight seal thus further preventing fluid from leaking from the connection. Finally, this technology will enable use of power tools to torque the tubular connection at higher torque without risk of side loading the O-rings. 
   From the foregoing description, it should be understood that various changes can be made in the above constructions without departing from the scope of the invention. It is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense. For example, the tube need not include the upset bead, and may be secured to the female connecting block in any other conventional fashion.