Abstract:
A pressure fluid conduit coupling fitting and method of making same, wherein the nipple tube fitting shank is made of specially grooved rigid material. A conventional elastomeric hose conduit having an open end telescopically receives the grooved fitting shank, and a conventional crimp-collar is sleeved over and shrunk-deformed onto the hose open end to permanently sealably secure the coupled conduit connection. An external circumferential surface of the fitting shank has one or more circumferentially continuous sharp edge external grooves of a shallow depth and predetermined width that are defined by the shank ribs formed between the grooves. The junction of the groove sidewalls with the respectively adjacent shank rib surface defines a circumferentially continuous sharp edge formed generally as a 90° junction of these groove sidewalls and rib surface, plus or minus a few degrees. These specially contoured sharp edge, shallow depth external grooves enhance the fluid sealing capacity (pressure rating) of the coupling connection while reducing the magnitude of collar shrink crimping required, and minimize the chances of hose damage because of over-crimping.

Description:
FIELD OF THE INVENTION 
     This invention relates to fluid sealing connections between rigid and flexible tubular fluid conduits, and more particularly to automotive hose couplings such as those used for connecting conduits in automotive power steering systems, and for coolant conduits for transmission and engine oil cooling systems, and the like. 
     BACKGROUND OF THE INVENTION 
     Crimp-type collar couplings used for sealingly telescopically coupling together rigid and flexible pressurized fluid conduits used in automotive power steering systems, and in transmission and engine cooler systems and the like, consist of a variety of designs. The sealing surface of the rigid tube at its nipple end, i.e., the end that is inserted into the open end of the flexible hose of the connected conduits so as to telescopically overlap therewith, may have a shank that is smooth or, alternatively a shank that has raised ribs, rolled ribs, or one of many other external. groove configurations. These different groove configurations are employed to enhance the sealing against fluid leakage between the flexible hose (usually made of a suitable elastomeric material), and the metal or other material used to construct the rigid tube. During the collar crimping procedure used in making the coupling, a generally cylindrical malleable metal shell is employed as a crimping collar and encircles the outside circumference of the hose. This collar is permanently circumferentially and radially-shrunk deformed to thereby apply mechanical radial compression pressure to the hose and thus builds up a permanent restraining stress for frictionally clamping the hose onto the tube nipple. This shrink force is also intended to squeeze the hose inner surface or hose innermost layer (in the case of a multilayer laminated hose) into any and all grooves or valleys of whatever rib design is provided on the nipple shank sealing surface. This adds a mechanical interlock structure reinforcing the frictional clamping to thereby assure that the assembly will remain intact against tensile forces tending to pull apart the flexible hose and rigid tube at their coupling. 
     One feature that prior coupling designs hitherto appear to have in common is that when a plurality of machined, cast, molded or rolled ribs or grooves are provided in the nipple shank exterior surface configuration, all sharp edges (where the radial sidewalls of each groove intersect the cylindrical nipple shank outer surface) are made “non-aggressive.” This is done either by initial design for eliminating or modifying them by subsequently forming them into a generous radius, chamfer or bevel edge. These non-aggressive edges assure that the tubular flexible hose of the coupled conduits is not cut during the aforementioned collar crimping operation employed to render the coupling permanent and sealed tight. 
     Thus conventional thinking has been that if the tube were cut during crimping by the presence of such a sharp edge, premature failure of the coupling assembly would result. On the other hand, sharp edges hitherto have been used on the barbs of rigid tubular nipples that are used in power steering or oil cooler hose. Nevertheless where grooves or ribs, instead of barbs, have been used on a nipple shank to enhance a sealing surface function the sharp edges that might otherwise have been formed, such as by leaving square cut groove corners as initially formed by lathe-turned cuts, have been purposely removed or avoided for the aforementioned reasons. 
     OBJECTS OF THE INVENTION 
     Accordingly, an object of the present invention is to provide an improved automotive hose coupling employing one or more specially contoured external grooves to enhance the sealing between the telescopic junction of the nipple shank of a rigid tubular conduit and a flexible hose in conjunction with a crimping collar that is permanently shrunk-deformed to apply radial compression pressure to the hose, and which coupling is improved from the standpoint of maximizing its sealing pressure capability while not causing the flexible hose to be cut by the crimping forces produced between the inner surface of the hose and the outer surface of the grooved tube shank of the coupling. 
     Another object is to provide an improved method of making an improved coupling of the foregoing character that is economical, reliable and that reduces the amount of compressive force needed for crimping the collar on the hose to effect a good seal, thereby reducing the internal stresses in the hose and minimizing the chance of damage occurring because of over-crimping in constructing the coupling. 
     SUMMARY OF THE INVENTION 
     In general, and by way of summary description and not by way of limitation, the invention achieves one or more of the foregoing, as well as other objects, by providing a pressure fluid conduit coupling, and method of making same, wherein an improved nipple tube fitting conduit is made of specially grooved rigid material for use with a conventional elastomeric hose conduit having an open end that telescopically receives an open end of a shank of the nipple fitting, and is then permanently secured together by a conventional crimp-collar sleeved over and shrunk-deformed onto the hose open end. An external circumferential surface of the tubular shank of the fitting is provided with one or more circumferentially continuous sharp edge external grooves that are defined by the ribs formed between the grooves. At least two adjacent grooves of a plurality of such grooves are spaced axially from one another by a predetermined distance W 2 . Each of these two grooves have a predetermined axial width dimension W 1  defined by generally radially extending axially spaced sidewalls facing one another. The bottom wall of each groove extends axially between the associated groove sidewalls and is formed at a radial depth represented by the predetermined dimension H, as measured from the external maximum outside diameter of the nipple shank ribs formed between such grooves. The external circumference of the fitting shank ribs between such grooves has a cylindrical contour of constant diameter. The junction of each of the groove sidewalls with the respectively adjacent shank rib surface defines a circumferentially continuous sharp edge formed generally as a 90° junction of these walls, plus or minus a few degrees. 
     Preferably for couplings designed for connecting conduits ranging in shank outside diameter from about 0.25 inches to about 0.75 inches, the groove depth dimension H is in the order of 0.008 inches, the groove width dimension W 1  is in the order of about 0.030 to about 0.035 inches, and the groove spacing dimension W 2  is in the order of about 0.060 to about 0.070 inches. However, improved results also can be obtained within a range of such dimensional parameters, e.g., the groove depth dimension H may range between about 0.004 inches to about 0.015 inches, the groove width dimension W 1  may range between about 0.025 inches to about 0.040 inches, and the groove spacing dimension W 2  may range from about 0.055 inches to about 0.070 inches. Preferably the number of the grooves in the plurality of grooves ranges from about four to eight, and the groove dimensions W 1 , W 2  and H apply to all of such grooves and are uniform and constant from groove-to-groove. 
     Preferably the crimp-collar is crimped to permanently deform the same with a magnitude to create, in the hose inner surface area impinged by at least one of the sharp edge comers of the grooves, an internal stress in the hose up to about 700 psi. Also, the crimp-collar is preferably shrunk by an amount sufficient only to radially compress the thickness dimension of the wall of the flexible hose conduit, where the hose wall is encircled by the collar, to about 80 percent of its free state thickness. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The foregoing as well as additional objects, features and advantages of the present invention will be better understood from the following detailed description of the best mode presently known to the inventor of making and using the invention, from the appended claims, and from the attached drawings (which are to engineering scale unless otherwise indicated), wherein: 
     FIG. 1 is a fragmentary perspective view of a first embodiment of an automotive hose coupling constructed in accordance with the present invention. 
     FIG. 2 is a fragmentary exploded view of the components of the coupling of FIG.  1 . 
     FIG. 3 is a fragmentary plan view of a second embodiment coupling of the invention modified only in that it utilizes a conventional flat-type crimp collar. 
     FIG. 4 is a fragmentary plan view of the coupling construction of FIGS. 1 and 2 of the first embodiment. 
     FIG. 5 is a fragmentary elevational view of the subassembly of the shank nipple end of the rigid tube, utilized in the embodiments of FIGS. 1-4, with an interior reinforcing tube, this reinforced tubular shank subassembly being shown by itself prior to insertion into a hose and prior to being crimped. 
     FIG. 6 is an end view looking at the right hand end of the subassembly of FIG. 5, as viewed in FIG.  5 . 
     FIG. 7 is a fragmentary view of the portion of FIG. 5 encompassed by the circle labeled  7  therein and shown on a greatly enlarged scale thereover. 
     FIG. 8 is a cross sectional view taken on the line  8 — 8  of FIG.  5 . FIGS. 9 and 10 are respectively side elevational and end views of the reinforcing tube used in the subassembly of FIGS. 5-8. 
     FIG. 11 is a greatly enlarged fragmentary diagrammatic view as computer drawn on the basis of finite element analysis (FEA) of a preferred groove construction of the invention. 
     FIG. 12 is a view similar to FIG. 11 also showing a computer generated diagram based on FEA analysis of a groove construction employing slightly different dimensional parameters than those of FIG. 11, and 
     FIG. 13 is a fragmentary part elevational and part cross-sectional view taken on the line  13 — 13  of FIG.  4 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring in more detail to the accompanying drawings, FIG. 1 illustrates a completed first embodiment coupling  18  constructed in accordance with the invention in which a conventional rigid tubular power steering fluid conduit  20 , usually constructed of steel (e.g., 1008/1010), stainless steel, copper or brass material, is removably connected to a metal male connector fitting  26  by a conventional hex nut compression fitting  22  threadably received on a male threaded end  24  (FIG. 2) of fitting  26 . A plurality of grooves  28  are provided on a tubular shank  42  of fitting  26  (FIG. 2) that are specially constructed in accordance with the invention. The rounded male nipple end  30  of shank  42  is telescopically inserted into the mating open end  32  of a flexible elastomeric hose conduit  34  and permanently secured to fitting  26  by a crimp-collar  36 . Crimp-collar  36  is shown by way of example as a conventional triple bubble crimp-type collar constructed of malleable metallic material and shown in its crimped state , in FIGS. 1,  2 ,  4  and  13 , as circumferentially and radially compressed. 
     Fitting  26  is shown complete in FIG.  2  and comprises, in addition to the externally threaded male end  24 , an integral hex nut portion  40  and the cylindrical shank portion  42  that is provided with a hose stop flange  44  spaced closely adjacent nut portion  40 . Shank  44  terminates at its axially open end at the tapered nipple open end  30  that is designed to facilitate telescopic insertion into the open end  32  of hose  34  in a conventional manner. Shank  42  between stop flange  44  and nose  30  is provided with the plurality of the special grooves  28 , shown by way of example as being eight in number and defining therebetween the seven ribs  46 . 
     As shown in FIGS. 8,  9  and  10 , fitting  26  is preferably a reinforced subassembly, a conventional cylindrical open ended metal reinforcing tube  50  being telescoped with a close clearance fit into shank  42  of fitting  26 . Tube  50  is designed to be at least axially coextensive with the portion of fitting shank  42  that is axially overlapped in assembly with crimp-collar  36 . Thus, as shown in FIG. 8, tube  50  is flush at its right hand end (as viewed in FIG. 8) with the end of shank nose  30 , and its left hand end terminates just past the hose stop flange  44 . 
     The second embodiment coupling construction  18 ′ shown in FIG. 3 is identical to coupling construction  18  except that the crimp-collar  36 ′ is of the conventional flat crimp-type instead of the triple bubble crimp-type (“TBC”) coupling  36 . 
     In accordance with a principal feature of the present invention, and as best seen in the enlarged view of FIG. 7, each of the fitting shank grooves  28  is basically a “square-cut” groove. By way of example, each groove  28  may be form-tool machined in the metal material of the shank  42  of fitting  26  so as to have a predetermined cross sectional configuration in a plane defined by the central axis and a radius of shank  42 . In the illustrated example each groove  28  is defined by a pair of axially opposed radially extending sidewalls  54  and  56  that intersect the outer cylindrical peripheral surface  58  of an associated mutually adjacent rib  46  at a right angle to thereby define a 90° sharp edge  60 . Edge  60  is thus a square-shoulder-type edge purposely unaltered from the lathe-turned machine cut used in forming groove  28 , instead of such an aggressive groove edge  60  then being radiused, chamfered or beveled as in prior practice. Preferably the bottom wall surface  62  of each groove  28  is cylindrical and concentric with the cylindrical peripheral rib surface  58 . Likewise, preferably the junction of each groove sidewall  54 ,  56  with the groove bottom surface  62  is formed as a fillet junction, shown as fillets  64  and  66  in FIG.  7 . 
     In addition to the junction of grooves  28  with ribs  46  being formed as “sharp edges”  60 , and as best seen in FIG. 7, the invention is also characterized by a further feature, namely the predetermined dimensional relationship of grooves  28  with ribs  46  as to the width dimension W 1  between the groove sidewalls  54  and  56  as measured axially of shank  42 , the spacing between each adjacent pair of grooves  28  which defines the width dimension W 2  of each rib  46  also as measured axially of fitting  26 , and the groove depth denoted H in FIG. 7, which is the dimension measured radially of shank  42  between the outside diameter of each rib  46  and the outside diameter of groove bottom wall  62 . Exemplary values for these dimensional parameters W 1 , W 2  and H have been determined initially by finite element analysis (FEA) and verified by prototype testing, as described in more detail hereinafter. 
     To assemble and construct coupling  18 , utilizing the components described hereinabove, an undeformed crimp-collar  36  is first sleeved over the open end of the undeformed hose  34 , so that the fitting end  70  of collar  36  is preferably flush with the open end  32  of hose  34 . It is to be understood that collar  36 , as well as hose  34  as shown in FIG. 2, are shown after crimp deformation of these respective components. 
     Then fitting  26  is telescopically inserted, nose end first, into open end  32  of hose  34  until hose end  32  abuts hose stop flange  44  of fitting  26 , as best seen in FIG.  13 . Then collar  36  is crimped in a conventional fashion using conventional crimping equipment, so as to circumferentially and radially shrink-deform the malleable material of collar  36  a given amount to thereby permanently deform the same into a permanently set configuration indicated somewhat diagrammatically in FIG. 13, as well as in FIGS. 1,  2  and  4 . This shrink-deformation of collar  36  thus radially compresses that portion of hose  34  telescopically axially overlapping fitting  26  and forces the wall inner surface  72  of hose  34  to bulge into and thereby partially penetrate each of the grooves  28 . This mechanical interengagement of hose  34  with groove ribs  46 , in addition to the frictional grip of wall  72  on the external periphery of the ribbed shank  42 , provides a very strong joint that resists axial separation of fitting  26  from hose  34  even under tensile forces that typically exceed the tensile stress limit of hose  34 . 
     From the standpoint of reduced fluid leakage and enhanced sealing of highly pressurized fluid through the coupled junction of the conduits  20  and  34  via coupling  18 , it has been found that surprising and substantially improved results are obtained from sharp groove edges as compared to various ribbed and grooved configurations that use non-aggressive groove edge surfaces where they are engaged by the encircling rubber hose, as by the prior practice of putting radii, chamfers and/or bevels on all sharp edges remaining from groove formation, if such be present. The invention also features a groove depth H that is relatively shallow so as not to impart severe internal stresses in the rubber material of hose  34  that could cause it to cut or tear on one or more of the sharp edges  60 . Both FEA analysis and empirical testing to date have shown the “sharp-edge groove” design of the invention to be far superior to the rib shank coupling fittings of prior art constructions. 
     More particularly, in the development of the present invention, an FEA study was conceived and conducted to determine if theoretically improved results could be obtained from applying the foregoing principles of the invention. The goal was to maximize the sealing pressure capability of the coupling joint, while not creating internal stresses in hose  34  severe enough to cause it to cut. Accordingly a Finite Element Analysis (FEA) was created to evaluate the stresses and sealing pressures on a coupled hose using grooves as described previously, namely a plurality of equally axially spaced grooves  28 , to create a better seal between the external surface of metal shank  42  of fitting  26  and the inner diameter wall surface  72  of hose  34 . The groove width W 1 , groove depth H and spacing W 2  between the grooves, i.e., the axial width of each rib  46  denoted W 2  in FIG. 7, were correlated with one another and then varied as between data runs in order to determine the optimum design that would provide maximum sealing pressure without severely stressing rubber tube  34 . From this analysis, preferred combinations were selected and parts were manufactured for prototype testing. Tests were run to prove out the design, as well as determine how the parts compare to existing designs. These test results have shown the design of the invention to provide surprisingly superior results. 
     An additional benefit that was discovered is that the hose does not have to be compressed as much during crimping to achieve a good seal with the design of the invention. This, in turn, further reduces the internal stresses in the hose, and minimizes the chance of damage occurring because of over-crimping. 
     A computer print-out of two of the dimensional combinations are shown semi-diagrammatically in FIGS. 11 and 12, the sample dimensions for H, W 1 , and W 2  being labeled above each figure (in inches). As indicated above, several variations of the sizes of the grooves and their spacing were analyzed. The analysis was also done on a hose with no grooves cut in the fitting  26 . To keep consistency, each theoretical crimp variation in the crimp collar was compressed a distance corresponding to 80% of the free-state height (wall thickness radially of the hose) of the hose. The values for the hose material were taken from specifications for a material identified as a fluoroelastomer 01-560, which has a specified failure limit of 1560 psi of stress. Due to difficulty encountered in extracting accurate values from the cross-sections, which in turn was due to the fact that the FEA software analysis has a tendency to stretch across the sharp corners of the grooves, the numbers of the nearest finite elements that did not stretch across the corners were used in the analysis problem. Indeed, the software would not run the problems when a radius was inputted to the data on the corners of the grooves. 
     Using as a base point data that was calculated and analyzed on a fitting tube shank with no grooves at all, the theoretical results from the stress plot showed that only 332 psi of stress is concentrated at the maximum crimped area of the collar on the ungrooved tube. The sealing plot showed that the seal on the smooth tube shank can only sealably withstand up to 197 psi of fluid pressure. 
     However, for fittings  26  constructed with the sharp edge grooves  28  and ribs  46 , as described hereinabove, the following theoretical results were obtained from some of this FEA analysis: 
     
       
         
               
               
               
               
               
               
             
               
               
               
               
               
               
             
           
               
                   
               
               
                   
                 H 
                 W 1   
                 W 2   
                   
                 Sealing Pressure 
               
               
                   
                 Dimension 
                 Dimension 
                 Dimension 
                 Stress 
                 at Corner 
               
               
                 No. 
                 (inches) 
                 (inches) 
                 (inches) 
                 (psi) 
                 of Grooves 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                 1 
                 .000 
                 .000 
                 .000 
                 332 
                 197 
               
               
                 2 
                 .005 
                 .005 
                 .030 
                 540 
                 295 
               
               
                 3 
                 .005 
                 .005 
                 .040 
                 303 
                 314 
               
               
                 4 
                 .005 
                 .010 
                 .030 
                 303 
                 359 
               
               
                 5 
                 .005 
                 .010 
                 .040 
                 872 
                 328 
               
               
                 6 
                 .005 
                 .015 
                 .030 
                 791 
                 302 
               
               
                 7 
                 .005 
                 .015 
                 .040 
                 1100 
                 330 
               
               
                 8 
                 .010 
                 .005 
                 .030 
                 540 
                 295 
               
               
                 9 
                 .010 
                 .005 
                 .040 
                 702 
                 329 
               
               
                 10 
                 .000 
                 .010 
                 .030 
                 936 
                 359 
               
               
                 11 
                 .010 
                 .010 
                 .040 
                 872 
                 369 
               
               
                 12 
                 .010 
                 .015 
                 .030 
                 948 
                 453 
               
               
                 13 
                 .010 
                 .015 
                 .040 
                 1320 
                 440 
               
               
                 14 
                 .015 
                 .005 
                 .030 
                 540 
                 295 
               
               
                 15 
                 .015 
                 .005 
                 .040 
                 702 
                 395 
               
               
                 16 
                 .015 
                 .010 
                 .030 
                 1400 
                 539 
               
               
                 17 
                 .015 
                 .010 
                 .040 
                 1450 
                 492 
               
               
                 18 
                 .015 
                 .015 
                 .030 
                 948 
                 553 
               
               
                 19 
                 .015 
                 .015 
                 .040 
                 1100 
                 550 
               
               
                 20 
                 .015 
                 .005 
                 .050 
                 424 
                 431 
               
               
                 21 
                 .015 
                 .005 
                 .060 
                 387 
                 305 
               
               
                 22 
                 .015 
                 .010 
                 .050 
                 584 
                 591 
               
               
                 23 
                 .015 
                 .010 
                 .060 
                 549 
                 513 
               
               
                 24 
                 .015 
                 .015 
                 .050 
                 716 
                 728 
               
               
                 25 
                 .015 
                 .015 
                 .060 
                 517 
                 691 
               
               
                 26 
                 .015 
                 .020 
                 .030 
                 777 
                 796 
               
               
                 27 
                 .015 
                 .020 
                 .040 
                 775 
                 799 
               
               
                 28 
                 .015 
                 .025 
                 .030 
                 672 
                 709 
               
               
                 29 
                 .015 
                 .025 
                 .040 
                 668 
                 669 
               
               
                 30 
                 .015 
                 .030 
                 .030 
                 955 
                 934 
               
               
                 31 
                 .015 
                 .030 
                 .040 
                 1026 
                 1280 
               
               
                 32 
                 .020 
                 .010 
                 .040 
                 437 
                 468 
               
               
                 33 
                 .020 
                 .010 
                 .050 
                 467 
                 500 
               
               
                 34 
                 .020 
                 .015 
                 .040 
                 522 
                 562 
               
               
                 35 
                 .020 
                 .015 
                 .050 
                 716 
                 672 
               
               
                 36 
                 .020 
                 .020 
                 .040 
                 775 
                 738 
               
               
                 37 
                 .020 
                 .020 
                 .050 
                 742 
                 694 
               
               
                   
               
             
          
         
       
     
     It will be seen from the foregoing FEA study results that when the groove depth (H) is 0.015 inches and the groove width (W 1 ) is 0.030 inches (runs Nos. 30 and 31), the sealing pressure capability is the greatest (i.e., 934 and 1280 psi). It also appears that as the space (W 2 ) between the grooves increases, the sealing pressure capability increases (again, see runs nos. 30 and 31). Based on these results, a prototype was constructed using a groove spacing of approximately 0.060 inches, because it was calculated from the FEA results that the sealing pressure might well increase even more by increasing the figure from 0.040 to 0.060. Since the groove depth (H) is a parameter that seems to have much less effect on sealing pressure obtained, for a theoretical FEA prototype test sample this dimension was reduced to 0.008 inches in order to further reduce the chances of cutting the inner wall  72  of hose  34 . The FEA study using these modified parameters provided the following surprisingly improved results: 
     
       
         
               
               
               
               
               
               
             
           
               
                   
               
               
                   
                 H  
                 W 1   
                 W 2   
                   
                 Sealing Pressure 
               
               
                   
                 Dimension 
                 Dimension 
                 Dimension 
                 Stress 
                 at Corner 
               
               
                 No. 
                 (inches) 
                 (inches) 
                 (inches) 
                 (psi) 
                 of Grooves 
               
               
                   
               
             
             
               
                 38 
                 0.008 
                 0.032 
                 0.065 
                 646 
                 1020 
               
               
                   
               
             
          
         
       
     
     Prototype samples for actual testing were then constructed using run No. 38 parameters and both types of collars  36  and  36 ′. Both crimp styles gave superior test results when compared to competitive commercial coupling construction. A difference was observed in subsequent testing in the results as between these two styles of crimp-collars, i.e., the flat crimp style proved better. However, it is believed that the TBC style may prove equal or work very well with a different hose construction. 
     A thermal cycling test was suspended at 20 cycles with no leakage evident on any of the designed couplings constructed according to the aforementioned parameters. 
     Based on the results of the foregoing FEA analysis, data and study, it is theoretically concluded that the depth H of the grooves is found to be not as significant a factor as the width W 1  of the groove or the distance W 2  between grooves. The analysis also indicates a finding that for a given groove depth, the wider the groove the higher the stresses will be, and therefore the sealing pressures achieved will be higher. Thus it is evident that runs nos. 30 and 31 using the 0.03 inch groove width (W 1 ) display an extremely high amount of stress as compared to the rest of the cross-sections. On the other hand, the groove widths of 0.010 inches and 0.005 inches show adequate theoretical sealing values while at the same time not creating a great deal of internal stress in the hose. On the other hand, run No.  38  using a groove width of 0.032 inches but a reduced groove depth (H) of 0.008 inches while increasing the groove spacing (W 2 ) to over 0.060 inches resulted in providing about five times the sealing pressure of a smooth tube while only doubling the internal hose stresses. 
     Thus, from the foregoing description and appended drawings as referenced therein, it will now be apparent to those skilled in the art that a coupling construction  18 ,  18 ′ in accordance with the foregoing disclosure amply fulfills the aforestated objects and provides many features and advantages over the prior art. The simple labyrinth sealing groove design of the invention using square grooves cut into the surface of the metal tube, so as to provide sharp edge intersections of the radial groove walls with the cylindrical surface of the mutually adjacent flanking ribs thus generated on the tube shank, greatly increases the fluid sealing pressure capacity of the coupling. Nevertheless, at the same time cutting the grooves only to a shallow depth does not allow the rubber tube to be over-stressed so as to cause cracking or cutting of the hose inner diameter. The amount of metal needed to be removed in lathe-turning is also reduced. A further benefit is that the hose crimp-collar does not have to be compressed as much during crimping as in standard practice in order to achieve a good seal utilizing the groove design of the invention. This in turn further reduces the internal stresses in the hose, further minimizes the chance of damage occurring because of over-crimping and minimizes the effect of creep because the rubber is compressed along the entire grooved surface area. Moreover, when the grooves are formed by lathe cut turning, the need for radiusing, beveling or chamfering each of the edges of the cut in the manufacturing operation is eliminated. 
     Of course, it also will be understood that the principles of the invention can be applied to equivalent coupling constructions in which the components are varied from the examples disclosed. For example, fitting  26  may be made of other rigid material such as high-strength injection-molded reinforced plastic material that is glass filled, and various suitable metallic materials that may be cast and/or machined. The elastomeric conduit  34  provided with coupling  18 ,  18 ′ may be one of a variety of conventional high-pressure elastomeric hose constructions. Preferably the hose material has a hardness range of 70 to 80 durometer and a tensile strength of at least 1000 psi. Typical application fluid working pressures up to about 300 psi are presently the design working criteria for the disclosed coupling constructions. The crimping collars  36  and  36 ′ may be any of the standard malleable metal crimping collars conventionally employed in making crimp-couplings for flexible hose conduits. It is also believed that the angulation of groove sidewalls  54  and/or  56  may also be varied from their 90° intersection with the cylindrical surface  58  of the mutually adjacent ribs  46 , as by providing a groove sidewall-rib surface angular intersection variation ranging from about (+)5°&gt;90° to about (−)5°&lt;90° without thereby substantially impairing the improved results provided by the invention, provided that such modified groove edge intersection remains “aggressive”, i.e., a sharp linear line-to-line intersection defining the groove edge configuration lying in a plane defined by the tube axis and any radius extending from the same.