Abstract:
An integrated in-line tube and check valve assembly fabricated by end-form mandrel expanding an outlet end portion of deformable tube stock, such as metal, of nominal starting diameter, and concurrently end-forming a valve seat on the inside of the expanded tube section where it necks down and integrally joins the upstream nominal diameter portion of the tube. A valve ball and a valve spring are then fitted into the expanded tube section, together with a spring holder if needed. The expanded end portion of the tube is then again deformed by an end-form swaging operation that reduces the diameter of the expanded tube outlet end so as to form a cavity within the tube in which the spring is captured in compression for resiliently biasing the valve ball against the valve seat.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     This invention relates to a check valve formed integrally with a tubular flow conduit and a method of manufacturing the same, as distinguished from securing a separate check valve assembly to the flow conduit.  
         [0002]     In many applications it is desirable to incorporate a check valve in a fluid flow conduit or line to prevent fluid from flowing in one direction while allowing fluid to flow in the other direction. In certain of those prior applications a check valve has been integrated directly in the fluid line, thereby avoiding the necessity of using self-contained separate valve assemblies that must be joined in an appropriate manner to the tubing or pipe system. In such integrated applications, cost savings have been realized by using the tubing itself as the casing or body portion of the check valve assembly that is thus integrated with the tube. Such integrated check valve assemblies also eliminate leakage points from seals because they avoid breaking the continuity of the tubing.  
         [0003]     Prior examples of integrating a check valve into a length of tubing stock are disclosed in the expired U.S. Pat. No. 3,387,625 Laure and in the expired U.S. Pat. No. 4,611,374 Schnelle et al. Both of these prior art patents incorporate a ball-type check valve in a flow conduit made of material that is capable of being shaped or worked. The integral valve cage or chamber as well as valve seat thus are formed by reducing the diameter of the tubing at two spaced points to thereby form both ends of the valve cage. One end is thus necked down to serve as the valve seat for the ball. The other end is likewise necked down to serve as a retainer either for a valve spring assembled in the valve cage (Laure &#39;625), or for a valve-ball-retainer comprising a series of circumferentially spaced inwardly extending ball-retaining indentations that hold the ball from release from the cage, while allowing fluid flow around the ball through the tube (Schnelle et al &#39;374).  
         [0004]     While the aforementioned integrated in-line check valve and flow tube assemblies provide the aforestated advantages of avoiding assembling a separate check valve assembly to the tube, they are disadvantageous from the standpoint of requiring the nominal tube diameter to be reduced by the necking down operation both upstream and downstream of the ball valve element of the check valve, thereby reducing the fluid flow capacity of the tubular flow line.  
       SUMMARY OF THE INVENTION  
       [0005]     In general, and by way of summary description and not by way of limitation, the present invention provides an improved in-line integrated tube and check valve assembly that comprises a fluid-flow conduit in the form of an elongated hollow tube having a linear end section open at one axial end to serve as a fluid flow outlet of the tube. The tube has a check valve element, preferably in the form of a ball, captured in an enlarged valve cavity integrally formed in the end section of the tube and axially spaced from the open outlet end of the tube. The tube has a nominal constant diameter upstream of the check valve cavity, and the tube wall forming the enlarged cavity has a cross sectional dimension greater than this nominal tube diameter. The tube cavity wall forms a valve seat at the upstream end of the valve cavity. Preferably a valve spring is also captured in compression in the cavity and lightly resiliently biases the valve element against the integrated valve seat.  
         [0006]     The invention also provides an improved method of assembling the check valve element into the tube of deformable material. First the outlet and contiguous end portion of the tube are expanded by an end forming, cold working operation for a given axial length. The valve seat is formed within the tube end portion as it is being so end-form expanded, the valve seat being located where the expanded end portion integrally joins the unexpanded upstream portion of the tube that remains at the nominal diameter. Then a valve element and valve spring are inserted via the tube outlet and positioned within the expanded end portion of the tube with the valve element seated against the valve seat. Then the expanded tube outlet end portion is again deformed, but this time by an end-form swaging operation that reduces its diameter from the outlet up to a given location downstream of the valve spring to thereby form a valve cavity with a transition stop-shoulder wall that captures the spring within the valve cavity and in compression for lightly biasing the valve element against the valve seat. Preferably the tube outlet end portion is thus swage reformed back to the nominal diameter of the tube. In addition, the reformed tube end portion may be further end-form cold worked to form upset hose stop and sealing beads, compression flare configurations or other attachment configurations in the reformed tube geometry as desired for coupling the outlet end portion of the tube to flow line continuation structure.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0007]      FIGS. 1 through 2 F are each part elevational, part center-sectional fragmentary views,  FIG. 1  showing an outlet end portion of tubular conduit stock illustrating an exemplary but preferred embodiment of the invention in finished form.  
         [0008]      FIG. 2A  is a view of the outlet end portion of the tube stock cylindrical (right circular) starting material of constant nominal diameter.  
         [0009]      FIG. 2B  is a view of the tubular stock after completion of a first stage end-forming expansion operation.  
         [0010]      FIG. 2C  is a view of the tubular stock after a second stage end-forming expansion operation.  
         [0011]      FIG. 2D  illustrates the step of positioning a check ball and associated biasing spring into the expanded tube stock of  FIG. 2C  with an appropriate assembly tool inserted axially into the open outlet end of the tube stock.  
         [0012]      FIG. 2E  illustrates the tubular stock after the diameter of the end portion of the tube has been end-form swaged back to nominal diameter downstream of the valve cavity, thereby forming the downstream end of the cavity as an annular shoulder for holding the larger end of the valve spring.  
         [0013]      FIG. 2F  is a view illustrating the removal of the positioning tool from the tubular stock to thereby allow the large end of the biasing spring to seat against the stop shoulder formed in the valve cavity. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0014]     Referring in more detail to the accompanying drawings,  FIG. 1  illustrates a preferred but exemplary embodiment of an in-line integrated tube and check valve assembly  10  of the invention. Assembly  10  comprises an outlet end portion  12  of an elongated hollow tube of cylindrical right-circular cross sectional configuration. End portion  12  has an upstream wall  16  of given nominal constant diameter at its upstream end and an open outlet end  14  at is downstream end. Assembly  10  thus has a constant diameter upstream tube wall  16  typically specified as a given nominal standard tubular diameter. Assembly  10  also has an integral valve casing wall  18  of right-circular cylindrical cross sectional configuration made up in part by a constant diameter cylindrical wall section  20  having a diameter preferably about  25 % greater than that of tube wall  16 . Valve cavity  18  also includes a conically tapering wall section  22  that is integrally joined as formed to wall  20  at its large diameter end and to wall  16  at its small diameter end. Wall  22  is thus well adapted to serve as a valve seat for a check valve element, preferably in the form of a valve ball  24 , housed within valve casing  18 . A compression coil spring  26  is also received within valve casing  28  and has a tapering cross section with its small diameter end convolution  28  engaging ball  24  and the larger diameter end convolution  30  engaging an annular stop in the form of a retaining shoulder wall portion  32  that joins cavity wall portion  20  to a downstream reduced diameter outlet end portion  33  of conduit  12 . Wall  34  of downstream outlet end portion  33  preferably has an internal diameter no less than that of upstream wall  16 .  
         [0015]     The normal direction of flow of fluid through assembly  10  is indicated by the arrow F in  FIG. 1 . Normal fluid flow pressure acting against check ball  24  is sufficient to overcome spring bias to allow ball  24  to move to the left as viewed in  FIG. 1  from the closed position shown in  FIG. 1  to an open position within valve casing  18 . Check ball  24  thus operates as a typical one-way check valve in the flow line of conduit tube  12 , with positive seating being provided by spring  26  lightly forcing ball  24  against the internal valve seat (close to the junction of wall sections  22  and  16 ) to thereby reliably prevent reverse fluid flow in conduit  12 .  
         [0016]     As shown only in  FIG. 1 , the tube and check valve assembly  10  may have additional end-formed cold worked sections, such as the pair of hose bumps  36  and  38  that assist in positioning and sealing an encircling flexible hose (not shown) inserted over the outlet end  14  of tube section and retained thereon by a conventional crimp collar.  
         [0017]     The preferred embodiment of the method of the invention for assembling check valve ball  24  into tube  12  of deformable material is illustrated in sequence in the forming and assembly steps illustrated in  FIGS. 2A, 2B ,  2 C,  2 D,  2 E and  2 F respectively.  
         [0018]     Tube end portion  12  is shown in  FIG. 2A  as a preform  12   a , i.e., in its initial, starting material state, and preferably is made of deformable metallic material such as low carbon steel, stainless steel, aluminum or brass, and thus is capable of permanent deformation by conventional cold working end forming machines and equipment. The starting material  12   a  is shown in  FIG. 2A  preferably as a predetermined length of linear tubing  12  having a right-circular cylindrical wall  16  of constant diameter and uniform radial thickness and thereby defining the end portion conduit  12   a  that terminates in an axially open outlet end  14 .  
         [0019]     In the first forming step of the method, the end portion wall  16  is radially expanded to form an intermediate portion  40  extending a given length upstream from outlet end  14  and having a diameter larger than that of wall  16  and integrally joined to wall  16  by a conical portion  42  having a taper angle less than that of wall  22 . This expansion stage is preferably performed by a conventional end-forming head expansion tooling and technique (not shown). Typically in this process tube  12   a  is put in a segmented die that clamps portion  16  upstream of the region for forming wall  22  and has an internal cavity profile matching that of tube wall  40  and conical intermediate wall  42 . An expanding mandrel tool is forced endwise axially into the open end  14  of tube wall  16 , and has a shape and diameter suitable to cold work expand wall  16  out to the diameter of wall  40  shown in  FIG. 2B , and also to form the conical wall transition  42 .  
         [0020]     In the next stage of the method illustrated in the progression from  FIG. 2B  to  FIG. 2C , the end forming process is repeated by re-chucking the intermediate workpiece  12   b  from  FIG. 2B  into an end forming machine having the proper end form tooling and sizing to end form portion  40  to a larger diameter to form the expanded end portion length  44  of constant diameter extending axially from end  14  up to the reformed conical cavity transition wall, now having a steeper taper and being designated as finished wall  22  in  FIG. 2C . Wall  44  preferably has a diameter approximately 25% greater, and may be up to 50% greater, than the original diameter of wall  16  of preform  12   a , and is formed to the same diameter as the finished cavity wall  20  of the assembly  10  described hereinabove.  
         [0021]     In the next step of the method, illustrated in  FIG. 2D , the sub-assembly of valve ball  24  and biasing coil spring  26  are inserted via open outlet  14  and positioned within said expanded end portion  44  with check ball  24  seated against the internal valve seat formed at the junction of conical section  22  and tube wall  16 . Preferably this positioning step is performed with the aid of a customized assembly tool  50  that includes an elongated shank  52  dimensioned so as to protrude out of the outlet end  14  when positioned as shown in  FIG. 2D . Tool  50  carries at its working end a pair of L-shaped pusher fingers  54  and  56  each having a stop foot  58  and  60  respectively that abut shank  52  when fingers  54  and  56  are pivoted out to extend perpendicular to shank  52  as shown in  FIG. 2D . The outer ends of fingers  54  and  56  are respectively notched at  62  and  64  to seat fingers  54  and  56  within the end coil  30  of spring  26  in secure pushing relation on the spring. The initial assembly position of tool  50  and associated fingers  54  and  56  relative to the check ball  24  in its seated position is such as to slightly compress spring  26  and to thereby hold fingers  54  and  56  spaced a given distance from conical wall section  22 . Tool  50  is then suitably fixtured so as to be held in the position of  FIG. 2D  during the performance of the next end-forming step of the method.  
         [0022]     In this next step of the method, illustrated by the transition from the form of  FIG. 2D  to the form of  FIG. 2E , the downstream end portion  44  of tubular stock is again deformed, but by a conventional cold working swaging operation, designed to permanently deform and thereby reduce the diameter of an outlet end portion  33  of expanded wall  44  that now extends from the outlet  14  to a location axially along portion  44  that is appropriate to form the spring stop wall  32  at the junction of casing wall  20  and the newly shrunken tube wall  34  of end portion  33 . The reduction of expanded tubing section  44  down to the reduced diameter tubing section  34  is preferably performed in a conventional swaging machine (not shown) that has a suitable cavity formed in die blocks. The tubing is forced endwise (axially) back down into this die cavity to cold work the same and thereby shrink the diameter of the tubing down to section  34 . Preferably wall  34  is of circular cross section and of a constant diameter and generally equal to that of upstream portion  16  of end portion  12 .  
         [0023]     In the next step of the method illustrated by the sequence of progression from  FIG. 2E  to  FIG. 2F , tool  50  is retracted by withdrawing it (to the left as viewed in  FIG. 2F ) toward tube outlet  14 . As fingers  54  strike stop wall  32  during this initial retraction motion, they are pivoted inwardly toward one another to the collapsed finger position of  FIG. 2F . In this condition the overall outside diameter of the collapsed fingers is slightly less than the inside diameter of tube portion  34  to thereby permit retraction of the fingers and removal of tool  50  completely out from the finished integrated check valve and tube assembly shown in  FIG. 2F . Also, during this initial retraction, end convolution  30  of spring  26  is carried back until it is released from the collapsing fingers and thus seats against stop wall  32 , as shown in  FIG. 2F .  
         [0024]     The integrated tube and check valve assembly  10  of  FIG. 2F  may be further worked from its form in  FIG. 2F  to that shown in  FIG. 1  wherein conventional hose bumps  36  and  38  have been formed by typical end upset operations in a conventional tube upset forming machine. It will also be understood that other finishing operations may be performed on the configuration of the assembly of  FIG. 2F , such as forming a compression flare on outlet end  14  or other conventional structure to facilitate coupling to downstream conduit flow structures other than hoses or plastic tubing.  
         [0025]     From the foregoing description it will now be seen that the method and apparatus of the invention provide many advantages over the prior art, including eliminating a separate drainback valve subassembly component that must be attached by fittings and seals to an outlet end of a tube, this part being eliminated by end forming the valve shell directly into the tube. Moreover, unlike the aforementioned prior art patents discussed above, the flow diameter of tube  12  need never be reduced smaller than the nominal diameter of wall  16 . Hence fluid flow through the integrated check ball assembly is not restricted by diametrical reductions in the tubing diameter. Also, check ball  24  operates in an enlarged diameter valve casing  18  so that the cross sectional flow area around valve ball  24  when open can be equal to the cross sectional flow area of wall section  16 , or nearly so. Hence, fluid flow is not hampered by ball  24  operating in a constricted diameter tubing section as in the prior art.  
         [0026]     The conical form of biasing spring  26 , with its largest diameter abutting stop wall  32  and coil  30 , provides a stabilized biasing arrangement for valve ball  24  even though operably “floating” as it opens into the large diameter cavity provided by valve casing wall  20 . The swaging operation utilized to form tubing portion  34  in  FIGS. 2E and 2F  is preferably designed to make portion  34  long enough between outlet  14  and valve casing  18  to accommodate another attachment end form operation, such as the hose bead bumps  36 ,  38 , or a suitable compression flare forming operation. The invention thus accomplishes these additional advantages as well as incorporating the advantages set forth above with respect to the Laure &#39;625 patent and Schnelle et al. &#39;374 patent.  
         [0027]     Note also that the invention preferably integrates the check valve assembly into a linear tubular outlet end portion of the fluid flow conduit line. Therefore, conventional mass-production, high efficiency end-forming machines can be advantageously utilized to perform all of the cold working permanent deformation operations required to form the improved in-line integrated tube and check valve assembly  10  of the invention.