Abstract:
The invention provides a ball valve excelling in economy due to the efforts devoted to the reduction of cost, enjoying light weight and high reliability, manifesting high and uniform accuracy, and enabling manufacture of compact finished products having a small interface dimension, and provides a method for the production of the ball valve. The ball valve includes a body formed from a pipe having a predetermined length by subjecting opposite terminal parts (ends) of the pipe to a plastic processing including flaring and diametrical contraction. The body has at a central position a seat-shaping part (seat) formed with a stem-inserting hole, a stem inserted into the stem-inserting hole, a ball disposed non-rotatably at a lower terminal of the stem, and a pair of inserting members having an annular shape forced into the body from opposite terminals of the body. Opposite terminal faces of the body are compression-formed so that the pair of inserting members receive and support the ball rotatably.

Description:
[0001]     This application is a divisional of U.S. application Ser. No. 10/182,552, filed Jul. 30, 2002, which is a national stage application of International application No. PCT/JP01/00763, filed Feb. 2, 2001, now allowed. 
     
    
     TECHNICAL FIELD  
       [0002]     This invention relates to a ball valve that is fitted in a pipe for cold or hot water, air or gas, and used therein to start, stop or control the flow of the relevant fluid, and to a method for the production thereof.  
       BACKGROUND ART  
       [0003]     Generally, a forged or cast blank or a round bar material is cut to form a main body, and necessary internal parts are incorporated, screwed or bolted in the main body, thereby assembling ball valves of this class.  
         [0004]     These ball valves, however, are expensive because they entail high material costs on account of large numbers of man-hours, high prices of blanks, and large numbers of component parts, and require high process costs for the cutting and the assemblage. They have comparatively great weights as well. Further, since the blanks for processed parts necessitate margins for machining in advance, the costs of materials inevitably increase proportionately.  
         [0005]     To cope with these problems, the concept of forming a ball valve by resorting to the technique of press working utilizing a pipe has been proposed. (Refer to JP-A SHO 62-165081, JP-A SHO 63-266276 and JP-A HEI 10-122390.)  
         [0006]     However, since the ball valve produced by the press working technique using a pipe has a construction such that it acquires a sealing property by having a ball tightened in a valve seat part, such as a ball seat, which is an elastic member during the assembly of the ball valve, the incorporation of internal components into the pipe necessitates a step of tentative assemblage using the internal components as an integral unit.  
         [0007]     The ball valve, therefore, encounters the problem of adding a step of tentative assemblage and a step of dissolving the tentative assemblage, increasing the total number of steps of operation and boosting the cost of production.  
         [0008]     Even if the tentative assemblage of internal components should be avoided, manufacturing ball valves uniformly with high accuracy as finished products by the technique under discussion has proved extremely difficult.  
         [0009]     The screw connection is prevalently adopted generally for connecting a valve with a small diameter to a pipe. When the ball valve utilizing a pipe is joined to a pipe by the screw connection, since the construction of this ball valve requires a screw part different from the valve seat member to be welded to the terminal part of the body made of the pipe or fastened to the terminal part (expanded diametrically in advance) of the body made of the pipe, this screw connection incurs the problem of complicating the process of production of the ball valve and unduly elongating the interface dimensions of the valve.  
         [0010]     This invention which has been developed in view of the problems mentioned above is aimed at providing a ball valve excelling in economy due to the efforts devoted to the reduction of costs, enjoying light weight and high reliability, manifesting high and uniform accuracy, and enabling manufacture of compact finished products having a small interface dimension, and is aimed at providing a method for the production of the ball valve.  
       SUMMARY OF THE INVENTION  
       [0011]     To attain the above objects, the present invention provides a ball valve comprising a body formed from a pipe having a predetermined length, by subjecting opposite terminal parts of the pipe to a plastic processing including flaring and diametrical contraction. The body has at a central position a seat-producing part formed with a stem-inserting hole, a stem inserted into the stem-inserting hole, a ball disposed non-rotatably at a lower terminal part of the stem, and a pair of inserting members with an annular shape forced into the body from opposite terminals of the body. Opposite terminal faces of the body are compression-formed so that the pair of inserting members receive and support the ball rotatably. In the ball valve, the plastic processing is angular flaring work so that the body has angular opposite terminal faces, and the paired inserting members have similar angular outer peripheral faces.  
         [0012]     The present invention also provides a method for the production of a ball valve, comprising cutting a pipe in a predetermined length, subjecting opposite terminal parts of the length of the pipe to plastic processing including flaring and diametrical contraction, thereby forming a body, forming a stem-inserting hole in seat producing parts formed at an approximately central position of the body, then forcing one of a pair of annular inserting members into the body from one side thereof, joining a ball non-rotatably to a lower terminal of a stem inserted into the stem-inserting hole, forcing the other of the pair of inserting members into the body from the other side thereof, and causing the pair of inserting members to receive and support the ball rotatably, with a predetermined allowance for tightening furnished for the ball, while compression-forming opposite terminal faces of the body.  
         [0013]     The present invention further provides a ball valve having a construction comprising a predetermined length of a pipe having stem-inserting holes at an approximately central position of the pipe, stems inserted in the stem-inserting holes, a ball joined non-rotatably to lower terminals of the stems, and a pair of annular inserting members set on inner peripheries of opposite terminals of the pipe. Opposite terminal faces of the pipe are diametrically contracted or compressed to join the pair of inserting members to the pipe and cause the pair of inserting members to receive and support the ball rotatably.  
         [0014]     The present invention further provides a method for the production of a ball valve, comprising cutting a pipe in a predetermined length, forming stem-inserting holes in the pipe at an approximately central position thereof, inserting stems into the stem-inserting holes, setting a ball in a non-rotatable manner to lower terminals of the stems, setting a pair of annular inserting members to inner peripheries of opposite terminals of the pipe and causing the pair of inserting members to receive the ball from opposite sides of the pipe and rotatably support the ball, and diametrically contracting or compressing the opposite terminals of the pipe until the inserting members and the pipe are joined.  
         [0015]     The present invention further provides a method for the production of a ball valve, comprising cutting a pipe in a predetermined length, forming stem inserting holes in the pipe at an approximately central position thereof, setting an annular inserting member on an inner periphery of one of opposite terminals of the pipe, and diametrically contracting or compressing the one terminal of the pipe, thereby fixing the inserting member. Stems are then inserted into the stem-inserting holes, and a ball is non-rotatably joined to lower terminals of the stems. Thereafter, another annular inserting member is set on an inner periphery of the other terminal of the pipe, thereby causing the pair of inserting members to receive and support the ball rotatably, and the other terminal of the pipe is diametrically contracted or compressed against the other inserting member, thereby joining the other inserting member and the pipe.  
         [0016]     The present invention further provide a ball valve comprising a pipe of a predetermined length having stem-inserting holes formed therein and terminals diametrically contracted to form seal-retaining parts, a pair of seal rings (one of which is set in one of the seal-retaining parts) stems inserted into the stem-inserting holes, and a ball joined non-rotatably to a lower terminal of the stems. The ball has one side thereof colliding with the one seal ring, and the other of the seal rings is allowed to collide against the other side of the ball. An insert ring is incorporated on a rear terminal side of the other seal ring, and the other seal ring and the insert ring are retained by the other of the seal-retaining parts.  
         [0017]     The present invention further provides a method for the production of a ball valve, comprising cutting a pipe in a predetermined length, diametrically contracting terminals of the pipe, thereby forming seal-retaining parts of a tapered shape and stem-inserting holes. One of a pair of seal rings is set on one of the seal-retaining parts, then a ball is joined to a stem inserted into one of the stem-inserting holes, thereby allowing one side of the ball to collide against the one seal Subsequently, the other of the pair of seal rings is set on the other side of the ball, an insert ring is incorporated in the other seal ring on the rear terminal side thereof, and then the other of the seal-retaining parts is caused to set and retain the other seal ring and the insert ring.  
         [0018]     According to this invention, therefore, the attempt to allow the product a decreased weight can be fulfilled because the product using an inexpensive pipe as the blank for its main body has a lighter weight than the conventional cast or forged product. Since the product of this invention requires no cutting step as compared with the conventional products which require cutting steps for the sake of their main bodies, lids and various joined parts, it permits a marked decrease in the time for production and adapts itself for mass production as well. As a result, the cost of production can be greatly lowered, and a ball valve veritably excelling in economy can be produced. Further, the ball valve to be obtained by this invention enjoys inexpensiveness and has increased reliability because it uses a body of one-piece construction and has joined portions and component parts in very small numbers.  
         [0019]     The ball valve can manifest a sealing force and an operating torque stably because it is formed by expanding the diameter and contracting the diameter of a given pipe. Since insert members are forced in as pressed at the opposite terminals thereof, and the pressure welding of a ball seat to a ball is attained by uniform exertion of pressure, the ball valve to be obtained as a finished product enjoys high accuracy.  
         [0020]     Further, since various members, such as the insert members and the ball, can be inserted into the body and readied for assemblage without requiring tentative assemblage, the time for assemblage is shortened. Since the insert members are not required to be furnished with portions for securing mutual distances, the ball valve to be obtained has a decreased weight, and the insert members incorporated therein can easily assume various states of needed contact and facilitate adaptation of a product.  
         [0021]     The ball valve, despite the use of a pipe, does not need to elongate the interface dimension. Thus, the ball valve is obtained in a compact construction composed of only a small number of components.  
         [0022]     In the invention described above, the ball valve is configured by performing a burring work on a stem-inserting hole to form a tubular part and a stopper piece projecting from part of the tubular part, while forming a notched groove for regulating rotation in a flange part disposed on a stem. Thus, the stopper piece to come into working contact with the notched groove to regulate the rotation of a ball, an O-ring fitted in a fitting groove of the stem can contact the inner wall surface of the tubular part, and a stepped part can be formed on the upper edge part of the tubular part and packing can be fitted in the stepped part.  
         [0023]     Since the consequent impartation of the function of a stopper to the interior of the body contributes to attainment of compaction of the product and reduction of the cost of production and results in integrating the body with the stopper function, the ball valve produces an open-shut motion with increased accuracy and allows the handle of the valve to operate with a simple construction. Thus, the ball valve enjoys high yield of production and veritably excels in mass-producibility. Further, this invention warrants production of a ball valve that adapts to widely-varied characteristics (temperature, pressure, etc.) of a fluid and exhibits an ideal sealing property. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0024]      FIG. 1  is an explanatory diagram illustrating a method for the production of a ball valve in the first aspect of this invention.  
         [0025]      FIG. 2  is a cross section illustrating the ball valve in the first aspect of this invention.  
         [0026]      FIG. 3  is a plan view of the body shown in  FIG. 2 .  
         [0027]      FIG. 4  is a cross section illustrating another example of the ball valve in the first aspect of this invention.  
         [0028]      FIG. 5  is a plan view of  FIG. 4 .  
         [0029]      FIG. 6  is a cross section illustrating an example of providing a body with a stepped part.  
         [0030]      FIG. 7  is a front view illustrating a stem part.  
         [0031]      FIG. 8  is a bottom view of  FIG. 7 .  
         [0032]      FIG. 9  is a cross section illustrating yet another example of the ball valve in the first aspect of this invention.  
         [0033]      FIG. 10  is a plan view of  FIG. 9 .  
         [0034]      FIG. 11  is a cross section of a tube having a predetermined length, illustrating one example of a process for the production of a ball valve in the second aspect of this invention.  
         [0035]      FIG. 12  is a cross section illustrating, in a contracted diameter, the neighborhood of the central part of the pipe of  FIG. 11 .  
         [0036]      FIG. 13  is a cross section illustrating the state of the pipe of  FIG. 12  having internal parts incorporated therein.  
         [0037]      FIG. 14  is a cross section illustrating a ball valve in the second aspect of this invention.  
         [0038]      FIG. 15  is a cross section illustrating another example of the ball valve in the second aspect of this invention.  
         [0039]      FIG. 16  is a partially magnified cross section of  FIG. 14 .  
         [0040]      FIG. 17  is a partially magnified cross section of  FIG. 15 .  
         [0041]      FIG. 18  is a plan view of the body of  FIG. 14 .  
         [0042]      FIG. 19  is a cross section of the insert members of  FIG. 16 .  
         [0043]      FIG. 20  is a cross section of a pipe having a predetermined length, illustrating one example of the process for the production of a ball valve in the third aspect of this invention.  
         [0044]      FIG. 21  is a cross section illustrating one side of the pipe of  FIG. 20  in a diametrically contracted state.  
         [0045]      FIG. 22  is a cross section illustrating the pipe of  FIG. 21  in a state having internal components incorporated therein.  
         [0046]      FIG. 23  is a cross section illustrating the pipe of  FIG. 22  in a state being diametrically contracted with a jig.  
         [0047]      FIG. 24  is a magnified cross section of a seal ring in the third aspect of this invention.  
         [0048]      FIG. 25  is a magnified cross-section of an insert ring in the third aspect of this invention.  
         [0049]      FIG. 26  is a magnified cross section illustrating the seal ring in a state having the insert ring incorporated therein  
         [0050]      FIG. 27  is a partially cutaway plan view of the pipe, illustrating the relation between a stem-inserting hole and a thrust washer.  
         [0051]      FIG. 28  is a cross section illustrating the ball valve of the third aspect of this invention in a state being provided with a rotatable cap nut.  
         [0052]      FIG. 29  is a cross section illustrating the ball valve of the third aspect of this invention in a state being provided with a soldered cap nut.  
         [0053]      FIG. 30  is a cross section illustrating the pipe provided at the terminal thereof with a cap nut fitted thereto by the work of flaring.  
         [0054]      FIG. 31  is a cross section illustrating one example of providing the pipe at the terminal thereof with a joining part.  
         [0055]      FIG. 32  is a diagram illustrating another example of the body shown in  FIG. 21  in the third aspect of this invention.  
         [0056]      FIG. 33  is a partially magnified cross section illustrating another example of the construction for sealing the stem in this invention.  
         [0057]      FIG. 34  is a partially cutaway plan view illustrating another working example of the handle.  
         [0058]      FIG. 35  is a magnified cross section taken through  FIG. 34  along line A-A.  
         [0059]      FIG. 36  is a referential plan view depicting the work of forming a semi-finished product of a handle by stamping from a plate material. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0060]     This invention will be described more specifically below with reference to the accompanying drawings. For purposes of this description, the term “inner” means closer to the center of the valve with respect to a central axis of the valve body (i.e., the axis along which flow occurs), while “outer” means farther from the center of the valve.  
         [0061]      FIGS. 1 through 10  are intended to illustrate a method for the production of a ball valve as contemplated by the first aspect of this invention.  
         [0062]     In the diagrams, reference numeral  1  denotes a pipe. This pipe  1  is a thin-wall (non-thick-wall) type seamless pipe of copper alloy or stainless steel. Otherwise, it may be a seamed pipe  1  produced by shaping a steel plate in the form of a roll and then converting the roll into a cylinder by joining the opposed edges of the roll as by welding. A body  2  of a ball valve is formed by cutting a predetermined length of this pipe  1 , namely the length of a prospective valve box of a ball valve, deburring the opposite ends of the length of the pipe severed by cutting, and then subjecting the opposite parts of the pipe  1  to the work of flaring. The flaring work in this case consists of plastic processing an angular (hexagonal, for example) forcing retaining part  3  that assumes a radial plane. Further, the central position of the body  2  is constricted or beaten to form a flat seat-shaping part  4 , and a stem-inserting hole  5  is formed in the internal region of the seat-shaping part  4 .  
         [0063]     With reference to  FIG. 2 , reference numeral  12  denotes a ball furnished with a through hole  12   a . This ball  12  has a stem fitting face  14  formed at the position for setting a stem  15 . By joining a non-circular projecting part  16  formed at the lower terminal of the stem  15  to the stem fitting face  14 , the ball  12  and the stem  15  can be joined in a non-rotary state (i.e., those parts do not rotate with respect to each other). A flange part  17  formed in the lower part of the stem  15  prevents the stem  15  from being flung out by the pressure of a fluid.  
         [0064]     Reference numeral  22  denotes a handle. This handle  22  is fixed in a non-rotary state to the stem  15  and clamped fast with a nut  25  through a spring washer  24  and a washer  23  disposed respectively in the upper and the lower part of the handle  22 .  
         [0065]     Numerals  6 ,  6  denote an example of a pair of annular insert members. These insert members  6  are symmetrically incorporated bilaterally relative to the ball  12 . The insert members  6  each retain on the inner peripheral side of the leading terminal part thereof a seat ring  9  endowed with a sealing property. Due to a sealing member (O ring)  10  made of resin and set on the outer periphery of insert member  6 , each insert member can perform the function of a gasket against the inner peripheral face of the body  2 .  
         [0066]     The insert members  6  are each formed either by rolling a thick-wall pipe or a thick-wall plate, then joining the opposed edges of the roll as by welding, thereby giving rise to a metallic tube, and cutting the tube by rolling or press working or by drawing a thick-wall plate material into the shape shown in the diagram by the press working. Otherwise, they may be formed by precision casting, such as the lost-wax process, or by sintering a metallic powder.  
         [0067]     Further, the insert members  6  contemplated by this invention possess such a thickness as to manifest fully satisfactory strength during the course of joining, and also possess fully satisfactory strength to withstand the force exerted during the forced insertion into the pipe  1 . That is, the ball valve of this invention is directed toward allocating functions, decreasing weight and compacting construction by adopting a configuration which derives the strength necessary for a pressure vessel mainly from the body  2  formed of a thin-wall pipe  1  and the strength to withstand the impact of joining pipes or of effecting the forced insertion into the pipe  1  or the strength necessary for maintaining the bearing stress between the ball  12  and the seat ring  9  mainly from the insert member  6  which is a thick-wall part. The insert members  6 ,  6  are each furnished at the terminal end thereof on the opposite side relative to the ball  12  with a tapered part  7  disposed at a suitable angle along the respective angularly shaped outer peripheral faces  8 ,  8 . These insert members  6  may be endowed with a suitable form of union, such as a female thread  6   a  that is used in the present case. Thus, the body  2  may have suitably incorporated therein a portion for union, such as a female thread, without requiring an alteration in the length of the body  2  which Is formed of a predetermined length of the pipe  1 .  
         [0068]      FIG. 3  is intended to illustrate an example of providing the body in the interior thereof with a stopper mechanism for a handle. With reference to this diagram, burring work is performed on the stem-inserting hole  5  to form a tubular part  11  of a small length and a stopper piece  13  integrally projecting from part of this tubular part  11 . Meanwhile, a notched groove  19  for regulating rotation is formed in the flange part  17  provided for the stem  15  as illustrated in  FIG. 8 , and the ball  12  is disposed so as to have the rotation thereof regulated to an angle of about 90 degrees by a stopper mechanism formed by meshing the stopper piece  13  and the notched groove  19 . Then, by allowing an O-ring  18  inserted in a fitting groove  15   a  of the stem  15  to contact the inner peripheral face of the tubular part  11  as illustrated in  FIG. 2 , the ball valve can be infallibly sealed with a compact structure. Further, by forming a stepped part  20  on the upper edge part of the tubular part  11  and fitting a washer  23 , a gland  43  and gland packing  42  at the stepped part  20  as illustrated in  FIG. 6 , the stem  15  can retain the sealing property and increase the torque performance of torque. In this case, the operating torque of the handle may be relied on to disperse the force exerted on the stopper mechanism and prevent the stopper mechanism from being deformed by providing the flange part  17  with two notched grooves  19  indicated with a chain line, and meshing these notched grooves  19  and the two stopper pieces  13  as illustrated in  FIG. 8 .  
         [0069]     Now, one example of the method for producing the ball valve in this invention will be described specifically below with reference to the drawings.  
         [0070]     With reference to  FIG. 1 , the body  2  furnished with the forcing retaining part  3  of an approximately hexagonal shape is formed by cutting the pipe  1  in a predetermined length and subjecting the opposite parts of the pipe  1  to plastic processing resorting to the work of flaring.  
         [0071]     The process of seat shaping and perforation is carried out by drawing the approximately central position of the body  2 , thereby forming the seat-shaping part  4  and perforating the seat-shaping part  4 , thereby forming the stem-inserting hole  5 . Subsequently, burring work is performed on the stem-inserting hole  5  Due to this burring work, the tubular part  11  and the stopper piece  13  produced by projecting part of the tubular part  11  are formed.  
         [0072]     Then, one of the pair of annular inserting members  6  similar in shape to the forcing retaining part  3  is forced into the body  2  through one side thereof, and thereafter the ball  12  is non-rotatably joined to the lower terminal end of the stem  15  inserted in the stem-inserting hole  5  as illustrated in the same diagram. In this case, the notched groove  19  for regulating rotation to an approximate angle of 90 degrees is formed in the flange part  17  provided for the stem  15 , and the stopper piece  13  is meshed with the notched groove  19  and incorporated in such a manner in the body as to regulate the rotation of the ball  12 . Further, the other inserting member  6  is forced in through the forcing retaining part  3  on the other side of the body  2 . Thereafter, the ball valve is produced by causing the seat rings  9  of the pair of inserting members  6 ,  6  to support the ball  12  rotatably with a predetermined tightening margin allowed for the ball  12  and, meanwhile, simultaneously beating the terminal face parts (diametrically contracted parts)  26  on both sides of the body  2  with jigs  47 , thereby compression-forming the terminal face parts along the contour of the tapered part  7  of the inserting member  6 . Thus, the ball  12  is supported on the seat rings  9  so as to retain the sealing property and the property of torque as predetermined.  
         [0073]     The ball valve using the body  2  of such a straight type as illustrated in  FIG. 2  and  FIG. 4  is produced through the process described above. In the process involving a flaring step as illustrated in  FIG. 9 , the body  2  is formed in the shape illustrated in  FIG. 9  by first circularly flaring the opposite side parts of the pipe  1  and then flaring them in a hexagonal shape. The rest of this process is identical with the preceding process.  
         [0074]     In the embodiment of the ball valve of this invention, since the construction of the ball valve varies with the bore size (ball port diameter), it is proper to apply the construction illustrated in  FIG. 2  to the ball valve of a full port type and the construction illustrated in  FIG. 4  to the ball valve of a reduced port type.  
         [0075]      FIGS. 11 through 19  depict a method for producing a ball valve contemplated in the second aspect of this invention.  
         [0076]     Like parts used in the ball valve and the method for production thereof in the present aspect of this invention and in the preceding aspect of the invention will be denoted by like reference numerals and will be omitted from the following description.  
         [0077]     In  FIG. 12 , is a seal retaining part  3   a  is formed in a tapered shape in the pipe  2  at an approximately central position thereof by plastic processing such as swaging or press working. The seat-producing parts  4  are formed in a planar shape as by drawing one each on the outside and inside of the pipe  1  at a position close to the seal-retaining parts  3   a , and the stem-inserting hole  5  is formed as well in the area inside the seat-producing part  4 .  
         [0078]     Now, the ball valve and the method for production thereof contemplated by the second aspect of this invention will be described below.  
         [0079]     First, the pipe  1  is cut to obtain a length thereof needed to form the body  2  of ball valve as illustrated in  FIG. 11 . Then, the pipe  1  is diametrically contracted in the neighborhood of the central part thereof as illustrated in  FIG. 12  to form the seal-retaining parts  3   a ,  3   a  having a tapered shape. The seat-producing parts  4  having a planar shape are formed in the central part of the pipe  1  at positions close to the seal-retaining parts  3   a ,  3   a , and the stem-inserting hole  5  in a circular shape is formed by punching in the area inside the seat-producing part  4 .  
         [0080]     Then, the stem  15  is inserted into the stem-inserting hole  5  from the inner side of the body  2  and, at the same time, the ball  12  is inserted into the pipe  1  from either of the sides thereof, with the stem-inserting face  14  held in the direction parallel to the flow path so as to retain the projecting part  16  of the stem  15  as joined in a non-rotary state to the stem-inserting face  14 .  
         [0081]     The seat rings  9 ,  9  and the sealing members (O-rings)  10 ,  10  are respectively fitted in the insert members  6 ,  6  as illustrated in  FIG. 14 . The insert members  6 ,  6  are inserted into the pipe  1  from the opposite terminal ends thereof until the seat rings  9  which are the leading terminal parts of the inserting members  6  receive and support the ball  12  rotatably from opposite sides The sealing members  10  are incorporated in such a state as to contact the seal-retaining parts  3   a  closely to complete a seal.  
         [0082]     Subsequently, outer seal-retaining parts  3   b ,  3   b  are formed in a tapered shape by diametrically contracting or compressing the pipe  1  by swaging or press working so as to substantially align the through hole  9   a  of the seat ring  9  with the through hole  12   a  of the ball  12  and so that the inserting members  6 ,  6  and the pipe  1  are joined.  
         [0083]     Since the seal-retaining parts  3   b  are formed closely along the contour of the tapered parts  7  of the inserting members  6 , they exert a wedging effect on the inserting members  6 ,  6  and move the inserting members  6 ,  6  slightly toward the bail  12 , with the result that the pair of seat rings  9 ,  9  are accurately positioned because their mutual distance is adjusted to the predetermined magnitude. When the sealing members  10 ,  10  are made to depress the inner seal-retaining parts  3   a ,  3   a , the inserting members  6  are aligned more accurately because the wedging effect of the tapered shape of the inner seal-retaining members  3   a ,  3   a  exerts a force in the axial direction on the inserting members  6 .  
         [0084]     It would be advantageous to perform the work of diametrical contraction or compression on the entire periphery of the outer seal-retaining parts  3   b  along the contour of the tapered parts  7  thereof. So long as each outer seal-retaining part  3   b  is disposed at least at one place along the contour of the tapered parts  7 , the sealing property between the inserting members  6  and the body  2  can be retained because the sealing members  10 ,  10  are moved toward the ball  12  and brought into contact with the inner seal-retaining parts  3   a ,  3   a . The process described above is preferably automated with proper means, such as jigs. Further, the tapered parts  7  of the body  2 , while the valve is in use, fulfill the function of preventing the inserting members  6  from being extracted out of the valve by the inner pressure.  
         [0085]     The diametrical contraction can be effected by drawing up to a plurality of repetitions until the diameter is contracted to the predetermined magnitude. Since the division of the work into the plurality of parts manifests a function of increasing the strength of the part subjected to the diametrical contraction, it is effective in increasing the strength of the ball valve and enabling the inserting members  6 ,  6  to be positioned more accurately. The quantity of the diametrical contraction and the number of forming processes involved in this case may be properly decided liberally to suit the relevant operation to be performed.  
         [0086]      FIG. 15  is a cross section illustrating another example of a method for production of the ball valve contemplated by the second aspect of the invention. Like parts used in the present aspect of this invention and in the preceding aspect of the invention will be denoted by like reference numerals and will be omitted from the following description.  
         [0087]     In the present example, the production is effected by a procedure which comprises preparing the pipe  1  by cutting the pipe to a predetermined length, forming the stem-inserting hole  5  in the approximately central position of the pipe  1 , fitting an inserting member  6  having an annular shape in the inner periphery on one side of the pipe  1 , diametrically contracting or compressing the pipe  1  until the inserting member is fixed to the pipe  1 , and then inserting the stem  15  into the stem-inserting hole  5  and joining the ball  12  in a non-rotary state to the lower terminal of the stem  15  as well.  
         [0088]     The procedure further comprises fitting a second inserting member  6  of an annular shape to the inner periphery on the other side of the pipe  1 , causing the pair of inserting members  6 ,  6  to receive and rotatably support the ball  12 , and further diametrically contracting or compressing the pipe  1  toward the inserting member  6  inserted into the interior of the pipe  1  on the other side until the inserting members  6  and the pipe  1  are joined. During the course of the diametrical contraction or compression, the diametrically contracted parts  26  formed by diametrically contracting the pipe  1  are meshed with depressed parts  26   a  disposed at proper positions along the outer periphery of the inserting members  6 ,  6  to fix the inserting members  6 ,  6  to the pipe  1  to prevent them from rotating.  
         [0089]     The depressed parts  26   a  are each in the form of a notched depression having a slope  26   b  of a proper angle on the tube-connecting part (outer) side of the inserting member  6 , and a substantially vertical wall on the ball  12  side as illustrated in  FIG. 17 .  
         [0090]     By diametrically contracting or compressing the neighborhood of either of the terminal parts of the pipe  1  and then similarly diametrically contracting or compressing the neighborhood of the other terminal part, it is possible to move the inserting members  6 ,  6  by the wedging effect toward the ball  12  and bring the seat rings  9  as aligned axially into tight contact with the ball  12 .  
         [0091]     In the embodiment of the ball valve of this invention, the ball valve is varied in construction with the bore size (ball port diameter) thereof. It is advantageous to adopt the construction illustrated in  FIG. 15  for the ball valve of a full port type as in the present example, and adopt the construction illustrated in  FIG. 14  for the ball valve of a reduced port type.  
         [0092]     In either of the first and second aspects of this invention, by providing the inserting members  6 ,  6  to be inserted each at the opposite terminal portions thereof with mutually parallel external flat parts  6   b  formed in an approximately hexagonal shape as illustrated in  FIG. 19 , or with mutually parallel external flat portions formed at places of an even number of not less than two prior to the diametrical contraction or compression of the outer periphery of the body  2 , it is made possible to form mutually parallel handle parts  2   a  in the neighborhood of the opposite terminals of the body  2  as illustrated in  FIG. 3  and  FIG. 18  and enable the handle parts  2   a  to be fixed with a fixing jig, such as a wrench, and utilized for performing the tube fitting.  
         [0093]      FIGS. 20 through 32  depict the ball valves and the methods for production thereof as contemplated by a third aspect of this invention.  
         [0094]     In  FIG. 21 , a seal-retaining part  3   a  having a tapered shape is formed by diametrically contracting one of the opposite terminal parts (ends) of the pipe  2  by plastic processing, such as swaging or press working. The seat-shaping parts  4  having a planar shape are formed one each on the inside and the outside of the pipe  1  as by drawing at the close to the seal-retaining parts  3   a  and stopping the diametrical contraction, and the stem-inserting hole  5  is formed in the area inside the seat-producing parts  4 .  
         [0095]     In  FIG. 24 , an annular seal ring made of resin is intended to fulfill simultaneously the functions of a seat ring and a gasket of the body  2 . The ball valve uses a pair of such seal rings  27  and they manifest the function of a gasket for closely sealing the angular parts on the inner periphery side with a sealing part  27   a  of the ball face and an outer periphery side  27   b  with the inner peripheral surface of the seal-retaining part  3   a  of the body  2 .  
         [0096]     In  FIG. 25 , reference numeral  28  denotes an insert ring formed of metal in an annular shape. This insert ring  28  has formed on the outer peripheral surface thereof a tapered part  28   a  and a straight part  28   b . This tapered part  28   a , due to the wedge effect generated during the diametrical contraction of the pipe  1 , increases the accuracy of positioning of the seal ring  27  relative to the ball  12 .  
         [0097]     Then, the straight part  28   b  is endowed with the function of preventing the pipe  1  and the seal ring  27  from being deformed under the load of drawing during the diametrical contraction of the pipe  1 . In this case, when the tapered part  28   a  of the insert ring  28  is fitted into a fitting part  27   c  formed in a conical cross section on the rear terminal face of the seal ring  27 . At the same time, the insert ring  28  is aligned by fitting a projecting part  28   c  of the insert ring  28  to a stepped part  27   d  of the seal ring  27  as illustrated in  FIG. 26 , the seal ring  27  follows such motions until the seal ring  27  is incorporated in a concentric state in the ball valve.  
         [0098]     A thrust washer  18   a  is interposed between the flange part  17  and the seat-shaping part  4  both formed at the lower part of the stem  15 . The diameter of this thrust washer  18   a  is set at the magnitude D that has an allowance in advance for the elliptic strain due to the diametrical contraction of the pipe  1  (d+Δd) (D&gt;d+Δd) as illustrated in  FIG. 27 . This diameter is large enough to avoid hindering the smooth motion of the stem.  
         [0099]     With reference to  FIG. 23 , a first jig  29   a  is made to support the side of the seal-retaining part  3   a  formed at one of the terminal parts of the pipe  1 , a second jig  29   b  is made to support the seal ring  27 , and forming jigs  30   a ,  30   b  are disposed on the other terminal part side (end) of the pipe  1 . With the first forming jig  30   a  pressing in the direction of the arrow, the pipe  1  is diametrically contracted by plastic processing, such as swaging or press working, and a seal-retaining part  3   c  is formed in a tapered shape. In this case, by pressing the forming jig  30   a  across a distance L, it is made possible to adjust the mutual distance of (distance between) the pair of seal rings  27 ,  27  to a predetermined magnitude and position the seal rings accurately.  
         [0100]     With reference to  FIG. 28  and  FIG. 29 , reference numeral  22  denotes the handle. This handle  22  is attached in a non-rotary state to the stem  15  and is provided with a stopper adapted to stop the handle rotation at angular intervals of about 90 degrees, and is fixed by tightening with the nut  25  through the spring washer  24  and a washer  23  which are disposed respectively on and beneath the handle  22 .  
         [0101]     As another example, the provision of a stopper mechanism similar to the preceding aspects of the invention is conceivable. To be specific, the stem-inserting hole  5  is subjected to burring work to form the tubular part  11  having a short length and a stopper piece  13  projecting integrally from part of the tubular part  11  as illustrated in  FIG. 32 . Meanwhile, the notched groove  19  for regulating rotation is formed in the flange part  17  and, due to the stopper mechanism obtained by meshing the stopper piece  13  with the notched groove  19 , the ball  12  is disposed so as to have the rotation thereof regulated at an angle of about 90 degrees. Further, by setting the washer  23 , a gland  43  and gland packing  42  in the upper edge part of the tubular part  11  as illustrated in  FIG. 6 , the stem  15  can retain the sealing property and enjoy an improvement in the property of torque.  
         [0102]      FIGS. 28 through 31  depict varying examples of the joining parts which are formed at the opposite terminal parts of the ball valve contemplated by the third aspect of this invention.  
         [0103]      FIG. 28  illustrates a construction produced by forming flared parts  31  one each at the opposite terminal parts (ends) of the pipe  1 , causing the leading (inner) terminal projecting parts  32   a  of cap nuts  32 ,  32  to abut the flared parts  31 , and slanting the leading terminal projecting parts  32   a  of the cap nuts  32 ,  32  as by roller pressing until these parts closely contact the flared parts  31 .  
         [0104]      FIG. 29  illustrates a construction produced by inserting the cap nuts  33  into the opposite terminal parts (ends) of the pipe  1  and joining them by welding  33   a , such as soldering.  FIG. 30  illustrates an example of the construction produced by having the cap nuts  34  incorporated in advance in the opposite terminals of the pipe  1 , then flaring the opposite terminal parts of the pipe  1  to form diametrically expanded parts  35 , and allowing the cap nuts  34  to be disposed rotatably at the positions of union as illustrated in the diagram.  
         [0105]      FIG. 31  illustrates a construction produced by flaring the opposite terminal parts of the pipe  1  at an approximately right angle to form engaging parts  36 , and joining fitting parts  37   a  of adjoining members  37  and the engaging parts  36  with special clamps  38 .  
         [0106]     Now, one example of the method for production of the ball valve contemplated by the third aspect of this invention will be described.  
         [0107]     For a start, the pipe  1  is cut in a length for forming the body  2  of the ball valve as illustrated in  FIG. 20 . Then, the seal-retaining part  3   a  is formed in a tapered shape by diametrically contracting one of the terminal parts (ends) of the pipe  1 , the seat-shaping part (i.e., seat)  4  having a planar shape is formed in the central part of the pipe  1  at a position close to the seal-retaining part  3   a , and the stem-inserting hole  5  is formed in a circular shape by performing a punching work in the area inside the seat-producing part  4  as illustrated in  FIG. 21 .  
         [0108]     Thereafter, the seal rings  27  are inserted into the pipe  1  and set at the positions of the seal retaining parts  3   a . In this case, the seal rings  27  manifest the function of a gasket to the body  2  by having the outer (external) peripheral surface  27   b  thereof tightly seal the inner (internal) peripheral surfaces of the seal-retaining parts  3   a.    
         [0109]     The stems are inserted into the stem-inserting hole  5  from the inside of the body  2  with the thrust washers  18   a  retained on the flange parts  17  of the stems  15  and, at the same time, the ball  12  is inserted in the direction making the stem-fitting surfaces  14  thereof parallel with the flow path into the pipe  1  from the side thereof not yet diametrically contracted until the projecting parts  16  of the stems  15  are connected in a non-rotary state to the stem-fitting surfaces  14 . Then, the ball  12  will collide against the seal rings  27  in a slightly resilient state. In this case, the seal rings  6  simultaneously fulfill the functions of a seat ring and a gasket and contribute to the reduction of the number of component parts of the ball valve.  
         [0110]     Then, the other of the pair of seal rings  27  is inserted into the pipe  1  from the side thereof not yet diametrically contracted (second side) and, at the same time, the insert ring  28  is inserted into the pipe  1  until the tapered parts  28   a  of the insert rings  28  are meshed with the fitting parts  27   c  of the seal rings  27  as illustrated in  FIG. 23 . The various steps of the process described above are preferably properly automated to suit the particular construction.  
         [0111]     Thereafter, the forming jigs  30   a  and  30   b  are set on the other terminal part side of the pipe  1 , with the jig  29   a  supporting the seal-retaining part  3   a  formed in the first opposite terminal part of the pipe  1  and the jig  29   b  supporting the seal ring  27  as illustrated in  FIG. 23 . The forming jig  30   b  fulfills the function of supporting the rear (outer) end of the insert ring  28  and, at the same time, inserting the jig leading end into through hole  28   d  of the insert ring  28 , through holes  27   e  of the seal ring  27 , and through holes  12   a  of the ball  12  so as to align and support the relevant members.  
         [0112]     Then, with the forming jig  30   a  pressing in the direction of the arrow, the pipe  1  is subjected to plastic processing, such as swaging or press working, to be diametrically contracted and, at the same time, the seal-retaining part  3   c  of a tapered shape is formed. In this case, by pressing the forming jig  30   a  across a distance L, it is possible to move the insert ring  3   a  and the seal ring  27  slightly toward the ball  12  due to the wedging effect generated during the formation of the seal-retaining parts  3   c  having a tapered shape, and to adjust the mutual distance of (distance between) the pair of seal rings  27 ,  27  to a predetermined magnitude and position the seal rings accurately.  
         [0113]     The diametrical contraction involved at varying steps mentioned above may be effected by drawing up to a plurality of repetitions until the diameter is contracted to the predetermined magnitude. Since the division of the work into the plurality of parts manifests a function of increasing the strength of the part subjected to the diametrical contraction, it is effective in increasing the strength of the ball valve and enabling the parts of the seal rings  27  and the insert rings  28  to be positioned more accurately. The quantity of the diametrical contraction and the number of forming processes involved in this case may be properly decided liberally to suit the relevant operation to be performed.  
         [0114]      FIG. 32  depicts another example of the body  2  shown in  FIG. 21 . It represents the case of burring the stem-inserting hole  5  illustrated in the first and the second aspect of this invention to form a stopper mechanism for the stem (handle) inside the body. The other component parts of the present construction are similar to those of the preceding example.  
         [0115]     One example of the ball valve contemplated by yet another aspect of this invention will be described below. The present example can be applied to other aspects than the first through third aspects of the invention. Like parts will be denoted by like reference numerals and omitted from the following description.  
         [0116]     In  FIG. 33 , reference numeral  1  denotes a pipe. This pipe  1  is a pipe of a thin-wall type made of copper alloy or stainless steel. Alternatively, the pipe  1  may be produced by shaping a steel plate in the form of a roll and then joining the opposed ends of the roll by such means as welding, thereby imparting a cylindrical form thereto. This pipe  1  is cut in a predetermined length, namely the length for forming a valve box of a prospective ball valve, the opposite terminals of the length of the pipe  1  are burred, and subsequently plastic processing is performed on the opposite terminal parts of the pipe  1  to form the body  2  of the ball valve. A retaining vessel  39  furnished with an angular through hole  39   a  for non-rotatably receiving the stem  15  and a retaining ring  40  are formed of a thin plate material by plastic processing, casting, hot forging or injection molding. Then, the flange part  17  of the stem  15  to be inserted into the stem-inserting hole  5  of the body  2  is placed in the retaining receptacle  39 , a thrust washer  41  is formed in the retaining vessel  39  on the upper side of the flange part  17 , and this thrust washer  41  is interposed between the rear side of the seat-shaping part (seat)  4  of the body  2  and the flange part  17  as illustrated in the diagram. Meanwhile, the gland packing  42  inserted into the retaining ring  40  is positioned on the upper side of the seat-shaping part  4  and set in the stem  15 , and the nut  25  is helically fitted to the stem  15  and then fixed by tightening through the gland  43  and the washer  23 .  
         [0117]     The construction thus obtained provides such advantages as preventing the thrust washer  41  and the gland packing  42  from being deformed or fractured while in service, increasing the sealing effects thereof, and enabling them to withstand protracted use without being affected by the characteristic properties (temperature and pressure) of a fluid.  
         [0118]      FIG. 34  depicts another example of the handle that can be applied to the various aspects of this invention even when the body is not provided therein with a stopper mechanism for the handle. This handle is produced by deriving an intermediate portion  45   a  for a handle  45  from a plate material  44  by punching and forming a stopper projecting piece  46  in the intermediate portion  45   a  by plastic processing.  
         [0119]     This handle enjoys a great practical value because it yields no waste material, manifests an effect of allowing mass production and contributes to the reduction of cost.  
       INDUSTRIAL APPLICABILITY  
       [0120]     The ball valve and the method for production thereof contemplated by this invention as described above are suitable for such a ball valve as is set in piping for cold or hot water, air or gas, and is operated to open or shut or control the flow of the fluid. Since the ball valve of this invention weighs less than the conventional counterparts made by casting, it realizes a reduction in weight of the product and permits a great cut in the time spent for the production and allows quantity production of ball valves. As a result, the method of production of this invention permits a great decrease in the cost of production and allows provision of ball valves highly excelling in economy. Though this invention is directed toward the ball valve and the method for production thereof, it may be suitably applied to the formation of bodies for valves, such as butterfly valves.