CN1326387A - Apparatus and method for forming pipe with increased wall-thickness at its end - Google Patents

Abstract

Apparatus for and method of extruding a metal pipe having a uniform inner diameter, and forward and rearward end sections (62, 66) which are thicker than the middle section (64) of the pipe. A metal billet (54) having a bore (56) is inserted into an open ended cylindrical bore of a stationary contain er (12). The billet (54) is moved axially within the bore of the container (12) by a press (13) which includes a pressing surface (38, 39) and a mandrel (44 ) extending forwardly from the pressing surface through the bore of toward the billet (54). The mandrel (44) has a cylindrical large diameter rearward portion (48), a cylindrical small diameter middle portion (50) and a forward ly and outwardly tapering forward portion (52). Metal from the billet (54) is forced through the small diameter bore of a two part removable first die (20 ) around the middle portion (50) of the mandrel (44) by moving the press forwardly for a first distance to form a preliminary forward end section (62 ) of pipe. The press is moved forwardly for a second distance for forcing meta l from the billet through the bore of the first die (51) around the rearward portion (48) of the mandrel for extruding the middle section (64) of pipe an d causing the preliminary forward end section (62) of pipe to pass over the tapered forwardportion (52) of the mandrel to form the forward end section (62) of pipe. The press is moved forwardly for a third distance for forcing metal from the billet through the relatively large bore of a second die (53) around the rearward portion (48) of the mandrel to form the rearward end section (66) of pipe.

Description

The equipment and the method that are used for the pipe of shaped ends wall thickness increasing

The present invention relates to the manufacturing of pipe, particularly be molded over the fluid delivery tube of commercial being called " both-end extra strong pipe ".This pipe has a forward end or " pin " shape end, behind the mid portion of a lengthening and one to end or " case " shape end.The internal diameter of three parts of all of this pipe is identical.The forward direction of pipe, back to the external diameter of end obviously greater than the external diameter of the mid portion of pipe.Therefore, the thickness of the mid portion of pipe obviously be thinner than pipe forward end or the back to the end.

The present invention relates to a kind of equipment that is used for that moulding is commercial and is known as the fluid delivery tube of " both-end extra strong pipe ".This pipe has a forward end or " pin " shape end, behind the mid portion of a lengthening and one to end or " case " shape end.The internal diameter of three parts of all of pipe is identical.The forward direction of pipe, back to the external diameter of end obviously greater than the external diameter of the mid portion of pipe.Therefore, the thickness of the mid portion of pipe be thinner than significantly pipe forward end or the back to the end.The forward direction of pipe, back process through machined and/or screw thread to the extra thickness of end, so that the forward end of first pipe or " pin " shape end can be connected to end or " case " shape end with the back of second pipe.

In the past, the both-end extra strong pipe of metal is by the mid portion of extruded tube respectively and end and forward direction, back is welded to the end on the opposite end of mid portion and makes.Because the weakness zone of potential pipe is being represented in the weld zone, thereby makes the each several part of pipe thicker than its common required thickness.This process is not only lost time but also very expensive.For realizing that the required extra material of extra thickness has also increased the material cost of pipe.The weight of the increase of pipe has also further increased the cost in the transportation and handling procedure.

Many metal extrusion equipment and methods that are used to utilize a press, mould and plug blank to be squeezed into pipe have been developed.Yet, do not have known being used to push as yet to have homogeneous internal diameter and two opposed end to have the equipment or the system of the integral tube of the external diameter bigger than the intermediate portion.These and other difficulty that is run in the pipe extrusion equipment of prior art or method is overcome by the present invention.

Therefore, main purpose of the present invention provides a kind of equipment that is used for metal stock is squeezed into pipe, a kind ofly has constant or the integrally formed pipe with less external diameter is compared in homogeneous internal diameter and intermediate portion with one of two opposed end in order to produce.

Further purpose of the present invention provides a kind of equipment that is used for as described above metal stock being squeezed at single continuous extrusion operation pipe.

Another object of the present invention provides and a kind of metal stock is squeezed into the method for pipe, and the external diameter that wherein said pipe has uniform internal diameter and intermediate portion is littler than the external diameter of two opposed ends of pipe.

A further object of the present invention provides a kind of method that as described above metal stock is squeezed into pipe in a single continuous process.

Another purpose of the present invention provides a kind of uneven plug of external configuration that is used in the metal extrusion press, and described metal extrusion press is used for metal stock is squeezed into a kind of external diameter pipe littler than the external diameter of two opposed ends with homogeneous internal diameter and intermediate portion.

Another object of the present invention provides a kind of equipment that is used for metal stock is squeezed into pipe, wherein the external diameter of the mid portion of pipe is littler than each the external diameter in two opposed ends of pipe, and the internal diameter of an end of pipe is littler than the internal diameter of the mid portion of pipe and opposed end.

Consider the purpose of these and other, those skilled in the art will be clear that, the present invention lies in the relative section of specification and by its accompanying claims and covers.

The present invention has substantially the equipment and the method for the metal tube of internal diameter uniformly about being used to squeeze out.The forward direction of described metal tube, back thicker than the mid portion of pipe to the end.Heating of metal blank with a cylindrical vertical hole is inserted in the after-opening of cylindrical hole of a fixed container.Movably split internal mold for one and be arranged in the hole of container and adjacent, and external mold is positioned at the outside of container and adjacent with the front end of container with the forward end of container.Internal mold has the less relatively cylindrical hole in footpath always.External mold has the relatively large cylindrical hole in footpath always.Blank by a press in the hole of container longitudinally central axis move, described press comprises forward direction pressed surface and plug that stretches to blank from this pressed surface forward of a circle.This plug has relatively large back to part of columniform diameter, the mid portion that columniform diameter is less relatively and edge direction forward the outward-dipping conical butt forward direction part of diameter from the diameter of centre part to the forward direction part.By making press move forward one first distance, force metal on the blank round the small diameter portion of plug hole, so that squeeze out the initial forward end of pipe by internal mold.Make this press move forward a second distance, after the major diameter of plug, pass the hole of internal mold to part to force the metal on the blank, so as the initial forward end that squeezes out the mid portion of pipe and make pipe through the inclination of plug to forward part.This makes the initial forward end of pipe laterally be expanded to the degree that internal diameter equals the internal diameter of mid portion along its longitudinal center's axis, and wall thickness is expanded to the degree greater than the wall thickness of the mid portion of pipe.Internal mold is pulled down from container, and make press move forward one the 3rd distance, in order to forcing metal back round plug from the blank, so that squeeze out the identical and wall thickness of the mid portion of internal diameter and pipe back greater than the pipe of the mid portion of pipe to the end to the hole of partly passing external mold.

Yet feature of the present invention can be by with reference to being understood the explanation of one of as shown in the drawing its version, among the figure best:

Fig. 1 is the longitudinal sectional view of main function components that is used to form the extrusion equipment of the present invention of both-end extra strong pipe;

Fig. 2 is the side view of the mandrel segment of described equipment;

Fig. 3 is the same end-view of splitting mould that forms the part of described equipment;

Fig. 4～12nd illustrates the view of the forming operation process of the forward end of pipe and mid portion;

Figure 13～18th, the view of the back forming operation process to the end that pipe is described;

Figure 19 a, 19b, 19c and 19d are vertical sectional view expression whole extrusion equipment of the present invention, that can link together along common line A-A, B-B and C-C; And

Figure 20 is a view similar with Figure 10, an improved plug of expression.

At first referring to Figure 19 a, 19b, 19c and 19d, pipe extrusion equipment of the present invention is denoted as 10 generally.Equipment 10 comprises after one to a support 72 and a forward direction support 70 that links to each other to support by four connecting rods 74 and back.Its press that totally is denoted as label 13 is installed on the pipe extrusion equipment 10, between support 70 and 72, so that longitudinally central axis 18 vertically moves.

Press 13 comprises a crosshead 78 between support 70 and 72.A piston 75 is connected on the rear side of crosshead 78 by a horizontal connector 79.Piston 75 is slidably mounted in the single action hydraulic cylinder 77, and this hydraulic cylinder 77 is fixed to the back on support 72.Hydraulic cylinder 77 is connected on the unshowned high pressure liquid potential source by underground 73.Crosshead 78 is supported on a pair of cannelure 81 and is subjected to connecting the guiding of track 74, so that longitudinally axis 18 vertically moves forward and backwardly.Crosshead 78 has a lateral aperture 65 coaxial with longitudinal axis 18.Two hydrodynamic cylinder pressures 81 are fixed on the hydraulic cylinder 77 by a structural support 82.Its piston that is totally marked by label 85 comprises that one is slidably mounted in piston head 89 in the hydraulic cylinder 81 and one and extends out and be fixed to piston rod 93 on the upper end of crosshead 78 from hydraulic cylinder 81.Hydraulic cylinder 81 is connected on the unshowned high pressure liquid potential source by underground 76.The action of hydraulic cylinder 77 makes piston 75 and crosshead 78 move forward towards support 70.The relatively large size of hydraulic cylinder 77 provides at the forward end place of extruder and has forced blank to pass through the required bigger power of mould structure that will describe.Make crosshead 78 and piston 75 move backward to their original position by activating hydraulic cylinder 81, thereby piston head 89 is moved in hydraulic cylinder 81 backward.Press 13 also comprises a cylindrical housings or bar portion 36, this bar portion 36 be fixed on the front side of crosshead 78 and longitudinally axis 18 extend forward.Two hydrodynamic cylinder pressures 69 are fixed on the rear side of crosshead 78 and by underground 68 and are connected on the high pressure liquid potential source.

Bar portion 36 has a chamber 40 and a forward end 47, this forward end comprise one lead to chamber 40 to open front 49.Modular ring 38 be arranged in housing 36 to open front 49 and comprise the forward direction pressed surface 39 of a cylindrical hole 42 and a circle.Plug 44 is arranged in chamber 40 and has its shape and is made into can combine with the forward end of drive rod 46 back to end 45.A lining 59 is fixed on the forward end of drive rod 46 with bar portion 36 with having certain fit clearance.This helps support drive bar 46 and makes plug 44 keep centering.The back of drive rod 46 is connected with a piston 71 that is slidably mounted in the hydraulic cylinder 69 to the end.Hydraulic cylinder 69 can make plug 44 selectively longitudinally axis 18 with respect to bar portion 36 forward, backward the motion.Plug 44 is coaxial with longitudinal center axis 18.Plug 44 has a columniform back and divides 50 and mid portions 50 that reduce from diameter to the outward-dipping conical butt forward direction part 52 of the forward end of plug to the cylindrical midsection that 48, one diameters of part reduce.The forward end of plug 44 have with the back to the identical diameter of part 48.Plug 44 freely extends through the hole 42 of modular ring 38.Modular ring 38 is not fixed in the bar portion 36, but is supported on the plug 44.

Housing or container 12 are supported on the forward direction support 70.Housing 12 is fixed on the linking arm 80 of a pair of relative extruding.Linking arm 80 is fixed on the end that extends back 85 of a pair of piston that is totally marked by reference number 84.The forward end of piston 84 is slidably mounted in two hydrodynamic cylinder pressures 88, and this pair hydrodynamic cylinder pressure links to each other with the high pressure liquid potential source by underground 90.Hydraulic cylinder 88 is fixed on the forward direction support 70.Housing 12 accommodates a cylindrical tube or a sleeve pipe 14 with a circular hole 16, and circular hole 16 is coaxial with longitudinal axis 18.Hole 16 has the after-opening 15 of a circle and the open front 17 of a circle.Equally also be arranged in hole 16 referring to Fig. 1 and 3, one columniform internal molds 20, and adjacent with the open front 17 in hole.Internal mold 20 is laterally separated along line 20, forms two discerptible half module 20a and 20b.Totally the outer membrane module that is marked by label 23 is positioned at the outside of the open front 17 in hole 16.Outer membrane module 23 comprises a die holder 24, and this die holder has behind the hole 37, one to end 41 and a forward end 43.An external mold 26 is positioned at hole 37 at the back of die holder 24 to 41 places, end.A backup plate 30 is positioned at forward end 43 places of die holder 24.External mold 26 has a circular hole 28.Backup plate 30 has a circular hole 32.The slightly larger in diameter in hole 32 is 28 diameter in the hole.The diameter in the hole 22 of internal mold 20 is littler than the diameter in hole 28.

Pipe by extrusion equipment 10 moulding of the present invention is to be formed by a cylinder blank 54 with a columniform vertical hole 56.The size of blank 54 should make the gap that has a specified quantitative between the outer surface of blank is with respect to the inner surface of the sleeve pipe 14 of determining hole 16.The diameter in the hole 56 of blank 54 has a specific gap with respect to the part 48 of plug and 52 external diameter.The bar portion 36 of press 13 moves and all power forward of press 13 is applied on the blank 54 along axis 18.

Outer membrane module 23 is positioned at a snap ring 92, and this snap ring is positioned at the back on the end of a dismountable housing or outer mould bases 98.Mould bases 93 is positioned at a horizontal chambers 100 on the forward direction support 70.Chamber 100 has an after-opening 103 and an open front 99.Mould bases 98 has a central horizontal hole 97, it have one to open front 86 and one to after-opening 87.The back of hole 97 has a countersunk 96 to part, and snap ring 92 and outer membrane module 23 are housed in this countersunk 96.Fixed head 94 is positioned at the forward end place of the countersunk part in hole 97.Fixed head 94 has a hole 91, and the diameter in this hole is greater than the diameter in the hole 32 of backup plate 30.

Outer mould bases 98 is remained on the back on the end of chamber 100 by a disengageable stop mechanism, and what this disengageable stop mechanism was total is marked by reference number 102.Stop mechanism 102 comprises a pair of valve 104 that is provided with in the face of ground mutually, and valve 104 is slidably mounted in the transverse holes 101 that intersects with chamber 100.Each valve 104 links to each other with an end of a piston 108.The other end of each piston 108 is slidably mounted in the hydraulic cylinder 110.Each hydraulic cylinder 110 is fixed on the forward direction support 70.Hydraulic cylinder 110 can be controlled so as to selectively at operating position and a valve 104 off-position chamber 100 outside between the mobile valve 104 of a valve 104 shown in Figure 19 d in chamber 100.When valve 104 during in its operating position, they stop outer mould bases 98 any forward motion and keep outer membrane module 23 to be resisted against on the forward end and internal mold 20 of container 12.When valve 104 was in its off-position, outer mould bases 98 can be from the chamber 100 moves through open front 99.

Guide pipe 95 is fixed on the front side of fixed head 94.Guide pipe 45 is coaxial with longitudinal axis 18, and onwards passes open front 99.Make a workbench 112 be fixed on the guide pipe 95 and extension below pipe 95.A plurality of guide rollers 114 are positioned on the upper surface of workbench 112.

Described the details of pipe former of the present invention, both-end extra strong pipe blank then is according to following explanation moulding.

Referring to Fig. 1, plug 44 is returned in the bar portion 36, so that can make blank 54 between the opening 15 of plug 44 and chamber 16.Then, blank 54 is packed in the hole 16 of container 12.In case blank 54 has been loaded in the hole 16, as shown in Figure 4, hydraulic cylinder 69 is activated, force driver 46 to travel forward with respect to crosshead 78 and bar portion 36.Thus, plug 44 is stretched out forward with respect to bar portion 36 ground by driver 46, thereby the back of plug is arranged in the forward end place of bar portion 36 and in the hole 42 of modular ring 38 to part 48.This moment, plug 44 is remained on the fixed position with respect to ring 38 ground.Activate hydraulic cylinder 77, make comprise crosshead 78, bar portion 36, plug 44 and modular ring 38 interior press 13 as an individual unit travel forward.As shown in Figure 5, press 13 longitudinally axis 18 travels forward, thereby plug 44 extends through the hole 56 of blank 54, passes the hole 22 of internal mold 20, passes the hole 28 of external mold 26 and passes the hole 32 of backup plate 30.As shown in Figure 5, bar portion 36 also enters in the hole 16.As shown in Figure 5, modular ring 38 is being about to be resisted against the back on the end of blank 54 before blank applies forward pressure.

A preferred variation of described first step is, activates hydraulic cylinder 69 and passes the hole 56 of blank 54 to promote plug 44, meanwhile blank is supported on the movable carriage.Activate hydraulic cylinder 77, make press 13 towards container 12 motions, thereby plug 44 and blank 54 are brought in the hole 16 of container, be in position shown in Figure 5.

Blank is pressed in the back on the end of internal mold 20 by additional the travelling forward of press 13.A little extrusion billet 54 that travels forward of press 13, and force the metal on the blank to be filled in the inner surface of sleeve pipe 14 and the space between the blank fully.Metal at the forward end place of blank 54 also is forced to upcountry to shift to the part 48 that the diameter of plug 44 reduces as illustrated in fig. 6, thereby forms protruding or " reinforcement " 60 of an inside drum of material.This moment, the power forward of bar portion 36 is being pushed blank 54.Blank thereby on length, reduce slightly, and the corresponding volume of blank is transferred in the gap between sleeve pipe 14 and the blank 54 and in the gap between plug and the blank, to form " reinforcement " 60.As shown in Figure 7, the mid portion 50 that reduces at the diameter of plug and the back crossover sites between part 48 of plug are determined the initial forward end of pipe or the length of " pin " shape portion 62 with respect to internal mold 20.

As shown in Figure 7, carry out continuously extruded by making bar portion 36 travel forward one first distance to blank 54, with force metal on the blank between the mid portion 50 that the diameter at the inner surface of internal mold 20 and plug reduces first annular opening or gap 51 pass through, form the cylindrical initial forward end 62 of pipe.Initial forward end 62 will finally become " pin " the shape end or the forward end of pipe.By making press 13 second distance that travels forward mold the mid portion 64 and the forward direction part 67 of pipe.At the moment, the cylindrical major diameter rear portion 48 of plug arrives the back to part of internal mold 20.Back when part 48 enters the hole 22 of internal mold 20 when plug as shown in Figure 8, forms one second annular opening 53 at the inner surface of internal mold 20 and plug back between part 50.The internal diameter of second annular opening 53 is bigger than the internal diameter of first opening 51.This means that also second annular opening, 53 to the first annular openings 51 are narrow.Therefore, force metal from blank 54 by opening or gap 53, become one and have the tubular extrusion part thick than thin-walled by the pressure forward of bar portion 36.So just, the cylindrical midsection that has begun pipe is divided 64 moulding.Simultaneously, as shown in Figure 8, the initial forward end 62 of pipe arrives the taper forward direction part 52 of plug, and beginning is with respect to axis 18 lateral magnifications.Because the cross section of blank 54 is much larger than the cross section of production tube, the extruding pipe fitting is than the long several times of blank.The length of extruding pipe fitting is determined by the ratio (or extrusion ratio) of the cross-sectional area of the cross-sectional area of blank and pipe.For example, for 12: 1 extrusion ratio, press 13 whenever advanced one inch, with the extruding pipe fitting that molds 12 inches.Because plug is maintained fixed with respect to housing or bar portion 36, so this elongation when extruding is slided the extruding pipe fitting on the external diameter of plug 44.

Fig. 9 represents when forcing blank to cross the taper forward end 52 of plug 44 blank 54 further to be squeezed, and the mid portion 64 of pipe is elongated, and the initial forward end 62 of pipe enlarges continuously.

Figure 10 and 11 expressions are used for the finishing of extrusion process of the forward end of pipe.When front end by the taper forward direction part 52 of plug of the front end of the initial forward end 62 of pipe, it becomes cylindrical, as shown in figure 10.Simultaneously, the internal diameter of the forward end 62 of expansion is identical with the internal diameter of mid portion 64.The initial forward end 62 of pipe is fully expanded in Figure 11, thereby finishes the forward end of pipe or the moulding of " pin " shape end, and this is marked by reference number 56.

As shown in figure 12, when bar portion 36 moved on, the length of the mid portion 64 of pipe extended gradually, when the Len req of extruding pipe till.After the mid portion 64 that molds pipe, hydraulic cylinder 77 is quit work, and activate hydraulic cylinder 81 and 85 simultaneously, so that carriage release lever portion 36 and container 12 backward.The pipe fitting that blank 54 and part are extruded also moves backward with container 12, as shown in figure 13.This has produced a little gap between container 12 and die holder 24, and has eliminated the pressure forward on the mould bases 98.Then, activate hydraulic cylinder 110,100 remove valve 104 from the chamber, and dismountable mould bases 98 is moved forward, so that produce a gap 57 between die holder 24 and container 12, as shown in figure 14.Gap 57 is wideer than internal mold 20.Hydraulic cylinder 81 is quit work, and activate hydraulic cylinder 77 once more, so that move forward bar portion 36.This forces internal mold to shift out container 12 forward and enters space 57, as shown in figure 15.When internal mold 20 left the open front 17 in hole 16, two half modules of internal mold 20 separated and leave the mid portion 64 of pipe, as shown in figure 16.Housing 98 moves backward and bar portion 36 and container 12 move forward to the after-opening 103 of chamber 100, thereby the front surface of die holder 24 and container 12 leans, as shown in figure 17.Hydraulic cylinder 110 is activated, so that make valve 104 in the front of mould bases 98 return chamber 100.

The remainder of blank 54 is used to form the back to part or " case " shape part of pipe.

Activate hydraulic cylinder 77, so that make press 13 and bar portion 36 move forward one the 3rd distance.One the 3rd annular opening or gap 55 are determined in back space between the inner surface in part 48 and hole 28 at plug.Press 13 moves forward one the 3rd distance forces metal to pass the 3rd annular opening or gap 55 from blank 54.The hole 28 of external mold 26 has the diameter bigger than the hole 22 of internal mold 20, thereby the thickness in annular opening or gap 55 is greater than the thickness in second annular opening or gap 53.Therefore, form the thicker relatively back of pipe from the metal that is forced through the 3rd opening 55 of blank 54 to end 66, as shown in figure 18.The back to the external diameter of end 66 obviously greater than the external diameter of the mid portion 64 of pipe.This moment, the extruding of pipe is finished.After the whole Len req of extruding pipe, blank is residual a little not crimping section.This not crimping section mark by the reference number among Figure 18 68.By primer fluid cylinder pressure 69 with plug is shifted out backward the extruding pipe fitting and by primer fluid cylinder pressure 88 with mobile containers 12 backward, can be in extruder not crimping section 68 remove from pipe.Moving backward of container 12 released the not crimping section 68 of blank to outside the hole 16, and under the end saw of pipe.Preferably, make to comprise that the extruding pipe fitting of crimping section 68 does not move a very short distance backward, be beneficial to remove not crimping section 68.By primer fluid cylinder pressure 110 valve 104 is moved on its off-position outside the chamber 100 and will push pipe fitting and remove.Making mould bases 98 pass open front 99 ground 100 removes from the chamber.This makes extruding pipe fitting can be from the chamber 100 be removed by open front 99.Can for example adopt shear, means that any hope such as saw, grinding, flame cutting, laser cutting is adopted not crimping section 68 remove from the rear end of extruding pipe fitting.Then, from chamber 100, remove the extruding pipe fitting.This extruding pipe fitting is for being used for follow-up accurately machined blank pipe.The end of pipe is offered screw thread and machined in a conventional manner, to be formed into QC.

Referring to Figure 20, express an improved plug that is totally marked by reference number 44 ' is arranged in container 12 in the expansion step of the forward end of pipe situation among the figure.Plug 44 ' has the frusto-conically shaped portion 52 ' that a columniform back outwards tilts to the front end of plug from the mid portion 50 ' of tube reducing to the cylindrical part 50 ' of 48 ', one tube reducing in end and.Plug 44 ' is back identical with plug 44 with mid portion to part plug.Yet the conical butt forward direction part of plug 44 ' is different with plug 44.The external diameter of the forward end of plug 44 ' is greater than the external diameter of mid portion 50, and less than the external diameter of back to part 48 '.When front end by the tapering part 52 ' of plug 44 ' of the front end of the initial forward end 62 of pipe, part 62 becomes cylindrical, as shown in figure 20.Yet the internal diameter of the forward end 62 of expansion is less than the internal diameter of the mid portion 64 of pipe.

Thus, describe the present invention, its content new, that require to obtain protection of the patent right is defined by the claims.

Claims (33)

1. An apparatus for extruding a metal tube of substantially uniform inner diameter, said tube having a forward end, a rearward end, and a middle portion having an outer diameter significantly smaller than said middle portion the outer diameter of one of said forward end and rearward end, said apparatus comprising: (a) a rack; (b) a container supported on a frame, said container having a longitudinal central axis and a longitudinal cylindrical first hole coaxial with said longitudinal central axis for receiving a container having a longitudinal cylindrical hole a cylindrical metal blank, said container having a front opening communicating with said first hole and a rear opening communicating with said first hole; (c) a cylindrical inner mold having a cylindrical second hole coaxial with said first hole, said inner mold having an outer diameter equal to that of said first hole, said second hole having smaller than the diameter of the first hole, the inner mold is longitudinally divided into two substantially equal half-moulds, an inner position in the first hole adjacent to the front opening and the said inner mold is movable along said longitudinal central axis through said front opening between an external location outside said first aperture; (d) an outer mold assembly positioned in front of said container and having a longitudinal cylindrical third hole coaxial with said first and second holes and having a diameter larger than said second hole One of the outer mold assembly and the container is movable along the longitudinal central axis between an operating position and a non-working position, and in the operating position, the container and the outer mold assemblies abut at the front opening, and in the inoperative position, the outer mold assembly and the container are spaced sufficiently apart to enable the inner mold to be moved to the outer position , for removal from said device; (e) a press located behind said container and movable toward and away from said container along said longitudinal central axis, said press having a circular forward pressing surface facing the rear opening of said container and a mandrel extending forwardly from said pressing surface toward said rear opening, said pressing surface and said mandrel being coaxial with said first hole, said pressing surface having an inner diameter equal to that of said first hole substantially the same outer diameter with sufficient clearance to enable longitudinal movement of the pressing surface within the first hole, the mandrel comprising an outer diameter smaller than the inner diameter of the second hole diameter cylindrical rearward portion, a cylindrical intermediate portion having an outer diameter smaller than that of the rearward portion, and an outer cylindrical portion extending forward from the intermediate portion with an outer diameter from that of the intermediate portion a frustoconical forward portion having a diameter equal to varying substantially equal to the outer diameter of said rearward portion; and (f) an actuator for moving one of said outer mold assembly and said container relative to the other of said outer mold assembly and said container along said longitudinal axis. 2. The apparatus according to claim 1, characterized in that the longitudinal length of each part of the mandrel relative to the longitudinal length of the inner mold and the specified length of the blank is such that when the blank is pushing forward into engagement with the inner die and pushing the press forward a first distance along the longitudinal central axis to a point where the rearward portion is rearward of the second hole at the end to force the metal on the billet around the mandrel through the second hole so that when the initial forward end of the tube is extruded, the intermediate portion is at the second bore, wherein the initial forward end of the tube has an outer diameter equal to the diameter of the second bore and an inner diameter equal to the diameter of the intermediate portion, the press is forward along the longitudinal central axis moving a second distance while the rearward portion is within the second hole, which causes the metal on the billet to be forced through the second hole around the rearward portion of the mandrel to extrude the middle portion of the tube, wherein the middle portion of the tube has an outer diameter equal to the inner diameter of the second bore and an inner diameter equal to the outer diameter of the rearward portion, the press moves forward a first The two distances also allow the initial forward end of the tube to pass through the forward portion of the mandrel so that the initial forward end expands transversely relative to the longitudinal central axis to form the tube's a forward end, wherein the forward end of the tube has an inner diameter equal to the outer diameter of the rearward portion of the mandrel and a thickness greater than the thickness of the middle portion of the tube, on the device from After removing the inner die and while the outer die assembly is in the working position, the press moves forward a third distance along the longitudinal center axis, which forces the metal on the blank around the The rear portion of the mandrel passes through the third hole so as to extrude the rear portion of the tube, wherein the rear portion of the tube has an inner diameter equal to the outer diameter of the rear portion and The inner diameter of the third hole is equal to the outer diameter. 3. The apparatus of claim 1, wherein the outer mold assembly comprises: (a) a mold base having a fourth hole, said mold base having a rearward end and a forward end; (b) an overmold located in said fourth aperture and containing said third aperture at the rearward end of said overmold holder; and (c) a stop located in said fourth hole at the forward end of said mold base, said stop having a cylindrical fifth hole having a diameter greater than that of said fourth hole. 4. The apparatus of claim 1, wherein said mandrel has a rearward end, and said press comprises: (a) a housing having a chamber for receiving said mandrel and a forward end having an aperture leading to said chamber; (b) a die ring at the forward end of said housing at said front opening, said die ring comprising said forward pressing surface and a cylindrical bore having an inner diameter equal to the outer diameters of the rearward portion of the mandrel are substantially equal; and (c) a driving device operably connected to the rearward end of said mandrel for driving said mandrel along said longitudinal center axis in a rearwardly retracted position and a forwardly extended position; position, in which the rearward portion of the mandrel is in the chamber, and in the forward position, in which the rearward portion of the mandrel is in the ring hole, and the remainder of the mandrel ahead of the die ring. 5. The apparatus of claim 1, further comprising an actuator for moving one of said outer mold assembly and said container relative to said longitudinal center axis. The outer mold assembly and another move in the container. 6. The apparatus of claim 5, wherein said actuator is a fluid actuator comprising: (a) a hydraulic cylinder secured to said frame; and (b) a piston slidable within said hydraulic cylinder and having a rearwardly facing end extending rearwardly of said hydraulic cylinder and operatively connected to said container. 7. The apparatus of claim 6, wherein said one first fluid actuator is on one side of said longitudinal central axis and one second fluid actuator is on the opposite side of said longitudinal central axis , and the container is secured to the pistons of the first and second fluid actuators. 8. The apparatus of claim 1, wherein the outer mold assembly comprises: (a) a bracket having a central bore coaxial with said longitudinal central axis, said central bore having a forward opening and a rearward opening; (b) a die holder in said central bore at the forward opening of said central bore, said die holder having a cylindrical fourth bore, a rearward end and a forward end; and (c) an overmold located in said fourth aperture at the rearward end of said overmold assembly and containing said third aperture; The stopper in the fourth hole, the stopper has a cylindrical fifth hole, the diameter of which is larger than the diameter of the fourth hole. 9. The apparatus of claim 8, wherein said outer die assembly further includes a snap ring in said central bore and surrounding said die holder. 10. The apparatus of claim 9, wherein said outer mold assembly further includes a retainer plate in said central bore and forward of said die holder, said retainer plate having a cylindrical bore , the hole is coaxial with the longitudinal central axis and has a diameter larger than that of the fifth hole and smaller than that of the fourth hole. 11. The apparatus of claim 10, wherein said outer mold assembly further comprises a forwardly opening guide tube fixed to said fixed plate and extending forwardly through said central hole, said The guide tube has an inner diameter at least as large as the inner diameter of the bore of the fixing plate. 12. The apparatus of claim 1, wherein said frame has a chamber having a rear opening and a front opening, said outer mold assembly being positioned in said chamber so as to extend along said The longitudinal central axis moves longitudinally, and the apparatus further includes a releasable stop mechanism for releasably retaining the outer mold assembly in the chamber in operative contact with the inner mold. 13. The apparatus of claim 12, wherein said frame has a transverse aperture extending transversely with respect to said central longitudinal axis and intersecting said chamber, said releasable stop mechanism including a shutter slidably mounted in said transverse aperture between an operative position in which at least a portion of said shutter is in said chamber and a non-operative position in which , the shutter is outside the chamber. 14. The apparatus of claim 13, wherein said releasable stop mechanism further includes an actuator for selectively moving said shutter between said operative position and said inoperative position. Location. 15. The apparatus of claim 14, wherein the actuator is a fluid actuator. 16. The apparatus of claim 1 further comprising a guide table forward of said outer die assembly for supporting said tube as it is extruded and guide. 17. The apparatus of claim 16, wherein the guide table has upwardly extending rollers for supporting the extruded tube. 18. The apparatus of claim 17, further comprising a guide tube extending from the outer mold assembly to the guide table for guiding the extruded tube from the outer mold assembly. The mold assembly is guided to the guide table. 19. A mandrel for a metal extrusion machine for extruding a metal tube having a uniform inner diameter as a first dimension, a forward end, a rearward end and an intermediate portion between said forward end and rearward end, said intermediate portion has an outer diameter as a second dimension, and said rearward end and forward end each have a ratio said second dimension being a large outer diameter, said mandrel comprising: (a) a cylindrical rearward portion having an outer diameter equal to said first dimension; (b) a cylindrical intermediate portion having an outer diameter substantially smaller than the outer diameter of said rearward portion; and (c) a forward portion having a frustoconical outer surface extending forwardly from said intermediate portion with an outer diameter ranging from equal to the outer diameter of said intermediate portion to equal to that of said rearward portion Changes in outer diameter. 20. A method of extruding a cylindrical metal tube having a constant inner diameter, said tube having a forward end, a rearward end and a middle section, said middle section having an outer diameter of substantially smaller than the outer diameter of each of the forward and rearward ends, the method comprising: (a) positioning a cylindrical metal blank having a cylindrical longitudinal hole in a cylindrical first hole of a container by inserting said metal blank from a rear opening into said first hole, said first hole Having a longitudinal central axis, the container has a front opening leading to the first hole and houses an inner mold within the first hole adjacent to the front opening and a The outer mold adjacent to the front opening, the inner mold has a cylindrical second hole, the diameter of which is smaller than the diameter of the first hole, and the outer mold has a third hole, the hole The diameter is smaller than the diameter of the first hole and larger than the diameter of the second hole, the inner mold and the outer mold can be selectively moved along the longitudinal central axis, the inner mold includes two separable half mold; (b) a press is arranged along said longitudinal central axis, said press having a circular forward pressing surface facing said container and a mandrel extending forwardly from said pressing surface towards said container, The pressing surface and the mandrel are coaxial with the first hole, the pressing surface having an outer diameter substantially the same as the inner diameter of the first hole with sufficient clearance to enable the a pressing surface moves longitudinally within said first hole, said mandrel having a cylindrical rear portion having a diameter smaller than said second hole, a cylindrical middle portion having a diameter smaller than said rear portion, and a a forwardly extending frusto-conical forward portion varying in diameter from equal to the diameter of said intermediate portion to equal to the diameter of said rearward portion; (c) moving said press forwardly along said longitudinal central axis so that said mandrel extends through the hole of said blank and said intermediate portion is located in said second hole so as to form a first annular opening, when the forward pressing surface engages the blank for the first time, the juncture of the intermediate portion and the rearward portion is spaced rearwardly from the inner die to push the blank on said inner mold; (d) moving said press forward a first distance along said longitudinal central axis to a point where the junction of said intermediate portion and said rearward portion is at the rearward end of said second bore to force the metal on the billet through the first annular opening to extrude an initial forward end of the tube having an outer diameter equal to the inner diameter of the second bore and an inner diameter equal to the outer diameter of the intermediate portion; (e) moving said press forward a second distance along said longitudinal central axis with said rearward portion in said second bore to form a second annular opening for forcing said Metal on the billet passes through the second annular opening, extruding the middle portion of the tube having an outer diameter equal to the inner diameter of the second bore and a diameter equal to the rearward portion and during the press moves forward the second distance such that the initial forward end of the tube passes the forward portion of the mandrel so that the initial forward end of the tube is opposite expands laterally about the longitudinal central axis to an inner diameter equal to the inner diameter of the middle portion of the tube and an outer diameter greater than the outer diameter of the middle portion of the tube; (f) moving one of said outer mold and said container along said longitudinal central axis so that said outer mold is spaced from said stationary container by a distance at least equal to the longitudinal extent of said inner mold; (g) removing said inner mold from said first aperture through said front opening so that said inner mold is forward of said container; (h) removing said inner mold half from said tube and mandrel; (i) moving one of the outer mold and the container rearwardly along the longitudinal central axis so that the outer mold engages the container and the rearward portion is within the third circular hole, to forming a third annular opening; (j) moving said press forward a third distance along said longitudinal center axis for forcing metal on said billet through said third annular opening to extrude the rearward portion of said tube an end portion having an inner diameter equal to the outer diameter of the rearward portion and an outer diameter equal to the inner diameter of the third bore; and (k) removing said extruded tubing from said mandrel. 21. A method of extruding a metal tube as claimed in claim 20, wherein by moving said mandrel rearwardly along said longitudinal center axis until said mandrel is behind said extruded tube, The extruded tubing is removed from the mandrel. 22. The method of extruding a metal tube according to claim 20, wherein in step (f) of claim 20, said container is positioned relative to said outer die and said core along said longitudinal center axis. The rod moves backwards for forcing the inner mold out of the first hole. 23. The method of extruding a metal tube as claimed in claim 20, wherein after said mandrel is moved forward by said third distance, an unextruded portion of said billet remains in said first well, and the method comprises the following additional steps: (a) moving said mandrel rearwardly along said longitudinal central axis until said mandrel is behind said extruded tubing; (b) moving one of the outer mold and the container forward along the longitudinal central axis, thereby spacing the outer mold from the container; and (c) removing an unextruded portion of the billet from the rearward end of the extruded tube. 24. The method of extruding a metal tube as claimed in claim 23, wherein in step (b) of claim 23, said container is positioned relative to said outer die and said core along said longitudinal center axis. The rod moves rearwardly to force the unextruded portion of the billet out of the first hole. 25. A method of extruding a cylindrical metal tube having a uniform inner diameter as a first dimension, a forward end, a rearward end and a an intermediate portion between portions, the intermediate portion having an outer diameter as a second dimension, and the rearward and forward end portions each having an outer diameter larger than the second dimension, the method comprising The above steps: (a) pressing a cylindrical metal blank in a cylindrical bore of a container through a first annular opening having an inner diameter smaller than said first dimension and an outer diameter equal to said second dimension, so that extruding an initial forward end of the tube having an inner diameter smaller than the first dimension; (b) extruding said metal billet in said bore through a second annular opening having an inner diameter equal to said first dimension and an outer diameter equal to said second dimension so as to extrude said the middle part of the tube; (c) moving the initial forward end of the tube over a mandrel having a frusto-conical outer surface shaped to expand the initial forward end of the tube to form an inner diameter the forward end of the tube having an outer diameter equal to the first dimension and greater than the second dimension; and (d) extruding said metal billet in said bore through a third annular opening having an inner diameter equal to said first dimension and an outer diameter greater than said third dimension to extrude said tube the rearward end of the . 26. An apparatus for extruding a metal tube having a forward end, a rearward end and an intermediate section having an outer diameter substantially smaller than the forward end and an outer diameter of each of the rearward ends, an inner diameter of the forward end that is smaller than an inner diameter of each of the rearward ends and the intermediate portion, the apparatus comprising: (a) a rack; (b) a container supported on a frame, said container having a longitudinal central axis and a first longitudinal cylindrical hole coaxial with said central longitudinal axis for receiving a container having a longitudinal cylindrical hole; a cylindrical metal blank, said container having a front opening communicating with said first hole and a rear opening communicating with said first hole; (c) a cylindrical inner mold having a cylindrical second hole coaxial with said first hole, said inner mold having an outer diameter equal to that of said first hole, said second hole having having a diameter smaller than the diameter of said first hole, said inner mold being divided longitudinally into two substantially equal half-moulds at an inner position within said first hole adjacent to said front opening and between an external location outside said first aperture, said inner mold being movable along said longitudinal central axis through said front opening; (d) an outer mold assembly located in front of said container and having a longitudinal cylindrical third hole coaxial with said first and second holes and having a diameter larger than said second hole One of the outer mold assembly and the container is movable along the longitudinal central axis between an operating position and a non-working position, wherein in the operating position, the container and the outer mold assembly part abuts at the front opening, and in the rest position, the outer mold assembly and the container are sufficiently spaced apart so that the inner mold can be moved to the outer position for access from the removed from the above equipment; (e) a press located behind said container and movable toward and away from said container along said longitudinal central axis, said press having a circular forward pressing surface facing the rear opening of said container and a mandrel extending forwardly from said pressing surface toward said rear opening, said pressing surface and said mandrel being coaxial with said first hole, said pressing surface having an inner diameter equal to that of said first hole substantially the same outer diameter with sufficient clearance to enable longitudinal movement of the pressing surface in the first hole, the mandrel comprising an outer diameter smaller than the inner diameter of the second hole diameter cylindrical rearward portion, a cylindrical intermediate portion having an outer diameter smaller than that of said rearward portion, and a frustoconical forward portion extending forward from said intermediate portion, the portion varies from equal to the outer diameter of the intermediate portion to greater than the outer diameter of the intermediate portion and smaller than the outer diameter of the rearward portion; and (f) an actuator for moving one of said outer mold assembly and said container relative to the other of said outer mold assembly and said container along said longitudinal axis. 27. A mandrel for a metal extrusion machine for extruding a metal tube having a uniform inner diameter as a first dimension, one forward end, one rearward end and an intermediate portion between said forward end portion and rearward end portion, said intermediate portion having an inner diameter as a first dimension and an outer diameter as a second dimension, said rearward end portion and a forward ends each having an outer diameter larger than said second dimension, said forward end having an inner diameter smaller than said first dimension, said mandrel comprising: (a) a cylindrical rearward portion having an outer diameter equal to said first dimension; (b) a cylindrical intermediate portion having an outer diameter substantially smaller than the outer diameter of said rearward portion; and (c) a forward portion having a frustoconical outer surface extending forwardly from said intermediate portion with an outer diameter ranging from equal to the outer diameter of said intermediate portion to less than said first dimension and greater than the outer diameter of the intermediate portion. 28. A method of extruding a cylindrical metal tube having a forward end, a rearward end and a middle section having an outer diameter substantially smaller than the forward end and the outer diameter of each of the rearward end portions, the forward end portion having an inner diameter smaller than the inner diameter of each of the rearward end portion and the intermediate portion, the method comprising: (a) by inserting a cylindrical metal blank having a cylindrical longitudinal hole from a rear opening into a cylindrical first hole of a container, placing said metal blank in said first hole, said first the bore has a longitudinal central axis, the container has a front opening to the first bore and accommodates an inner mold in the first bore adjacent the front opening and a front opening in the container an outer mold external and adjacent to said front opening, said inner mold having a second cylindrical hole having a diameter smaller than that of said first hole, said outer mold having a third hole, The hole has a diameter smaller than the diameter of the first hole and larger than the diameter of the second hole, the inner and outer dies are selectively movable along the longitudinal central axis, the inner die includes two separable mold halves; (b) a press is arranged along said longitudinal central axis, said press having a circular forward pressing surface facing said container and a mandrel extending forwardly from said pressing surface towards said container, The pressing surface and the mandrel are coaxial with the first hole, the pressing surface having an outer diameter substantially the same as the inner diameter of the first hole with sufficient clearance to enable the a pressing surface moves longitudinally in said first hole, said mandrel has a cylindrical rearward portion having an outer diameter smaller than the inner diameter of said second hole, a cylindrical middle portion having a smaller diameter than said rearward portion , and a frusto-conical forward portion extending forwardly from said intermediate portion with an outer diameter ranging from equal to the outer diameter of said intermediate portion to greater than the outer diameter of said intermediate portion and smaller than the diameter of said rearward portion ground change; (c) moving said press forward along said longitudinal central axis so that said mandrel extends through the hole of said blank and said intermediate portion is located in said second hole so as to form a first annular shape opening, when the forward pressing surface engages the blank for the first time, the junction of the intermediate portion and the rearward portion is spaced rearwardly from the inner die to push the blank pressed against the inner mold; (d) moving said press forward a first distance along said longitudinal central axis to a point where the junction of said intermediate portion and said rearward portion is at the rearward end of said second bore to force the metal on the billet through the first annular opening, extruding an initial forward end of the tube having an outer diameter equal to the inner diameter of the second bore and an inner diameter equal to the outer diameter of said intermediate portion; (e) moving said press forward a second distance along said longitudinal central axis with said rearward portion in said second bore to form a second annular opening for forcing metal From the blank through the second annular opening, extrude a central portion of the tube having an outer diameter equal to the inner diameter of the second bore and a diameter equal to the diameter of the rearward portion. inner diameter, and the initial forward end of the tube passes the forward portion of the mandrel while the press moves forward by the second distance such that the initial forward end of the tube is opposite expanding transversely about the longitudinal central axis to an extent with an inner diameter smaller than the inner diameter of the middle portion of the tube and an outer diameter greater than the outer diameter of the middle portion of the tube; (f) moving one of said outer mold and said container along said longitudinal central axis so that said outer mold is spaced from said stationary container by a distance at least equal to the longitudinal extent of said inner mold; (g) removing said inner mold from said first aperture through said front opening so that said inner mold is forward of said container; (h) removing the mold halves of the inner mold from the tube and mandrel; (i) moving one of the outer mold and the container rearwardly along the longitudinal central axis so that the outer mold engages the container and the rearward portion is within the third circular hole, to forming a third annular opening; (j) moving said press forward a third distance along said longitudinal central axis for forcing metal from said billet through said third annular opening to extrude the rearward end of said tube portion, the rearward end having an inner diameter equal to the outer diameter of the rearward portion and an outer diameter equal to the inner diameter of the third bore; and (k) removing said extruded tubing from said mandrel. 29. A method of extruding a metal tube as claimed in claim 28, wherein by moving said mandrel rearwardly along said longitudinal center axis until said mandrel is positioned behind said extruded tube, The extruded tubing is removed from the mandrel. 30. The method of extruding a metal tube as claimed in claim 28, wherein in step (f) of claim 20, said container is positioned relative to said outer die and said core along said longitudinal center axis. The rod moves backwards for forcing the inner mold out of the first hole. 31. The method of extruding a metal tube as recited in claim 28, wherein after said mandrel is moved forward by said third distance, an unextruded portion of said billet remains in said first well, and the method comprises the following additional steps: (a) moving said mandrel rearwardly along said longitudinal central axis until said mandrel is behind said extruded tubing; (b) moving one of the outer mold and the container forward along the longitudinal central axis, thereby spacing the outer mold from the container; and (c) removing an unextruded portion of the billet from the rearward end of the extruded tube. 32. The method of extruding a metal tube as claimed in claim 31, wherein in step (b) of claim 23, said container is positioned relative to said outer die and said core along said longitudinal center axis. The rod moves rearwardly to force the unextruded portion of the billet out of the first hole. 33. A method of extruding a cylindrical metal tube having a forward end, a rearward end and an intermediate portion between said forward end and rearward end, The intermediate portion has an inner diameter as a first dimension and an outer diameter as a second dimension, the rearward end portion has an inner diameter as the first dimension and an outer diameter greater than the second dimension, the forward an end having an outer diameter greater than said second dimension and an inner diameter as a third dimension less than said first dimension, said method comprising the steps of: (a) pressing a cylindrical metal blank in a cylindrical bore of a container through a first annular opening having an inner diameter smaller than said third dimension and an outer diameter equal to said second dimension to extrude extruding an initial forward end of the tube having an inner diameter smaller than the third dimension; (b) pressing said metal blank in said bore through a second annular opening having an inner diameter equal to said first dimension and an outer diameter equal to said second dimension to extrude said the middle part of the tube; (c) moving the initial forward end of the tube over a mandrel having a frusto-conical outer surface shaped to expand the initial forward end of the tube to form the a forward end of the tube having an inner diameter equal to the third dimension and an outer diameter greater than the second dimension; and (d) pressing said metal blank in said bore through a third annular opening having an inner diameter greater than said first dimension and an outer diameter greater than said second dimension to extrude said tube Rear end.

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