Abstract:
Method and apparatus for friction welding termination elements at first and second ends ( 21, 23 ) of a cylindrical shaft ( 15 ) in alaignment with an axis. A shaft receiver ( 17 ) receives the cylindrical shaft ( 15 ), and a first chuck ( 70 ) grips and rotates the cylindrical shaft ( 15 ) in alignment with the axis. A second chuck ( 75 ) grips the cylindrical shaft ( 15 ) and translates the second chuck ( 75 ) between first and second axial positions. A first termination receiver ( 155 ) receives the first termination ( 30 ) and axially translates same to a first installation position. An installation drive ( 90 ) urges the first termination ( 30 ) axially toward the cylindrical shaft ( 15 ) as it is rotated. A second termination receiver axially translates second termination ( 32 ) to a second installtion position in allignment with the axis. A second installation drive ( 91 ) urges the second termination element ( 32 ) axially toward the cylindrical shaft as it is rotated. The first chuck ( 70 ) is rotated at approximately between 500 to 6000 rmp. The first installation drive arrangement ( 90 ) applies between 250 to 3000 pounds of axial force for between 1 and 15 seconds during a heating phase, and between 1500 to 12000 pounds of axial force for between 0.5 and 10 seconds during a forging phase.

Description:
RELATIONSHIP TO OTHER APPLICATION(S)  
       [0001]    This application claims the benefit of the filing date of U.S. Provisional Patent Application Ser. Nos. 60/313,741; 60/313,734; and 60/313,739; all of which were filed on August 20, 2001 in the names of the same inventors as herein. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    This invention relates generally to arrangements for welding tubular products, and more particularly, to a welding arrangement that will weld tubular products that require low cycle time, minimal misalignment, and near perfect radial alignment of the welded ends.  
           [0004]    2. Description of the Related Art  
           [0005]    To date many tubular products have been manufactured with the appropriate ends attached by conventional welding techniques. In the automotive industry, for example, particularly drive shaft manufacturing, the weld yokes, (or ends) often are pressed onto or into a tube end. After the press operation, the ends typically are welded by wire feed or other conventional welding techniques. The required press fit renders this method of manufacturing to be plagued with significant cost. It is of greater significance that only one end of the drive shaft is completed at a time. That is, after the completion of the first weld, the tube is turned over and reinserted into the known welding machine. Almost always the radial alignment and concentricity between the two ends is lost before the second weld yoke is attached. This form of manufacture, therefore, has significant inherent problems that are common in the industry. In addition, conventional wire feed welding imposes limits on the minimum wall thickness that can reliably be joined in production, and the quality of the weld cannot readily be ascertained.  
           [0006]    In another known system, known magna pulse and magna arc methods are used in the construction of drive shafts and other tubular products. Again, typically one side of the tubular product is completed at a time. This causes set up problems that limit the ability to maintain radial alignment and verification of the quality of the weld is difficult to accomplish. Double ended magna arc or pulse welders are complex, difficult to repair and maintain, and expensive. In addition, They also require that extremely close tolerances be in squareness, cleanliness, and flatness of the components prior to and during the weld process to maintain a proper arc gap. This is difficult to accomplish and maintain in a production environment.  
           [0007]    It is, therefore, an object of this invention to provide a system wherein the weld ends of a tubular assembly can be welded simultaneously in a simple, cost-effective and production robust manner.  
           [0008]    It is also another object of this invention to provide a system wherein the weld ends of a tubular assembly can be maintained in a predetermined axial relationship as the ends are welded simultaneously.  
           [0009]    It is another object of this invention to provide a welding arrangement that obviates the need for the press fit process and the associated close tolerance machining required for a press fit, as well as the additional material required on the yokes for the internal press fit.  
           [0010]    It is also an object of this invention to provide a process that is cost effective, requires a short cycle time, holds near perfect concentricity of the tubular elements, and maintains near perfect radial alignment.  
           [0011]    It is a further object of this invention to provide a welding system wherein a plurality of parameters that affect product quality can be recorded during the process to verify consistent weld quality.  
           [0012]    It is additionally an object of this invention to provide an arrangement that can be applied in the welding of flat plate(s) to tubes or other forms of cylindrical stock.  
           [0013]    It is yet a further object of this invention to provide a high level of precision and low cycle time in the manufacture of drive shafts, to preclude drive shafts that suffer from linear or radial misalignment in their welded ends, whereby high levels of noise, vibration and harshness (NVH) would result.  
         SUMMARY OF THE INVENTION  
         [0014]    The foregoing and other objects are achieved by the present invention which provides, in accordance with an apparatus aspect thereof, an arrangement for welding first and second shaft termination elements at respective first and second ends of a cylindrical shaft, and in alignment with a predetermined axis. In accordance with this aspect of the invention, there is provided a shaft receiver for receiving the cylindrical shaft, and a first chuck assembly having a plurality of first gripping elements for gripping the cylindrical shaft at the first end thereof and maintaining the cylindrical shaft in alignment with the predetermined axis. A rotatory drive is coupled to the first chuck assembly. There is additionally provided a second chuck assembly having a plurality of gripping elements for gripping the cylindrical shaft at the second end thereof in alignment with the predetermined axis and a chuck assembly drive for translating the second chuck assembly between first and second axial positions. A first shaft termination element receiver receives the first shaft termination element and axially translates same to a first installation position in alignment with the predetermined axis. A first installation drive arrangement urges the first shaft termination element axially toward the cylindrical shaft as the cylindrical shaft is rotated in response to the rotatory drive. Additionally, a second shaft termination element receiver receives the second shaft termination element and axially translates same to a second installation position in alignment with the predetermined axis. A second installation drive arrangement urges the second shaft termination element axially toward the cylindrical shaft as the cylindrical shaft is rotated in response to the rotatory drive.  
           [0015]    In a specific illustrative embodiment of the invention, there is additionally provided a shaft receiver drive arrangement for translating the shaft receiver between a first shaft receiver position where the cylindrical shaft is supported by the shaft receiver at a transaxial location that is substantially in axial alignment with the first chuck assembly, and a second shaft receiver position distal from the first shaft receiver position.  
           [0016]    In one embodiment, the cylindrical shaft is axially displaceable with respect to the shaft receiver, and the chuck assembly drive includes a pneumatic drive.  
           [0017]    In a further embodiment, the rotatory drive urges the first chuck assembly to rotate at approximately between 600 to 4000 rpm. In such an embodiment, the cylindrical shaft is a drive shaft for a vehicle, and the rotatory drive urges the first chuck assembly to rotate preferably at approximately between 600 to 4000 rpm.  
           [0018]    The plurality of first gripping elements of the first chuck assembly includes, in certain embodiments, first and second sets of jaws. The first set of jaws is arranged to communicate with the cylindrical shaft prior to the second set of jaws, and may be regulated by mechanical cam. The first set of jaws may additionally include a precision alignment arrangement for locking the cylindrical shaft at a predetermined axial location. Such a precision alignment arrangement includes a plurality of angulated guideways associated with respective jaws of the first set of jaws, the angulated guideways having a precise angular orientation with respect to one another. The plurality of angulated guideways are equiangularly distributed about the predetermined axis.  
           [0019]    The second set of jaws is provided, in certain embodiments, with a clamping arrangement for locking the cylindrical shaft at the predetermined axial location determined by the first set of jaws. Preferably, the first and second sets of jaws are hydraulically actuated, whereby the second set of jaws is operated in response to a first hydraulic pressure applied to the first set of jaws exceeding a predetermined break-over first hydraulic pressure value. The break-over first hydraulic pressure has a magnitude sufficient to cause the first set of jaws to lock the cylindrical shaft at the predetermined axial location.  
           [0020]    In a further embodiment of the invention, there is provided a non-rotating housing about which the first chuck assembly is rotated by the rotatory drive. The first chuck assembly is installed on a rotatable housing, and there is further provided a fluid delivery arrangement disposed at the interface of the non-rotating and the rotatable housings. In one embodiment of this first apparatus aspect of the invention, the fluid delivery arrangement is provided with a first fluid channel system for supplying pressurized clamping fluid for causing the first chuck assembly to grip the cylindrical shaft and a second fluid channel system for supplying pressurized unclamping fluid for causing the first chuck assembly to release the cylindrical shaft. There is provided in the first fluid channel system a first fluid passageway at the interface of the non-rotating and the rotatable housings. In this embodiment, the second fluid channel system has a first fluid passageway at the interface of the non-rotating and the rotatable housings, and there is further provided a pressurized fluid supply port installed on the non-rotating housing. Additionally, there is provided a fluid drain port installed on the non-rotating housing.  
           [0021]    A bearing arrangement is interposed between the non-rotating and the rotatable housings, and there is further provided a fluid seal for limiting flow of a pressurized fluid through the bearing arrangement.  
           [0022]    In a further embodiment of the invention, the first and second installation drive arrangements urge the first and second shaft termination elements, respectively, axially toward the cylindrical shaft as the cylindrical shaft is rotated by applying respective first and second axial forces in respective axially opposing directions. The respective first and second axial forces each are exerted at respective magnitudes of axial force for respective determined periods of time. At least one of the first and second axial forces is applied at a plurality of magnitudes of axial force for respective determined sequential periods of time. In another embodiment, at least one of the first and second axial forces is applied in response to a distance of axial displacement resulting from the application of the respective first and second axial forces. The respective determined sequential periods of time correspond to engagement phases of an installation of the first shaft termination element. In an advantageous embodiment, the engagement phases of the installation of the first shaft termination element comprise a heating phase and a forging phase. In an embodiment where the cylindrical shaft is a drive shaft for a vehicle, the first installation drive arrangement is operated to apply approximately between 250 to 1000 pounds of axial force for a duration of approximately between 1.5 and 3 seconds during the heating phase, and applies approximately between 2500 to 12000 pounds of axial force for a duration of approximately between 2 and 5 seconds during the forging phase.  
           [0023]    Prior to performing the heating and forging phases there is provided in one embodiment the further phase of scrubbing the first shaft termination element against the first end of the cylindrical shaft. In an embodiment applied to a drive shaft for a vehicle, the first installation drive arrangement is operated to apply approximately between 50 to 350 pounds of axial force for a duration of approximately between 0.5 and 2 seconds during the further phase of scrubbing.  
           [0024]    In a still further embodiment, at least one of the first and second axial forces is applied in response to a temperature resulting from the application of the respective first and second axial forces, the temperature being controlled in response to the modulation of the weld force between tube ends and their respective yokes while rotating the tube. The cylindrical shaft is rotated at a fixed preselected speed that is determined in response to the diameter of the cylindrical shaft. In some embodiments, the cylindrical shaft is rotated at a speed that achieves a determined rotational surface speed of the cylindrical shaft.  
           [0025]    In accordance with a method aspect of the invention, there is provided a method of welding first and second shaft termination elements at respective first and second ends of a cylindrical shaft, and in alignment with a predetermined axis, the inventive method provides the steps of:  
           [0026]    cylindrical shaft loading a cylindrical shaft having first and second ends onto a shaft receiver located at a proximal location, whereby the cylindrical shaft is supported so that its longitudinal axis is substantially coaxial with the predetermined axis;  
           [0027]    first element loading the first shaft termination element onto a first shaft termination element receiver;  
           [0028]    second element loading the second shaft termination element onto a second shaft termination element receiver;  
           [0029]    first translating the first shaft termination element receiver whereby a principal axis of the first shaft termination element is disposed coaxially with the predetermined axis;  
           [0030]    second translating the second shaft termination element receiver whereby a principal axis of the second shaft termination element is disposed coaxially with the predetermined axis;  
           [0031]    axially urging the cylindrical shaft toward the first shaft termination element and through a first chuck assembly;  
           [0032]    first actuating the jaws of the first chuck whereby the cylindrical shaft is clamped in the region of the first end thereof to a transaxial location where the longitudinal axis of the cylindrical shaft is coaxial with the predetermined axis;  
           [0033]    axially translating the second shaft termination element and a second chuck assembly to a predetermined axial location in the region of the second end of the cylindrical shaft;  
           [0034]    second actuating the jaws of the second chuck whereby the cylindrical shaft is clamped in the region of the second end thereof to a transaxial location where the longitudinal axis of the cylindrical shaft is coaxial with the predetermined axis;  
           [0035]    rotating the first chuck at a predetermined rate of rotation;  
           [0036]    first urging the first shaft termination element axially into communication with the first end of the cylindrical shaft; and  
           [0037]    second urging the second shaft termination element axially into communication with the second end of the cylindrical shaft.  
           [0038]    In one embodiment of this method aspect of the invention, prior to performing the step of axially translating, there is further provided the step of withdrawing the shaft receiver to a distal location.  
           [0039]    In a further embodiment, there are further provided the steps of:  
           [0040]    first releasing a first axial force applied to the first shaft termination element in response to the step of first urging;  
           [0041]    second releasing a second axial force applied to the second shaft termination element in response to the step of second urging;  
           [0042]    releasing the jaws of the second chuck; and  
           [0043]    withdrawing axially the second chuck assembly to a distal axial location.  
           [0044]    The further may include the additional steps of:  
           [0045]    restoring the shaft receiver to the proximal location;  
           [0046]    releasing the jaws of the first chuck; and  
           [0047]    reverse axially urging the cylindrical shaft out of the first chuck assembly, whereby the cylindrical shaft is supported by the shaft receiver.  
           [0048]    In some embodiments the step of first actuating includes the further steps of:  
           [0049]    first subset actuating a first subset of jaws;  
           [0050]    controlling the performance of the step of first subset actuation to ensure all of the jaws in the first subset ofjaws maintain an equal radial relationship during the step of first subset actuation with respect to the predetermined axis.  
           [0051]    In further embodiments, the step of first actuating includes the further step of second subset actuating a second subset of jaws, the step of second subset actuating being performed after the step of first subset actuating. The step of first actuating is performed in response to a step of applying an hydraulic pressure, and the step of second subset actuating is performed in response to the hydraulic pressure exceeding a predetermined hydraulic pressure magnitude.  
           [0052]    In accordance with a further method aspect of the invention, there is provided a method of welding a shaft termination element an end of a cylindrical shaft that includes the steps of:  
           [0053]    gripping the cylindrical shaft with a plurality of coordinated grippers whereby the cylindrical shaft is retained coaxially with a predetermined axis;  
           [0054]    further gripping the cylindrical shaft with a plurality of further grippers whereby the cylindrical shaft is retained with additional force coaxially with the predetermined axis;  
           [0055]    loading the shaft termination element onto a shaft termination element receiver;  
           [0056]    translating the shaft termination element receiver whereby a principal axis of the shaft termination element is disposed coaxial with the predetermined axis; and  
           [0057]    axially urging the cylindrical shaft and the shaft termination element toward each other.  
           [0058]    In one embodiment of the invention, there is further provided the step of releasing partially the cylindrical shaft during rotation of same to permit self-centering.  
           [0059]    In a further embodiment, the step of gripping the cylindrical shaft is performed on a cylindrical shaft datum. The step of loading the shaft termination element includes, in certain embodiments, the further step of gripping the shaft termination element on a shaft termination datum. Additionally, the step of translating includes the further step of establishing a spatial relationship between the cylindrical shaft datum and the shaft termination datum. The use of such datums enables high runout accuracy to be achieved, illustratively on the order of 0.006 inches T.I.R., down to 0.002 inches T.I.R., when components permit.  
           [0060]    In one embodiment of the further method aspect of the invention there is further provided the step of welding the cylindrical shaft and the shaft termination element to each other. The step of welding includes, in certain embodiments, the further steps of:  
           [0061]    rotating the chuck at a predetermined rate of rotation; and  
           [0062]    urging the shaft termination element axially into communication with a first end of the cylindrical shaft whereupon a friction weld is formed.  
           [0063]    In some situations, the cylindrical shaft might not be true, so as to have a slight bend, but still be within determined parameters. When rotated initially, such a shaft will be difficult to weld. It is desirable to release partially the clamping of the shaft whereby it is free to self-center during slow initial rotation. In this manner, a reasonably centered clamping of a slightly bent shaft can be achieved.  
           [0064]    The step of urging the shaft termination element axially into communication with a first end of the cylindrical shaft is terminated in response to a step of measuring a thermal emissivity during of the period that the step of urging is performed. There is further provided the step of measuring a duration of the period during which the step of urging is performed. In other embodiments, there is further provided the step of measuring a thermal emissivity during of the period that the step of urging is performed. In yet further embodiments, there is provided the step of measuring an axial displacement of the shaft termination element relative to the first end of the cylindrical shaft during of the period that the step of urging is performed. In a manufacturing environment where it is desired to achieve a predetermined overall length for the combined shaft and shaft termination element, the axial displacement caused during the urging of the shaft termination onto the shaft can be varied.  
           [0065]    In other embodiments, there are provided the steps of:  
           [0066]    discontinuing the step of rotating the chuck; and  
           [0067]    forging the shaft termination element with the first end of the cylindrical shaft.  
           [0068]    The step of discontinuing the step of rotating the chuck is performed in response to a step of measuring a thermal emissivity during of the period that the step of urging is performed.  
           [0069]    In another embodiment, there are further provided the steps of:  
           [0070]    further loading a further shaft termination element onto a further shaft termination element receiver;  
           [0071]    further translating the further shaft termination element receiver whereby a principal axis of the further shaft termination element is disposed coaxial with the predetermined axis; and  
           [0072]    further axially urging the cylindrical shaft and the further shaft termination element toward each other.  
           [0073]    The steps of axially urging and further axially urging are performed simultaneously to achieve a weld at both ends of the cylindrical shaft simultaneously. At least one of the steps of axially urging and further axially urging are controlled in response to a step of monitoring a thermal emissivity during the at least one of the steps of axially urging and further axially urging. Additionally, there is provided the further step of further monitoring a thermal emissivity, whereby both ends of the cylindrical shaft are thermally monitored.  
           [0074]    During performance of the steps axially urging and further axially urging, the shaft termination element, the cylindrical shaft, and the further shaft termination element are maintained coaxially with the predetermined axis. In certain embodiments, the steps of axially urging and further axially urging are performed sequentially.  
           [0075]    In a still further embodiment, there are further provided the steps of:  
           [0076]    discontinuing the step of rotating the chuck;  
           [0077]    forging the shaft termination element with the first end of the cylindrical shaft; and  
           [0078]    further forging the further shaft termination element with the second end of the cylindrical shaft, the steps of forging and further forging being performed simultaneously.  
           [0079]    The step of forging includes the step of applying an axial force between the shaft termination element and the first end of the cylindrical shaft of approximately between 2500 and 12000 pounds.  
           [0080]    There is additionally provided in certain embodiment the step of further welding the cylindrical shaft and the further shaft termination element to each other. The step of further welding includes the further step of urging the further shaft termination element axially into communication with a second end of the cylindrical shaft whereupon a further friction weld is formed.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWING  
       [0081]    Comprehension of the invention is facilitated by reading the following detailed description, in conjunction with the annexed drawing, in which:  
         [0082]    [0082]FIG. 1 is a simplified schematic representation of a synchronous welding system constructed in accordance with the principles of the invention, as viewed from above;  
         [0083]    [0083]FIG. 2A is a simplified schematic front representation of the synchronous welding system of FIG. 1;  
         [0084]    [0084]FIG. 2B is a simplified schematic side representation of the synchronous welding system of FIG. 2A;  
         [0085]    [0085]FIG. 3A is a simplified schematic front representation of the synchronous welding system of FIG. 1 showing a tubular portion of a drive shaft having been translated to the left so as to be within a drive chuck arrangement and in position for communication with a first end piece;  
         [0086]    [0086]FIG. 3B is a simplified schematic side representation of a portion of the synchronous welding system of FIG. 3A showing a drive shaft support in a withdrawn position;  
         [0087]    [0087]FIG. 4 is a simplified schematic front representation of the synchronous welding system of FIG. 1 in the condition of FIG. 3A and further showing that a driven chuck arrangement is to be translated toward the left to engage the drive shaft;  
         [0088]    [0088]FIG. 5 is a simplified schematic front representation of the synchronous welding system of FIG. 1 in the condition of engagement of the driven chuck arrangement with the drive shaft, and further shows that the end pieces are urged in the direction of the arrows to effect friction welding as the driven chuck arrangement is rotated, with the chucks engaged;  
         [0089]    [0089]FIG. 6 is a simplified schematic front representation of the synchronous welding system of FIG. 1 in the condition of release of the axial force (in the direction of the arrows) arrangement with the drive shaft and the driven chuck in a disengaged condition;  
         [0090]    [0090]FIG. 7 is a simplified schematic front representation of the synchronous welding system of FIG. 1 with the driven chuck assembly having been restored to the left, disengaged from the drive shaft;  
         [0091]    [0091]FIG. 8 is a simplified schematic side representation of a portion of the synchronous welding system of FIG. 8 showing the drive shaft support in a deployed position for supporting the drive shaft;  
         [0092]    [0092]FIG. 9 is a simplified schematic front representation of the synchronous welding system of FIG. 1 with the drive chuck assembly in the released condition, and the completed drive shaft with the end pieces affixed thereto;  
         [0093]    [0093]FIG. 10 is a simplified schematic partially phantom representation of the driven chuck assembly and the stationary fixture;  
         [0094]    [0094]FIGS. 11A, 11B, and  11 C are respective simplified schematic front, cross-sectional side, and back representations of a chuck arrangement constructed in accordance with the principles of the invention; and  
         [0095]    [0095]FIG. 12 is an expanded representation of FIG. 11B showing in greater detail additional internal features, such as fluid passageways. 
     
    
     DETAILED DESCRIPTION  
       [0096]    [0096]FIG. 1 is a simplified schematic representation of a synchronous welding system  100  constructed in accordance with the principles of the invention, as represented from above. As shown in this figure, a human operator  11  loads a drive shaft tube  15  onto a deployable drive shaft support that is designated generally as  17  that will be discussed in greater detail below in connection with FIGS. 3B and 9. Human operator  11  may be replaced, in other embodiments of the invention, with a robotic delivery system (not shown). The human operator is shown in this figure to be holding a further drive shaft tube, designated herein as drive shaft tube  15 ′. Drive shaft tube  15 ′ is in all respects substantially identical to drive shaft tube  15  that is shown to be already installed on deployable drive shaft support  17 , and its corresponding portions are similarly designated, but with the addition of a prime (′).  
         [0097]    Drive shaft tube  15  is shown to have a first portion  20  having a first diameter determined at a first datum line  21 . The drive shaft tube also has a second portion  23  having a second diameter determined at a second datum line  24 . Datum lines  21  and  24  are used as the reference for most dimensions of the drive shaft tube during manufacture thereof. The end to be achieved in the processing to be effected by synchronous welding system  100  on drive shaft tube  15  is the installation by friction welding of a first end piece  30 , which in this embodiment of the invention is a constant velocity joint, onto the end of first portion  20 , and the installation of a second end piece  32 , which in this embodiment of the invention is a portion of a universal joint, onto the end of second portion  23 . Such installation of the first and second end pieces is to be performed simultaneously while, in this specific illustrative embodiment of the invention, all of the elements are supported on a common axis, to achieve high radial and axial alignment as described herein.  
         [0098]    Synchronous welding system  100  is comprised of several major subsystems that include, in this specific illustrative embodiment of the invention, a base  40 , a driven chuck assembly designated generally as  45 , a translatable chuck assembly designated generally as  50 . Driven chuck assembly  45  is installed on base  40  and has associated therewith a rotatory drive arrangement designated generally as  55 . Rotatory drive arrangement  55  in this embodiment, has an electric motor  56  that is mechanically coupled to driven chuck assembly  45  by a drive belt  57  that transfers rotatory energy from electric motor  56  to driven chuck assembly  45 . In this embodiment, a fixture in the form of a driven chuck assembly  45  and electric motor  56  maintain their position with respect to base  40  during all operations. However, translatable chuck assembly  50  is translatable in the direction of dual-head arrow  51  along base  40 . Such translation of translatable chuck assembly  50  is effected by any known means, including pneumatic and/or hydraulic actuation (not shown). Finally, there is provided the aforementioned deployable drive shaft support  17 , which as will be described is deployable to avoid interference with the translation of translatable chuck assembly  50 .  
         [0099]    [0099]FIG. 1 additionally shows that a further first end piece  30 ′ and a further second end piece  32 ′ are shown to be pre-loaded in receptacles  60  and  61  of the respective chuck assemblies  45  and  50 . More specifically, in this specific illustrative embodiment of the invention, further first end piece  30 ′ is pre-installed in receptacle  60  which, as will be described below, clamps onto further first end piece  30 ′ and transports same to the location of first end piece  30  after first end piece  30  has been installed onto drive shaft tube  15 . Similarly, further second end piece  32 ′ is pre-installed in receptacle  61 , and also clamps onto further second end piece  32 ′ and transports same to the location of second end piece  32  after second end piece  32  has been installed onto drive shaft tube  15 .  
         [0100]    [0100]FIG. 2A is a simplified schematic front representation of synchronous welding system  100  of FIG. 1. Elements of structure that previously have been discussed are similarly designated. As shown in FIG. 2A, driven chuck assembly  45  has a chuck assembly  70  that is shown in this figure to have a plurality of chuck jaws  71  in an open condition. Similarly, translatable chuck assembly  50  has a chuck assembly  75  that is shown in this figure to have a plurality of chuck jaws  76  in an open condition.  
         [0101]    The drive shaft tube is shown in this figure to be supported by deployable drive shaft support  17 . The deployable drive shaft support is formed of a support platform  80  that is itself supported to be pivotable on hinged arms  81 , pivotal deployment of deployable drive shaft support  17  being effected by actuation of an hydraulic cylinder  84 .  
         [0102]    [0102]FIG. 2B is a simplified schematic side representation of the synchronous welding system of FIG. 2A, and shows the rotatory coupling between electric motor  56  and chuck assembly  70  via drive belt  57 . In this figure, chuck assembly  70  is shown to have a plurality of chuck jaws  71  distributed circumferentially therearound. Also, an end representation of further first end piece  30 ′ is shown in this figure to facilitate comprehension of its spatial relationship in the uninstalled position with respect to the rotating center of chuck assembly  70 .  
         [0103]    [0103]FIG. 3A is a simplified schematic front representation of the synchronous welding system of FIG. 1 showing drive shaft tube  15  having been translated to the right so as to be within chuck assembly  70 . Elements of structure that previously have been discussed are similarly designated. Chuck jaws  71  are shown to be closed on first portion  20  of drive shaft tube  15 . In the present specific illustrative embodiment of the invention, chuck assembly  70  may have over 12 chuck jaws  71 . Accuracy of the clamping is achieved by a sequential closure of the chuck jaws. More specifically, in this specific illustrative embodiment of the invention, three chuck jaws (not specifically designated) are first closed on first portion  20  of drive shaft tube  15 . The three jaws are controlled in their operation by a cam plate (not specifically identified) that ensures that the three chuck jaws maintain radial equality as they translate radially toward, and communicate with first portion  20  of drive shaft tube  15 . Once the controlled three of chuck jaws  71  are closed against drive shaft tube  15 , then the remaining chuck jaws are closed without disturbing the axial location of drive shaft tube  15  established during closure of the three cam-controlled chuck jaws. In one embodiment, chuck jaws  71  are hydraulically actuated, and sequential operation of the closure of the chuck jaws is effected by hydraulic pressure break-over that results from the hydraulic pressure build-up that results from the engagement of the three cam-controlled chuck jaws. That is, as the three cam-controlled chuck jaws communicate with first portion  20  of drive shaft tube  15 , hydraulic pressure builds in the supply system (not shown). Upon reaching a predetermined hydraulic pressure that is of sufficient magnitude to ensure axially stable engagement of drive shaft tube  15 , hydraulic fluid, illustratively by operation of a pressure-responsive valve (not shown) is diverted to actuate selective ones or all of the remaining chuck jaws.  
         [0104]    [0104]FIG. 3B is a simplified schematic side representation of a portion of the deployable drive shaft support  17  portion of synchronous welding system  100  showing deployable drive shaft support  17  in a withdrawn position. As shown, in this specific illustrative embodiment of the invention, extension of hydraulic cylinder  84  causes support platform  80  to be pivoted in the direction of arrow  86 . Such pivotal withdrawal of support platform  80  is required to prevent collision with translatable chuck assembly  50  when it is translated along base  40  as described below.  
         [0105]    [0105]FIG. 4 is a simplified schematic front representation of synchronous welding system  100  wherein deployable drive shaft support  17  is in the condition of FIG. 3A. Elements of structure that previously have been discussed are similarly designated. Deployable drive shaft support  17  (not shown in this figure) has been withdrawn. As shown, chuck jaws  71  of chuck assembly  70  are shown in an engaged condition with first portion  20  of drive shaft tube  15 . Translatable chuck assembly  50 , however, is shown to have chuck jaws  76  of chuck assembly  75  to be in the open condition. Translatable chuck assembly  50  is therefore ready to be translated leftward, in the direction of arrow  88 .  
         [0106]    [0106]FIG. 5 is a simplified schematic front representation of synchronous welding system  100  wherein translatable chuck assembly  50  has been translated leftward, and chuck jaws  76  of chuck assembly  75  are closed to communicate with second portion  23  of drive shaft tube  15 . In this specific illustrative embodiment of the invention, the closure of chuck jaws  76  is effected in accordance with the procedure described hereinabove in connection with the closure of chuck jaws  71  of chuck assembly  70 . More specifically, three chuck jaws (not specifically designated) are first closed on first portion  23  of drive shaft tube  15 . The three jaws are controlled in their operation by a cam plate (not specifically identified in this figure) that ensures that the three chuck jaws maintain radial equality as they translate radially toward, and communicate with first portion  23  of drive shaft tube  15 . The cam plate is shown cross-sectionally in FIG. 11B. Once the controlled three of chuck jaws  76  are closed against drive shaft tube  15 , then the remaining chuck jaws are closed without disturbing the axial location of drive shaft tube  15  established during closure of the three cam-controlled chuck jaws. As previously described, the chuck jaws are hydraulically actuated, and sequential operation of the closure of the chuck jaws is effected by hydraulic pressure break-over that results from the hydraulic pressure build-up that results from the engagement of the three cam-controlled chuck jaws.  
         [0107]    As shown in FIG. 5, chuck jaws  71  and chuck jaws  76  being engaged with drive shaft tube  15  permits the rotatory motion that is applied to chuck assembly  70  by operation of electric motor  56  (not shown in this figure) and drive belt  57  to transmit via drive shaft tube  15  to chuck assembly  75 . Thus, chuck assembly  70 , drive shaft tube  15 , and chuck jaws  76  rotate as a unit. Once drive shaft tube  15  is rotated, hydraulic actuators  90  and  91  are shown to be drawn in so as to urge first end piece  30  and second end piece  32  axially in the directions of respective arrows  93  and  94 . However, first end piece  30  and second end piece  32  are clamped so as not to be rotatable. Thus, when the non-rotatable end pieces are urged into communication with rotating drive shaft tube  15 , the friction causes a heat sufficient to effect welding to be generated. During the frictional heating, first end piece  30 , drive shaft tube  15 , and second end piece  32  are maintained in precise axial alignment.  
         [0108]    In accordance with the invention, the force applied in the directions of respective arrows  93  and  94  is not necessarily constant, and may be applied in stages. More specifically, in one specific illustrative embodiment of the invention, there is provided a first force stage where the end pieces are each merely scuffed against the rotating drive shaft tube  15  in order to square-off the mating surfaces. In a practical embodiment of the invention, this first stage, which may be termed a “scrub” stage, has a duration of approximately one (1) second. The axial force applied during this first stage may be on the order of several hundred pounds. Then, in a second stage, additional axial force is applied to effect the heating to a level adequate to achieve welding. This second stage, which may be termed a “heating” stage, may in one embodiment have a duration of approximately two (2) seconds. The axial force applied during this second stage may be approximately between four hundred and two thousand (400-2000) pounds.  
         [0109]    In a highly advantageous embodiment of the invention, the temperature during heat phase is monitored with commercially available equipment to insure that the weld temperature of each end of the tube and their respective yokes is correct to obtain a proper weld. Proper temperature is obtained, in a practical embodiment, by modulating the magnitude of the weld force between the tube ends and their respective yokes while rotating the tube at a fixed preselected speed. This method allows components of different diameters at each end to be welded successfully. It is to be noted that different diameters will have different surface speeds, and since the heat generated is a function of surface speed and the applicable coefficient of friction, the variation in the applied force will make up for the difference in the surface speed of each end of the tube. The coefficient of friction, of course, is constant for the same material, i.e., at both ends of same tube.  
         [0110]    Finally, in a third stage a forging axial force is applied simultaneously to first end piece  30  and second end piece  32 . The third stage may, in one embodiment of the invention have a duration of approximately three and one-half (3.5) seconds. The axial force applied during this third stage may be approximately six thousand (6000) pounds. As stated, precise axial alignment is maintained between the components, ultimately resulting in an axially true drive shaft.  
         [0111]    It is therefore seen that three methods of accomplishing both welds at one time are disclosed for this invention. The first is an open loop system where the thermal and force characteristics of the weld are only recorded and verified. This verification data is compared against predetermined acceptable weld criteria. The data may be derived from thermal sensors and pressure transducers (not shown). In addition, a linear displacement transducer may, in certain embodiments, be employed to ascertain the extent to which the axial dimension of the drive shaft is affected by the welding process. The second method involves monitoring of the distance per stage. The third and preferred method is the closed loop control of burn off, heat up, and forge force. This is accomplished in some embodiments from the feedback obtained from a thermal probe (not shown) that produces a data signal that may be applied against a predetermined weld temperature set point and acted upon by a system controller (not shown). The feedback pressure sensor is correlated to the forge force applied in the referenced third stage of the friction weld. In this closed loop method, the forge force is the primary control loop in the final stage of the friction weld. The force on the servo rams is the inner, cascaded control loop in the burn off (first stage) and heat up (second stage) portions of the weld process. The finished length, as measured by a linear gauge (not shown) is verified, but is not a primary control parameter.  
         [0112]    [0112]FIG. 6 is a simplified schematic front representation of synchronous welding system  100  in the condition of releasing of the axial force (in the direction of the arrows  100  and  101 ) arrangement with the drive shaft and the driven chuck in a disengaged condition. Elements of structure that previously have been discussed are similarly designated.  
         [0113]    As shown in FIG. 6, hydraulic actuators  90  and  91  are in extended position, whereby the axial forging force on drive shaft tube  15  exerted via first end piece  30  and second end piece  32  has been released. In addition, chuck jaws  76  of chuck assembly  75  are opened, and therefore translatable chuck assembly  50  is now ready to be translated in the direction of arrow  101 .  
         [0114]    [0114]FIG. 7 is a simplified schematic front representation of synchronous welding system  100  with translatable chuck assembly  50  having been restored to the left, and thereby is disengaged from drive shaft tube  15 , which now forms a portion of a completed drive shaft. Elements of structure that previously have been discussed are similarly designated. In this figure, deployable drive shaft support  17  is shown in the deployed condition ready to accept drive shaft tube  15  with first end piece  30  and second end piece  32  installed thereon.  
         [0115]    [0115]FIG. 8 is a simplified schematic side representation of deployable drive shaft support  17  in a deployed position for supporting drive shaft tube  15 . As shown, hydraulic cylinder  84  is in a withdrawn condition, whereby support platform  80  is raised in the direction of arrow  105 .  
         [0116]    Referring once again to FIG. 7, chuck jaws  71  of chuck assembly  70  are in the open condition. Thus drive shaft tube  15  with first end piece  30  can be axially removed from chuck assembly  70 .  
         [0117]    [0117]FIG. 9 is a simplified schematic front representation of synchronous welding system  100  with drive shaft tube  15  with first end piece  30  and second end piece  32  installed thereon fully disengaged from driven chuck assembly  45  and translatable chuck assembly  50 , and supported by deployable drive shaft support  17 . At this stage, the completed drive shaft can be removed from deployable drive shaft support  17  and replaced by drive shaft tube  15 ′, illustratively by human operator  11  in FIG. 1, to commence welding of another drive shaft using drive shaft tube  15 ′, further first end piece  30 ′, and further second end piece  32 ′.  
         [0118]    [0118]FIG. 10 is a simplified schematic phantom representation of driven chuck assembly  45 . Elements of structure that previously have been discussed are similarly designated. As shown in this figure, chuck assembly  70  is located as a subassembly of driven chuck assembly  45 , and there is additionally provided an end piece carrier that is generally designated as  150 . The end piece carrier is translatable in the directions of two-headed arrow  153 . End piece carrier  150  is shown to have a receptacle  155  in which is deposited further first end piece  30 ′ in anticipation of it being installed on further drive shaft tube  15 ′ (not shown in this figure) of FIG. 1.  
         [0119]    Human operator  11 , or a robotic arrangement (not shown), installs further first end piece  30 ′ into receptacle  155 . Upon completion of the prior drive shaft formed of first end piece  30 , drive shaft tube  15 , and second end piece  32 , the completed drive shaft is removed from deployable drive shaft support  17  by human operator  11 , and further drive shaft tube  15 ′ is installed thereon by the human operator. End piece carrier  150  is translated toward the left whereby further first end piece  30 ′ is caused to be installed in a first central clamping station  160 . Such translation is effected by actuation of hydraulic actuator  162 , which urges end piece carrier  150  along tracks  165 . First central clamping station  160  maintains the relocated further first end piece  30 ′ in a clamped so as to be non-rotatable and axially co-located with further drive shaft tube  15 ′ (not shown in this figure) during the friction welding process, which proceeds as described hereinabove with respect to the welding of first end piece  30  and drive shaft tube  15 .  
         [0120]    In controlling the operation of the translation of end piece carrier  150 , its location is determined by a sensor  157  that is of the proximity type. Sensor  157  issues an electrical signal responsive to the proximity of sensor arm  158 .  
         [0121]    [0121]FIGS. 11A, 11B, and  11 C are respective simplified schematic front, cross-sectional side, and back representations of chuck assembly  70 . Elements of structure that previously have been discussed are similarly designated. As shown in FIG. 11A, chuck assembly  70  is provided with a housing  180  having a substantially planar forward surface  182  having a central aperture  185  therethrough. Radially inward of central aperture  185  are a plurality of chuck jaws  71 . Twelve such chuck jaws are shown in this figure, and it can be seen in FIG. 11B that more than one row of jaws are employed in this specific illustrative embodiment of the invention. Chuck jaws that are located proximal to cam plate  187  are designated as chuck jaws  71 , and those that are disposed axially inward are designated chuck jaws  71 ′. Cam plate  187  controls the rate of actuation and the centralization of three of chuck jaws  71 , one of which is controlled chuck jaw  71 ″. The two other controlled chuck jaws are not shown in this cross-sectional representation. The operation of cam plate  187  has been described hereinabove in connection with FIG. 5.  
         [0122]    Chuck assembly  70  is, as previously stated, rotatable in response to electric motor  56  (not shown in this figure) and drive belt  57  (not shown in this figure). The chuck assembly is rotated on bearings  190 , shown in FIG. 11B.  
         [0123]    [0123]FIG. 11C is a representation of chuck assembly  70  from the back. Central aperture  185  is designated from this direction as  185 ′. FIGS. 11B and 11C show drain port  193  and drain line  194  through which hydraulic oil is discharged. These elements will be described in greater detail in connection with FIG. 12.  
         [0124]    [0124]FIG. 12 is an enlarged representation of chuck assembly  70 , as shown in FIG. 11B, further showing in greater detail additional internal features. Elements of structure that previously have been discussed are similarly designated. As shown in FIG. 12, chuck assembly  70  is provided with a rotatable housing  200  and a non-rotating housing  201 . The rotating and non-rotating housings are shown on opposite sides of bearings  190 . Rotatable housing  200  is coupled to housing  180  by a fastener  205 . Thus, housing  180  is also rotatable.  
         [0125]    Non-rotating housing  201  has a stationary fluid inlet port  207  that, in this specific illustrative embodiment of the invention, receives pressurized fluid (not shown) from a source (not shown). The pressurized fluid received at stationary fluid inlet port  207  is delivered via an internal channel  208  to an unclamping supply port  209  for effecting unclamping of chuck jaws  71 . Pressurized fluid for clamping of the chuck jaws is received at a clamping fluid inlet port  210  that is connected by a channel  212  (shown in phantom) to chuck jaws  71 ″. Further fluid channels (not shown) are provided to supply pressurized fluid for clamping and unclamping to the other chuck jaws.  
         [0126]    As can be seen, unclamping supply port  209  and clamping fluid inlet port  210  are but labyrinth grooves in non-rotating housing  201  at the interface of rotatable housing  200 . In a practical embodiment of the invention, there is provided between the non-rotating and rotatable housings a clearance of approximately 0.002″. End seals  215  and  216  limit leakage to the bearings of the fluid that bypasses internal drain port  220 . In this specific illustrative embodiment of the invention, two such drain ports are provided. Fluid that is bypassed via the bearings is expelled at drain line  194 , and the remaining fluid is expelled at external port  193 .  
         [0127]    Although the invention has been described in terms of specific embodiments and applications, persons skilled in the art can, in light of this teaching, generate additional embodiments without exceeding the scope or departing from the spirit of the invention claimed herein. Accordingly, it is to be understood that the drawing and description in this disclosure are proffered to facilitate comprehension of the invention, and should not be construed to limit the scope thereof.