Abstract:
In this system an unbalancing force, as set by an unbalance load injection device integrated into a work piece balancing machine and its balance computer, is injected into an injection planethrough an operating portion of the machine. This injected load is in effect transferred by computation to a calibrating plane of a known standard or a masterwork part loaded into and rotatably driven by the balancing machine. The values of the unbalancing force as generated by the unbalance injecting device and by calculation into the rotating master are sensed by synchronizer and vibration pick-ups. Data reflective of the injected imbalance are furnished to the balance computer for the calibration thereof. The principle of this self-calibration is to use a workpiece drive spindle and unbalance injector device that can introduce a known unbalance, set by adjusting the unbalance injector device to inject a predetermined load at a known angle into the master to effect master unbalance. This induced unbalance is picked up by synchronizer units and used as the parameters in the calibration process of the balance compute. This allows the machine to accurately determining the imbalance in other work pieces. Subsequently conventional unbalanced work parts processed by the calibrated machine can be balanced by the machine with a higher-level of accuracy in accordance with balancing data of the calibrated balance computer.

Description:
[0001]    Provisional application Serial No. 60/303,195 filed Jul. 5, 2001 is hereby cited for purposes of priority and such is hereby claimed. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    This invention generally relates to the precise correction of imbalance of rotating work pieces and more particularly to new and improved self-calibrating work piece balancing machines having the capability to automatically determine and correct the imbalance of rotating parts and to automatically self-calibrate under predetermined operating conditions and further to new and improved processes for the automatic calibration of work piece balancing machines.  
           [0004]    2. Description of the Prior Art  
           [0005]    Production equipment such as automatic work piece balancing machines for rotating metallic work pieces at high rotational speeds and effecting the dynamic balancing thereof by adding balancing weights in appropriate locations thereon or by removal of mass therefrom have been successfully employed for many years. Highly developed machines in this category have balance computers that calculate the amount of weight adjustment needed for dynamically balancing different work pieces and control the balancing speeds and many other machine operations. More particularly these balance computers function with the machine hardware to precisely locate the positions in selected balancing planes on the work piece where weight correction is needed for work piece balancing and for activating the tools to accomplish the actual weight correction. These precisioned operations are required for an effective single balancing operation or for the repeated rotational balancing of a quantity of unbalanced work pieces in mass production operations.  
           [0006]    For such work, the balancing machines need to be precisely calibrated so that the exact location on each individual work piece for weight-adjustment can be quickly and precisely determined and the appropriate balance weight adjustment quickly made. Prior to the present invention, work piece balancing machines required a time consuming and tedious manual process of stopping and starting the rotating machine to manually add and remove calibration weights to a master or selected standard work piece for calibrating the machine. Such prior calibrating procedures were prone to various human errors and required great skill and care to avoid calibration mistakes. Personal care also had to be taken by the operator since it was generally necessary to physically handle, add, and remove calibration weights with respect to the standard or master and the starting and stopping of the machine for the calibration thereof.  
         SUMMARY OF THE INVENTION  
         [0007]    In contrast to the prior machines and calibration processes, the new and improved self-calibrating work piece balancing equipment and processes of this invention reduces machine down-time for calibration and to a large extent eliminates the labor and skill including attention to precise detail previously required of the operator to manually calibrate a balancing machine. This advancement is achieved in this invention by the unique incorporation of one or more automatic load or force injecting units, hereinafter referenced as unbalance injector devices, into a new and improved dynamic balancing machine featuring automatic self calibration. These on-board devices provide hands free selection and changing of calibration loads and along with other machine equipment cooperate to form and complete a new and improved self-calibrating work piece balancing machine. These unbalance injection devices are uniquely operative in this invention in that known unbalancing loads are automatically injected into the rotating chucks or other workpiece mountings of the machine to establish inertia axes offset from the rotational axis of a standard or master work piece rotatably driven therein. Known moments are resultantly established at predetermined correction planes that extend through the work piece whose values are fed to a balance computer of the machine for the automatic calibration thereof. Such calibration can be readily and quickly accomplished with minimal operator input and in many cases, while the master is being continuously rotatably driven. Moreover, these unbalance injector devices are generally arranged into the machine construction so that they are offset to one or both ends or extremities of a calibrating master or known standard workpiece operatively mounted for rotation in the machine. The physical characteristics of the calibrating work piece are not changed such as in prior calibration procedures and the calibrating workpiece are not physically handled or touched by the calibrating operator except for machine loading and unloading.  
           [0008]    For single plane calibration, base line imbalance measurements are taken from the rotating master or known standard and fed to a balance computer incorporated into the balancing machine where the data is registered. The unbalance injection device is then automatically activated to inject known imbalance loads into a base injection plane of the machine. This plane may transversely extend through the unbalance injector device and the spindle or other machine component securing the calibrating work piece and operatively mounting the injector device for rotation of these components about a spin axis. This injected force is, in effect, linearly translated as an unbalancing load to the master in a predetermined correction or calibration plane parallel to the base plane and transverse of the work piece spin axis. The cradle supporting the work piece mounting and spinning equipment is usually mounted by suspension spring construction and is subject to vibratory excitation from the rotational imbalance of the master or standard during machine calibration, as well as from unbalanced workpieces subsequently balanced by the machine.  
           [0009]    Vibratory and positional signals reflecting these known imbalance loads and the location of the eccentricity as applied to the standard or master by the unbalance injector device are received by synchronizer and vibration pick up units. Data from these pick-ups are fed to the balance computer in a first calibration thereof. The machine is stopped and the part rotated relative to the work piece holding chuck or other securement a predetermined number of degrees, 180 degrees for example. Known imbalance loads from the imbalance injection device are again injected into the machine and translated to the standard or masterwork piece in the correction plane and the final calibration readings are taken. With known calibration imbalance loads applied in specific locations in known correction planes, the balance computer will identify and store the known imbalance data and calibrate with reference thereto.  
           [0010]    With such calibration, the computer will subsequently recognize imbalance loads and eccentricities in unbalanced work pieces being processed with the machine and effect the accurate weight correction and location to effect the dynamic balancing of such work pieces.  
           [0011]    For double plane calibration at least two unbalance injecting devices and associated controller are integrated the balancing machine and the balance computer thereof so that known unbalancing loads injected into a rotating portion of the machine are translated from the injection planes through the machine into calibration planes through a calibrating master or known standard workpiece operatively mounted in the machine. These calibrating planes are spaced apart from one another and the unbalancing loads cause the inertia axis of the master or standard to misalign with respect to the spin axis thereof. The magnitude of the resulting dynamic unbalance is used to calculate the moment or couple generated at a predetermined spin rpm. The injected unbalances generate vibrations, which are picked up by spaced pick up devices and generate data supplied to the balance computer to effect the calibration thereof.  
           [0012]    This new and improved self-calibrating machine can be easily calibrated by different machine operators of varying skills including those that are mechanically oriented and can follow prescribed procedures but have little calibration experience. The machine may be conditioned for the automatic calibration mode after a known standard work piece or master is operatively mounted therein by operator initiative in simply starting the machine. Under computer control the known standard part is brought to a balancing speed and the unbalance injection device or devices under command from the balance computer are automatically actuated by the controller thereof so that the machine quickly and automatically calibrates the balance computer to the known imbalance injected into the master without human intervention.  
           [0013]    This invention is further drawn to new and improved self-calibrating balancing machines for rotating and determining balancing points on work pieces and to the physical balancing of work pieces and to new and improved machine calibration methods. With these machines and methods, work pieces such as propeller shafts, crankshafts and road wheels for vehicles can be quickly loaded into the machine and balanced with extraordinary and repeatable accuracy. In this invention, known and predetermined forces are automatically applied to a rotating standard or master calibrating work piece and are effective in a predetermined calibrating plane thereof to achieve the rotational imbalance thereof. Data directly resulting from these imbalance loads is fed to a balance computer of the machine to effect the calibration of the machine computer. This imbalance data is supplied from a synchronizer or positional pick up and from vibration pick-ups associated with the balancing machine and stored in the memory of the balance computer for subsequent reference in calculating the rotational imbalance and correction of unbalanced work pieces subsequently processed in the machine.  
           [0014]    These self-calibrating balancing machines are generally equipped with specialized tooling that quickly makes the balancing adjustment by adding or subtracting work piece balancing weight in predetermined balancing planes thereof. With such equipment, unbalanced parts can be loaded and spun to predetermined speeds and then automatically balanced to provide improved quantity production. The machines of this invention require only minimal down-time for automatic calibration purposes and with improved accuracy to further improve operating efficiency particularly as compared to the prior manual calibration of balancing machines.  
           [0015]    A general feature, object and advantage of this invention is to provide (1) new improved work piece balancing machines capable automatic self calibration and without stopping once a calibrating work piece is installed in the machine and (2) new and improved methods of calibrating such machines with at least one onboard unbalance injector device which can be operated to automatically inject predetermined imbalance forces to a known standard work piece and in at least one predetermined calibration plane thereof while it is being rotatably driven at predetermined speeds to effect calibration of a balance computer associated with the machine.  
           [0016]    Another feature, object and advantage of this invention to provide a new and improved automated work piece balancing machine having a balance computer as part thereof that is functional to: (1) serially spin and determine the rotational imbalance of work pieces each generally having a principal inertia axis that is not parallel to the axis of rotation thereof and operatively mounted therein and the weight variances necessary to correct such imbalance to physically effect the correction of such imbalance and (2) self-calibrate by effecting the injection of known loads of imbalance into predetermined points in at least two calibration planes of a calibrating standard work piece and then to feed data detailing such imbalances into a balance computer to teach the computer to recognize such imbalances and calibrate relative thereto. This allows the balance machine to be subsequently employed in the accurate dynamic balancing of interchangeable and unbalanced work pieces.  
           [0017]    Another feature, object and advantage of this invention is to provide a new and improved process for automatically calibrating a work piece balancing machine in which a master or known standard work piece is continuously rotating during the calibration of the machine and in which the master or standard is rotatably driven and at least one unbalance force injecting device is utilized to inject known imbalance loads to the rotating workpiece to produce the rotational imbalance of the master and the feeding of resulting and exact imbalance data to an associated balance computer so that the balance computer is precisely calibrated and the machine can be subsequently employed with great accuracy to spin and detect imbalances in other work pieces and effect the accurate rotational balancing thereof.  
           [0018]    Another feature object and advantage of this invention is to provide a new and improved self calibrating work piece balancing machine and method of calibration in which known imbalance loads are injected into a master or other calibrating work piece being rotatably driven in the balancing machine without physically changing the master such as by adding calibrating weights thereto.  
           [0019]    These and other features, objects and advantages of this invention will become more apparent and understood from the following specifications including the detailed description and drawings in which: 
       
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS  
       [0020]    [0020]FIG. 1 is a side view of a balancing machine along with a diagram of a balance computer operatively connected thereto illustrating one embodiment of the invention;  
         [0021]    [0021]FIG. 1 a  is an enlargement of the encircled portion  1   a  of FIG. 1 illustrating parts of an unbalance injector device utilized in this invention;  
         [0022]    [0022]FIG. 1 b  is a pictorial view of part of the balancing machine of FIG. 1 
         [0023]    [0023]FIG. 2 is a front view of the balancing machine of FIG. 1;  
         [0024]    [0024]FIG. 3 is a schematic diagram of the embodiment of the invention illustrated n FIGS. 1 and 2;  
         [0025]    [0025]FIG. 4 is a front view of another preferred embodiment of the invention;  
         [0026]    [0026]FIG. 5 is a schematic diagram illustrative of the embodiment of the invention of FIG. 4;  
         [0027]    [0027]FIGS. 6 a ,  6   b  and  6   c  are interrelated curves illustrating self calibration operations of a work piece balancing machine according to this invention;  
         [0028]    [0028]FIGS. 7 a ,  7   b  and  7   c  are interrelated curves illustrating a prior art process of manually calibrating of a work piece balancing machine;  
         [0029]    [0029]FIG. 8 is a side view of another preferred embodiment of this invention;  
         [0030]    [0030]FIG. 8 a  is a pictorial view of the FIG. 8 embodiment of the invention;  
         [0031]    [0031]FIG. 8 b  is a pictorial view of one pair of balancing rings used in the FIG. 8 embodiment of this invention;  
         [0032]    [0032]FIG. 9 is a front view of still another preferred embodiment of this invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0033]    Turning now in detail to the drawings there is illustrated in FIGS. 1 through 3, a single plane balancing machine  10  for spinning and dynamically balancing a rotatable drum or other work piece  12 . The work piece  12  is securely mounted on a work piece holding unit or chuck  14  operatively mounted to and forming an extension of a cylindrical spindle  16 . For machine calibration, the workpiece  12  is a known standard work piece or a balanced master into which a known unbalancing force is injected as will be further explained below.  
         [0034]    The spindle, work piece holding unit, and any master or work piece mounted thereon are accordingly supported for unitized rotation about a spin axis  18  by upper and lower spindle mounting brackets or plates  20 , 22  vertically spaced from one another. The upper plate may be fixed to a stationary support  21  and have a centralized annular hole  23  therein through which the spindle extends. The lower plate is operatively connected mounted to the upper plate by a pair of flat supporting suspension springs  24 ,  26 , laterally spaced from each other. The spindle mounting is accordingly resilient and the work piece  12  and the spindle and mount exhibit significant vibration when the unbalanced work piece is rotatable driven.  
         [0035]    Torque for the rotational drive of the spindle and the components mounted thereon is provided by a selectively energizable electric motor  28  that is secured to the plate  22  or other suitable mounting. The motor has an upwardly extending and rotatable output shaft  30 . This shaft has a drive pulley  32  fixed thereto that operatively receives an endless drive belt  34  which extends laterally and around a driven pulley  36 . Pulley  36  is fixed to the lower end of the cylindrical spindle  16  just below the lower support plate  22 . With this arrangement, power is readily transferred from the motor to the spindle for the rotational drive of the work piece  12  about spin axis  18 .  
         [0036]    In addition to the work piece holder, the spindle operatively mounts an unbalance injector device  42  operatively associated with the machine which can be set to inject predetermined unbalancing loads into the rotating standard or master work piece  12  for calibrating the work piece balancing machine  10 . The unbalance injector device  42  may be a balancing unit such as one capable of injecting balancing loads into rotating tools for tool balancing purposes, a milling or drilling tool for example.  
         [0037]    Among the commercial units, that can be utilized in this invention to inject loads into the work piece  12  are balancing units such as the EM 2000 high speed balancer or others supplied by BalaDyne Corporation, 1665 Highland Drive, Ann Arbor, Mich. 48108. and the automatic balancing system SBS or the SB-4500 balancer supplied by Schmitt Industries, Inc. 2765 NW Nicolai St Portland Oreg. 95210. U.S. Pat. No. 5,757,662 issued May 26, 1998 to S. W. Dyer et al for Electromagnetically Actuated Rotating Machine Unbalance Compensator, hereby incorporated by reference, discloses a balancing unit and electronic controls that may be readily integrated into the balancing machine and methods of this invention.  
         [0038]    In any event, the unbalance injector device  42  may have a pair of interior counter-weight rings  44 , 46  see FIG. 1 a, operatively mounted to a rotatable upper, axially-extending shaft portion of the spindle or to the rotatable workpiece holding unit  14  of the spindle. The unbalance force injection unit further comprises a driver  48  having a coil assembly  50  gapped from and disposed outwardly of the rings  44 , 46  that mounts to a housing of the spindle or other stationary component  52 .  
         [0039]    As applied to the present invention when a predetermined unbalancing load is required for calibrating purposes, electronic controller  54  best diagrammatically illustrated in FIG. 3 and operatively connected to the coil assembly by line  56  are activated by the balance computer to initiate load injections on signals transmitted from a balance computer  60  through line  59  connecting the controller to the balance computer. The controls  54  are accordingly operative to send power pulses to the coil assembly of the driver  48  of the unbalance injector device and effect the electromagnetic rotational stepping of the counter-weight rings  44 ,  46  to different predetermined rotary positions. Rotation of the rings to different preestablished positions results in the application or injection of a predetermined imbalance load into a base or injection plane IP extending through the work piece holding end of the spindle.  
         [0040]    For machine calibration, the known unbalancing load is translated from the rotating spindle of the machine to the attached rotating master work piece  12  and particularly to a location on the master that is in a predetermined calibration or correction plane CP. This calibration plane extends thorough the master at a set distance from the base or injection plane and is parallel thereto.  
         [0041]    The unbalance injector device  42  of the embodiment of FIGS.  1 - 3  is adjusted and set by the controller to automatically inject the predetermined unbalancing load into the spindle or chuck of the machine when the machine drives the work piece to a predetermined rpm. This unbalancing load is subsequently injected into the work piece  12  as a transversely oriented load and in the transverse calibration or correction plane extending therethrough for calibration proposes. This known unbalancing load is physically applied to the rotating workpiece holding component of the machine by the displaced rings  44 , 46  of the rotating components of the unbalance injection device and by translation to the workpiece  12  in the predetermined correction plane CP thereof.  
         [0042]    While the unbalancing load is physically applied to the spindle and work piece holding device through base or injection plane IP extending therethrough, the calculated resulting imbalance force from unit  42  is linearly displaced to the predetermined calibrating or correction plane CP extending through the work piece at an offset location outboard of the injection or base plane IP. In a single plane balancing operation, the applied unbalancing load and the resulting injector force are equal.  
         [0043]    As diagrammatically illustrated in FIGS. 1 and 3, the work piece balancing machine  10  has a balance computer  60  associated therewith which is programmed to effect the calculations necessary to effect the balancing of work pieces being processed by the machine  10 . The balancing computer is calibrated with the functional work piece imbalance positional signals from a synchronizer pick up  62  positioned adjacent the work piece holder unit  14  or the work piece itself. Additionally electrical signals generated by unbalanced work piece vibrations are fed into the balance computer  60  from a vibration pick up  66  that is operatively connected to one of the support springs such as spring  24  or other suitable vibrating support forming part of the machine and connected to the balance computer  60  by lead  67  as diagrammatically illustrated in FIG. 3.  
         [0044]    For machine startup operation, an operator preferably calibrates the machine by installing a known standard or masterwork piece on the machine  10  and energizes the balance computer and controller for automatic calibration. The machine rotatably drives the standard to a predetermined balancing speed and a minimized unbalance load, programmed into the controller, is injected into the standard work piece. Positional and known unbalance data resulting from the minimized load injection into the rotating master or other work piece mounting unit are recorded by the synchronizer and vibration pick ups and fed to the balance computer where such data is stored in the memory to calibrate to such imbalance. In the next run, the unbalance injection device is ordered to apply a predetermined unbalancing calibration load into the system and the results are again fed to the balance computer. The difference between the two readings taken from the unbalance pickups is the gain of the system.  
         [0045]    Optionally for further calibration to compensate for the unbalance in the spindle and eccentricity of the part relative to the rotational axis of the spindle, additional steps are taken. This includes the stopping of the machine so that the operator can disengage the work piece and rotate the work piece on its rotational axis and relative to the workpiece holding chuck  14  a predetermined number of degrees, 180 for example. The work piece is then reattached to the machine chuck for the rotational drive thereby and ramped to a predetermined speed The unbalancing injection device is activated to again inject a minimized unbalancing load into the work piece as previously described. The calibration load is then injected and the final reading are taken and sent to the balancing computer for finalizing the calibration thereof.  
         [0046]    After such calibration is completed, unbalanced work pieces can be quickly loaded one after the other and spun to balancing speeds whereby the calibrated balance computer can calculate the particular imbalance of the work piece being processed and effect the precise correction thereof with appropriate weight position and the quantity of weight adjustment in the balancing planes thereof.  
         [0047]    Double Plane Balancing  
         [0048]    FIGS.  4 - 6  illustrate another preferred embodiment of the invention that carries forward principles of the embodiment of FIGS.  1 - 3 . Primarily they share in the aspect directed to the automated injection of predetermined unbalancing loads into a load injection plane utilizing unbalance injector device while the workpiece holding device is spinning a known standard or master work piece at a predetermined rotational speed. This injection of known unbalancing force into the machine such as the work piece holding chuck thereof results in a corresponding unbalancing force being injected into the master work piece being driven by the machine and in a predetermined correction plane thereof. Data from the resulting workpiece imbalance vibrations and the corresponding eccentricity the unbalanced master or standard is supplied to the balancing computer for the calibration thereof.  
         [0049]    However, the machine of FIGS.  1 - 3  can not precisely balance elongated work pieces, such as mass produced propeller or crank shafts or other units, whose principal inertia axes are not parallel to their associated axes of rotation. This non-parallel relationship of the inertia and rotational axes in such parts is known as dynamic unbalance. Correction of unbalances such as dynamic unbalance in an elongated work piece requires the addition of two weights to the work piece and in two separate and spaced-apart correction planes so that other machines and process steps are needed and their associated balancing computers need to be calibrated.  
         [0050]    In the construction of FIGS.  4 - 5 , a balancing machine  100  capable of balancing such elongated work pieces provided. This machine has an electric or otherwise powered drive motor  102  which is operatively mounted in a housing  104  supported on a generally rectilinear lower base plate  106  in turn secured to a floor or other fixed support  108 . The machine has a cradle  110  resiliently supported by four vertically extending corner suspension spring units  112  extending upwardly from attachment with the base plate  106 . The upper ends of these spring units adjustably mount into threaded adjustment fittings  114  secured to the sides of the cradle, for cradle leveling or positioning purposes. Moreover, with this resilient suspension spring construction the cradle, the work piece-spinning sub-assembly  116  operatively mounted thereon as well as the work piece, here in the form of a master or known standard engine crank shaft  118  operatively mounted therein experience significant vibrations from work piece imbalances.  
         [0051]    As in the embodiment of FIGS.  1 - 3 , data from such vibrations and the location of injected imbalance loads are supplied to the balance computer  120  of the machine for calibration purposes as will be explained hereinafter.  
         [0052]    The work piece spinning equipment or sub-assembly  116  equipment includes a horizontally extending spindle  122  having its cylindrical outboard end  123  mounted for rotation in a bearing assembly  124  secured in a supporting end housing  126  that extends upwardly from attachment with the cradle  110 . The inboard end  127  of the spindle mounts a hook drive  128 , which drivingly fits onto the adjacent end of the crankshaft  118 , which for calibrating purposes is a master or known standard crankshaft as previously indicated. As shown the master crankshaft  118  is supported for rotation in the machine about a horizontal spin axis  130  by suitable bearings such as a front roller bearing  132  secured to a stationary part of the spindle or other component and by a rear roller bearing operatively mounted on upright  136 . Additional support is provided by upright  138 . The uprights  136  and  138  are securely attached by their bases to cradle  110  by appropriate fastener devices that provide for the adjustment of the uprights to accommodate work pieces of different lengths and other configurations Upper clamping retainers  140 ,  142  operatively mounted on the stationary uprights  136  and  138  have bottom rollers which contact main bearing surfaces of the crankshaft to operatively retain it in the spinning equipment of the machine.  
         [0053]    The crank shaft  118  is rotatably driven about the axis  130  by the motor  102  which has a rotatable output shaft  144  having a pulley  146  operatively mounted on the end thereof which accommodates and drives an endless drive belt  148  which loops around a spindle drive pulley  150  that is drivingly secured at its inner diameter to the spindle  122 .  
         [0054]    In addition to the drive pulley  150 , the spindle  122  operatively mounts left and right side unbalance injection devices  152 , and  154 . Each of these devices is substantially the same in construction as the unbalance injection device  42  of the machine of FIGS.  1 - 3 . Each device  152 ,  154  may comprise a pair of interior counterweight rings operatively mounted in side by side relationship. These rings have known imbalance loads so that they can be rotated to different angular positions to effect the loading of the spindle with predetermined imbalancing loads for calibration purposes.  
         [0055]    Moreover, as in the previous embodiment the counterweight rings are actuated by a driver such as a surrounding coil disposed outwardly of the pair of rings. The coil is secured in an outer housing that may be fastened to a stationary housing or other component of the machine. The unbalancing injector devices  152 , 154  are supplied with injector command signals from a controller  160  through lines  162  and  164  diagrammatically shown in FIG. 5. The controller  160  operates automatically on command signals from the balance computer through signal line  165 . Accordingly, the unbalance injector devices are selectively operative on computer command to serially inject unbalance loads into the machine driving the master workpiece in the laterally spaced injection planes IP-1 and IP-2. These unbalancing loads are translated to the correction planes CP-1 and CP-2 of the workpiece respectively to effect the establishment of inertia axis that is not parallel to the spin axis of the crankshaft. A known imbalance is created in the master, which will be used for calibration of the machine  
         [0056]    As in the previous embodiment, the balance computer  120  is operationally utilized to determine the specifics of the imbalance in unbalanced work pieces to be processed in the machine  100 . The balance computer  120  is supplied with imbalance positional data of a workpiece from the synchronizer pickup  162  communicating with the balance computer  120  by data line  163 . However, because the master being used for calibration purposes is eccentrically loaded by the imbalance injector device in the two correction planes its inertia axis does not align with the centerline or rotational axis  130 . Consequently, a known dynamic imbalance is created in the master. This imbalance generates vibrations of particular amplitudes recorded by left and right side unbalance vibration pick-ups  166  and  168 . These pick-ups are operatively mounted with respect to the reiliently sprung cradle to receive vibration inputs therefrom. Picks up signals resulting from these vibrations are sent to the input/output board  170  of the balance computer  120 .  
         [0057]    For calibrating purposes, the rotationally balanced master or a standard work piece  118  with known imbalances and other physical measurements and characteristics, which is operatively loaded into the machine as by the machine operator or an automatic loader so that the hook drive  128  drivingly engages the drive end of the master crankshaft. Then the operator simply starts the calibration drive by a suitable control such as a push button. Base line reading with minimized load injections are taken and stored in the computer memory as in the previous embodiment of FIGS.  1 - 3 . After this the machine accelerates the part to a balancing speed and without stopping serially injects the unbalancing loads into the master or standard in the two horizontally spaced correction planes thereof and the data reflective of these unbalancing loads are automatically sent by operation of the synchronizer and vibration pick ups to the balance computer for the self-calibration thereof.  
         [0058]    [0058]FIGS. 6 a ,  6   b  and  6   c  depict the known load injection and self-calibration operation of the balancing machine and methods of the embodiments of FIGS. 4 and 5. More particularly FIG. 6 a  shows the continuous and constant rotational speed of the motor and the master or standard work piece  118  driven by the machine. As an example during the initial third of the operation, both of the unbalance injector devices  152  and  154  are in a return or home position. FIG. 6 b  illustrates the calibrating position of the unbalance injector device  152  at time T-1 by signals from the controller  160  as required by the balance computer  120 . This first load injection into the injection plane IP-1 and translated to calibrating plane CP-1 results in increased amplitude of plane 1 or calibrating plane CP-1 vibrations “a” which are picked up by the vibration sensor  166 . At a subsequent time T-2 for example, the balancing computer  120  directs the unbalance device controller  160  to return the unbalance injection device  152  to home and simultaneously effect the calibration operation of unbalancing injection device  154 . As shown in FIGS. 6 c  this results in the reduction of plane 1 vibration amplitude and an increase in the plane 2 amplitude of the vibrations “b” from the injection of the calibrating load into the work piece in plane 2 or calibrating plane CP-2.  
         [0059]    This staged increased amplitude of vibrations in planes 1 and 2 resulting from the serial injection of known calibration loads into the spindle of the machine is translated to the workpiece in calibrating planes CP-1 and CP-2. These timed injections are diagrammatically represented by the large amplitude signals “a” and “b” for each revolution. Data representative of the known unbalances and their sites of insertion are supplied to the balance computer for the initial calibration thereof. These calibrating load injections take place without machine stoppage as previously described,  
         [0060]    [0060]FIGS. 7 a ,  7   b  and  7   c  are graphical representation of the calibration operation of a prior art workpiece-balancing machine that requires manual calibration and are presented for comparison with the corresponding calibration of the machine of this invention, FIGS. 6 a ,  6   b  and  6   c . The time intervals DT-1 and DT-2 shown as dashed lines between the curves of FIGS. 7 a  represent prior art machine down times for stopping and starting the machine and for the hands on activity of the operator for manually adding and subtracting calibration weights to the master or standard. Such down times are eliminated in automatic two-plane calibration of the present invention. This demonstrates the material improvement in the machine and efficiency of this invention over the prior art. Moreover, these new processes and machines sharply eliminate the opportunity for operator error and materially reduces calibration burden.  
         [0061]    Turning now to FIG. 8, there is illustrated another two plane dynamic balancing machine  300  that features self-calibration similar to that of the machines and processes of FIGS.  1 - 3  and  4 - 6 . The machine  300  has a pair of laterally spaced support walls  304  and  306  that extend upwardly from base plate  308  that securely mounts to the floor  309  or other stationary support. The walls  304  and  306  have enlarged and upstanding rear portions  310  and  312  that provide end support for a pair of laterally spaced and forwardly extending, spring suspension arms  314  and  316 . The forward ends of these spring suspension arms attach to a cradle unit  318  operatively mounted thereto which has suitable bearings such as ball races  319  that support a spindle assembly  320  therein for rotation about a vertical spin axis  322 . Additionally the base plate  308  supports a servo unit such as an electric or hydraulic drive motor  326  thereon which has an upwardly extending output shaft  328  that rotatably drives a pulley  330  on the distal end thereof that receives and drives an endless drive belt  332  which loops around and drives a chuck drive pulley  334 . The pulley  334  is drivingly secured by threaded fasteners  336  to a chuck assembly  338  supported by the spindle assembly. More particularly the chuck assembly  338  extends upwardly from attachment with the upper end of the spindle assembly  320  by threaded fasteners  340  so that it rotates about the spin axis  322 . The chuck further has a pneumatically actuated collet  343  that is operable in the releasable attachment of a road wheel assembly  344  to the chuck  338 .  
         [0062]    The chuck assembly  338  further operatively carries a pair of spaced unbalancing injector devices,  342  and  344  which have construction such as described about the embodiments of FIGS.  1 - 3  and FIGS.  4 - 6 . More particularly these unbalance injector devices  342 ,  344  may each have a pair of weighted rings  346 , 348  pictorially illustrated in FIGS. 8 b  operatively mounted to the spindle. As in the previous embodiments these devices may have an outer driver such as a selectively energized coil separated by an air gap and outwardly of the rings. The driver as in prior embodiments is attached to a fixed housing not shown. This coil is operatively connected to a controller  352  through leads  354  and  356  that is operable to effect energization of the coil to step the rings to different predetermined positions on the chuck  338  and relative to one another to effect the injection of different and predetermined unbalancing loads to the spindle for calibration purposes.  
         [0063]    The wheel assembly  344  although a master for calibration purposes has two vertically spaced correction planes CP-1 and CP-2 assigned there to since its inertia axis will be changed by known weight application in each of these planes so as to be out of parallel with respect to the spin axis  322 .  
         [0064]    As in the preceding embodiments, this embodiment of the invention has a balance computer  360  associated therewith which is employed to receive data from vibration pick up units  364  and  366  whose housings are mounted to the walls  304  of the frame  302 . These units receive vibration signals from the elongated pick-up rods  367 ,  369  extending from the pick-up devices into operative engagement with the spindle  320  or other suitable vibrating component of the machine. In addition to the vibration pick-up units  364 ,  366 , a synchronizer or once-per-turn pick up  368  is mounted to a fixed housing or wall  370  adjacent to the chuck  338  and is operative to deliver signals to the balance computer  360  with positional data regarding the imbalance loads so that effective balancing weight can be applied to precise positions in the correction planes of the wheel assembly to effect the balancing thereof The balance computer communicates with the controller  352  through signal line  372  so that the controller timely injects the predetermined unbalancing loads into the injection planes extending through the spindle of the balancing machine.  
         [0065]    The balance computer  360  of the machine is precisely and efficiently calibrated relative to known imbalances for the optimized dynamic balancing of unbalanced parts. This is accomplished by the employment of programmed unbalancing load injector devices,  342  and  344 , which may be substantially the same as the pair of units of the FIGS. 4, 5 and  6 . The load injectors, operatively mounted to the spindle assembly, are signaled by controller  352  to serially inject unbalancing loads into the spindle assembly in injection planes IP-1 and IP-2 for calibration purposes. These planes respectively extend transversely though the load injector units and the spin axis  322  and are parallel to the correction planes CP-1 and CP-2 to which these loads are translated as described in connection with the two plane balancing of FIGS. 4, 5 and  6 . As with the other two plane balancing embodiment of this invention, signals from the known imbalance loads and their locations are picked up by the vibration sensors or velocity transducers  364 , 366  and synchronizer  368  and sent to the balance computer  360 . This calibrating data recognized by the balancing computer is stored in memory thereof so that subsequent unbalanced wheel assemblies can be balanced by machine  300  with optimized accuracy  
         [0066]    [0066]FIG. 9 depicts a propeller or prop shaft balancing machine  400  that is self-calibrating as in the other embodiments. The machine  400  has a base  402  mounted to a support such as floor  404 . The machine further comprises pairs of horizontally spaced suspension spring units  406  and  408  that extend upward from connection with the base into connection with left and right side cradles  410  and  412 . The left side cradle supports an outer housing fixed thereto that operatively mounts a cylindrical spindle  414  therein for rotation about a horizontal spin axis  416 . The spindle is rotatably driven by an electric or hydraulic motor  420  supported on a base  422 . The motor has a rotatable output connected by coupling  424  to the outer end of the spindle  414 . The inboard end of the spindle has a chuck  426  operatively mounted thereto which is adjustable to operatively receive the end of an elongated master or known propshaft  428  thereto for the rotational drive of the propshaft about axis  416 . The aft end of the propshaft is secured into a right side chuck  430  that in turn is mounted to the end of a spindle  432  supported by a housing  436  secured on cradle  408  of the right side suspension.  
         [0067]    Importantly the chucks have unbalance injection devices  440  and  442  operatively mounted thereon which like the embodiment of FIGS.  4 - 6  and  8  are operable under command of a controller  444  to be selectively energizable to inject unbalance loads into the propshaft for calibration purposes as in the previous embodiments. Vibration pickups  446  and  448  are operatively mounted to the left and right side spring suspensions  406  and  408  which are subjected to the vibratory energy of left and right side imbalance loads as in the previous embodiments. Data from the injected loads are delivered to a balance computer  450  by feeds from the vibration pick-ups  446  and  448 . A once per turn pick up or synchronizer  452  provides the positional data of the imbalance loads which are fed to the balance computer  450  for calibration thereof.  
         [0068]    The prop shaft of FIG. 9 has a universal, constant velocity, or other connector-joint  460  therein. With such constructions, the injection plane of the unbalance injector device  434  will be in plane IP-1 and transversely through the joint  460 , which is translated to correction plane through the master workpiece and calibration plane CP-1 for calibration purposes. In contrast, the imbalance load injection of the unbalance injector device  440  will be through the IP-2 extending through the device  440  and the chuck  426  which is translated from the machine spindle to correction plane CP-2 that extends through the prop shaft for purposes of calibration as in the preceding embodiments.  
         [0069]    Diagrammatically illustrated are weight welding units  470  which are operatively supported by overhead gantry  472  for welding balancing weights to the prop shaft in accordance with dynamic balancing data from the balancing computer. The weight welder provision may however be automated in manner disclosed in U.S. copending application Ser. No. 10/121,583 filed Apr. 12, 2002 by P. Loetzner, P Hemingray and C. Maas for Rotatable Shaft Balancing Machine and Method assigned to the assignee of this invention and hereby incorporated by reference  
         [0070]    In the FIG. 9 embodiment of this invention, an unbalanced production part can be used for the calibration of the machine  400  with some modification of the above process or method that involves stopping of the machine. For such variation, the machine is stopped once to reorient the part in the machine. No down time is required for changing the calibration weights. To begin such modified calibration, a normal production part such as those formed by process machines is randomly selected and placed into the machine  400  for the rotational drive thereby. The machine is started and the selected workpiece is rotationally accelerated to a calibrating speed. At this time, the known imbalance loads are serially inject into the rotating workplace in the separate correction planes and the machine automatically calibrates itself as previously described.  
         [0071]    The operator then stops the machine  400 , rotates the production part 180 degrees on its spin axis, and reconnects the part to the drive chuck or other drive. The machine is again started and to rotatably drive the selected part to a balancing speed. The calibration weights are again automatically and serially injected into the two correction planes. Again the vibrations resulting from these subsequent known unbalancing loads and positional signals from the synchronizer are picked up and the calibration data therefrom are directed to and stored in the associated computer so that subsequent unbalanced propshafts can be accurately balanced by the machine  400 .  
         [0072]    While this invention has been described in terms of certain preferred embodiments and methods thereof, it will be appreciated that other forms and methods could readily be adapted by one skilled in the art. Accordingly, the scope of this invention is to be considered limited only by the following claims.