Abstract:
A portable journal turning lathe for machining a shaft at a job site, including a pair of clamping rings that are adapted to be centered at spaced apart locations along the length of the shaft to be machined. Extending between the clamping rings is a plurality of guide shafts which slidingly support a split ring clamshell assembly. A cutting tool carrier is affixed to the rotatable ring portion of the clamshell assembly so that when the movable ring is driven the tool carrier orbits the shaft being machined. A plurality of feed screws driven by a servomotor translates the clamshell assembly along the guide shafts.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     I. Field of the Invention  
         [0002]     This invention relates generally to apparatus for repairing and refurbishing the bearing surfaces of rotating shafts of large machines at a job site, and more particularly to a portable journal turning lathe that can easily be transported to a location in the field where a machine is to be repaired, mounted in place on the machine&#39;s shaft to be turned and then operated to remove any scoring and other surface irregularities from the shaft so that it is ready for replacement of its bearings.  
         [0003]     II. Background of the Invention  
         [0004]     In my earlier U.S. Pat. No. 6,065,378 I describe a portable journal turning lathe including a pair of clamping rings that are adapted to be centered at spaced-apart locations along a length of a shaft to be refurbished. Extending between the clamping rings is a plurality of guide shafts which slidingly support a split-ring clamshell assembly. A cutting tool carrier is affixed to the rotatable ring portion of the clamshell assembly such that when the movable ring is driven, the tool carrier orbits the shaft being refurbished. A single feed screw driven by a servomotor translates the clamshell assembly along the guide shaft.  
         [0005]     In the earlier arrangement described in my &#39;378 patent, only a single feed screw was used to move the clamshell assembly along the guide shafts. As such, the lathe described in my &#39;378 patent had some tolerance problems when doing large shafts. When the cutting tool would dig into the shaft to be machined it would create resistance on the longitudinal movement of the clamshell assembly on the guide shafts. The side opposite the feed screw lags behind so that the cut of the cutting assembly was not square and concentric to the shaft being machined.  
         [0006]     The journal turning lathe of the present invention obviates this drawback. Rather than having a single feed screw, my present invention employs two feed screws which are positioned and simultaneously driven so as to hold the clamshell carrying the cutting tool square and concentric to the cylindrical workpiece being machined. In the case of the present invention compared to my earlier arrangement, the workpiece is more effectively machined.  
       SUMMARY OF THE INVENTION  
       [0007]     The foregoing features and advantages of the present invention are achieved by providing a portable lathe for turning a shaft that comprises first and second clamping rings adapted to be centered at spaced-apart locations along the length of the shaft or pipe to be turned. Supported by the first and second clamping rings are pluralities of elongated, cylindrical guide shafts. A clamshell assembly is slidingly supported on the plurality of guide shafts, the clamshell assembly being of the type including a stationary ring member and a movable ring member journaled for rotation relative to the stationary ring member. A cutting tool carrier is mounted on the movable ring member of the clamshell assembly for supporting a cutting tool. A first drive means includes a pair of diametrically positioned and simultaneously, synchronously driven lead screws for translating the clamshell assembly along the guide shafts and a second drive means is mounted on the stationary ring member and that rotates the movable ring member carrying the tool carrier in a circular orbit about the workpiece.  
         [0008]     The first and second clamping rings each include a plurality of threaded radial bores extending through them and threadingly fitted into these is a corresponding plurality of adjustable shaft-centering screws which can be readily adjusted for rending a clamshell assembly concentric with the access of the shaft to be turned at the time of setup. 
     
    
     DESCRIPTION OF THE DRAWINGS  
       [0009]      FIG. 1  is a perspective view of the portable journal turning lathe comprising a preferred embodiment of the present invention;  
         [0010]      FIG. 2  is a front perspective view showing the drive gear assembly;  
         [0011]      FIG. 3  is a sectional view of the journal turning lathe of  FIG. 1 . 
     
    
       [0012]     The foregoing features, objects and advantages of the invention will become apparent to those skilled in the art from the following detailed description of a preferred embodiment, especially when considered in conjunction with the accompanying drawings in which like numerals in the several view refer to corresponding parts.  
       DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0013]     Referring first to  FIG. 1 , there is indicated generally by  10  a portable journal turning lathe constructed in accordance with the present invention. It is adapted to be mounted on a shaft or pipe (not shown) whose surface is in need of machining. The journal turning lathe  10  is seen to comprise a first and second clamping rings  12  and  13  having an inside diameter large enough to surround the workpiece to be machined. Clamping ring  12  and clamping ring  13  have substantially the same shape and size. Each includes semi-circular segments  14  and  16  which can be releasably fastened together along a parting line  20  by swing bolts  21  to form an annulus.  
         [0014]     Threaded bores  22  are radially formed through the thickness dimension of the clamping rings. A plurality of centering bolts  24  are threadedly fitted into the threaded bores  22 . The centering bolts  24  are moved in and out of the threaded bores  22  in a radial direction to accommodate a range of workpiece sizes that are to be machined.  
         [0015]     Integrally formed to clamping ring segment  14  of clamping ring  12  are a pair of ring guides  26  and  28 . Likewise, integrally formed in semi-circular segment  14  of clamping ring  13  are ring guides  30  and  32 . Ring guides  34  and  35  are each integrally formed in semi-circular segment  16  of clamping ring  12 . Ring guides  36  and  38  are also integrally formed in semi-circular ring segment  16  of clamping ring  13 . The ring guides  36 ,  38 ,  30 ,  32 ,  34 ,  36  and  38  each include a longitudinally extending bore as at  40 . Fitted into longitudinal bore  40  of ring guides  26  and  30  is a first guide shaft  42  comprising a smooth, cylindrical steel rod. An identical guide shaft  44  extends between ring guides  28  and  32 . Set screws at as  46  secure guides shafts  42  and  44  in their respective bores  40 . Guide shaft  48  extends between ring guide  34  and ring guide  36 . Setscrews  46  secure guide shaft  48  into the longitudinally extending bore  40  of ring guides  34  and  36 . A final guide shaft  50  extends between ring guides  35  and  38 , and setscrews  46  secure guide shaft  50  into the longitudinally extending bore  40 .  
         [0016]     A clamshell assembly  52  is slidingly supported along guide shafts  42 ,  44 ,  48  and  50 . This clamshell assembly may be of the type more particularly described in my earlier U.S. Pat. No. 5,549,024, the teachings of which are hereby incorporated by reference as it is set forth in full herein. As explained in the &#39;024 patent, the split frame clamshell assembly  52  includes a stationary ring member  54 . Disposed beneath a protective shroud  56  and journaled for rotation on bearings (not shown) which extend in the axial direction from the flat side surface of the stationary ring  54  is a movable gear ring  58  only a small portion of which can be seen through an opening formed in the protective shroud  56  in  FIG. 3 . This movable gear ring is adapted to be driven by a suitable motor (not shown). The manner which the motor is configured to drive the rotatable gear ring  58  of the clamshell assembly  52  is fully disclosed in the afore-referenced &#39;024 patent. The split ring clamshell comprises two semi-circular segments  60  and  62  that join together along a parting line  64  and may be securely clamped together by swing bolts. Integrally formed to the exterior side surface of the stationary clamshell ring  54  are four clamshell guide member  68 ,  70 ,  72  and  74 . These guide members each include a longitudinal bore, as at  76 , for receiving linear bearings  78 , the linear bearings surrounding guide shafts  42 ,  44 ,  48  and  50 . A cutting tool carrier  80  is attached to the movable ring gear  58  and machines the workpiece as explained in the &#39;024 patent.  
         [0017]     As shown in  FIG. 2 a  drive assembly generally designated by  86  is integrated with the first clamping ring  12 . The drive assembly  86  imparts controlled transitional movement of the clamshell assembly  52  along the guide shafts  42 ,  44 ,  48  and  50  between the clamping rings  12  and  13 . The first clamping ring  12  comprises a stationary ring  88  adapted to be clamped to the cylindrical work piece and a rotatable ring  90  which is journaled for rotation on the stationary ring  88 , wherein the rotatable ring  90  has a plurality of gear teeth  92  on its peripheral surface. A servo, two-speed gear box  93  is mounted on the stationary ring  88 . An output shaft  94  extends from a drive motor  95  with a pair of drive gears  96  mounted on the output shaft  94 . The gearbox further including a spur gear  98  which is mounted on a spur gear axle  100  and secured on the axle by a bushing  102 . The drive gears  96 , and the spur gear  98  form a gear train which engages the gear teeth  92  on the peripheral surface of the rotatable ring  90 . The gear train effects a speed reduction between the drive motor speed and the speed at which the rotatable ring is driven. The gear teeth  92  on the rotatable ring  90  engage a pinion gear  108 . The pinion gear is mounted on a pinion gear axle  110  which are embedded in ring guides  28  and  34 . The bushing  112  is pressed in the drive gear cover (not shown), which holds the gear  108  and shaft  110  in place.  
         [0018]     The teeth of pinion gear  108  engage a pair of feed screw drive gears  114  and  115  which are each mounted in ring guides  28  and  34 . Two threaded feed screws  116  and  117  are each operatively coupled to the feed screw drive gears  114  and  115  which is held onto the threaded feed screws  116  and  117  by a feed screw drive gear nut  118 . The threaded feed screws  116  and  117  are each journaled for rotation at opposite ends in the first clamping ring  12  and the second clamping ring  13 .  
         [0019]     Disposed on the clamshell assembly  52  and surrounding the feed screw  116  and  117  are feed nuts  120 . The feed nuts  120  engage the clamshell drive assembly  52  and rotation of the feed screws will translate the clamshell assembly  52  along the guide shafts  42 ,  44 ,  48  and  50  between the clamping rings  12  and  13 .  
         [0020]     Once the clamshell assembly  52  has completed a pass down the workpiece during its cutting stroke at a low speed, it is returned to the starting position by first pressing a “reverse” switch on the servo motor  95  and shifting the two speed gear box  93  to its “fast” state for a quick return of the clamshell assembly  52 .  
         [0021]     This invention has been described herein in considerable detail in order to comply with the Patent Statutes and to provide those skilled in the art with the information needed to apply the novel principles and to construct and use such specialized components as required. However, it is to be understood that the invention can be carried out by specifically different equipment and devices, and the various modifications, both as to the equipment and the operating procedures, can be accomplished without departing from the scope of the invention itself.