Abstract:
A belt sander includes a housing and an endless sanding belt supported by the housing. A first shaft is connected to the housing, and the housing is pivotable about the first shaft. A second shaft is connected to the housing and offset from the first shaft. The sander is mounted to the rotating portion of a rotary machining clam shell trackway and revolved around a pipe surface to be sanded while biasing the sander against the surface. The sander may also be pivotable to sand a tapered surface.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application represents the national stage application of International Application PCT/US2008/050206 filed 4 Jan. 2008, which claims the benefit of U.S. Provisional Patent Application 60/883,448 filed on Jan. 4, 2007, which are incorporated herein by reference in their entirety for all purposes. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to portable machining tools or machine in place machining tools, and, more particularly, to an overlay sander that can smooth the weld overlay on a pipe. 
     BACKGROUND OF THE INVENTION 
     It is sometimes necessary to machine in place existing equipment for the purpose of testing, repairing and/or reconditioning the equipment. This process may be a result of the original fabrication of the machine or testing thereof, machine breakdown or malfunction, or may be part of a repair or maintenance program to overcome normal wear and tear or to prevent a malfunction of the equipment. 
     For example, relatively large piping which may be part of a pipeline, building, plant machinery, ship or other structures/devices, can include overlays which are a result of a welding process during the initial fabrication of the piping, or a repair or maintenance of the equipment. The overlays are basically weld buildup rings, or weld crowns, of inconel (a hard, tough material), or other material, around the outer perimeter of the piping or piping component such as a nozzle or valve, in the vicinity of the weld. The necessity of providing a juncture on a pipe that is professionally finished with a defect-free weld has been appreciated for some time, and more particularly in the case of nuclear power plants and pipelines, for example, the necessity of providing junctures that are reliable and durable is of the utmost importance. Consequently, the weld crowns need to be smoothed out in order for testing equipment to be used to check for cracks, wall thickness, etc. Further, the equipment size, location and connection to other structures may determine that it is advantageous to machine the equipment in place, rather than remove it from its operational configuration for refurbishment. 
     A known method of smoothing out the weld crowns is to use an axial feed slide mounted to a “clamshell” and cut or machine the overlay. Clamshells are portable pipe lathes that are connected to the outside of the pipe, where the cutting tool can move around the outside perimeter of the pipe to machine the outside of the pipe. Such devices are known in U.S. Pat. Nos. 4,739,685, 4,939,964, 5,549,024 and 6,619,164, for example. One problem with this method is that the machine would cut round and most overlays are not perfectly round. Because of this, more material has to be removed than necessary to get the entire overlay to be smooth. This also requires extra time. 
     The time element can be critical in pipelines, nuclear reactors, and the like, where downtime can be very costly and the necessity of providing junctures that are reliable and durable is of the utmost importance. Frequently, the working conditions associated with the pipe machining equipment have been quite hostile either to the machine or to the machine operator. For example, in nuclear reactors, the necessity for pipe replacements has been such that these types of maintenance procedures are required quite frequently. However, maintenance personnel may only work in an area that is radioactively hot for extremely short periods of time. Accordingly, the desirability of an apparatus for finishing pipes which can be set up in a minimal amount of time, can complete the machining in a minimum of time, and can be initialized and dismantled in a minimal amount of time has obtained increasing importance and acceptance in the industry. 
     What is needed in the art is an apparatus and method of machining an exterior surface of equipment, particularly piping, that can machine in place existing equipment and which can smooth weld crowns or other elements that may not be perfectly round, or perform other machining, efficiently. 
     SUMMARY OF THE INVENTION 
     The present invention provides an apparatus and method of machining an exterior surface of equipment, particularly piping, that can machine in place existing equipment and can smooth weld crowns or other elements which may not be perfectly round, or perform other machining, efficiently. More particularly, the present invention provides an overlay sander for such purposes. 
     The foregoing features and other advantages of the invention appear in the detailed description which follows. In the description, reference is made to the accompanying drawings which illustrate a preferred embodiment of the invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of an embodiment of an overlay sander mounted to a clamshell that, in turn, is mounted to piping, according to the present invention; 
         FIG. 2  is a perspective exploded view of the overlay sander of  FIG. 1 ; and 
         FIG. 3  is a detail perspective view of the area  3 - 3  of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring now to the drawings, and, more particularly, to  FIG. 1 , there is shown a machining apparatus  50  connected to pipe structure  52  having an overlay, weld crown or other work surface  54 . Weld crown  54  is shown schematically, but will typically have an irregular width and height. Machining apparatus  50  includes a portable pipe lathe or clamshell  56  as is described in U.S. Pat. Nos. 4,739,685, 4,939,964, 5,549,024 and/or 6,619,164, for example, and incorporated herein by reference. Clamshell  56  is not limited by the cited references, but can also include other embodiments of similar devices. Clamshell  56  generally includes stationary portion  58  fixedly connected to pipe structure  52 , and ring gear housing  60 , each of which include adjoining semicircular segments which allow them to be positioned circumferentially around the pipe. The two are joined together by bearings internal to the construction. As such, the rotatable portion  62  can be made to spin about the central axis of stationary portion  58  when the ring gear is driven by a motor driven drive gear. An overlay sander  64  is connected to rotatable portion  62 . 
     Referring more particularly to  FIG. 2 , overlay sander  64  works in part by using an air cylinder  33  to hold the contact or tracking wheel  40  against the overlay surface  54 , with the moving belt  1  in between the wheel  40  and the surface  54 . The housing  2  has a window in its perimeter right below the wheel  40  where the belt  1  is exposed to the surface of the pipe to be sanded. The cylinder  33  pressure can be regulated to pivot the sander about the axis of shaft  31  and thereby change the force exerted on the work surface by the sander, which determines the rate of removal of material from the work surface by the belt  1 . Air cylinder  33  is connected to pivot bracket  28  via shoulder bolt  41 , and is also connected to cylinder mount bracket  29 . Cylinder mount bracket  29  connects to tilt adjustment block  27 . Swivel elbow fittings  36  connect the cylinder  33  to air hose connections (not shown), one for extending the cylinder and the other for retracting it. 
     Pivot bracket  28  connects to belt housing  2  with shafts  30  and  31 , with a bushing  16  between each shaft and the hole in the housing  2  through which the respective shaft  30  or  31  extends, and with shaft  30  threaded into pivot bracket  28  and shaft  31  extending through the bracket  28  and threaded into tilt adjustment block  27 . Shaft  31  establishes the pivot axis of the overlay sander, so cylinder  33  pivots the sander about the axis of shaft  31 . Shaft collars  34  fix the housing  2  and attached sander assembly to the shaft  30 . Set screws  35  fix side adjustment block  42  to height adjustment block  26 , which is slideable up and down in tracks  37  and  38  that are fixed to slide  25 . Starwheel  32  includes a lead screw that is threaded into the block  26  so that turning the starwheel adjusts the position of the block  26  along the tracks  37  and  38 . 
     Referring to  FIGS. 2 and 3 , tilt adjustment block  27  and side adjustment block  42  are connected by several components, including intermediate block  43 , arcuate slot brackets  44 , and linear slot brackets  45 . Tilt adjustment block  27  and intermediate block  43  are connected by a fastener  51  in a slot  53  that permits tilt adjustment block  27  to slide relative to intermediate block  43  in the direction height adjustment block  26  may slide. The tilt adjustment block  27  also rotates relative to side adjustment block  42  about an axis parallel to the direction along which side adjustment block  42  may be moved. This permits the overlay sander  64  to tilt and sand up to 45° tapered surfaces. 
     Referring to  FIG. 3 , overlay sander  64  is tilted as follows: first, fasteners  46  and  47  are loosened, but are not removed from the assembly. This permits blocks  27  and  43  and arcuate slot brackets  44  to slide in the direction of the slots on linear slot brackets  45 . Note that this step is only necessary if intermediate block  43  is originally abutted against side adjustment block  42  so that intermediate block  43  may be rotated in subsequent steps. Next, fastener  48  is loosened, but is not removed from the assembly. Intermediate block  43 , tilt adjustment block  27 , housing  2 , belt  1  and other components may be commonly tilted thereafter relative to side adjustment block  42 . When the components have been rotated to a satisfactory working position, the fasteners  46 ,  47 , and  48  are tightened to prevent further rotation and secure the assembly. 
     Referring again to  FIG. 2 , on the drive side, drive wheel  39  is connected to housing  2  with drive wheel bracket  18  and bearing  14 . Drive wheel  39  further connects to motor  20  using square adapter shaft  24 , drive adapter shaft  21  and bearing  19 . Motor  20  can be an electric, pneumatic or hydraulic motor. Motor  20  further includes motor mount  8  and housing mount  22  that connects the motor  20  to the housing  2 , and adapter plates  23  and  49  that allow electric, pneumatic and/or hydraulic fittings  70  and  71  to connect to motor  20 . 
     The path of endless belt  1  is defined by the axes of wheels  40 ,  39  and roller wheel  4 , and is generally parallel to those axes, which are also generally parallel to the axes of shafts  30  and  31 . The connection of the sander to the clamshell biases the sander against the workpiece, under the force of the cylinder  33 , so as to permit the sander to follow the surface of the workpiece as the sander removes material from the workpiece. The result is that the surface may not have a fixed center, but being perfectly round is not a requirement in many applications. 
     Slide  25  is bolted to the face of any size clamshell. An electric variable speed reversible motor (not shown) is used to drive clamshell  56  so overlay sander  64  can be driven either clockwise or counterclockwise around overlay  54 . Side adjustment block  42 , in conjunction with tracks  37  and  38  and height adjustment block  26 , are used to move overlay sander  64  so contact wheel  40  is directly above workpiece  52  and weld overlay  54 . Contact wheel  40  is connected to housing  2  with alignment shaft  3 , left alignment bracket  13 , bearings  14  and washer  17 . Starwheel  32  is used to position contact wheel  40  about ½″ above workpiece  52 . Belt housing  2  is then positioned along shafts  30  and  31  over the top of the overlay  54  by using the shaft collars  34  and guide shaft bushings  16 . Belt  1  is put on housing  2 . Belt adjustment nut  5  slides in tracks in the housing  2 . Spring  12  is compressed between bushing  7  and nut  5  to bias nut  5  away from knob  15 , that has a threaded shank that is threaded into the nut  5 . Roller wheel  4  is mounted to nut  5  with a shoulder bolt  11  and bearings  10 . Belt  1  is tensioned by turning knob  15  to adjust the position of slide nut  5  to change the tension exerted on the belt  1  by the wheel  4 . 
     The sanding is done by first starting clamshell  56  rotating by turning on the electric drive. The overlay sander drive motor  20  is then started to get belt  1  spinning. The cylinder  33  is extended to push contact wheel  40  against work surface  54 , with the belt  1  between the contact wheel  40  and the work surface  54 . Overlay sander  64  is rotated once around overlay  54 , and then the electric drive for the clamshell  56  is reversed to go the other way around overlay  54 . This is repeated until the entire overlay surface is smooth. Cylinder  33  is retracted to lift contact wheel  40  off the surface and the clamshell  56  rotation is stopped. The overlay is now smooth but not necessarily round. 
     The present invention can include a control box (not shown), and associated wiring and air hoses) that is used to start/stop the motors and adjust the air pressure. The present invention can include a tripper mechanism (not shown), as is described in U.S. Pat. No. 5,881,618 for example, which can be used to advance starwheel  32  if desired. A reversing tripper (not shown) can also be installed on machine apparatus  50  to reverse the direction of the clamshell automatically. Also, the direction of the belt  1  of the overlay sander  64  could also be reversed. 
     A preferred embodiment of the invention has been described in considerable detail. Many modifications and variations to the preferred embodiment described will be apparent to a person of ordinary skill in the art. Therefore, the invention should not be limited to the embodiment described.