Automatic dredge pump rebuilder

Abstract

To rebuild the interior of a shell of a volute-type centrifugal dredge pump, a radial arm carrying a welding torch swings about the axis of the shell to repeatedly traverse the interior of the shell and automatically shifts the welding path at the end of each traverse. The radial arm advances or retracts radially as it rotates to follow the eccentricity of the volute configuration. The advance or retraction of the radial arm in response to its rotation is accomplished by a sprocket chain that walks around the periphery of a fixed sprocket on the axis of rotation, the diameter of the fixed sprocket being selected in accord with the eccentricity of the volute configuration.

I claim: 
     
       1. In an apparatus employing a welding device to deposit a series of contiguous weld beads on the interior wall of a hollow workpiece having coaxial upper and lower openings with the pattern of the series of the welding beads of a desired eccentricity relative to the axis of said openings, the combination: a base structure intersecting said axis in the region of said openings;   a horizontal guideway mounted on the base structure radially of said axis for rotation about the axis;   a carriage movable along said guideway;   a support for said welding device mounted on said carriage;   first power means on said base structure to turn the guideway about said axis;   second power means on the .[.base structure.].  .Iadd.carriage .Iaddend.to extend and retract said support for the welding device relative to the carriage to or from the interior wall of the hollow workpiece;   third power means to raise and lower said support for the welding device relative to the carriage;   fourth power means to swing said welding device up and down in an arc relative to the support; and   means responsive to rotation of the guideway relative to the base structure to shift the carriage along the guideway in accord with the desired eccentricity of the pattern of the series of beads.     
     
     
       2. A combination as set forth in claim 1 which includes a control system to govern said power means respectively, said control system including a control panel mounted on said guideway. 
     
     
       3. A combination as set forth in claim 2 in which said control system includes a second control panel outside of the workpiece. 
     
     
       4. A combination as set forth in claim 2 in which said control system includes a relatively small portable remote control unit for temporary use for inching one of said power means in the course of setting up the apparatus to operate on the workpiece. 
     
     
       5. In an apparatus employing a welding device to deposit a series of contiguous weld beads on the interior wall of a hollow workpiece having coaxial upper and lower openings with the pattern of the series of the welding beads of a desired eccentricity relative to the axis of said openings, the combination of: a base structure intersecting said axis in the region of said openings;   a linear guideway mounted on the base structure for rotation about said axis;   a carriage movable linearly along said guideway;   a support for said welding device mounted on said carriage;   a first power means on said base structure to turn the guideway about said axis;   a second power means on the .[.base structure.].  .Iadd.carriage .Iaddend.to extend and retract said support for the welding device relative to the carriage to or from the interior wall of the hollow wall of the workpiece;   third power means to raise and lower said support for the welding device relative to the carriage;   fourth power means to swing said welding device up and down in an arc relative to the support; and   means mechanically responsive to rotation of the guideway relative to the base structure about said axis to shift the carriage along the guideway in accord with the desired eccentricity of the pattern of the series of beads.     
     
     
       6. A combination as set forth in claim 5 in which said responsive means comprises: a fixed member having a circular peripheral surface concentric to said axis; and   flexible means in wrapping engagement with said peripheral surface, said flexible means having two opposite portions extending tangentially from the peripheral surface and connected to said carriage.   
     
     
       7. A combination as set forth in claim 5 in which said responsive means comprises: a fixed sprocket concentric to said axis; and   a sprocket chain attached to the carriage and in engagement with one side of the fixed sprocket.   
     
     
       8. A combination as set forth in claim 7 which includes means to maintain the sprocket chain under tension. 
     
     
       9. A combination as set forth in claim 8 in which said tension means is yieldable to permit the sprocket chain to be shifted from one side to the other of the fixed sprocket. 
     
     
       10. A combination as set forth in claim 7 in which said sprocket is removable to permit a sprocket of one diameter to be substituted for a sprocket of a different diameter to change the eccentricity of the pattern of the series of beads. 
     
     
       11. A combination as set forth in claim 7 in which the sprocket chain is engageable with opposite sides of the fixed sprocket selectively to cause the welding device to follow oppositely curved eccentric patterns. 
     
     
       12. A combination as set forth in claim 5 in which said responsive means comprises: a fixed eccentric cam and a cooperative follower to follow the cam, the follower being attached to the carriage. 
     
     
       13. A combination as set forth in claim 12 which includes spring means acting between the carriage and the guideway to urge said follower against the cam. 
     
     
       14. In an apparatus employing a welding device to deposit a series of contiguous weld beads on the interior wall of a hollow workpiece having coaxial upper and lower openings with the pattern of the series of the welding beads of a desired eccentricity relative to the axis of said openings, the combination of: a base structure intersecting said axis in the region of said openings;   a linear guideway mounted on the base structure for rotation about said axis;   a carriage movable linearly along said guideway;   a support for said welding device mounted on said carriage;   a first power means on said base structure to turn the guideway about said axis;   a second power means on the .[.base structure.]. .Iadd.carriage .Iaddend.to extend and retract said support for the welding device relative to the carriage to or from the interior wall of the hollow wall of the workpiece;   third power means to raise and lower said support for the welding device relative to the carriage;   fourth power means to swing said welding device up and down in an arc relative to the support; and   means to shift the carriage along the linear guideway in accord with the desired eccentricity of the pattern of the series of beads.     
     
     
       15. A combination as set forth in claim 14 in which said base structure rests on the support surface on which the workpiece rests. 
     
     
       16. A combination as set forth in claim 15 in which the base structure is disconnected from the workpiece. 
     
     
       17. A combination as set forth in claim 15 in which the base structure has a plurality of legs and the legs are adjustable with respect to the spread of the legs. 
     
     
       18. A combination as set forth in claim 14 which includes a pair of limit switches responsive to travel of the carriage along the guideway to de-energize said first power means at the opposite ends of the beads of weld metal. 
     
     
       19. A combination as set forth in claim 14 which includes a sleeve on the carriage with said support for the welding device slidable longitudinally in the sleeve, said second power means acting between the sleeve and the support for the welding device to extend and retract the support for the welding device relative to the carriage.   
     
     
       20. A combination as set forth in claim 19 in which said carriage forms a vertical guideway for said sleeve and said third power means acts between the carriage and the sleeve to raise and lower the sleeve thereby to raise and lower the welding device. 
     
     
       21. A combination as set forth in claim 14 in which an arm extends from the carriage; in which the welding device is pivotally mounted on the outer end of the arm;   and in which the fourth power means is mounted on the arm to control the angle of the welding device relative to the arm.   
     
     
       22. A combination as set forth in claim 14 which includes a control system for causing the welding device to traverse the interior of the workpiece automatically with automatic step-over at the end of each traverse, said control system including: means to de-energize the first power means for a predetermined time period at the desired termination point of each bead;   means to energize one of said second, third, and fourth power means during said time period to shift the welding device to the desired starting point of the next successive bead;   means to interrupt the welding operation by said welding device for substantially the duration of said time period;   means to energize and reverse said first power means at the end of the time period; and   means to resume the welding operation of said welding device at the end of the time period.   
     
     
       23. A combination as set forth in claim 22 which includes a manually operable selector switch for each of said four power means and a manually operable inching switch for each of the four power means, each of the selector switches having a position for automatic control of the corresponding power means to automatically carry out an operating cycle and an alternate position to permit manual control of the corresponding power means by the corresponding inching switch.   
     
     
       24. A combination as set forth in claim 22 in which the control system includes: limit switches responsive to travel of the carriage on the guide means to de-energize the first power means at the desired termination points of the beads; and   means effective at the beginning of each of said time periods to energize one of said second, third, and fourth power means for a time interval that is less than said time period to shift the welding device to the desired starting point of the next successive bead during the time period.   
     
     
       25. A combination as set forth in claim 24 which includes means responsive to the two limit switches to interrupt the welding operation by the welding device when either of the two limit switches is operated by the carriage and to resume the welding operation when neither of the two limit switches is operated. 
     
     
       26. A combination as set forth in claim 24, which includes a timer responsive to the two limit switches to operate for a given time period whenever either of the two limit switches is operated; and   which includes means responsive to said timer to reverse and energize the first power means at the end of said time period.   
     
     
       27. A combination as set forth in claim 26 which includes a second timer responsive to the two limit switches to operate for a given time interval less than said time period whenever either of the two limit switches is operated; and which includes means to energize one of said circuits of said second, third, and fourth means for the duration of said time interval.   
     
     
       28. A combination as set forth in claim 26, which includes a spring-loaded switch for momentary manual operation to determine the initial direction of rotation of the first power means at the start of the deposition of a series of the weld beads.   
     
     
       29. A combination as set forth in claim 24 in which said series of eccentric beads terminates at the rim of one of said upper and lower openings of the hollow workpiece; and in which one of said limit switches is operative at the position of the carriage corresponding to the radius of the opening.   
     
     
       30. A combination as set forth in claim 29 in which said one limit switch is mounted on one of said carriage and said guideway; in which an actuator for the limit switch is mounted on the other of said carriage and said guideway to operate said one limit switch; and   in which one of said limit switch and said actuator is yieldable to yield to additional travel of the carriage to permit the first power means to be briefly energized for additional travel of the carriage when said one limit switch is operated, the additional travel shifting the welding device to the beginning point for the next successive eccentric bead.   
     
     
       31. In an apparatus for rebuilding a workpiece by a welding torch wherein the torch makes successive traverses of an area of the workpiece with automatic stepover and automatic reversal of the direction of travel of the torch at the end of each traverse, the improvement comprising: means to cause the torch to pause in its travel for a predetermined time period at the end of each traverse; and   means to cut off the supply of heat to the torch during the pause;   said pause serving to permit the molten metal to cool at the end of each bead before the next succeeding bead is started and in the welding of a relatively narrow area of the workpiece preventing overheating of the narrow area.     
     
     
       32. In an apparatus employing a welding device to deposit a series of contiguous weld beads on the interior wall of a hollow workpiece having coaxial upper and lower openings with the pattern of the series of the welding beads of a desired eccentricity relative to the axis of said openings, wherein the workpiece rests on a support surface with its two coaxial openings spaced apart vertically,   the combination of: a support structure resting on an area of said support surface that is defined by the lower of the two coaxial openings of the workpiece, said support structure extending upwardly into the interior of the workpiece;   a linear guideway rotatably mounted on the base structure and positioned for rotation about the axis of said openings; .Iadd.   a carriage movable along said guideway; .Iaddend.   a support for said welding device mounted on said carriage;   first power means on said base structure to rotate the guideway about said axis;   second power means on the .[.base structure.]. .Iadd.carriage .Iaddend.to extend and retract said support for the welding device relative to the carriage to or from the interior wall of the hollow workpiece;   third power means to raise and lower said support for the welding device relative to the carriage;   fourth power means to swing said welding device up and down in an arc relative to the support; and   means to shift the carriage along the guideway in accord with the desired eccentricity of the pattern of the series of beads.     
     
     
       33. A combination as set forth in claim .[.31.]. .Iadd.32 .Iaddend.in which the means to shift the carriage along the guideway in accord with the desired eccentricity of the pattern of the series of beads is mechanically responsive to rotation of the guideway about said axis; and in which said responsive means is reversible with respect to the direction of rotation of the guideway means that shifts the carriage outwardly of said axis,   whereby the apparatus may be set up initially and operated to apply welding beads to the lower portion of the interior wall of the hollow workpiece, then the support structure and parts thereon may be removed from the interior of the workpiece, then the hollow workpiece may be turned upside down on said support surface and then with said responsive means reversed the support structure may be set up on the area of said support surface defined by the lowermost of the two openings of the hollow workpiece to apply welding beads to the remainder of the interior wall of the workpiece.   
     
     
       34. A combination as set forth in claim 33 in which said responsive means comprises: a sprocket fixedly mounted on said support structure eccentrically of the axis of rotation of said guideway; and   a sprocket chain attached to the carriage, said sprocket chain being engageable selectively with opposite sides of the fixed sprocket.   
     
     
       35. A combination as set forth in claim 33 in which said responsive means comprises: an eccentric cam fixedly mounted on the base structure and a cooperative follower that is operatively connected to the carriage.   
     
     
       36. A method of depositing a series of contiguous welding beads on the interior wall of an eccentric pump shell having coaxially side openings on its two opposite sides respectively, characterized by the use of the combination of: a support structure;   a linear guideway mounted on the support structure for rotation about an upright axis of rotation;   a carriage movable along said guideway;   a support for said welding device mounted on said carriage;   four power means operative respectively to turn the guideway about said axis of rotation, to extend and retract said support for the welding device relative to the carriage to or from the interior wall of the hollow workpiece, to raise and lower said support for the welding device relative to the carriage, and to swing said welding device up and down in an arc relative to the support; and   means to shift the carriage along the guideway in accord with the desired eccentricity of the pattern of the series of beads,     said method including the steps of: placing said shell on its side on a support surface with said side openings spaced apart vertically;   placing said support structure on the area of said support surface that is defined by the lower side opening of the pump shell with said axis of rotation of the guideway coinciding with the axis that is common to the two side openings of the shell;   adjusting said guideway, said carriage, said support and said welding device, and energizing said power means as required to deposit welding beads on a lower portion of the interior wall of the pump shell;   removing the support structure from the interior of the pump shell;   turning the pump shell upside down on said support surface to reverse the positions of the two side openings of the pump shell;   mounting said support structure on the area of the support surface that is defined by the lower side opening of the reversed pump shell with said axis of rotation of the guideway coinciding with the axis of the two side openings of the pump shell; and   adjusting said guideway, said carriage, said support, and said welding device, and energizing said power means as required to deposit welding beads on the remainder of the interior wall of the pump shell.     
     
     
       37. A method as set forth in claim 36 in which the means to shift the carriage along the guideway is mechanically responsive to rotation of the guideway about said axis of rotation and is reversible with respect to which direction of rotation of the guideway causes shift of the carriage outwardly of said axis of rotation; and which includes the step of reversing said responsive means in preparation for depositing welding beads after the pump shell is turned upside down. 
     
     
       38. A method as set forth in claim 37 in which said responsive means comprises a fixed sprocket on said base structure concentric to said axis of rotation and a sprocket chain attached to the carriage, the sprocket chain being selectively engageable with opposite sides of the fixed sprocket; and in which the step of reversing the responsive means comprises shifting the sprocket chain from engagement with one side of the fixed sprocket to engagement with the opposite side of the fixed sprocket.