Patent Publication Number: US-2006005598-A1

Title: Weld box auto roll sensing and positioning system

Description:
FIELD OF THE INVENTION  
      The present invention relates to a tube milling and welding system and, more particularly, to a feedback and control system for optimizing weld quality during the operation of a tube milling and welding system.  
     BACKGROUND OF THE INVENTION  
      Tube milling operations typically include taking stock material from a roll and through a series of operations converting it into a welded tube. The first step of the process includes removing burrs and uneven edges from the stock material. The stock material is then passed through a series of rolls mounted on shafts. The rolls apply a forging pressure to progressively curve the stock material toward the form of a cylinder. Once the material is formed substantially into a cylinder it is welded into a tube. In a typical milling operation, the rate of speed that the stock material travels through the mill and the position of each of the rolls are substantially fixed for a given size stock material. Therefore, any slight deformity in the stock material can decrease weld quality. Hence, timely inspection of each welded seam is critical. Without timely inspection, a tremendous amount of material can be wasted due to improper seam alignment and/or forging pressure.  
      Ideally, when cylindrical tubing is formed from stock material on conventional tube milling machines, a weld box joins opposing edges of the stock material at generally the same height. The most common method for inspecting the edge alignment is for an operator to hold a gloved hand on the welded seam. The operator then feels for inconsistencies in the welded seam. This method produces safety and accuracy concerns. Alternatively, an operator cuts samples of the welded tube and inspects sample seams under a microscope. Such inspection can be time consuming, cost prohibitive and due to the random nature of sample testing, ineffective. Yet another method of inspecting weld quality includes utilizing a digital camera to substantially continuously image the welded seam. The images are then presented on a monitor for a technician to inspect. However, as a result of the edge conditioning, tube forming, and welding processes, the welded seam and environment tend to be very dirty. Therefore, the image quality tends to be poor, resulting in an ineffective inspection. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein:  
       FIG. 1  is a perspective view of a tube mill arranged in accordance with the principles of the present invention;  
       FIG. 2  is a cross-sectional view taken through line II-II of  FIG. 1 ;  
       FIG. 3  is a block diagram of a controller and a welding portion of the tube mill of  FIG. 1 ; and  
       FIG. 4  is a flow chart illustrating a method of monitoring and controlling the tube mill of  FIG. 1 .  
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
      The following description of the preferred embodiment is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses.  
       FIG. 1  depicts a tube mill  10  including a pre-stage portion  12 , a welding portion  14 , and a sizing and cutting portion  16 . A roll of stock material  18  is introduced to the pre-stage portion  12 . The stock material  18  includes a roll of sheet material such as sheet metal. The pre-stage portion  12  gradually forms the stock material  18  into a semi-tubular member  18   a  of approximately 320 degrees. The semi-tubular member  18   a  is then introduced to the welding portion  14  of the tube mill  10 . The welding portion  14  simultaneously compresses the semi-tubular member  18   a  into a substantially 360 degree cylinder and joins opposite edges thereof to provide a continuous tube  18   b  of generally constant diameter. The tube  18   b  then exits the welding portion  14  and is introduced to the sizing and cutting portion  16 . The sizing and cutting portion  16  is adapted to cut the tube  18   b  into a plurality of links (not shown) having predetermined lengths as may be desired. It should be appreciated that while the pre-stage portion  12  has been disclosed as producing a semi-tubular member  18   a  of approximately 320 degrees, a pre-stage portion  12  producing a semi-tubular member having an alternative geometry is intended to be within the scope of the present invention.  
      It is envisioned that the pre-stage portion  12  includes a seam preparation station, a plurality of forming stations, an edge conditioning station, and a seam guide. The seam preparation station generally removes burrs from the edges of the stock material  18 . This may be achieved with grinding wheels, wire brushes, or any other material removing means. The plurality of forming stations form the stock material  18  from a substantially planar member into the semi-circular member  18   a . This is achieved by forcing the stock material  18  through a series of rollers spaced progressively closer apart. The edge conditioning station de-burrs the edges of the stock material  18  a second time to ensure a controlled finish. The seam guide includes at least one fin for guiding the edges of the stock material  18  toward the welding portion  14  at a predetermined spacing that is suitable for welding.  
       FIG. 2  depicts the welding portion  14  including a weld box  20 , a controller  22 , and a weld apex  24 . As described above, the stock material  18  travels through the welding portion  14  to be welded into a tube  18   b . More specifically, as the semi-circular member  18   a  travels through the weld box  20  and beneath the weld apex  24 , the weld apex  24  forms a substantially continuous weld bead joining the edges of the semi-circular member  18   a . In an exemplary embodiment, the weld box  20  is constructed of sheet metal and includes sidewalls  20   a  having dual walled construction. The sidewalls  20   a  are adapted to substantially continuously carry a coolant flow, such as chilled water. It is envisioned that the sidewalls  20   a  may define an elongated serpentine channel between the dual walls for carrying the coolant flow. The coolant flow removes heat from inside the weld box  20  that is generated by forging and welding the stock material  18 . It should be appreciated that while only the sidewalls  20   a  have been disclosed as being dual walled, a weld box  20  having dual walled top and/or bottom walls is also intended to be within the scope of the present invention. It should further be appreciated that the weld box  20  is envisioned to include an inlet port (not shown) and an outlet port (not shown). The inlet port is for delivering the coolant flow to the sidewalls  20   a  and the outlet port is for removing the coolant flow from the sidewalls  20   a , thereby providing a continuous flow. Furthermore, it is envisioned that the weld box  20  could be filled with an inert gas. In an exemplary embodiment, the weld box  20  is filled 98% with argon gas. The argon gas is heavier than oxygen, which comprises the remaining 2% of atmosphere in the weld box  20 , and, therefore, serves to prevent impurities such as water, oil, or any other contaminant from obstructing the weld apex  24  during the welding and forming processes. Furthermore, an oxygen sensor (not shown) is employed to substantially continuously monitor the level of oxygen in the weld box  20  and terminate operation of the tube mill  10  if the level rises above 2%.  
      While the weld apex  24  forms the weld bead, the weld box  20  positions the stock material  18 . The weld box  20  includes first and second rolls  26  rotatably supported on shafts  41 . In an exemplary embodiment, the rolls  26  and shafts  41  are constructed of a thermally conductive material, such as aluminum or steel. The rolls  26  apply a forging pressure for compressing and guiding the stock material  18  through the weld box  20 . The first and second rolls  26  include substantially parallel rotational axes, each identified by B, and a common lateral axis A. The lateral axis A is substantially perpendicular to the rotational axes B. The first and second rolls  26  each include concave forming surfaces  28  integrally formed with top caps  30  and bottom caps  32 . In the embodiment illustrated, the forming surfaces  28  are designed to generally conform to the shape of the tube  18   b . The top and bottom caps  30 ,  32  include external cylindrical surfaces  30   a ,  32   a . It should be appreciated, however, that rolls  26  having alternative geometries are intended to be within the scope of the present invention. For example, the rolls  26  may include cylindrical rolls. It should also be appreciated that in the embodiment illustrated, the shafts  41  rotatably supporting the rolls  26  are hollow. Similar to the sidewalls  20   a  discussed above, the hollow shafts  41  are adapted to carry a coolant flow, such as chilled water. The coolant flow serves to remove heat from the rolls  26  generated by forging the stock material  18  during normal operation of the tube mill  10 . It is envisioned that the hollow shafts  41  would also include an inlet port (not shown) and an outlet port (not shown) for delivering and removing the coolant flow therefrom.  
      For each of the first and second rolls  26 , the weld box  20  further includes a vertical position sensor  34 , a horizontal position sensor  36 , a load sensor  38 , and a roll translating device  40 . The vertical and horizontal position sensors  34 ,  36  are in data communication with the controller  22 . In an exemplary embodiment, the vertical and horizontal position sensors  34 ,  36  each include an optical transmitter and an optical sensor. For example, the optical transmitters may include laser-generating devices and the optical sensors may include charge coupled devices. The optical transmitters of the vertical position sensors  34  project an optical signal to a top surface of the rolls  26 . The optical signals deflect off of the top surfaces of the rolls  26  and are received by the optical sensors. Similarly, the horizontal position sensors  36  project an optical signal to the external cylindrical surfaces  30   a  of the top caps  30  of the rolls  26 . The optical signals deflect off of the external cylindrical surfaces  30   a  and are received by the optical sensors. The vertical and horizontal position sensors  34 ,  36  then send signals to the controller  22 . The signals represent a characteristic of the optical signals received. For example, in one embodiment the position sensors  34 ,  36  send a signal identifying the magnitude of the optical signal received. The controller  22  then processes these signals to determine the vertical and horizontal positions of the rolls  26  relative to the weld box  20 , as will be described in more detail below. It should be appreciated that while the vertical and horizontal position sensors  34 ,  36  have been disclosed herein as including optical-based position sensors, alternative positioning sensors such as sonar-based sensors or any other type of sensor operable to detect position is intended to be within the scope of the present invention.  
      The load sensors  38  each include a form of load cell. The load cells are each envisioned to include a linear strain gage load cell, a non-linear strain gage load cell, a piezoelectric load cell, or any other type of electromechanical load detecting device capable of serving the principles of the present invention. In the embodiment illustrated, the load cells each include a load button  39  operably connected to a strain-gage (not shown) disposed in the load sensor  38 . The load sensors  38  also include a biasing member (not shown) such as a spring biasing the load buttons  39  toward the rolls  26 . The load buttons  39  are in constant engagement with the external cylindrical surfaces  32   a  of the bottom caps  32  of the rolls  26 . Therefore, any displacement of the rolls  26  along axis A displaces the load buttons  39  and deforms the strain gages disposed in the load sensors  38 . This deformation changes the electrical resistance across the strain gages. The load sensors  38  then send a signal representing this change in electrical resistance to the controller  22  for processing, which will be described in more detail below. It should be noted that during normal operating conditions, the stock material  18  being substantially uniform in size and construction, the stock material  18  should apply a substantially uniform force on the rolls  26 . However, the stock material  18  may include discrepancies in size and construction that alter the force applied to the rolls  26 . For example, a slightly wider or thicker portion of the stock material  18  may increase the force applied to the rolls  26 . Alternatively, a slightly narrower or thinner portion of the stock material may decrease the force applied to the rolls  26 .  
      Whenever a load discrepancy is identified, the controller  22  actuates the roll translating devices  40 . The roll translating devices  40  are connected to shafts  41  rotatably supporting the rolls  26  about their rotational axes B. The roll translating devices  40  are operable to translate the rolls  26  along their rotational axes B, as well as along the lateral axis A. It is envisioned that each of the roll translating devices  40  may include a single multi-axis electrical motor, two single-axis electrical motors, a hydraulic actuator, or any other device or combination of devices actuable by the controller  22  and operable to serve the principles of the present invention.  
       FIG. 3  depicts the controller  22  including a processor  42 , an electronic storage unit  44 , and a user interface  46 . The processor  42  of the controller  22  is in data communication with the roll translating devices  40 , the vertical position sensors  34 , the horizontal position sensors  36 , and the load sensors  38 . The electronic storage unit  44  is adapted to store a variety of operational parameters for the tube mill  10  and, more specifically, for the weld box  20 . The operational parameters include horizontal roll position parameters, vertical roll position parameters, and load parameters. For example, the horizontal and vertical position parameters are envisioned to include a distance value identifying a distance that the rolls  26  are to be positioned from the position sensors  34 ,  36 . The load parameters are envisioned to include a force value that the stock material  18  applies on the rolls  26  during normal milling operations. The user interface  46  includes a display device and an input device. In an exemplary embodiment, the display device includes a video monitor and the input device includes a keypad. The user interface  46  is adapted to display the operational parameters and any other relevant information to a technician. Furthermore, the user interface  46  is adapted to receive operational parameters to be stored in the electronic storage unit  44 . In this manner, a technician may enter operational parameters for a plurality of different tube milling operations into the user interface  46 . The user interface  46  then sends these parameters to the processor  42 , which appropriately stores them in the electronic storage unit  44 .  
       FIG. 4  depicts a flow chart illustrating a feedback and control process performed by the controller  22 . Upon introduction of a specific size stock material  18  to the tube mill  10 , the processor  42  receives information from a technician via the user interface  46 . This information identifies the specific stock material  18  being formed. The processor  42  then retrieves a set of operational parameters from the electronic storage unit  44  matching that stock material  18 , as identified by block  48 . As stated above, the operational parameters include vertical position parameters, horizontal position parameters, and load parameters. Subsequently, the processor  42  receives a horizontal position signal from each of the horizontal position sensors  36  and a vertical position signal from each of the vertical position sensors  34 , as identified by block  50 . The processor  42  then compares the horizontal and vertical position signals to the horizontal and vertical position parameters retrieved from the electronic storage unit  44 , as identified by block  52 . If the processor  42  determines that the position signals match the position parameters, the processor proceeds to block  56  and receives load signals from the load sensors  38 . Alternatively, if the processor  42  determines that any of the position signals do not match their respective position parameters, the processor  42  instructs the roll translating devices  40  to adjust the first and second rolls  26  in accordance with the difference between the position signals and position parameters, as identified by block  54 . Once the rolls  26  are properly positioned, the processor  42  proceeds to block  56  and receives load signals from the load sensors  38 .  
      During the forming and welding process, the processor  42  substantially continuously receives load signals from the load sensors  38 , as identified by block  56 . The processor  42 , therefore, substantially continuously compares the load signals with the load parameters retrieved from the electronic storage unit  44 , as identified at block  60 . If the load signals match the load parameters, the processor  42  returns to block  50  and repeats the process. However, if the load signals do not match to the load parameters, the processor  42  sends a signal to each of the roll translating devices  40 , as illustrated by block  62 . The signals actuate the roll translating devices  40  to displace the rolls  26  along axis A. Then the processor  42  returns to block  56  to continue receiving and processing load signals until the load signals match the load parameters. Once the processor  42  determines that the load signals match the load parameters it returns to block  50  to repeat the entire control loop.  
      It should be appreciated that the above-described adjustments based on the load and position signals are performed substantially continuously throughout normal operation of the tube mill  10 . This substantially continuous control loop ensures optimum edge alignment of the stock material  18  even when the stock material  18  includes a slight deviation in size or thickness. It should further be appreciated that in an exemplary embodiment, the load and position parameters may include ranges of distances and forces, respectively, representing satisfactory operating conditions. Thus, the processor  42  determines whether the position and load signals are within the ranges of parameters. Furthermore, it should be appreciated that while the weld box  20  has been disclosed as including two rolls  26 , a weld box including more or less than two rolls  26  is intended to be within the scope of the present invention.  
      The description of the invention is merely exemplary in nature and, thus, variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.