Abstract:
A low cost electrical discharge texturing machine which can texture work rolls having a broad range of diameters and lengths either on a production or research and development basis. The machine is relatively portable, for example, it can be mounted on a palate, and can be used at any location having an adequate electrical supply. Electrodes are mounted on the machine in a manner which maximizes flexibility in respect of the roll diameters that can be textured. The machine also has adjustable supports for the work rolls which can raise or lower a roll surface relative to the electrodes to provide additional flexibility in the roll dimensions that can be textured. Furthermore, the machine has programmable x-axis drives and these can optionally be used in combination with programmable roll drives.

Description:
FIELD OF THE INVENTION 
   The present invention has to do with an apparatus for electrical discharge texturing of the cylindrical working surface of a work roll. More specifically, the invention relates to a low cost electrical discharge texturing machine which can texture work rolls having a broad range of diameters and lengths either on a production or research and development basis. 
   BACKGROUND OF THE INVENTION 
   In the manufacture of sheet steel, sheet aluminum and other sheet metal products, paper, plastics and other sheet materials, work rolls or cylinders (referred to hereinafter as “rolls”) are employed in the finishing process, for example, in a steel mill, a paper mill or the like. The roll shape and surface are textured to a high degree of accuracy. Traditionally, the roll surface is textured by processes such as shot blasting, electrical discharge texturing (EDT), electron beam texturing, laser texturing and other methods known to those skilled in the art. 
   Electrical discharge texturing, also referred to as spark elctroerosion or electroblast texturing, is a known process for texturing the working surface of a roll. The process involves the computer controlled spark erosion of the roll surface. The sparks are caused to pass between electrodes and the roll surface through a dielectric fluid. The roll can be partially or completely immersed in the dielectric fluid or the electrode ends can be dammed off and flooded with dielectric fluid and/or the dielectric fluid can be flushed through the electrodes, the fluid exiting at the electrode ends near the roll surface. The electrodes can have a positive polarity or a negative polarity. When the polarity is negative, the spark passes from the electrodes to the roll surface and, when the polarity is positive, the spark passes from the roll surface to the electrodes. Controlled electrical current is generated and discharged through the dielectric fluid producing the ionic charges or sparks that thermally explode into or out of the roll surface. This charge melts the extreme outer layer of the roll, forming microscopic craters proportional in size and spacing to the energy supplied and the frequency of generation. The result is an extremely precise, predictable and controllable texture on the roll surface. 
   The rolls referred to herein are electrically conductive metal rolls that can be made from various ferrous or non-ferrous materials or combinations of both. In practice, the rolls are predominantly made with steel but they may optionally have an outer shell of copper or nickel. They also may be made from cast iron, tool steels, various alloys, titanium, tungsten carbide, combinations thereof and the like. 
   Rolls are textured for various reasons for use in steel mills, paper mills and the like. For example, rolls used in steel mills to roll steel sheet that is to be painted cannot be too smooth or the paint adhesion and appearance on the rolled steel sheet will have high variances of quality. Texturing of the rolls provides the rolled steel sheet with a textured surface to which paint adheres and flows better and reduces quality variance. This texturing is conventionally performed by an EDT apparatus wherein a bank of electrodes is moved adjacent the roll surface and/or the roll is moved parallel to the electrode faces as the roll is rotated. EDT machines have electrode positioners each of which moves its associated electrode generally along its central axis toward and away from the roll to control the voltage drop and, accordingly, the electrical ionization process. In some EDT machines the electrodes are positioned about 10° below the center line of the roll on one side and about 10° above the center line on the other side so that they can be thrown out of the way if the roll surface hits them during rotation. 
   Electrode positioners ensure that each electrode is properly spaced with respect to the roll surface so as to be close enough to generate momentary sparks through dielectric fluid but not too close so as to generate a continuous current flow without any sparks to perform the texturing operation. 
   EDT machines for commercial applications are large and expensive. In most cases they are also inflexible as to diameters and lengths of rolls that can be textured on a particular machine. It is an object of the present invention to make a smaller, less expensive EDT machine that can be used to texture a broad range of roll diameters and lengths. A further object of the invention is to make an EDT machine that is suitable for use in low volume production or research and development applications while maintaining the ability to texture the roll surface to the same or improved degree of accuracy as the large commercial scale machines. 
   SUMMARY OF THE INVENTION 
   The EDT machine of the present invention employs an oil tank-electrode assembly mounted on a carriage. The movement of the carriage can be programmed so that the assembly can be moved horizontally in parallel with the central axis of a work roll to traverse the full length of the roll, or along a portion of the length of the roll and/or back and forth at any pre-selected interval and distance along the length of the roll. Electrodes are mounted on the assembly so that their proximal ends (the ends near the roll surface) are in a higher plane than their distal ends or, at the most extreme setting, the electrodes are horizontal. As noted above, the electrodes also can be positioned so that they are 10° below or 10° above the center line of the roll. 
   The EDT machine of the invention allows for texturing of long and short rolls and rolls having large and very small diameters. The machine also has adjustable central axis supports for the rolls which can raise or lower a roll relative to the electrodes thereby providing additional flexibility in the roll dimensions that can be textured. 
   When more than one electrode is used, they are arranged in parallel in rows on the front or rear of the assembly or on the front and rear of the assembly. The front and rear rows can either be lined up or offset from one another. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view of an embodiment of the EDT apparatus of the invention. 
       FIGS. 2 and 2A  are partial top views of two embodiments of  FIG. 1 . 
       FIG. 3  is a partial section view of  FIG. 1  taken along section line  3 - 3  of  FIG. 2 . 
       FIG. 4  is a top view of an electrode. 
       FIG. 4A  is a side elevation view of the electrode of  FIG. 4 . 
       FIG. 4B  is a section view of  FIG. 4  taken along section line  4 B- 4 B. 
       FIG. 4C  is an end view of the right end of  FIG. 4 . 
       FIG. 5  is a partial section view taken along section line  5 - 5  of  FIG. 10 . 
       FIG. 5A  is a partial section view taken along section line  5 A- 5 A of  FIG. 10 . 
       FIG. 5B  is a partial section view taken along section line  5 B- 5 B of  FIG. 10 . 
       FIG. 6  is a partial perspective view of an EDT apparatus of the invention. 
       FIG. 7  is a partial perspective view of another EDT apparatus of the invention. 
       FIG. 8  is a partial perspective view of still another EDT apparatus of the invention. 
       FIG. 9  is a partial perspective view of another embodiment of an EDT apparatus of the invention. 
       FIG. 10  is a top view of  FIG. 8  after the roll  65  and roll drive elements  8 ,  37  and  38  have been removed. 
       FIG. 11  is a top view of  FIG. 10  with the addition of mechanisms for oscillating a roll along its center line. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1  is a perspective view of an embodiment of the EDT apparatus of the invention having an oil tank-electrode assembly  1  mounted on a carriage  2 . Three electrodes  4   f  are mounted in a row and in parallel on the front of assembly  1 . These can be offset from the three electrodes  4   b  mounted in a row and in parallel on the back of assembly  1  as illustrated in  FIG. 2 , a partial top view of  FIG. 1 , wherein the work tank  22  has not yet been filled with dielectric oil  40  (also referred to herein as “dielectric fluid”). (In  FIG. 3 , work tank  22  is filled with dielectric oil  40 .)  FIG. 2A  illustrates an embodiment wherein the electrodes are lined up (not offset) front to back. Work roll  5  is suspended at its central axis by rotational supports  6  and  7 . Drive motor  8  drives rotational support  6 , causing the roll  5  to rotate about its central axis during the EDT process. A dielectric oil tank  18  has sufficient capacity to supply enough dielectric oil to the assembly  1  to fill work tank  22  of the assembly  1  up to a level whereby the ends of electrodes  4   f  and  4   b  in close proximity to work roll  5  (the proximal ends of the electrodes) are immersed in the oil as illustrated in  FIG. 3 . In some embodiments, dielectric oil is flushed through the electrodes toward the roll surface. This causes debris to flow away from the roll. As the roll turns, it drags clean oil around the roll and debris is dragged away from the electrodes and settles to the tank bottom. The central axis  31  of roll  5  lies in a horizontal plane  30  and the tank ends  11  and  12  of assembly  1  are maintained in sealing contact with the cylindrical outer surface of the roll  5  at least up to a level sufficient to prevent the oil from spilling over the ends during operation of the EDT apparatus. 
   The assembly  1  is moved back and forth along the length of the roll  5  in parallel with the central axis by moving the carriage  2  along a slideway comprised of rails  14 . Servo module  15  also moves with the carriage  2 . Movement of the carriage  2 , rotation of roll  5  and power supply to electrodes  4   f  and  4   b  can be controlled by electrical controls  16  employing conventional means well known to those in the art. As the assembly  1  traverses roll  5 , the tank ends  11  and  12  maintain their sealing contact with the roll and clean sufficient oil off the roll to prevent or minimize oil loss that might otherwise be caused by dripping of the oil off of the roll. The dielectric oil is continuously circulated by pump  17  through the electrodes and cleaned and recycled. More specifically, the dielectric oil is pumped through flexible feed hose  41  into manifold  42  whereby it is distributed through hoses  43  to each electrode. The oil is discharged from the electrodes at the ends proximate the roll whereby the oil is collected by work tank  22 . When the oil level reaches overflow port  44 , it is returned through optional flexible return hose  45  to dirty oil tank  46 . The oil is cleaned up by conventional means and returned to tank  18 . Carriage movement may be caused by a hydraulic system, an electric motor, a magnetic system or other suitable system. When a hydraulic system is used to cause carriage movement, the hydraulic oil can be maintained in hydraulic oil tank  19  and pumped by pump  20 . Adjustable supports  27  and  28  can be used to raise or lower the roll to accommodate rolls of different diameters and can be moved laterally along the length of the apparatus to accommodate longer or shorter rolls. The entire EDT apparatus rests on machine support  21  and floor mounts  29 . 
     FIG. 3  is a partial section view of  FIG. 1  illustrating the horizontal plane  30 , central axis  31  of the work roll and the dielectric oil  40 . As noted above, sufficient dielectric oil is filled into the assembly to cover the proximal ends of the electrodes and at least partially immerse the roll in the dielectric oil. The level of the dielectric oil can slightly exceed the height of the horizontal plane as illustrated in  FIG. 3  or the level can be at or below the horizontal plane as long as the proximal ends of the electrodes are covered with oil. It should be noted that when rolls having different diameters are employed, tank ends  11  and  12  are modified to insure a seal around a sufficient portion of the roll to prevent dielectric oil leakage. 
   Also illustrated in  FIG. 3  is a portion of drive mechanism  10  which can be a threaded rod, chain drive or other suitable drive means to move the carriage  2  back and forth along the full length of the roll and/or along intermediate distances along the length of the roll. Carriage  2  is guided by rails  14 . A servo module  15  is shown for each electrode. 
   Each electrode has a central axis c-c as illustrated in  FIGS. 2 ,  2 A,  3  and  4 A in an electrode  4   b .  FIG. 4  is a top view of an electrode  4   b  comprised of electrode element  80  mounted on shaft  81  of hydraulic actuator  82 . The hydraulic actuator is part of an automatic electrode positioner system which is explained below. Other types of actuators, such as linear DC actuators, are known in the art and can be used with the invention.  FIG. 4A  is a side elevation view of the electrode of  FIG. 4  illustrating tube  83  for connection to a hose  43  (see  FIGS. 1 and 3 ) which optionally supplies dielectric oil to the electrode element  80 . A section view  FIG. 4B  illustrates a dielectric oil cavity  84  in the electrode element  80 , the cavity being open to flushing orifice  85  which is also illustrated in  FIG. 4C  in an end view of the electrode  4   b . The electrode elements can be moved along the direction of the central axis c-c toward or away from roll  5 . The proximal end  86  of the electrode element  80  (usually comprised of copper) is moved toward or away from the surface of roll  5  by hydraulic cylinder  82 . This movement is controlled by servo module  15  which automatically adjusts the distance between the proximal end  86  and the surface of work roll  5  by measuring voltage drop as it varies with changes in the distance. The distance is adjusted automatically in response to the voltage drop until the desired voltage drop is attained. The angle ∝ relative to a vertical plane as illustrated in  FIG. 3  in respect of an electrode  4   b  can optionally be adjusted but it cannot exceed 9° and in most applications it will be less than 90°. The ability to move the electrodes along their c-c axes and adjust the angle ∝ permit further flexibility in texturing rolls having a broad range of diameters. 
   It should be noted that the invention is not limited to the use of six electrodes as illustrated in the drawings. For example, one electrode can be used or one in the front of the assembly and one in the back, offset from one another or lined up, or three or more can be used provided that when multiple electrodes are used, they are arranged in rows and in parallel on the front or back of the assembly or on the front and back of the assembly and offset or lined up in the manner illustrated in the drawings ( FIGS. 2 and 2A ) and as described above. Each parallel row of electrodes defines a plane in which lies the center lines c-c of each electrode. The center line of the work roll can lie in the plane or can be in parallel with the plane. 
     FIGS. 5 ,  5 A and  5 B are partial section views taken at various sections along the length of the machine illustrated in  FIGS. 8 and 10  as indicated by the corresponding section lines in  FIG. 10 .  FIG. 5A  illustrates an end elevation of the tank  22  (with added electrodes  4   b  and  4   f ) mounted on carriage  2 . Sections of cylindrical rails  14  and drive mechanism  10  are illustrated as well as sections of optional guide rails  24  and a portion of machine support  21 . A guide rail  24  is also illustrated in a partial perspective view  6 . The rails can be used to provide added stability to assembly  1 . 
     FIGS. 5 and 5B  illustrate roll journal supports  51  and  52 , respectively. These are also shown in partial perspective views  FIGS. 8 and 9 . The height of support  51  is adjusted using support adjuster  53  and the height of support  52  is adjusted using support adjuster  54 . The support adjusters can employ various mechanisms including threaded rods, jacks or the like. 
     FIG. 7  is a partial perspective view of the  FIG. 1  EDT apparatus which is configured to texture a small diameter roll  55 . 
     FIG. 8  is a partial perspective view of an EDT apparatus of the invention employing a different roll support and roll drive configuration from the  FIG. 1  embodiment. Roll  65  has journals  66  and  67  which rest on journal supports  52  and  51 , respectively. Motor  8  drives shaft  37  which in turn drives belt  38  and the roll  65 . The apparatus has a threaded x-axis drive  10 , cylindrical rails  14  and optional guide rails  24 . Tank  22  is mounted on carriage  2 . For purposes of drawing clarity, the electrodes and related elements have not been illustrated. Elements  90  and  91  have to do with driving and controlling the drive of x-axis drive  10 . For example, element  90  can be a drive motor and clutch and element  91  can be a controller. The movement of carriage  2  and, accordingly, tank  22  (the oil tank-electrode assembly  1  when electrodes are included), can be controlled in various ways. For example, carriage  2  can simply be caused to traverse the entire length of the work surface of a roll in back and forth motions. Stepwise traversal can also be programmed into the controller, for example, moving a preselected distance and stopping for a preselected time and then moving the same or different preselected distance and stopping for the same or different preselected time or moving back and forth the same or different distances over the same or different interval of time. Accordingly, the frequency, distance and speed can be controlled and the movement can be continuous, reversing and/or stepping. Thus, a programmable controller used in combination with a linear drive as illustrated can be used to selectively treat the surface of a roll. This provides flexibility in the texturing and treatment of roll surfaces that heretofore has been unattainable. For example, with an EDT apparatus of the invention, one can now effectively treat historically bad areas of a roll surface in a different manner from areas that have not been problematic. 
   In  FIG. 9 , heavy roll  75  has journals  76  and  77  which rest on journal supports  52  and  51 , respectively. Motor  8  drives heavy duty shaft  39  which in turn drive two belts  38  and the roll  75 . It should be noted that motor  8  in the  FIG. 9  embodiment is mounted on adjustable support  28  whereas the motor  8  in  FIG. 8  is not mounted on an adjustable support. 
     FIG. 10  is a top view of  FIG. 8  except that roll  65  and roll drive elements  8 ,  37  and  38  were removed for drawing clarity. The x-axis drive  10  is illustrated as a threaded rod. 
   A top view of another embodiment of the invention is illustrated in  FIG. 11 . This is the same as the  FIG. 10  embodiment but with the addition of programmable cam drive  100  and rotational supports  101  and  102 . Cam drive  100  can cause a roll to rotate either clockwise or counterclockwise continuously, stepwise and/or reversing. It can also cause the roll to oscillate back and forth along its central axis and this is facilitated by spring  103  in rotational support  102 . The frequency and amplitude of the oscillations can be controlled and they can be continuous, intermittent, increasing and/or decreasing. The features provided by elements  100 ,  101 ,  102  and  103  can be used in combination with the programmable movement of the carriage  2  described above in respect of  FIG. 8  in addition to other features of the invention described herein to attain additional and heretofore unattainable flexibility in the texturing and treatment of roll surfaces.