Abstract:
While a cutting head of an edge shaving tool shaves a material, a resilient support for the cutting head is repetitively struck to impart shockwaves to the cutting head. An edge shaving tool operating in this fashion has a resilient cutting head support for supporting a cutting head at one end thereof and a shockwave generator mounted for repetitively striking a side of the resilient cutting head support.

Description:
BACKGROUND 
       [0001]    This invention relates to an edge shaving tool and a method of operating same. 
         [0002]    The process of shaving or cutting a desired profile on the edges of strip materials is widely used, and is usually referred to as “skiving” or “scarfing”. 
         [0003]    The process is commonly used to prepare the edges of a flat strip before the strip is formed into a pipe or tube or pole. The process is also used in the production of doctor and coater blades for the paper industry, and in shaving bearing materials to an exact width prior to press forming in order to set the resulting part diameter accurately. The process can also be used for beveling hinges, trowels, scrapers, and other miscellaneous hardware such as garage door tracks, drawer slides, building panels, office furniture and fixtures, medical equipment, and aerospace components. 
         [0004]    Typically, to skive a material, a static knife or other cutting head engages the edge of the moving strip to peel away the excess material, leaving the desired edge profile. The knife itself can be shaped, if necessary, to produce a desired edge shape. There are, however, a number of problems with this approach. For example, if the material speed is not at least about 15 metres/minute, cutting may not be smooth and the finish may be poor. While lubrication may be desirable to ease cutting and provide a smoother finish, particularly at lower speeds, lubrication may not possible where, for example, the material later requires laser seam welding, because lubricant vapor would spoil the laser beam focus and result in vapor deposits on the laser lens. Further, if there are variations in edge hardness—which is common in some stainless steels with badly slit material—cutting will be variable. Moreover, this approach requires a relatively high mill pull through force, as the cutting energy is solely supplied by the action of the material being pulled past the knife. Additionally, swarf handling can be problematic since the scrap typically sheds as continuous spirals, taking up much space. In consequence, the swarf may need to be chopped off and transported away from the machine. 
         [0005]    Knives must be precisely located relative to the edge of the strip. In typical systems, this is accomplished by servo locating the knives relative to the machine bed. With this arrangement, if one cutting station is adjusted, all downstream stations will normally also require adjustment. 
       SUMMARY 
       [0006]    In an embodiment, while a cutting head of an edge shaving tool shaves a material, a resilient support for the cutting head is repetitively struck in the shaving direction of the cutting head to impart shockwaves to the cutting head. 
         [0007]    In another embodiment, an edge shaving tool has a resilient cutting head support for supporting a cutting head at one end thereof and a shockwave generator mounted for repetitively striking a side of the resilient cutting head support. 
         [0008]    Other features and advantages will become apparent from the following description in conjunction with the drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    In the figures which illustrate example embodiments, 
           [0010]      FIG. 1  is a schematic view of an edge shaving tool made in accordance with a first embodiment, 
           [0011]      FIG. 2  is a graph of position versus time for the shockwave generator, 
           [0012]      FIG. 3  is a schematic view of a portion of the tool of  FIG. 1  illustrating operation, and 
           [0013]      FIG. 4  is a schematic view of an edge shaving tool made in accordance with a second embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0014]    In overview, an edge shaving tool is repetitively struck to impart shockwaves to a cutting head of the tool. These shockwaves may be in a direction opposite the direction of cutting and delivered at a relatively high frequency, such as 100 Hz. The cutting head then propagates this high frequency shockwave front into the material just ahead of the tool. 
         [0015]    The introduction of sufficiently powerful periodic shock impulses delivered at high frequency to the cutting head is believed to radically change the cutting physics. As the shockwaves propagate into the material which is just about to be shaved off in front of the cutting head, they cyclically compress this material. This may change the structure of this material by work hardening and crystallization and cause the material which is about to be removed to be internally ruptured by cleavage planes. With cleavage planes, the resultant swarf or scrap will peel off as the material is cut away and, as hardened swarf is brittle, it may readily break up instead of shedding in continuous spirals as with static knife systems. The resultant swarf is therefore easier to handle. 
         [0016]    The shockwaves move quickly, at an estimated speed of at about 1000 km/hr in steel. Thus, the shockwaves are ultrasonic and the inertia of the strip material alone provides adequate reaction force to the shockwaves. 
         [0017]    The strip material is drawn through a mill (at a speed that, depending on the application, may be as slow as only a few centimetres per minute or as fast as several hundred meters per minute) and the edge of the material is removed as the material is drawn past the cutting head. As the material just ahead of the cutting edge work hardens due the shockwaves, it is believed that this hardened material moves in a horizontal micro column relative to the adjacent mother material that is less affected by the shockwave to cause a micro shear break between the material just about to be removed, and the material below it which will remain. The micro shear break occurs along the cutting path and separates the about to be cut material segment before the cutting head edge actually reaches it. The material thus cracks off microscopically ahead of the cutting head. Consequently, the high frequency application of shockwaves greatly reduces abrasion of the actual edge of the cutting head and therefore greatly reduces the force required to pull the strip material through the mill (as compared with a system having a stationary cutting head or even a cutting head vibrating sinusoidally). The reduced abrasion also prolongs the life of the cutting head. Further, when the cutting edge of the cutting head sweeps over the cracked, and therefore pre-sheared, material, it polishes the pre-sheared surface, giving an excellent finish. 
         [0018]    A shockwave generator providing an impacting force of as low as 6 kg of force may be sufficient to provide the desired advantages, for example in shaving 1.5 mm thick aluminum. For heavier materials, such as 12 mm thick steel, impact forces of several hundred kg are suitable. 
         [0019]      FIG. 1  is a schematic view of an example edge shaving tool. Turning to  FIG. 1 , edge shaving tool  10  has a machine frame  11  supporting a pivot shaft  12  to which a basal mount  14  is mounted. Two pairs of equal length parallel link arms  16  (the front pair being visible) are pivotally mounted at one end to basal mount  14  and at a second end to an L-shaped end mount  18 . The basal mount  14 , end mount  18 , and link arms form a four-bar linkage such that the link arms  16  allow the end mount  18  to swing and follow the material edge without changing the angle of the end mount  18  and, therefore, without changing the engagement angle (rake angle) of a cutting head  32  mounted on the end mount  18 . 
         [0020]    A cutting head assembly  20  has a basal support  22  mounted to the end mount  18 . Two pairs of leaf springs  24   a,    24   b  are bolted to the basal support  22  and to an apical cutting head mount  26 . The leaf springs at the sides of the cutting head assembly provide a resilient linkage between the basal support  22  and apical cutting head mount  26 . The cutting head mount  26  has a tongue  28  projecting between leaf spring pair  24   b;  this tongue supports a shockwave generator  30 . The apical cutting head mount  26  mounts the cutting head  32  so that the cutting head projects from the outer end of the cutting head assembly  20 . 
         [0021]    The end mount  18  has a pair of slides  34  to which a block  36  is slidably mounted. The block terminates in an abutment, namely, grooved roller  38 . The position of the block  36 , and therefore of the roller  38 , is set by a screwjack  40  turned by knob  42 . 
         [0022]    Air cylinder  44  is mounted to frame  11 . The cylinder has a piston rod  46  to which one end of a link  48  is pivotably mounted. The opposite end of the link  48  is pivotably mounted to the two upper link arms  16 . The cylinder is closed such that the air pressure inside perpetually urges the piston  46  to extend. 
         [0023]    A bracket  50  affixed to the frame  11  carries a screwjack  52  terminating in clevis  54 . The screwjack  52  has a setting knob  56  which, when turned, pivots the basal mount  14  around pivot  12 . 
         [0024]    A strip material  60  is positioned adjacent the edge shaving tool  10  and fed in downstream direction D. Cylinder  44  acts as a pusher to preload the link arms  16  so that the roller  38  automatically follows the material edge  62 . Setting knob  56  of screwjack  52  is adjusted to pivot the basal mount  14  about pivot  12  and thereby set the angle of basal mount  14  relative to the frame  11 . This in turn sets the rake angle of the cutting head  32 , and this rake angle will not change even if end mount  18  is deflected due to any change in material width because of the four-bar linkage. 
         [0025]    Knob  42  is turned to extend or retract roller  38  relative to the cutting head  32  in order to control the cutting head engagement and cutting depth. Thus, the depth of cut is controlled by reference to the edge of the material rather than with reference to the machine bed (as was known in prior systems). Because of this, any adjustment in the cutting depth will not require adjustment of any downstream edge treatment tools provided those tools are also referenced to the edge of the material. 
         [0026]    The cutting head  32  is shown cutting a continuous shaving  66  off the material strip  60 . 
         [0027]    It will be apparent from this description that the shockwave generator  30  is at a downstream side of the cutting head assembly  20  and the roller  38  is at the upstream side of the cutting head assembly. 
         [0028]    A variety of shockwave generators may be used as shockwave generator  30 . For example, shockwave generator  30  may be a BCIR series pneumatic vibrator by the Invicta Vibrators division of Grantham Engineering Ltd. or a VMR—Vibra-Might Impact Piston Vibrator by Cleveland Vibrator Company. Also, the vibrator of CA674,879 issued Nov. 26, 1963 to Mee and Barnes, the contents of which are incorporated herein by reference or the vibrator of CA667,685 issued Jul. 30, 1963 to Mee and Barnes, the contents of which are incorporated herein by reference, with minor modification, could be adapted to act as impact piston vibrators. 
         [0029]    Impact piston vibrators are typical and is the type of shockwave generator illustrated in  FIG. 1 , with piston  70 . The piston reciprocates at a frequency dependent upon the model, and typically at between seventy-five and three hundred cps. A common frequency is 100 cps. The stroke of the piston can vary from a few millimeters to as much as about 15 cm, depending on the model.  FIG. 2  is a graph of time versus piston position for a typical impact piston vibrator. At the outer reach of the piston, at R, the end of the piston impacts the side of the cutting head assembly  20  at the apical cutting head mount  26 . In  FIG. 2 , the piston cycles every 0.01 seconds, and thus at 100 cps. 
         [0030]    Where the material is steel, the vibrator may have an output power of about 2.2 kW so that the end of the piston impacts the material with sufficient force. Indeed, the energy available from impacting pneumatic devices is high, just 5 cfm at 60 psi yields 3 air horsepower (i.e., about 2.2 kW). 
         [0031]    The operation of the tool is illustrated in  FIG. 3 . The piston rod of the shockwave generator  30  repeatedly impacts the side of the apical cutting head mount  26  transmitting shockwaves  90  into the cutting head  32  and the material  60 . The direction, I, of each impact is opposite to the downstream direction D of travel of the material. The shockwaves form cleavage planes  92  in the margin of the material in front of the cutting head  32  separating the swarf from the mother material and thereby reducing cutting head friction and allowing the swarf  66  to break up after shedding. The cutting edge passing over the material also has a polishing effect on finished cut edge  94 . 
         [0032]    Optionally, rather than the illustrated pneumatic shockwave generator, any other type of shockwave generator may be employed, such as a hydraulic shockwave generator, a controlled electrical motor rotating a cam connected to a piston rod, or a controlled linear motor. 
         [0033]    Optionally, rather than providing an adjustable depth roller  38 , the roller may be fixed and the cutting head depth may be adjustable. 
         [0034]    The fact that basal mount  14  can pivot on pivot shaft  12  not only allows adjustment of the rake angle, but also allows rotation of the cutting head assembly  20  to allow easy access to cutting head  32  thereby facilitating change-out of the cutting head. 
         [0035]    Screwjacks  40  and  52  may be replaced with any other position setting mechanisms. Air cylinder  44  may be replaced with any other mechanism to perpetually bias end mount  18  toward the material edge  62 . 
         [0036]      FIG. 4  illustrates a simplified embodiment. Turning to this figure, wherein like parts have been given like reference numerals, a tool  100  has a frame  111  with a pivot shaft  112  to which a first part  118   a  of end mount  118  is pivotably mounted. A knob  119  may be tightened against the end mount  118  to fix its angular position on pivot  112 . A second part  118   b  of the end mount telescopes with respect to the first part  118   a  on guides  121 . A spring  123  acts between the first and second parts of the end mount  118  to bias the second part  118   b  toward the edge  62  of a strip material  60  driven beside the tool. An arm  137  supporting a grooved roller  38  is slidably received in a guide  139 . The guide has internal threads to which screw  141  is threaded. The end of the screw pushes against arm  137  so that the position of the arm may be adjusted by turning screw head knob  42 . A resilient one-piece cutting head support  120  extends from end mount  118  and supports cutting head  32 . 
         [0037]    The end mount  118  has an extension  119  which supports shockwave generator  30  at the downstream side of the cutting head support  120 . 
         [0038]    With tool  100 , the rake angle of the cutting head  32  is set by loosening knob  119  and pivoting the end mount  118  on pivot shaft  112 , then re-tightening the knob. A drawback with this simplified embodiment is that if the material width changes, the rake angle changes and may need to be reset. 
         [0039]    Spring  123  biases the roller  38  against the edge  62  of the material and the depth of the cut may be adjusted by adjusting the relative position of the roller with respect to the cutting head  32  by turning knob  42 . As with the first embodiment, the shockwave generator  30  repetitively impacts the side of the cutting head support to impart shockwaves to the cutting head and, in turn, to the material. 
         [0040]    Other modifications will be apparent to those of skill in the art and, therefore, the invention is defined in the claims.