Patent Application
20150217471
This invention relates to an edge shaving tool and a method of operating same.
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”.
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.
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.
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.
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.
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.
Other features and advantages will become apparent from the following description in conjunction with the drawings.
In the figures which illustrate example embodiments,
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.
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.
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.
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.
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.
A cutting head assembly 20 has a basal support 22 mounted to the end mount 18. Two pairs of leaf springs 24a, 24b 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 24b; 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.
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.
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.
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.
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.
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.
The cutting head 32 is shown cutting a continuous shaving 66 off the material strip 60.
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.
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.
Impact piston vibrators are typical and is the type of shockwave generator illustrated in
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).
The operation of the tool is illustrated in
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.
Optionally, rather than providing an adjustable depth roller 38, the roller may be fixed and the cutting head depth may be adjustable.
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.
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.
The end mount 118 has an extension 119 which supports shockwave generator 30 at the downstream side of the cutting head support 120.
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.
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.
Other modifications will be apparent to those of skill in the art and, therefore, the invention is defined in the claims.
