Solid material comminution or disintegration – Apparatus – Comminuting elements
Reexamination Certificate
2002-03-07
2004-06-01
Rosenbaum, Mark (Department: 3725)
Solid material comminution or disintegration
Apparatus
Comminuting elements
C241S300000, C299S105000, C299S107000
Reexamination Certificate
active
06742735
ABSTRACT:
BACKGROUND OF THE INVENTION
Machines for cutting hard surfaces, such as concrete and asphalt, provide for a rotating wheel or drum with a plurality of cuffing tools mounted around the circumference of the wheel or drum such that each tool cuts a small portion of the hard surface, thereby advancing the cut. The tools of such machines are symmetrical around a longitudinal axis and have a hardened cutting tip and a cylindrical mounting portion rotatably retained in a tool mount on the circumference of the wheel or drum such that the tool can rotate about its longitudinal axis. Rotation of the tool within the mounting member causes the tool to wear symmetrically and thereby increasing its useable life. The concrete and asphalt which is cut by such tools, however, is so abrasive that such tools nonetheless often become so worn in a single day's use that they must be replaced. The tools rarely survive two days of use.
To replace the tools of a cutting machine, the worn tool is removed from the tool holder after which a new tool is inserted therein. As many as six hundred replacement tools are required daily for a machine used to scarf the surface of a lane of pavement of highway. It is, therefore, desirable to maximize the useful life of such tools and to provide tools which are easily inserted into the holders thereof to reduce the down time required to replace the tools in the machine.
Existing cutting tools have a tapered forward cutting end with a tungsten carbide tip. Behind the forward cutting end is a radial flange and behind the flange is a cylindrical shank having a diameter sized to fit within the cylindrical bore of the tool holder. Between the shank and the radial flange is a frustoconical portion having a ramp angle of approximately 45° which facilitates the alignment of the tool within the tool holder. The cylindrical shank has an enlarged diameter hub at the distal end thereof and fitted around the shank, between the hub and the frustoconical portion, is a spring loaded sleeve biased to expand radially outwardly so as to bind against the inner surface of the bore in the holder and thereby retain the tool in the holder.
In use, the tool rotates within the spring loaded retaining sleeve around the shank and the rear surface of the radial flange rotates on the forward surface of the tool holder. The rotation of the radial flange of the tool on the forward surface of the tool holder causes the forward surface thereof to become worn away and, over a period of time, an indentation or a counterbore wears in the forward surface of the tool holder, the diameter of which is substantially equal to the outer diameter of the cylindrical radial flange. Over time, the counterbore within the forward end of a tool holder can be as deep as {fraction (3/16)} of an inch.
When a replacement tool is inserted into the tool holder for which a counterbore has been worn into the forward surface thereof, the outer diameter of the radial flange of the replacement tool must rotatably fit within the inner diameter of the counterbore. If the outer diameter of the flange is equal to or larger than the inner diameter of the counterbore, it will bind against the inner surface of the counterbore and inhibit the rotation of the tool within the tool holder and thereby cause the tool to become prematurely worn. To prevent the outer circumference of such flange from locking within the counterbore in the tool block, it is desirable to provide tools for which the radial flanges thereof all have equal outer diameters. Such tools are presently cold formed using existing technology in which a metal blank is formed into the desired shape. Since the volume of the metal remains constant, cold forming require that the forming die include an opening through which excess metal can be released, and usually the portion having the largest diameter is chosen to receive the excess metal. Existing cold formed tools have an enlarge outer flange diameter which is irregular in shape because that is where excess metal is released. To insure that such radial flanges all have equal outer diameters, it is presently necessary to machine the outer circumferences of such flanges. The machining step, however, is expensive, and it would be desirable to manufacture tool bodies without requiring the machining of the outer circumference of the flange.
The rotatability of a tool within a tool holder is also reduced by resistance between the cylindrical shank and the spring loaded retaining sleeve. Although the sleeve is designed to be retained between the forward end of the hub and the frustoconical portion of the tool, if the sleeve is not properly positioned within the tool holder the forward end of the sleeve can become wedged against the frustoconical portion of the tool. The sleeve tends to ride up the 45 degree angle of the frustoconical section thereby increasing the friction between the parts.
Friction also occurs between the outer circumference of the hub at the distal end of the shank and the inner wall of the cylindrical bore into which the shank of the tool is fitted. When the tool is used to cut a hard surface, substantial forces are applied perpendicular to the longitudinal axis of the tool, and complimentary forces are applied between the inner surface of the cylindrical bore and the outer circumference of the hub. These transverse forces increase the resistance to rotation of the tool body within the tool holder and wear away the inner surface of the tool holder.
A third source of friction which reduces the rotatability of the tool is friction against the outer wall of the shank as it rotates within the retaining sleeve. As the tool is used, fine particles of hard material work their way under the radial flange and across the forward surface of the tool holder until they fall into the bore of the holder. Some of those particles work their way down the bore of the holder and between the outer wall of the shank and the inner wall of the retaining sleeve. Particles also enter from the rear of the tool holder, between the hub and the bore of the block and work their way between the shank and the retaining sleeve. Eventually the particles between the shank and the retaining sleeve form a paste of grit which binds between the parts and prevents rotation of the tool, and causes premature tool failure.
In my co-pending application, Ser. No. 09/121,726 filed Jul. 24, 1998, I disclosed an improved tool holder which resists wear from the rotation of the tool within the holder by providing a tungsten carbide wear ring in a countersink located in the forward and rearward ends of the bore of the tool holder. As further explained in my co-pending application, the coefficient of friction between the metal of the tool body and the surface of the tungsten carbide wear ring is less than the coefficient of friction between a tool body and the metal surfaces of existing tools, thereby facilitating rotation of the tool within the tool holder. Nonetheless, the friction between the outer circumference of the hub at the distal end of a tool body and the accumulation of particles within the parts also inhibits the rotation of the tool.
The replacement of tools in the tool holders of a machine is a very time consuming process because such machines typically retain 160 or more tools, each of which must be individually replaced. To replace the worn tools the tools must first be extracted from the bores of the tool holders, then the replacement tools are inserted. The tools are retained in the tool holders by expandable sleeves fitted around the shanks thereof and it is difficult to insert a replacement tool into the bore of the tool holder because the expanded sleeve defines a diameter larger than the diameter of the bore. To insert a tool in accordance with the prior art the tool must be first be axially aligned with the bore of the holder, then the forward end of the tool is pounded until the shank of the tool is fully driven into the bore.
It is difficult to insert the hubs of existing tools in the bores of tool holders because the diameter o
Marsh Robert L.
Rosenbaum Mark
The Sollami Company
LandOfFree
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