Rotatable Cutting Tool
A rotatable cutting tool with a shank for locating the rotatable cutting tool on a work face, a body and a hard tip wherein said body is of a generally tapered shape and has at least one flight wherein said at least one flight extends longitudinally and at least partially around the body whereby movement of the rotatable cutting tool through a substrate urges the tool to rotate.
The present invention relates to a rotatable cutting tool for boring and similar operations. The cutting tool is for insertion into a tool holder assembly that allows the cutting tool to rotate within the tool holder assembly. Typically, the tool holder assembly is mounted on a driven work face, such as a cutting head, a drum, a chain, or the like.
BACKGROUND OF THE INVENTIONRotatable cutting tools have found a variety of uses in applications in which the cutting tool is used to impact on or grind away a surface. One example of the use of rotatable cutting tools is as a component of a road planing tool in a road planing machine. Typically, road planing machines include a drum with blocks mounted on the drum to retain the rotatable cutting tools. The blocks are generally formed with a central bore for receiving the rotatable cutting tools. The rotatable cutting tools generally comprise an elongate steel body with a hard cemented carbide tip that has been mounted into a socket contained in the distal end of the steel body. The steel body includes a shank at the proximal end for insertion into the bore of the block. The shank permits rotation of the rotatable cutting tool within the bore in the block. In use, the drum rotates and the rotatable cutting tools impact on and grind away the road surface.
The tip is generally formed separately from the body of the rotatable cutting tool and mounted in an insert at the distal end of the body of the rotatable cutting tool.
Rotatable cutting tools are subjected to extreme forces as well as to severe wear conditions in use. Such extreme forces and severe wear conditions can quickly abrade the cutting tool. In order to maximise the usable life of a cutting tool, the cutting tool is permitted to rotate within the tool holder so that the wear is distributed around the cutting tool and not concentrated on any particular side of the tool.
It is desirable to ensure consistent rotation of the cutting tool within the holder during operation. The cutting tool is rotated by the impact of the tool on the surface. Examples of tips used in cutting tools include conical tips, dome shaped tips and compound tips where a cone or dome extends from a cylindrical shaft. Such tips are generally rotationally symmetrical. In order to facilitate rotation, profiled tips have been employed. Examples of profiled tips include multifaceted tips such as tips having a pyramid shape.
The rotation of the cutting tool within the holder can be impaired by debris working its way between the cutting tool and the tool holder. Impaired rotation of the cutting tool, or in the complete failure of the cutting tool to rotate results in the severe uneven wear of the hard tip and can possibly result in the displacement of the tip from the body of the cutting tool.
The cutting tools are attached to a driven member such as, for example, a chain, a wheel, or a drum. Typical applications for rotatable cutting tools include mining, ditching, trenching, drilling, road planing, auguring and other applications. The surface is broken and fractured by the impact of the rotatable cutting tool. Considerable amounts of debris may be generated and may comprise a large pieces, as well as very fine particles.
A flange or an extended region of the body of the rotatable cutting tool adjacent of the bore of the holder has been employed to minimise debris from building up between the holder and the rotatable cutting tool.
We have now found a rotatable cutting tool that provides improved rotational performance and reduces the likelihood of uneven wear and premature destruction. The rotatable cutting tool of the present invention provides both a rotational moment on impact and cutting through the debris as well as provides protection for the block to prevent infiltration of debris.
SUMMARY OF THE INVENTIONIn one form of the present invention there is provided a rotatable cutting tool comprising a shank for locating the rotatable cutting tool on a work face, a body and a hard tip wherein said body is of a generally tapered shape and comprises at least one flight wherein said at least one flight extends longitudinally and at least partially around the body whereby movement of the rotatable cutting tool through a substrate urges the tool to rotate.
The flight or flights extending from the body of the rotatable cutting tool present an oblique surface to a substrate through which the cutting tool passes. The forward movement of the cutting tool through the substrate causes the substrate to bear upon the oblique surface such that a rotational moment is applied to the cutting tool urging it to rotate.
The at least one flight extending from the body of the rotatable cutting tool extends longitudinally and at least partially around the body. It will be understood that by the term “at least partially around” it is meant a variety of configurations whereby the flight or flights extend in a generally longitudinal direction but include a lateral offset. For example, the flight or flights may extend transversely from the body of the rotatable cutting tool. In a preferred configurations, the flight or flights may extend in a spiral or helix from the body of the rotatable cutting tool. It will be appreciated that there are many similar configurations that may be employed to provide a flight that extends longitudinally and partially around the body of the rotatable cutting tool.
The at least one flight extending from the body of the rotatable cutting tool may be of constant dimension. Preferably, the flight or flights may increase in dimension as the flight or flights extend away from the tip of the rotatable cutting tool. Preferably the oblique surface provided to the direction of travel of the rotatable cutting tool increases in size as the flight or flights extend away from the tip. In order to provide sufficient strength in the flight or flights, the flight or flights may increase in breadth as they extend away from the tip.
The rotatable cutting tool of the present invention comprises a shank. The shank extends from the rear of the body and is preferably of a generally cylindrical form such that it can be rotate in the inserted into a bore. The shank preferably includes a locating means for locating the rotatable cutting tool at a desired depth within the bore. The locating means may be of any convenient configurations, but is preferably in the form of a circumferential channel or slot.
The work face may include suitable bores. Preferably, the work face has a plurality of blocks mounted on the work face, which blocks include suitable bores. By using blocks, it is generally easier to remove the rotatable cutting tools for replacement. Typically, the blocks may be configured to allow easy access to the rear of the block where a retaining means is generally used to hold of the rotatable cutting tools within the bores.
Insertion of the rotatable cutting tool into a block may expose the rear of the shank, including the locating means through the rear of the blocks. A retaining clip or a retaining ring may be received in a circumferential channel and may bear upon a boss disposed on the rear of the block. Removal of the retaining ring or clip allows for the easy removal of the rotatable cutting tool from the block. The rear of the block may preferably provided in an accessible location on the work surface.
The body of the rotatable cutting tool is of a generally tapered form. It will be appreciated that by “generally tapered form” is meant that the cross-section of the body generally increases in size from the tip of the rotatable cutting tool to the point at which the body undergoes the transition to the shank. The transition from the body to the shank may be a stepwise transition or a tapered transition or a combination thereof. The generally tapered form of the body may be a continuous taper whereby the increase in cross-sectional dimension of the body is constant from the tip to the shank. Alternatively, the taper may be a variable taper whereby the increase in cross-sectional dimension of the body can vary from the tip to the shank. The taper may also be a stepped taper that includes a number of stepped increases in cross-sectional area from the tip to the taper.
The body may have a circular cross-section extending along its length or may have a polygonal cross-section or a combination thereof.
The tip of the rotatable cutting tool is preferably multifaceted, such as in the form of a triangular or square pyramid. The tip is preferably formed from a cemented carbide or other wear resistant material. The hard tip is generally formed separately from the shank and body of the rotatable cutting tool and inserted into a recess at the leading end of the body. The hard tip may be retained in the body of the rotatable cutting tool by frictional engagement or is preferably brazed into the body.
In a preferred embodiment of the present invention in the rotatable cutting tool includes a hard tip in the form of a pyramid. The body of the rotatable cutting tool adjacent to the tip has a polygonal cross-section such that each apex of the cross-section of the body is generally aligned with an edge of the tip. Thus a face of the tip meets with a corresponding face on the body. The face on the body may be inclined at the same angle as the face of the tip or inclined at a different angle, preferably a lesser angle such that removal of debris created by the impact of the rotatable cutting tool is not impeded.
In this embodiment, it is preferred that the flights extend from the leading edge of the body at each apex of the cross-section of the body and sweep across the face of the body as they extend longitudinally. Desirably each flight is oriented and dimensioned to correspond to the other flights. As the tapered body extends from the tip, the increase in the cross-sectional dimensional may become greater and the cross-section of the body may transform to a circular cross-section.
Rotatable cutting tools are generally mounted on a work face by insertion of the shank into a bore such that the cutting tools are able to relatively freely rotate as a result of the impact of the cutting tool. We have found that the rotatable cutting tool of the present invention provides an improved free rotation within a bore. It is believed, without wishing to be bound by theory, without by providing flights that extend longitudinally and at least partially around the body of the rotatable cutting tool an increased rotational moment is generated as the rotational cutting tool passes through either the debris from a cut surface or the surface itself. In addition, it is believed, again without wishing to be bound by theory, that the flights assist in distributing the debris away from the bore and shank, thereby decreasing the likelihood of the rotation of the cutting tool being impaired.
The rotatable cutting tools of the present invention may be used in a variety of applications including mining, ditching, trenching, drilling, road planing, auguring and other applications. The cutting tools may be attached to a driven member such as, for example, a chain, a wheel, or a drum.
The present invention will now be described with reference to the accompanying drawings that serve to illustrate the invention and not limit its scope.
FIGS. 1 to 4 show a rotatable cutting tool according to one embodiment of the present invention. The rotatable cutting tool 1 having a shaft 2, a body 3 and a tip 4. The shaft 2 includes a circumferential channel 5 for receiving a retaining ring or retaining clip (not shown) to retain the rotatable cutting tool 1 in a holder (not shown) on the workface (not shown) of an implement. The tail end of the shaft is provided with a chamfered surface 6 for easy insertion of the shaft 2 into the bore (not shown) of a block (not shown).
The shaft 2, at its leading end has a collar 7 for engagement with the opening of the bore (not shown). The collar 7 assist in keeping debris from entering into the bore.
The tip 4 of the portable cutting tool 1 is formed from a cemented carbide. The tip 4 is in the shape of a triangular pyramid. The tip 4 has three wear faces 8.
The body 3 is in the form of a truncated triangular pyramid with the respective faces at a lesser angle to the direction of travel of the rotatable cutting tool 1. In this way, the faces 9 of the body 2 do not restrict the removal of debris created by the impact of the tip 4 on the surface to be removed.
The respective faces 9 on the body 3 form a shoulder 10 that engages the front end of the block (not shown).
The body 3 includes flights 11 that extend along the length of the body 3. The flights 11 initiate from the apex of the body 3 where it meets the tip 4 and radiate from the body 3. The flights extend away from the tip in a clockwise orientation to provide oblique surfaces 12 for pushing against debris and causing the rotatable cutting tool 1 to rotate in an anticlockwise direction. Between the oblique surfaces 12 are channels 13 through which some of the debris may pass. The flights 11 increase in size as they extend along the body 3 having greater trailing portions 14 to provide greater support for the leading surfaces 12 as they are subjected to greater force from the debris.
The flights 11 extend in a generally spiral form longitudinally along the body 3 of the rotatable cutting tool 1 and partially around the rotatable cutting tool 1.
FIGS. 5 to 8 show a second embodiment of the present invention in the form of a rotatable cutting tool 21 having a shaft 22, a body 23 and a tip 24. The shaft 22 and the tip 24 are in the same form as the respective shaft 2 and tip 4 from FIGS. 1 to 4. The body 23 of the rotatable cutting tool 21 is of a compound form having a leading portion 35 in the form of a truncated pyramid and a trailing portion 36 in the form of a truncated cone. An intermediate portion 37 provides for the transition between the leading portion 35 and the trailing portion 36.
Flights 31 extend from the apex of the leading portion 35, adjacent the tip 24 along the length of the body and in a clockwise direction partially around the body 23. The flights 31 have oblique surfaces 32 that increase in size as they extend along the length of the body 23.
We have found that providing a compound body form in the rotatable cutting tool we are able to provide a greater surface on the face radial to the axis of the tool. By transforming the cross-section of the body from a polygon to a circle and increasing its radius, better protection is provided to the bore in which the shank of the tool is mounted. This allows the flights to extend further from the axis of the tool, thereby increasing the rotational moment exerted by the passage of debris across the flights.
It will be appreciated by those skilled in the art that variations and modifications to the invention described here and will be apparent without departing from the spirit and scope thereof. The variations and modifications as would be apparent to persons skilled in the art are deemed to fall within the broad scope and ambit of the invention as herein set forth.
Claims
1. A rotatable cutting tool comprising a shank for locating the rotatable cutting tool on a work face, a body and a hard tip wherein said body is of a generally tapered shape and comprises at least one flight wherein said at least one flight extends longitudinally and at least partially around the body whereby movement of the rotatable cutting tool through a substrate urges the tool to rotate.
2. The rotatable cutting tool according to claim 1 wherein the at least one flight increase in dimension as the at least one flight extend away from the tip of the rotatable cutting tool.
3. The rotatable cutting tool according to claim 1 wherein the oblique surface provided to the direction of travel of the rotatable cutting tool increases in size as the flight or flights extend away from the tip.
4. The rotatable cutting tool according to claim 1 wherein a shank extends from the rear of the body and is of a generally cylindrical form whereby it is rotatable when inserted into a bore.
5. The rotatable cutting tool according to claim 1 wherein the shank includes a locating means for locating the rotatable cutting tool at a desired depth within the bore.
6. The rotatable cutting tool according to claim 1 wherein the generally tapered form of the body is a continuous taper whereby the increase in cross-sectional dimension of the body is constant from the tip of the shank.
7. The rotatable cutting tool according to claim 1 wherein the taper is a variable taper whereby the increase in cross-sectional dimension of the body varies from the tip to the shank.
8. The rotatable cutting tool according to claim 7 wherein the taper is a stepped taper that includes stepped increases in cross-sectional area from the tip to the taper.
9. The rotatable cutting tool according to claim 1 wherein the body has a circular cross-section extending along its length.
10. The rotatable cutting tool according to claim 1 wherein the body has a polygonal cross-section extending along its length.
11. The rotatable cutting tool according to claim 1 wherein the body has a cross-section that includes both circular and polygonal sections.
12. The rotatable cutting tool according to claim 1 wherein the tip of the rotatable cutting tool is multifaceted.
13. The rotatable cutting tool according to claim 12 wherein the tip is a square pyramid or a triangle pyramid.
14. The rotatable cutting tool according to claim 1 wherein the tip is formed from a cemented carbide or other wear resistant material.
15. The rotatable cutting tool according to claim 1 wherein the hard tip is formed separately from the shank and body of the rotatable cutting tool and inserted into a recess at the leading end of the body.
16. The rotatable cutting tool according to claim 1 wherein the rotatable cutting tool includes a hard tip in the form of a pyramid, the body of the rotatable cutting tool adjacent to the tip has a polygonal cross-section whereby each apex of the cross-section of the body is generally aligned with an edge of the tip and each face of the tip meets with a corresponding face on the body, and wherein the face on the body is inclined at a lesser angle whereby removal of debris created by the impact of the rotatable cutting tool is not impeded.
Type: Application
Filed: Mar 15, 2005
Publication Date: Sep 6, 2007
Inventor: Stewart Wright (Queensland)
Application Number: 10/592,585
International Classification: E21C 25/10 (20060101);
