Gear cutting – milling – or planing – Milling – With cutter holder
Reexamination Certificate
1999-08-12
2001-08-21
Wellington, A. L. (Department: 3722)
Gear cutting, milling, or planing
Milling
With cutter holder
C409S232000, C279S093000, C403S350000, C408S232000, C408S713000
Reexamination Certificate
active
06276879
ABSTRACT:
FIELD OF THE INVENTION
The present invention refers to a cutting tool assembly comprising a replaceable cutting head and tool shank on which the cutting head is releasably and co-axially mounted in a substantially self-clamping manner.
BACKGROUND OF THE INVENTION
The present invention particularly refers to a cutting tool assembly of the above-specified kind for use in rotary cutting operations, such as e.g. milling, where a rotary torque is transferred from a tool shank to a cutting head mounted thereon.
When rotary cutting tools of the above kind are designed to work at small cutting diameters, it is often desirable that their cutting head be mounted on a tool shank in a self-clamping manner, which is often obtained by forming the cutting head and the tool shank with locking sections such as disclosed, for example, in EP 0 118 806.
EP 0 118 806 discloses a replaceable cutting head and a tool shank coaxially coupled together and having locking sections in the form of a centrally disposed and axially extending dovetail-shaped protrusion in the cutting head and a correspondingly shaped recess in the tool shank, which protrusion and recess co-axially interact in a male-female fashion. The protrusion and the recess both have fixation wings which are circumferentially spaced apart so that, during assembling, the fixation wings of the protrusion are initially inserted between the fixation wings of the recess and, upon rotation of the cutting head relative to the tool holder, they reach their final position in which the fixation wings of the recess overlie the corresponding fixation wings of the protrusion. The cutting head and the tool shank are further provided with positioning sections located peripherally with respect to the locking sections and abutting each other upon the rotation of the cutting head relative to the tool shank, which results in the interlocking of the locking sections in their final position, whereby the self-clamping of the cutting head on the tool shank is provided.
In order to enable the above-described interaction between the fixation wings of the locking sections of the cutting head and the tool shank, contacting surfaces of these wings need to have at least small axial and radial gaps therebetween, which leads to the necessity of providing the cutting tool assembly with additional means for accurate mutual positioning of the locking sections. Such additional means may be, for example, in the form of a resilient slit formed in the tool shank, as described in WO96/11079.
It is the object of the present invention to provide a new cutting head and a new tool shank for use therewith which, inter alia, have advantages in the above respect.
SUMMARY OF THE INVENTION
In accordance with one aspect of the present invention, there is provided a replaceable cutting head for co-axial coupling thereof, along a coupling axis, with a tool shank in a self-clamping fashion, the cutting head having a cutting portion with at least one cutting edge formed adjacent a leading end thereof and a mounting portion extending between said cutting portion and a trailing end of the cutting head and mating with a mounting portion of the tool shank; said mounting portion of the cutting head comprising:
a centering section having a peripheral centering surface which extends circumferentially with respect to said coupling axis and has a substantially conical shape at least at two portions thereof, which portions diverge along said axis towards a broad end of the peripheral centering surface;
a positioning section having at least two peripherally disposed and circumferentially extending and spaced apart positioning surfaces adapted for the provision of an axial support of the cutting head on the tool shank, each positioning surface being inclined with respect to said coupling axis so that an axial distance therefrom to said broad end of the peripheral centering surface increases in a direction generally corresponding to the direction of cutting forces acting on said cutting edge during a cutting operation;
one of the positioning and centering sections being formed with at least two circumferentially spaced apart fixation wings with, respectively, either said positioning surfaces and or said portions of the centering surface belonging thereto.
In accordance with another aspect of the present invention, there is provided a tool shank for a co-axial coupling thereof, along a coupling axis, with a replaceable cutting head having at least one cutting edge, in a self-clamping fashion, the tool shank having a mounting portion mating with a mounting portion of the cutting head formed adjacent a trailing end thereof; the mounting portion of the tool shank extending rearwardly from a front face of the tool shank and comprising:
a centering section having a peripheral centering surface which extends circumferentially with respect to said coupling axis and has a substantially conical shape at least at two portions thereof, which portions diverge along said axis towards a broad end of the peripheral centering surface;
a positioning section having at least two peripherally disposed and circumferentially extending and spaced apart positioning surfaces, each positioning surface being inclined with respect to said coupling axis so that an axial distance therefrom to said board end of the peripheral centering surface increases in a direction which generally corresponds to the direction of cutting forces acting on said cutting edge;
one of the positioning and centering sections being formed with at least two circumferentially spaced apart fixation wings with, respectively, either said positioning surfaces or said portions of the centering surface belonging thereto.
Preferably, the mounting portion of the cutting head is an integral part of the cutting head's body with one of the positioning and centering sections of the mounting portion being disposed adjacent the cutting portion and the other one being disposed adjacent the trailing end of the cutting head and being formed with said fixation wings; the mounting portion of the tool shank being designed accordingly and at least its section formed with said fixation wings being in the form of an open-ended cavity.
During assembling of the cutting head and the tool shank of the present invention into a cutting tool, the fixation wings of the mounting portion of the cutting head are inserted between the fixation wings of the mounting portion of the tool shank and, upon rotation of the cutting head relative to the tool shank around the coupling axis, the positioning surfaces of the mounting portion of one of them climb and abut the positioning surfaces of the mounting portion of the other, thereby bringing the centering surface of the mounting portion of the cutting head into a tight fit and abutment with the corresponding centering surface of the mounting portion of the tool shank, providing thereby the interlocking of the mounting portions of the cutting head and the tool shank in a male-female fashion. Thereby, the self-clamping of the cutting head on the tool shank is achieved.
The inclined positioning surfaces of the mounting portions of the cutting head and the tool shank may have any shape suitable for the provision of a gradual screw-like attachment of the cutting head to the tool shank. Preferably, these surfaces are formed as sections of a helical surface with a helix angle defining their inclination relative to the coupling axis.
According to one embodiment of the present invention, the fixation wings are formed on the centering section of the mounting portion of the cutting head which is disposed adjacent the trailing end thereof, the centering surface being defined by peripheral surfaces of the fixation wings. In this case, the positioning section is disposed between the cutting portion of the cutting head and the centering section of its mounting portion, and the positioning surfaces belong to wedge-shaped protrusions formed on a base surface of the positioning section.
In another embodiment of the present invention, the centering section is di
Ergenbright Erica
Iscar Ltd.
Pennie & Edmonds LLP
Wellington A. L.
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