Patent Description:
More particularly the invention relates to a cutting head according to the preamble of claim <NUM> and a rotary cutting tool according to the preamble of claim <NUM>. Such a cutting head and such a cutting tool are known from <CIT>.

Within the field of cutting tools used in drilling operations, there are many examples of cutting heads releasably secured to tool shanks having head receiving pockets with 'circumferentially unconfined' pocket recesses.

<CIT> discloses a cutting tool assembly for rotary cutting operations comprising a replaceable cutting head and a tool shank, having a common longitudinal axis and mating peripheral surfaces. The cutting head has a cutting head mounting portion at a trailing end thereof and the tool shank has a cutting head receiving portion at a front face thereof. The cutting head mounting portion and the cutting head receiving portion of the tool shank each have at least two coupling portions bound by associated peripheral surfaces of the cutting head and the tool shank and mating in shape and dimensions. Each coupling portion has a base surface, a torque transmission wall and a fixation wall, the fixation wall of each cutting head coupling portion having an angular extension smaller than a corresponding angular distance between adjacent extremities of the fixation walls of two different tool shank coupling portions. The cutting tool is assembled by initially disposing the cutting head mounting portion in such a manner relative to the cutting head receiving portion as to insert the fixation walls of the cutting head coupling portions between the respective fixation walls of the tool shank coupling portions, and subsequently rotating the cutting head relative to the tool shank until the cutting head coupling portions fully overlie the corresponding tool shank coupling portions with their base surfaces and torque transmitting walls abutting each other and their fixation walls co-axially interacting in an interlocking male-female fashion, providing thereby the self-clamping of the cutting head on the tool shank.

<CIT> discloses a metal cutting tool having a cutting head releasably mounted on a front end of a tool shank, in a self-clamping manner. The tool shank's forward end is provided with a pair of shank coupling portions, each having a forwardly facing shank support surface. A pocket recess is defined between the shank's coupling portions. Within the pocket recess are a plurality of shank fixation surfaces which are parallel to a longitudinal axis of the tool shank. The cutting head has a cap portion and a fixation portion extending in rearward direction therefrom. The cap portion includes a pair of head segments, each having a rearwardly facing head base surface. The cutting head's fixation portion has a plurality of head fixation surfaces which are parallel to a longitudinal axis of the cutting head. In the assembled tool, the tool shank's forwardly facing shank support surfaces support the cutting head's rearwardly facing head base surfaces, while the plurality of head fixation surfaces abut the plurality of shank fixation surfaces.

It is an object of the present invention to provide an improved cutting head having a rigid mounting protuberance.

It is also an object of the present invention to provide an improved cutting head suitable for cutting operations with high feed rates.

It is a further object of the present invention to provide an improved cutting head compatible with a tool shank having a head receiving pocket with a 'circumferentially confined' central recess.

In accordance with the present invention, there is provided a cutting head, according to claim <NUM>, rotatable about a first axis in a first direction of rotation, and comprising:.

Also, in accordance with the present invention, there is provided a rotary cutting tool, according to claim <NUM>, comprising a tool shank extending along a second axis and having a head receiving pocket formed at a forward end thereof, the head receiving pocket comprising a shank support surface transverse to the second axis, and a central recess formed in the shank support surface, and a cutting head of the sort described above releasably secured to the head receiving pocket,
wherein in an assembled position:.

For a better understanding, the invention will now be described, by way of example only, with reference to the accompanying drawings in which chain-dash lines represent cut-off boundaries for partial views of a member and in which:.

A first aspect of the present invention relates to a cutting head <NUM>, <NUM> rotatable about a first axis A1 in a first direction of rotation R1.

It should be appreciated that throughout the description and claims, the same reference numerals have been used for features that are common to both the first and second embodiment cutting heads <NUM>, <NUM>.

In some embodiments of the present invention, the cutting head <NUM>, +<NUM> may preferably be manufactured by form pressing and sintering a cemented carbide, such as tungsten carbide, and may be coated or uncoated.

As shown in <FIG> and <FIG>, the cutting head <NUM>, <NUM> comprises a cap portion <NUM> and a rigid mounting protuberance <NUM> joined to the cap portion <NUM>.

It should be appreciated that the cutting head <NUM>, <NUM> may be of unitary one-piece construction, and the mounting protuberance <NUM> may have the same rigidity as the cap portion <NUM> and be devoid of resiliently displaceable elements.

As shown in <FIG> and <FIG>, the cap portion <NUM> has a plurality of N cutting portions <NUM> circumferentially alternating with a plurality of N head chip flutes <NUM>, and a head base surface <NUM> facing in an axial rearward direction DR. The plurality of cutting portions <NUM> define a cutting diameter DC corresponding to a cutting circle CC centered about the first axis A1.

In some embodiments of the present invention, N may be exactly <NUM>, and the cap portion <NUM> may have three cutting portions <NUM> circumferentially alternating with three head chip flutes <NUM>.

Also, in some embodiments of the present invention, the head base surface <NUM> may be planar.

As shown in <FIG> and <FIG>, each cutting portion <NUM> has a leading surface <NUM> facing axially forward, and with respect to the first direction of rotation R1, each leading surface <NUM> may intersect a circumferentially adjacent and rotationally forward head chip flute <NUM> to form a cutting edge <NUM>.

It should be appreciated that for embodiments of the present invention having three cutting portions <NUM> and thus three cutting edges <NUM>, the cutting head <NUM>, <NUM> may advantageously be used in cutting operations with high feed rates.

Also, as shown in <FIG> and <FIG>, each cutting portion <NUM> may have a torque transmission surface <NUM> facing opposite the first direction of rotation R1.

In some embodiments of the present invention, with respect to the first direction of rotation R1, each torque transmission surface <NUM> may communicate with a circumferentially adjacent and rotationally rearward head chip flute <NUM>.

Also, in some embodiments of the present invention, each torque transmission surface <NUM> may intersect the head base surface <NUM>.

Further, in some embodiments of the present invention, each torque transmission surface <NUM> may be planar.

As shown in <FIG> and <FIG>, the mounting protuberance <NUM> extends axially rearwardly from the head base surface <NUM> and exhibits N-fold rotational symmetry about the first axis A1.

It should be appreciated that throughout the description and claims, N-fold rotational symmetry does not include an infinite order of rotational symmetry.

In some embodiments of the present invention, the mounting protuberance <NUM> may be entirely surrounded by the head base surface <NUM>.

As shown in <FIG> and <FIG>, the mounting protuberance <NUM> has a plurality of N circumferentially spaced apart convex clamping surfaces <NUM>, each clamping surface <NUM> bisected by a radial clamping bisector plane PB containing the first axis A1.

In some embodiments of the present invention, the mounting protuberance <NUM> may have a plurality of joining surfaces <NUM> circumferentially alternating with the plurality of clamping surfaces <NUM>, and each joining surface <NUM> may intersect two circumferentially adjacent clamping surfaces <NUM>.

As shown in <FIG> and <FIG>, in a cross-section taken in a first plane P1 perpendicular to the first axis A1 and intersecting the cap portion <NUM>, the plurality of N head chip flutes <NUM> are inscribed by an imaginary first circle C1 having a first diameter D1 at a plurality of N radially innermost head flute points NH.

In some embodiments of the present invention, the first plane P1 may be located adjacent the head base surface <NUM>.

Also, in some embodiments of the present invention, each head flute point NH may be contained in a radial flute plane PF containing the first axis A1, and each radial flute plane PF may form a first angle α1 with a circumferentially adjacent radial clamping bisector plane PB.

Further, in some embodiments of the present invention, the first angle α1 may be less than thirty-five degrees, i.e. α1 < <NUM>°.

Yet further, in some embodiments of the present invention, with respect to the first direction of rotation R1, each radial flute plane PF may be located rotationally forward of its circumferentially adjacent radial clamping bisector plane PB.

As shown in <FIG> and <FIG>, in a cross-section taken in a second plane P2 perpendicular to the first axis A1 and intersecting the mounting protuberance <NUM>, the plurality of N clamping surfaces <NUM> are circumscribed by an imaginary second circle C2 having a second diameter D2.

In some embodiments of the present invention, in the cross-section taken in the second plane P2, the plurality of clamping surfaces <NUM> may form a plurality of spaced apart clamping arcs <NUM> coincident with the imaginary second circle C2.

Also, in some embodiments of the present invention, in the cross-section taken in the second plane P2, no portion of the mounting protuberance <NUM> may extend outside the imaginary second circle C2.

Further, in some embodiments of the present invention, in the cross-section taken in the second plane P2, each clamping surface <NUM> may have a first circumferential angular extent E1 greater than twenty-five degrees, i.e. E1 > <NUM>°.

Yet further, in some embodiments of the present invention, in the cross-section taken in the second plane P2, the plurality of joining surfaces <NUM> may be located inside the second imaginary circle C2.

According to the first aspect of the present invention, the first diameter D1 is greater than the second diameter D2, and the second diameter D2 is less than forty percent of the cutting diameter DC, i.e. D2 < <NUM>*DC.

It should be appreciated that the present invention provides a cutting head <NUM>, <NUM> in which the plurality of head chip flutes <NUM> have an advantageously high volume to efficiently evacuate chips without intersecting the mounting protuberance <NUM>.

In some embodiments of the present invention, the second diameter D2 may preferably be less than thirty percent of the cutting diameter DC, i.e. D2 < <NUM>*DC.

Also, in some embodiments of the present invention, the second diameter D2 may be greater than ten percent of the cutting diameter DC, i.e. D2 > <NUM>*DC.

As shown in <FIG> and <FIG>, in a cross-section taken in a third plane P3 perpendicular to the first axis A1 and intersecting the mounting protuberance <NUM>, the mounting protuberance <NUM> may be circumscribed by an imaginary third circle C3 having a third diameter D3 greater than the second diameter D2, i.e. D3 > D2,.

As seen in <FIG> and <FIG>, a head flute depth HD is defined as the radial distance between the head flute points NH and the cutting circle CC. Thus, the head flute depth HD is one-half the difference between the cutting diameter DC and the first diameter D1, or HD = ½ (DC - D1). Since one aim of the present invention is to have a cutting head with enlarged flutes, the head flute depth HD preferably is at least <NUM>% of one-half the cutting diameter DC, i.e., <NUM>% of the cutting radius.

In some embodiments of the present invention, the second plane P2 may be located between the first and third planes P1, P3.

Also, in some embodiments of the present invention, the third diameter D3 may be the maximum diameter of any imaginary circle circumscribing the mounting protuberance <NUM> in any cross-section perpendicular to the first axis A1.

As shown in <FIG>, in the first embodiment cutting head <NUM> of the present invention, the third plane P3 may not intersect the plurality of clamping surfaces <NUM>, and each clamping surface <NUM> may be partially cylindrical shaped.

Also, in the first embodiment of the present invention, the third plane P3 may intersect a plurality of N circumferentially spaced apart axial stopper portions <NUM>, and the imaginary third circle C3 may circumscribe the plurality of axial stopper portions <NUM>.

It should be appreciated that for some embodiments of the present invention, the plurality of axial stopper portions <NUM> may form a bulge <NUM> at the distal end of the mounting protuberance <NUM>.

As shown in <FIG>, each radial clamping bisector plane PB may intersect one of the axial stopper portions <NUM>.

In some embodiments of the present invention, each axial stopper portion <NUM> may have a stopper surface <NUM> facing axially forward.

Also, in some embodiments of the present invention, the plurality of axial stopper portions <NUM> may be axially spaced apart from the plurality of clamping surfaces <NUM> by an annular transition groove <NUM>.

As shown in <FIG>, in the second embodiment cutting head <NUM> of the present invention, the third plane P3 may intersect the plurality of clamping surfaces <NUM>, and each clamping surface <NUM> may be partially conical shaped.

Also, in the second embodiment of the present invention, the mounting protuberance <NUM> may extend a first distance L1 axially rearward of the head base surface <NUM>, the third plane P3 may be offset a second distance L2 from the second plane P2, and the second distance L2 may be greater than half the first distance L1 i.e. L2 > L1/<NUM>.

It should be appreciated that for some embodiments of the present invention, the mounting protuberance <NUM> may be dovetail shaped.

As shown in <FIG>, <FIG> and <FIG>, a second aspect of the present invention relates to a rotary cutting tool <NUM>, <NUM> having a tool shank <NUM>, <NUM> extending along a second axis A2, and the cutting head <NUM>, <NUM> releasably secured to a head receiving pocket <NUM> of the tool shank <NUM>, <NUM> at forward end <NUM> thereof.

It should be appreciated that throughout the description and claims, the same reference numerals have been used for features that are common to both the first and second embodiment cutting tools <NUM>, <NUM>.

In some embodiments of the present invention, the tool shank <NUM>, <NUM> may preferably be manufactured from tool steel.

Also, in some embodiments the cutting head <NUM>, <NUM> may be releasably secured to the head receiving pocket <NUM> without the requirement of an additional fastening member, such as a clamping screw.

As shown in <FIG> and <FIG>, the head receiving pocket <NUM> has a shank support surface <NUM> transverse to the second axis A2, and a central recess <NUM> formed in the shank support surface <NUM>.

In some embodiments of the present invention, the shank support surface <NUM> may face axially forward, and the central recess <NUM> may extend along the second axis A2.

Also, in some embodiments of the present invention, a plurality of N circumferentially spaced apart shank chip flutes <NUM> may extend from the shank's forward end <NUM> along the second axis A2.

In an assembled position of the rotary cutting tool <NUM>, <NUM>:.

In some embodiments of the present invention, a plurality of N drive members <NUM> may protrude axially forwardly from the shank support surface <NUM>, each drive member <NUM> may include a drive surface <NUM> facing in the first direction of rotation R1, and each drive surface <NUM> may make contact with one of the torque transmission surfaces <NUM>.

As shown in <FIG> and <FIG>, in a cross-section taken in a fourth plane P4 perpendicular to the first axis A1 and intersecting the central recess <NUM>, the plurality of N shank chip flutes <NUM> may be inscribed by an imaginary fourth circle C4 having a fourth diameter D4 at a plurality of N radially innermost shank flute points NS.

In some embodiments of the present invention, the fourth diameter D4 may be between ninety percent and one hundred and ten percent of the first diameter D1, i.e. D1*<NUM> < D4 < D1*<NUM>.

As seen in <FIG> and <FIG>, a tool flute depth TD is defined as the radial distance between the shank flute point NS and the cutting circle CC. Thus, the tool flute depth TD is one-half the difference between the cutting diameter DC and the fourth diameter D4, or TD = ½ (DC - D4). Since one aim of the present invention is to have a tool with enlarged flutes, the tool flute depth TD preferably is at least <NUM>% of one-half the cutting diameter DC, i.e., <NUM>% of the cutting radius.

Also, in some embodiments of the present invention, the fourth plane P4 may be coincident with the second plane P2.

As shown in <FIG> and <FIG>, the plurality of shank chip flutes <NUM> may be formed in a cylindrical shank peripheral surface <NUM> of the tool shank <NUM>, <NUM>.

In some embodiments of the present invention, the plurality of shank chip flutes <NUM> may extend helically along the second axis A2.

Also, in some embodiments of the present invention, the plurality of head chip flutes <NUM> may be corresponding extensions of the plurality of shank chip flutes <NUM>.

As shown in <FIG>, <FIG> and <FIG>, the central recess <NUM> may have a plurality of N circumferentially spaced apart abutment portions <NUM>, each abutment portion <NUM> may have a radially inward facing abutment surface <NUM>, and the plurality of clamping surfaces <NUM> may make clamping contact with the plurality of abutment surfaces <NUM>.

In some embodiments of the present invention, the plurality of joining surfaces <NUM> may not be in contact with the central recess <NUM>.

Also, in some embodiments of the present invention, the plurality of abutment portions <NUM> may circumferentially alternate with a plurality of intermediate portions <NUM>, and each intermediate portion <NUM> may have an intermediate surface <NUM> intersecting two circumferentially adjacent abutment surfaces <NUM>.

Further, in some embodiments of the present invention, the plurality of abutment portions <NUM> may be resiliently displaceable.

It should be appreciated that by virtue of the plurality of abutment surfaces <NUM> circumferentially alternating with the plurality of intermediate surfaces <NUM>, the head receiving pocket <NUM> may have a 'circumferentially confined' central recess <NUM>, which may improve the resilience of the plurality of abutment portions <NUM> and extend the useful life of the tool shank <NUM>, <NUM>.

It should also be appreciated that for embodiments of the present invention, in which the cutting head <NUM>, <NUM> is releasably secured to the tool shank <NUM>, <NUM> having a 'circumferentially confined' central recess <NUM>, and the head chip flutes <NUM> correspond with the shank chip flutes <NUM>, the head chip flutes <NUM> are required not to intersect the mounting protuberance <NUM>.

As shown in <FIG> and <FIG>, in the cross-section taken in the second plane P2, an imaginary fifth circle C5 coaxial with the second axis A2 may inscribe the central recess <NUM> and contact the plurality of abutment surfaces <NUM>.

In some embodiments of the present invention, in the cross-section taken in the second plane P2, the plurality of abutment surfaces <NUM> may form a plurality of spaced apart abutment arcs <NUM> coincident with the imaginary fifth circle C5.

Also, in some embodiments of the present invention, in the cross-section taken in the second plane P2, the plurality of intermediate surfaces <NUM> may be located outside the imaginary fifth circle C5.

Further, in some embodiments of the present invention, the imaginary fifth circle C5 may have a fifth loaded diameter DL5, and the fifth loaded diameter DL5 may be equal to the second diameter D2.

It should be appreciated that the fifth loaded diameter DL5 may be measured in the presence of radially outward forces being applied to the plurality of abutment surfaces <NUM>.

It should also be appreciated that in the absence of radially outward forces being applied to the plurality of abutment surfaces <NUM>, the imaginary fifth circle C5 may have a fifth unloaded diameter (not shown) less than the fifth loaded diameter DL5.

In some embodiments of the present invention, the head base surface <NUM> may contact the shank support surface <NUM> or a plurality of shoulder surfaces <NUM> offset therefrom.

It should be appreciated that in such an assembly configuration, apart from the plurality of clamping surfaces <NUM> making clamping contact with the plurality of abutment surfaces <NUM>, no other portion of the mounting protuberance <NUM> may contact the central recess <NUM>.

As shown in <FIG>, in a cross-section taken in one of the radial clamping bisector planes PB in the first embodiment cutting tool <NUM> of the present invention, the clamping surface <NUM> may be partially cylindrically shaped and extend parallel to the first axis A1, and the associated abutment surface <NUM> may be coincident therewith.

It should be appreciated that in such embodiments of the present invention, clamping contact between the plurality of clamping surfaces <NUM> and the plurality of abutment surfaces <NUM> is solely directed radially.

As shown in <FIG>, in the first embodiment cutting tool <NUM> of the present invention, each abutment portion <NUM> may have a stopping surface <NUM> facing axially rearward, and the plurality of stopper surfaces <NUM> may be axially spaced apart from the plurality of stopping surfaces <NUM>.

It should be appreciated that in instances of excessive axial 'pulling' forces acting on the first embodiment cutting head <NUM>, the head base surface <NUM> may not remain in contact with the shank support surface <NUM> and the plurality of stopper surfaces <NUM> may make contact with the plurality of stopping surfaces <NUM>, thus preventing the cutting head <NUM> from becoming detached from the tool shank <NUM>.

As shown in <FIG>, in a cross-section taken in one of the radial clamping bisector planes PB in the second embodiment cutting tool <NUM> of the present invention, the clamping surface <NUM> may be partially conically shaped and diverge away from the first axis A1 as it extends axially rearwardly, and the associated abutment surface <NUM> may be coincident therewith.

It should be appreciated that in such embodiments of the present invention, clamping contact between the plurality of clamping surfaces <NUM> and the plurality of abutment surfaces <NUM> is directed both axially and radially.

The present invention further relates to a method of assembling the rotary cutting tool <NUM>, <NUM>, comprising the steps of:.

the plurality of clamping surfaces <NUM> are retained against the plurality of abutment surfaces <NUM>.

In some embodiments of the present invention, in step d), the mounting protuberance <NUM> may be inserted into the central recess <NUM> until the head base surface <NUM> makes contact with the shank support surface <NUM>, or the plurality of shoulder surfaces <NUM>.

Also, in some embodiments of the present invention, in step e), the cutting head <NUM>, <NUM> may be rotated about its first axis A1 in a direction opposite to the first direction of rotation R1 until each drive surface <NUM> makes contact with one of the torque transmission surfaces <NUM>.

Claim 1:
A cutting head (<NUM>, <NUM>) rotatable about a first axis (A1) in a first direction of rotation (R1), and comprising:
a cap portion (<NUM>) having a plurality of N cutting portions (<NUM>) circumferentially alternating with a plurality of N head chip flutes (<NUM>), and a head base surface (<NUM>) facing in an axial rearward direction (DR); and
a rigid mounting protuberance (<NUM>) joined to the cap portion (<NUM>) and extending axially rearwardly from the head base surface (<NUM>), the mounting protuberance (<NUM>) exhibiting N-fold rotational symmetry about the first axis (A1), and a plurality of N circumferentially spaced apart convex clamping surfaces (<NUM>), each clamping surface (<NUM>) bisected by a radial clamping bisector plane (PB) containing the first axis (A1),
wherein:
the plurality of cutting portions (<NUM>) define a cutting diameter (DC) corresponding to a cutting circle (CC),
in a cross-section taken in a first plane (P1) perpendicular to the first axis (A1) and intersecting the cap portion (<NUM>), the plurality of N head chip flutes (<NUM>) are inscribed by an imaginary first circle (C1) having a first diameter (D1) at a plurality of N radially innermost head flute points (NH), and
in a cross-section taken in a second plane (P2) perpendicular to the first axis (A1) and intersecting the mounting protuberance (<NUM>), the plurality of N clamping surfaces (<NUM>) are circumscribed by an imaginary second circle (C2) having a second diameter (D2),
and wherein:
the first diameter (D1) is greater than the second diameter (D2),
the second diameter (D2) is less than forty percent of the cutting diameter (DC),
characterized in that
each cutting portion (<NUM>) comprises a cutting edge (<NUM>) formed at the intersection of an axially forward facing leading surface (<NUM>) and a circumferentially adjacent and rotationally forward head chip flute (<NUM>), the cutting edge (<NUM>) extending in a direction transverse to the first axis (A1).