U.S. patent application number 09/778437 was filed with the patent office on 2001-08-16 for solid hard metal head for a drill.
Invention is credited to Hauptmann, Udo, Prols, Tim.
Application Number | 20010013430 09/778437 |
Document ID | / |
Family ID | 7631111 |
Filed Date | 2001-08-16 |
United States Patent
Application |
20010013430 |
Kind Code |
A1 |
Hauptmann, Udo ; et
al. |
August 16, 2001 |
Solid hard metal head for a drill
Abstract
A solid hard metal head for a drill, including two main cutting
edges (2) arranged substantially diametrially opposite each other,
and two auxiliary cutting edges (3) likewise arranged substantially
diametrically opposite each other, with associated main cutting
edge (2) and auxiliary cutting edge (3) form an acute angle
(.alpha.) there between, and with the auxiliary cutting edges (3)
being arranged, with respect to the rotational direction (.omega.)
of the drill, in front of the respective, associated therewith,
main cutting edge (2).
Inventors: |
Hauptmann, Udo;
(Landsberg/Lech, DE) ; Prols, Tim; (Munich,
DE) |
Correspondence
Address: |
David Toren
BROWN & WOOD LLP
One World Trade Center
New York
NY
10048-0557
US
|
Family ID: |
7631111 |
Appl. No.: |
09/778437 |
Filed: |
February 7, 2001 |
Current U.S.
Class: |
175/415 ;
175/420; 175/420.1; 175/427 |
Current CPC
Class: |
B23B 2222/28 20130101;
B23B 51/02 20130101; B23B 2251/204 20130101; B23B 2226/75
20130101 |
Class at
Publication: |
175/415 ;
175/420; 175/420.1; 175/427 |
International
Class: |
E21B 010/62 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 16, 2000 |
DE |
100 06 932.0 |
Claims
What is claimed is:
1. A solid hard metal head for a drill, comprising two main cutting
edges (2) arranged substantially diametrically opposite each other,
and two auxiliary cutting edges (3) likewise arranged substantially
diametrically opposite each other, wherein associated main cutting
edge (2)and auxiliary cutting edge (3) form an acute angle
(.alpha.) therebetween, and wherein the auxiliary cutting edges (3)
are arranged, with respect to the rotational direction (.omega.) of
the drill, in front of the respective, associated therewith, main
cutting edges (2).
2. A solid hard metal head according to claim 1, wherein the acute
angle (.alpha.) between the associated main and auxiliary cutting
edges (2; 3), which lies in a plane extending transverse to a drill
rotational axis, lies in a range between 40 and 90.degree..
3. A solid hard metal head according to claim 1, wherein a recess
(4; 5) is formed between each two adjacent main and auxiliary
cutting edges (2; 3) in a circumference of a cross-sectional
surface, and wherein the recess (4; 5) has somewhat prismatic shape
and extends along an entire axial extent of the head (1).
4. A solid hard metal head according to claim 3, wherein a portion
of a side surface (6) of the recess (5), which is arranged, with
respect to the rotational direction (.omega.), in front of a
respective auxiliary cutting edge (3) and extends in an axial
direction along the rotational axis (A), has a chamfer (7) at an
end surface of the head (8).
5. A solid hard metal head according to claim 1, wherein at the
tip, the main cutting edge (2) ends at a chisel edge (9).
6. A solid hard metal head according to claim 1, wherein the main
cutting edges (2) have, in an axial direction, a slightly concave
shape.
7. A solid hard metal head according to claim 1, wherein the
auxiliary cutting edges (3) have, in an axial direction, a
pronounced concave shape.
8. A solid hard metal head according to claim 1, wherein an axial
spacing of the auxiliary cutting edges (3) is so selected that a
highest point of a generating curve of the auxiliary cutting edges
(3) does not project above an axial generating curve of the main
cutting edges.
9. A solid hard metal head according to claim 1, wherein the
auxiliary cutting edges (3) are radially displaced with respect to
a generating curve of the main cutting edges (2).
10. A solid hard metal head according to claim 1, wherein a
transitional surface (12), in a sector between adjacent main and
auxiliary cutting edges (2; 3), has a circumferentially concave
shape in an axial direction.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a solid hard metal head for
a rock drill used for drilling stones and concrete and securable in
mechanized hand-held tools for removal abrasive materials upon
application of a rotary percussion movement thereto.
[0003] 2. Description of the Prior Act
[0004] Drills for drilling in stone or concrete require, because
they are used for removal of abrasive materials, that the parts
insertable into the drill head be made of hard metal as they should
have a high hardness so that they would not be subjected to an
extensive wear. The insertable parts are fixedly secured in the
drill. Usually, the insertable parts are formed as hard metal
plates soldered in the head. Such a drill is disclosed in German
document DE 20 08 825. A relatively small flexural strength of the
heard metal plates leads to their breaking out of the remainder of
the drill, in particular, when the drill head encounters a
reinforcing metal.
[0005] German Publication DE 43 39 245 discloses forming an entire
drill head of a hard metal as a solid hard metal head. A solid hard
metal head has a compact, substantially convex, polygonal shape
with the lengths of its sides being substantially the same. Due to
this shape, the solid hard metal head has a high inner stiffness.
To prevent the main cutting edges from hooking in reinforcing
metal, usually, auxiliary cutting edges are provided between the
main cutting edges and which are arranged exclusively on the radial
edge of the head and are axially offset. The auxiliary cutting
edges, due to their penetration resistance and mass inertia,
prevent the main cutting edges from penetrating deeply into the
reinforcing metal by temporary lifting the drill from the
reinforcing metal. The manufacturing and economical drawbacks of
this drill result from a large volume of the solid hard metal head
when the drill is designed for drilling large-diameter bores.
[0006] In addition, it is anticipated that the auxiliary cutting
edge would have a slightly concave, in the axial direction, shape
with an obtuse angle being formed in a plane, which passes through
the radially outer cutting edges transvers to the drill rotational
axis, with the obtuse angle being symmetrical with respect to the
rotational axis. The concave, in the axial direction, shape of the
auxiliary cutting edge, in cooperation with the non-concave main
cutting edge, forms an axially extending free space for removal of
drillings from the tool tip and which prevents compression of the
drillings in front of the drill tip which otherwise would have
reduced the drill performance. The drawback of forming the
auxiliary cutting edges with a slightly concave shape consists in
that the auxiliary cutting edges, in combination with a non-concave
main cutting edges, make precise drilling more difficult.
[0007] German Publication DE 19 70 711.5 discloses a drill having a
one-piece, prismatic, solid hard metal head with more than two
rotationally symmetrical, radial cutting edges and which is
inserted in corresponding grooves formed in the drill body and
having axially extending surfaces, with the head being fixedly
secured with the drill body along the axially extending surfaces of
the groove and to the end surface of the drill body. The attachment
of the head to the end surface of the drill body, on one hand, and
the additional securing of the head, in the radially outer region
of the head, in the axial grooves with formation mortise and tenon
joints, on the other hand, provides for a breakproof securing of
the cutting edges, even in large diameter drills, so that they
would not be dislodged even upon engagement with the reinforcing
metal. However, with increased number of cutting edges, with the
same available power, a smaller force is applied to each edge,
which adversely affects drill performance. Another drawback of the
above-described rill consists in a need to form a plurality of
mortises corresponding to the number of the cutting edges, this
makes solving the problem of removing of the drilled abrasive
material more difficult.
[0008] European publication EP 88 44 48 discloses a solid hard
metal head with an "X"-shaped arrangement of four cutting edges,
with the main cutting edges and the auxiliary cutting edges, which
are formed as side cutting edges, being arranged, respectively,
diametrically opposite each other and with respective main and
auxiliary cutting edges forming an angle that deviates from
90.degree.. The main cutting edges form, in their plane, an obtuse
angle, with the tip being in the region of the rotational axis. The
auxiliary cutting edges extend perpendicular to the rotational axis
and are axially offset backward in such a way that the inner region
of a bore is cut with main cutting edges, and the outer region of
the bore is cut with the auxiliary, side, cutting edges. The so
formed side cutting edges have a tendency to break upon striking a
reinforcing metal, as a result of a high load applied to the side
edges.
[0009] The "X"-shaped, solid, hard metal head has essentially a
rotationally symmetrical, crosswise, axially mirror symmetrical,
prismatic shape. The base surface is provided with deep, concave,
obtuse-angled notches which extend radially inward along one-third
of the base surface parallel to the cutting edges over the longer
surfaces. The notches serve for removal of the cut abrasive
material. The side cutting edges trail the main cutting edges in
the rotational direction, forming with the respective main cutting
edges acute angles. As a result, a large recess is provided in
front of a main cutting edge. A small concave recess on each of the
short sides of the base surface is limited by the radial edge
region and serves for removal of some of the cut abrasive material
in front of the respective auxiliary or side cutting edge. The
drawback of this head consists in that because of an obtuse angle,
in the rotational direction, between the auxiliary cutting edge and
the trailing main cutting edge, a large rotational angle is needed
in order to overcome the mass inertia.
[0010] However, practically, it is impossible to provide for such
angle in low-speed large-diameter drills.
[0011] Accordingly, an object of the present invention is to
provide a solid hard metal head for a rock drill which would
insure, even with a large head diameter, application of high
localized forces to the cutting edges for achieving a high drilling
capacity.
[0012] Another abject of the present invention is to provide a
solid hard metal head for a rock drill which would insure adequate
removal of the cut abrasive material and a precise spot
drilling.
[0013] A further object of the present invention is to provide a
solid hard metal head for a rock drill which would insure
application of a reduced load to the cutting edges upon encounter
of the drilling head with reinforcing metal.
[0014] A still further object of the present invention is to
provide a solid hard metal head for a rock drill with break-proof
cutting edges.
SUMMARY OF THE INVENTION
[0015] This and other objects of the present invention, which will
become apparent hereinafter, are achieved by providing a solid hard
metal head for a drill including two main cutting edges arranged
substantially diametrically opposite each other, and two auxiliary
cutting edges likewise arranged substantially diametrically
opposite each other, with associated main cutting edge and
auxiliary cutting edge forming an acute angle therebetween, and
with the auxiliary cutting edges being arranged, with respect to
the rotational direction of the drill, in front of the respective,
associated therewith, main cutting edges.
[0016] Advantageously, the inventive solid hard metal head has a
drilling diameter from 12 mm to 40 mm. The arrangement of the
auxiliary cutting edges in front of the main cutting edges provides
for lifting of the drill when the drill strikes reinforcing metal,
which prevents application of a load to the main cutting edges when
the drill strikes reinforcing metal. The acute angle between the
associated main and auxiliary cutting edges, which lies in a plane
extending transverse to a drill rotational axis, lies in a range
between 40.degree. and 90.degree.. Thus, for overcoming mass
inertia, only a small rotational angle need be bridged.
[0017] A satisfactory removal of the cut abrasive material in front
of main cutting edge into a helical groove adjoining the solid hard
metal head of the drill is insured by providing between adjacent
cutting edges two radial concave recesses, respectively, extending
parallel to the respective edges and formed in the circumference of
the cross-sectional surface and having a prismatic shape in the
axial direction. A portion of a side surface of the recess, which
extends along the rotational axis, advantageously, in front of the
auxiliary cutting edge, provides for additional securing of the
solid hard metal head in groove-shaped tenons provided in the tool
body. These portions of the side surfaces advantageously are
provided with chamfers extending toward the end surface for
breaking the edge. The foregoing structure insures a break-proof
attachment of the solid hard metal head to the drill body and
provides for pressure-side support of the main cutting edges.
Providing, advantageously, a groove in the drill body, which is
associated with the diametrically opposite recesses, insures
self-centering of the solid hard metal head when it is being
attached to the drill body.
[0018] Advantageously, the main cutting edges are so formed that
they end, at the tip of the head, at a chisel edge and have a
slightly concave shape, whereby a somewhat acute angle is formed
with respect to the tip region, which provides for precise spot
drilling with the chisel edge, and a somewhat obtuse angle is
formed between the main cutting edges and the rotational axis with
respect to the radial outer region, which provides for a precisely
axial lead-in of the axial blows imparted to the drill, which
insures transmittal of the energy of axial blows to the cut
material with minimum losses. Advantageously, the auxiliary cutting
edges have a pronounced axially concave shape, therefore, a plane,
which passes through the radial outer regions of the auxiliary
cutting edges perpendicular to the rotational axis, is interrupted.
Thus, in combination with slightly axially concave shape of the
main cutting edges, there are provided axial recesses which insure
removal of the cut material from the drill (head) tip.
[0019] A transitional surface in a sector between adjacent main and
auxiliary cutting edges has advantageously a circumferentially
concave shape in an axial direction, which permits to obtain a
larger recess for transporting drillings and to obtain a high inner
stiffness of the solid hard metal head.
[0020] Forming the main and the auxiliary cutting edges as integral
arts of the solid hard metal head insures their precise positioning
relative to each other, which is not affected by manufacturing
tolerances associated with attachment of the head with the drill
body. In order to obtain a low vibration operation of the drill,
the axial spacing of the auxiliary cutting edges is so selected
that the highest point of the axial generating curve does not
project exactly over the axial generating curve of the main cutting
edges. A low-vibration operation and a uniform round bore geometry
is achieved by matching the generating envelopes of the main and
auxiliary cutting edges to each other, in particular, by an
appropriate radial displacement of the generating curve of the
auxiliary cutting edges relative to the main cutting edges.
[0021] The novel features of the present invention, which are
considered as characteristic for the invention, are set forth in
the appended claims. The invention itself, however, both as to its
construction and its mode of operation, together with additional
advantages and objects thereof, will be best understood from the
following detailed description of preferred embodiments, when read
with reference to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] The drawings show:
[0023] FIG. 1 a perspective view of the solid hard metal head of a
drill according to the present invention;
[0024] FIG. 2 a plan view of the solid hard metal head shown in
FIG. 1;
[0025] FIG. 3 a side view of the solid hard metal head shown in
FIG. 1; and
[0026] FIG. 4 an angular side view of the solid hard metal head
shown in FIG. 1
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0027] A solid hard metal head 1 of a drill according to the
present invention, which is shown in FIG. 1, has advantageously a
drilling diameter from 12 mm to 40 mm and an X-shaped arrangement
of four cutting edges 2, 3, with the main cutting edges 2 extending
diametrically opposite each other with respect to the rotational
axis A, and with respective main cutting edge 2 and auxiliary
cutting edge 3 forming an angle that deviates from 90.degree.,
namely, an acute angle. The auxiliary cutting edge 3 is arranged,
in the drill rotational direction .omega., in front of the
associated therewith, main cutting edge 2.
[0028] According to FIG. 2, an angle .alpha. between the main
cutting edge 2 and the auxiliary cutting edge 3, which lies in
plane extending perpendicular to the rotational axis A, amounts to
or is located within a range from 40.degree. to 90.degree.. With
respect to the generating curve of the main cutting edge 2, the
auxiliary cutting edge 3 is radially displaced. Between two
respective adjacent cutting edges 2, 3, there are provided two
concave recesses 4, 5 formed in the circumference of the
cross-sectional surface and having, in the axial direction, a
substantially prismatic shape. A portion of a side surface 6 of the
recess 5, which extends along the rotational axis A,
advantageously, in front of the auxiliary cutting edge 3, provides
for additional securing of the solid hard metal head 1 in mortises
provided in the tool body.
[0029] As shown in FIG. 3, the securing portion of the side surface
6 has a chamfer 7 extending toward an end surface 8 for breaking
the edge. The main cutting edge 2 which, at the tip, ends at chisel
edge 9, has a slightly concave shape in the axial direction. The
axial spacing of the auxiliary cutting edge 3 does not project
exactly over the axial generating curve of the main cutting edge
2.
[0030] As shown in FIG. 4, the auxiliary cutting edge 3 has a
noticeable concave shape in the axial direction, so that a plane
10, which extends through the radially outer regions of the
auxiliary cutting edges 3 transverse to the rotational axis, is
interrupted or cut. The pronounced concave shape of the auxiliary
cutting edge 3, in cooperation with the slightly concave shape of
the main cutting edge, forms a recess 11 for removal of drillings
from the drill tip. The transition surface 12, in the sector
between the adjacent cutting edges 2, 3, also has, in the axial
direction, a circumferentially concave shape.
[0031] Though the present invention was shown and described with
references to the preferred embodiments, such embodiments are
merely illustrative of the present invention and are not to be
construed as a limitation thereof, and various modifications of the
present invention will be apparent to those skilled in the art. It
is, therefore, not intended that the present invention be limited
to the disclosed embodiments or details thereof, and the present
invention includes all variations and/or alternative embodiments
within the spirit and scope of the present invention as defined by
the appended claims.
* * * * *