U.S. patent application number 11/983470 was filed with the patent office on 2008-05-15 for drill with a hard material drilling head.
This patent application is currently assigned to Hilti Aktiengesellschaft. Invention is credited to Olaf Koch.
Application Number | 20080110679 11/983470 |
Document ID | / |
Family ID | 38955132 |
Filed Date | 2008-05-15 |
United States Patent
Application |
20080110679 |
Kind Code |
A1 |
Koch; Olaf |
May 15, 2008 |
Drill with a hard material drilling head
Abstract
A one-piece drilling head (4) which is to be secured, in a
material-locking manner, at an end of a helical shaft of a drill,
is formed of hard material and includes four radially extending, in
a cross-shaped manner, legs (5) forming, respectively, two
diametrically opposite main cutting edges (6) and two auxiliary
cutting edges (7), with the main cutting edges (6) and the
auxiliary cutting edges (7) extending proceeding from a drilling
head drilling head tip (8), monotonously and strictly axially up to
a radially outer edge, and with an envelope surface (9') of the
auxiliary cutting edges (7) lying completely within an envelope
surface (9) of the main cutting edges (6) and contacts the same
only at the drilling head tip (8).
Inventors: |
Koch; Olaf; (Kaufering,
DE) |
Correspondence
Address: |
ABELMAN, FRAYNE & SCHWAB
666 THIRD AVENUE, 10TH FLOOR
NEW YORK
NY
10017
US
|
Assignee: |
Hilti Aktiengesellschaft
|
Family ID: |
38955132 |
Appl. No.: |
11/983470 |
Filed: |
November 9, 2007 |
Current U.S.
Class: |
175/395 ;
175/415 |
Current CPC
Class: |
B23B 2251/14 20130101;
B23B 2226/75 20130101; B23B 2251/50 20130101; B23B 2251/204
20130101; B28D 1/146 20130101; B23B 2240/08 20130101; B23B 51/02
20130101 |
Class at
Publication: |
175/395 ;
175/415 |
International
Class: |
E21B 10/44 20060101
E21B010/44; E21B 10/36 20060101 E21B010/36 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 15, 2006 |
DE |
10 2006 035 443.5 |
Claims
1. A one-piece drilling head (4) for a drill and formed of hard
material, comprising four radially extending, in a cross-shaped
manner, legs (5) forming, respectively, two diametrically opposite
main cutting edges (6) and two auxiliary cutting edges (7), and a
drilling head tip (8) wherein the main cutting edges (6) and the
auxilially cutting edges (7) extend, proceeding from the drilling
head tip (8), monotonously and strictly axially up to a radially
outer rim, and an envelope surface (9') of the auxiliary cutting
edges (7) lies completely within an envelope surface (9) of the
main cutting edges (6) and contacts the envelope surface (9) of the
main cutting edges (6) only at the drilling head tip (8).
2. A drilling head according to claim 1, wherein an angular
difference of radial standardized ridge angles of the envelope
surface (9) of the main cutting edges (6) and the envelope cutting
surface (9') of the auxiliary cutting edges (7) lies in a range
between 2.degree. and 10.degree..
3. A drilling head according to claim 1, wherein the main cutting
edges (6) and the auxiliary cutting edges (7) extend axially
linearly.
4. A drilling head according to claim 1, wherein the main cutting
edges (6) form, proceeding from the drilling head tip (8), a
straight line in an axial projection.
5. A drilling head according to claim 1, wherein the auxiliary
cutting edges (7) form, proceeding from the drilling head tip (8),
in an axial projection, a convexly curved line facing a following
main cutting edge (6).
6. A drilling head according to claim 5, wherein the auxiliary
cutting edges (7) are uniformly curved.
7. A drilling head according to claim 1, wherein a leg (5) of the
main cutting edge (6) forms, at the outer radial rim on a side
thereof facing in the rotational direction (.omega.), a tangential
ramp surface (10) axially spaced from the main cutting edge
(6).
8. A drill, comprising a helically shaped shaft (2); and a
one-piece drilling head (4) formed of a hard material and secured
on an axial end (3) of the shaft (2) in a material-locking manner,
the drilling head including four radially extending, in a
cross-shaped manner, legs (5) forming, respectively, two
diametrically opposite main cutting edges (6) and two auxiliary
cutting edges (7), and a drilling head tip (8), wherein the main
cutting edges (6) and the auxilially cutting edges (7) extend,
proceeding from the drilling head tip (8), monotonously and
strictly axially up to a radially outer rim, and an envelope
surface (9') of the auxiliary cutting edges (7) lies completely
within an envelope surface (9) of the main cutting edges (6) and
contacts the envelope surface (9) of the main cutting edges (6)
only at the drilling head tip (6).
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a boring tool with a hard
material drilling head and, in particular, to a rotary-percussion
drill for stone and reinforced concrete and to be used with a
high-power hand-held power tool. More specifically, the present
invention relates to the hard material drilling head for the
rotary-percussion drill.
[0003] 2. Description of the Prior Art
[0004] Usually, a drill which is mentioned above, has a helical
shaft extending axially along a rotational axis of the drill and
provided on its power tool-side end with a shank for insertion in a
chuck of the power tool and at its opposite workpiece-side end with
a hard material head brazed to the shaft. The drilling head has
four radially extending, in a cross-shaped manner, legs forming,
respectively, two diametrically opposite main cutting edges and two
auxiliary cutting edges, and a drilling head tip.
[0005] International Publication WO 2005/061838 discloses a
rotary-percussion drill with a one-piece head formed of hard
material and having four cutting edges which are arranged in a
cross-shaped manner and are convexly curved in the rotational
direction, and a drilling head tip.
[0006] European Publication EP 1 604 762 discloses a drill for
stone with a one-piece hard material drilling head butt-brazed to
the shaft and having four legs arranged in a cross-shaped manner
and forming two diametrically opposite straight main cutting edges
and two diametrically opposite auxiliary cutting edges concavely
curved in the rotational direction. The auxiliary cutting edges
have a ramp surface tangentially inclined in the rotational
direction (for axially lifting the drill at the power-tool side
upon encountering a reinforcing iron) and extend exclusively in the
radially outer region. Two diametrically opposite drilling head
cutting edges, which extend axially linear to respective drill tips
formed by the main cutting edges, are provided only in the radially
inner drilling head region of the drilling head. The radially inner
envelope surface of the drilling head region has a more acute ridge
angle than the radially outer envelope surface of the legs.
[0007] An object of the invention is to increase the drilling
capacity of the drill of the type described immediately above.
[0008] Another object of the invention is to increase robustness of
the drill upon encounter with reinforcing iron.
SUMMARY OF THE INVENTION
[0009] These and other objects of the present invention, which will
become apparent hereinafter, are achieved by providing a one-piece,
hard material drilling head having four radially extending, in a
cross-shaped manner, legs forming, respectively, two diametrically
opposite main cutting edges and two auxiliary cutting edges, and a
tip. The main cutting edges and the auxilially cutting edges
extend, proceeding from the drilling head tip, monotonously and
strictly axially (i.e., only regarding the axial components) up to
a radially outer rim of the drilling head in envelope surface of
the auxiliary cutting edges lies completely within an envelope
surface of the main cutting edges and contacts the envelope surface
of the main cutting edges only at the drilling head tip.
[0010] With the envelope surface of the auxiliary cutting edges
lying within the envelope surface of the main cutting edges, the
radial standardized ridge angle of the auxiliary cutting edges is
smaller than that of the main cutting edges. Thereby, with the
outer radial region of the drilling head substantially defining the
drilling capacity, the press-on force is concentrated on the main
cutting edges, whereas the auxiliary cutting edges serve for
protecting the drilling head upon encounter with reinforcing iron.
All of the four cutting edges provide for good centering and
guiding characteristics in the inner central region.
[0011] Advantageously, the angle difference of radial standardized
ridge angles of the envelope surface of the main cutting edges and
the envelope surface of the auxiliary cutting edges lies in a range
between 2.degree. and 10.degree.. This angle difference permits to
achieve an optimal drilling capacity and robustness.
[0012] Advantageously, the main cutting edges and the auxiliary
cutting edges extend axially linearly, whereby their envelope
surfaces are formed as strictly conical surfaces.
[0013] Advantageously, the main cutting edges form, proceeding from
the drilling head tip, a straight line in an axial projection.
Thereby, the main cutting edges have a minimal length and a
maximal, linear force density at a given press-on force.
[0014] Advantageously, the auxiliary cutting edges form, proceeding
from the drilling head tip, in an axial projection, a convexly
curved line facing a following (in the rotational direction) main
cutting edge. Thereby, the drillings, which are primarily removed
by the main cutting edge (following the auxilially cutting edge in
the rotational direction) are better advanced in the helical shaft
of the drill to which the drilling head is attached.
[0015] Advantageously, the auxiliary cutting edges, proceeding from
the drilling head tip, are uniformly curved (i.e., with a constant
curvature radius). Thereby, a more pronounced curvature at local
points of the auxiliary cutting edges, where the drillings can
accumulate, is avoided.
[0016] Advantageously, the leg of the main cutting edge forms, at
the outer radial rim on its side facing in the rotational
direction, a tangential ramp surface axially spaced from the main
cutting edge. Thereby, a ramp surface is also formed on the main
cutting edge and which prevents seizure of the outer corner of the
main cutting edge in ductile reinforcing iron upon a sidewise
encounter with the reinforcing iron.
[0017] 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 embodiment, when read
with reference to the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] The drawings show:
[0019] FIG. 1a a front view of a drilling head of a drill according
to the present invention;
[0020] FIG. 1b a side view of the drilling head shown in FIG. 1;
and
[0021] FIG. 1c a plan view of the drilling head shown in FIGS.
1-2.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0022] A drilling head 4 according to the present invention, which
is shown in FIGS. 1a, 1b, and 1c, is formed of a hard material and
is butt-brazed at an end 3 of a helically shaped shaft 2 of a drill
1 rotatable about a rotational axis A and percussively displaceable
therealong. The hard material drilling head 4 has four, radially
extending in a cross-shaped manner, legs 5 with two main cutting
edges 6 and two auxiliary or minor cutting edges 7. The main
cutting edges 6 and the auxiliary cutting edges 7 extend axially
linearly from a drilling head tip 8 up to the outer radial rim of
the drilling head, with an envelope surface 9' of the auxiliary
cutting edges 7 lying completely within an envelope surface 9 of
the main cutting edges 6 and contacting the envelope surface 9 of
the main cutting edges 6 only at the drilling head tip 8. The
angular difference of ridge angles, which are inscribed in the
conical tip, between the envelope surface 9 of the main cutting
edges 6 and the envelope surface 9' of the auxiliary cutting edges
7 amounts to 130.degree.-125.degree.=5.degree.. The main cutting
edges 6 form, in an axial projection, a straight line extending
from the drilling head tip 8. The auxiliary cutting edges 7 are
uniformly convexly curved, in a drill rotational direction .omega.,
with respect to respective following main cutting edges 6. The leg
5 of the main cutting edge 6 forms, at the outer radial rim on its
side facing in the rotational direction .omega., a tangential ramp
surface 10 axially spaced from the main cutting edge 6.
[0023] Though the present invention was shown and described with
references to the preferred embodiment, such is merely illustrative
of the present invention and is 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 embodiment
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.
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