U.S. patent application number 11/709178 was filed with the patent office on 2007-08-23 for drilling head.
Invention is credited to Michael Bayerl, Kay Heemann, Wolfgang Ludwig.
Application Number | 20070193783 11/709178 |
Document ID | / |
Family ID | 38427006 |
Filed Date | 2007-08-23 |
United States Patent
Application |
20070193783 |
Kind Code |
A1 |
Heemann; Kay ; et
al. |
August 23, 2007 |
Drilling head
Abstract
A drilling head, with a cross-sectional dimension (E) in a
direction normal to the drilling axis (A), includes two
diametrically opposite, free-standing, prong-shaped support members
(2) provided at a head-side of the drilling head, and a
diametrically extending hard material element (3) connected with
the two support members (2) and which forms at least one cutter (4)
at its head, in an axial direction, side and which lies freely in a
central region (Z) of the drilling axis (A) at a stem, in the axial
direction, side of the drilling head (1).
Inventors: |
Heemann; Kay; (Kaufering,
DE) ; Ludwig; Wolfgang; (Zaisertshofen, DE) ;
Bayerl; Michael; (Tuerkheim, DE) |
Correspondence
Address: |
ABELMAN, FRAYNE & SCHWAB
666 THIRD AVENUE, 10TH FLOOR
NEW YORK
NY
10017
US
|
Family ID: |
38427006 |
Appl. No.: |
11/709178 |
Filed: |
February 20, 2007 |
Current U.S.
Class: |
175/392 ;
175/417 |
Current CPC
Class: |
E21B 10/54 20130101 |
Class at
Publication: |
175/392 ;
175/417 |
International
Class: |
E21B 10/40 20060101
E21B010/40 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 21, 2006 |
DE |
10 2006 000 085.4 |
Claims
1. A drilling head having a drilling axis (A) and a cross-sectional
dimension (E) in a direction normal to the drilling axis (A), the
drilling head comprising, at a head side thereof, two diametrically
opposite, free-standing, prong-shaped support members (2); and a
diametrically extending hard material element (3) connected with
the two support members (2), forming at least one cutter (4) at a
head, in an axial direction, side thereof, and lying freely in a
central region (Z) of the drilling axis (A) at a stem, in the axial
direction, side thereof.
2. A drilling head according to claim 1, comprising at a bottom
formed between the two support members (2) at the head, in the
axial direction, side of the drilling head, an opening (5) of a
rinsing bore (6) coaxial with the drilling axis (A).
3. A drilling head according to claim 1, wherein a diametrical free
space (F) between the two support members (2) amounts to at least a
fifth of the cross-sectional dimension (E).
4. A drilling head according to claim 1, wherein the hard material
element (3) is connected with the support members (2) in a
material-locking manner.
5. A drilling head according to claim 1, wherein the hard material
element (3) is formed as a thin hard material plate having a
thickness (D) less than a tenth of the cross-sectional dimension
(E).
6. A drilling head according to claim 1, wherein the hard material
element (3) has a reduction of thickness (D) in a radial region (R)
of the drilling axis (A).
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a forked drilling head for
rock materials and, in particular, for an injection self-drilling
anchor.
[0003] 2. Description of the Prior Art
[0004] Forked drilling heads (also known as two-prong drilling
heads or fish-tail drilling heads) are characterized by a high
drilling capacity in a comparative soft rock material, e.g., when
drilling the cap rock when mining the coal semi-coke.
[0005] Such mass-produced drilling heads, to which the present
invention is limited, have, at a drilling diameter between 25 mm
and 60 mm, a small degree of complexity. So the number of separate
parts, such as hard material inserts that form cutters, is limited,
for manufacturing reasons, to a small number, maximum to five
parts. When the drilling head is used as a one-time usable
injection self-drilling anchor, with an anchor-serving tubular stem
of the drilling head being glued to a bore wall with a
twin-component resin mortar, the retaining of the dimensional
accuracy of the bore cross-sectional dimension becomes of a very
high importance. This is because it is the cross-sectional
dimension that determines the strength of the annular channel that
is filled with the twin-component resin mortar.
[0006] According to International Publication WO 8901086 and German
Publication DE 41 34 425, a forked rock drilling head, which is
equipped with hard material, has at its head side, two
diametrically opposite, radially and circumferentially freely
extending, prong-shaped support members, with a hard metal cutting
element brazed to each of the support members. At the base between
the support members, there is located an opening of a rinsing bore
extending coaxially with the drilling axis. However, with two
separate hard metal cutting elements, it is difficult to realize a
bore with a cross-sectional dimension within narrow tolerance
limits because the cutting elements can be displaced relative to
each other during brazing. In addition, during brazing, the hard
metal cutting elements are secured to the respective support
members separately.
[0007] German Publication DE 34 36 128 discloses a pot-shaped
drilling head for drilling bores for injection self-drilling
anchors and equipped with a single, diametrically extending, hard
metal plate. The hard metal plate, which has two diametrically
opposite cutting edges, is supported by the drilling head along its
entire axial length. The drawback of this drilling head, in
comparison with the forked drilling heads, consists in its small
drilling capacity during drilling of bores in gallery roofs of coal
mines.
[0008] Accordingly, an object of the present invention is to
provide a forked drilling head suitable for mass production.
[0009] Another object of the present invention is to provide a
forked drilling head capable to maintain a high dimensional
accuracy of a bore cross-width.
SUMMARY OF THE INVENTION
[0010] These and other objects of the present invention, which will
become apparent hereinafter, are achieved by providing a drilling
head having at its head side, two diametrically opposite,
free-standing, prong-shaped support members, a diametrically
extending hard material element connected with the two support
members and which forms at least one cutter at its head, in an
axial direction, side and which lies freely in a central region of
the drilling axis at its stem, in the axial direction side. The
diametrically extending hard material element itself defines the
dimensional accuracy of the bore cross-sectional dimension, so that
the dimensional accuracy does not depend on exact fixing of the
hard material element on the support members during the assembly of
the drilling head.
[0011] Advantageously, there is formed at a bottom, which is formed
between the two support members, at the head, in the axial
direction, side of the drilling head, an opening of a rinsing bore
coaxial with the drilling axis. Thereby, the central part of the
hard material element, which lies freely in the central region of
the drilling axis and which becomes very hot during the drilling
process, is directly cooled by the rinsing water. As a result, a
smaller portion of heat should be removed from the area that
connects the hard material element with the support members and
which has a heat transition coefficient. This increases the usable
life of the drilling head.
[0012] Advantageously, a diametrical free space between the two
support members amounts to at least a fifth of the cross-sectional
dimension of the drilling head. Thereby, a high drilling capacity
is reached when drilling the relative soft rock material such as
cap rock that prevails in mines with coal semi-coke. In addition,
the opening cross-section is sufficiently large for wet drilling
with a low water pressure from 5 to 30 bar.
[0013] Advantageously, the hard material element is connected with
the support members in material-locking manner (i.e., being
integral with each other), e.g., is brazed, which provides for a
connection capable to withstand high loads.
[0014] Advantageously, the hard material element is formed as a
thin hard material plate with a thickness of less than a tenth of
the cross-sectional dimension of the bit.
[0015] Thereby, the bending stiffness of the hard material element,
which is proportional to a cube of thickness, is sufficiently low
to prevent any damage of the connection from bending vibrations of
the support members caused by drilling.
[0016] Advantageously, the hard material element has a thickness
reduction in the radial region of the drilling axis, e.g., arcuate
notches provided on opposite sides. Thereby, this hinge region has
a particular low bending stiffness.
[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. 1 a longitudinal cross-sectional view of a drilling
head according to the present invention along line I-I in FIG. 2;
and
[0020] FIG. 2 a plan view of the drilling head shown in FIG. 1.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT
[0021] A forked drilling head 1 according to the present invention,
which is shown in FIGS. 1-2, has a drilling axis A, a
cross-sectional dimension E in a direction normal to the drilling
axis A, of 60 mm, and two diametrically opposite, with respect to
the drilling axis A, radially and circumferentially free-standing
prong-shaped support members 2. Both supports are brazed,
respectively, with a single, diametrically extending hard material
element 3 which forms, at its head, in the axial direction, side
two cutters 4. The hard material element 3 lies freely at its stem
side, in the central region Z of the drilling axis A. At the head
in the axial direction-side, bottom of the drilling head 1, which
is formed between the two support members 2, there is provided an
opening 5 of a rinsing bore 6 coaxial with the drilling axis A. A
diametrically extending free space F between the two support
members 2 of 20 mm amounts to a third of the cross-sectional
dimension. The hard material element 3 is formed as a thin hard
material plate having a thickness D of 3 mm, i.e., one twentieth of
the cross-sectional dimension E, and having an arcuate notch 7 on
each of its sides in the radial region R of the drilling axis
A.
[0022] 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.
* * * * *