Drill rod and drill bit with rocking connection

A drill bit is fictionally received over a drill rod via complementary generally frusto-conical male formation and socket. The socket has an inwardly protruding face at an angle with the longitudinal axis of the drill rod. The male formation on the drill rod has a depression in the form of an area where the convexity of the frusto-conical portion has been flattened at an angle so as to form a rocking formation at a selective location relative to the opposite ends of the male formation and the socket. A clearance space diverges away from the rocking formation toward a selective ends of the male formation and the socket. The frusto-conical male formation and the socket are a-circular and form positive driving engagement between the drill rod and the drill bit. An impact at the point of maximum clearance causes rocking about the rocking formation to break static friction and to facilitate release of the drill bit from the drill rod.

BACKGROUND OF THE INVENTION 
The invention relates to a combination of a drill bit and a drill rod, as 
well as a method of detaching, or releasing, a drill bit from a drill rod. 
The kind of drill rod and drill bit combination to which this invention 
relates typically comprises a drill rod having at one end thereof a 
frusto-conical male formation. At one end of the drill bit is an 
abrasion-resistant insert for drilling formations and at an opposed end of 
the drill bit is a frusto-conical socket that is complementary in shape to 
the frusto-conical end of the drill rod. 
Conventionally, the drill bit is received on the rod whereby the male 
formation of the drill rod and female socket of the drill bit are in a 
mating relationship. In operation, the forces transmitted from the drill 
rod to the drill bit are axial and rotary, or rotary alone. There is a 
frictional locking between these components to effect a driving connection 
of the drill bit to the drill rod. 
SUMMARY OF THE INVENTION 
In accordance with a first aspect of this invention, there is provided a 
combination of a drill rod and a drill bit in which the drill rod includes 
a generally frusto-conical end portion and an area of limited angular 
extent on the frusto-conical end portion which is flattened to provide a 
depressed face which is flat and of a predetermined width. The drill bit 
has, at one end thereof, a generally frusto-conical socket complementary 
to the frusto-conical end portion of the drill rod. The drill bit further 
has, along an area of limited angular extent, a generally radially 
inwardly protruding face complementary to the depressed face of the drill 
rod. The drill bit is received over the drill rod such that the generally 
frusto-conical socket surrounds the generally frusto-conical end portion 
of the drill bit and the protruding face seats on the depressed face. 
In accordance with a second aspect of this invention, there is provided a 
combination of a drill rod and a drill bit in which the drill rod has a 
generally frusto-conical male formation at one end thereof and a depressed 
face at an angular portion along the generally frusto-conical male 
formation. The drill bit has, at one end thereof, a generally 
frusto-conical socket formation complementary to the generally 
frusto-conical male formation in the one end of the male formation. The 
drill bit further includes a generally radially inwardly protruding face 
at an angular portion along a wall of the generally frusto-conical socket 
formation. The drill bit socket formation is received over the drill rod 
male formation with the depressed face and the protruding face in 
register. The combination of the drill bit and the drill rod includes 
rocking formations respectively on the depressed face and the protruding 
face which abut to form a clearance space between the inwardly protruding 
face and the depressed face. The clearance space extends from the rocking 
formations to an extremity of one of the frusto-conical male formation and 
the frusto-conical socket to provide lost motion in pivot about the 
rocking formation. 
In accordance with a third aspect of this invention, there is provided a 
method of releasing a drill bit received over an end of a drill rod in 
which the drill rod and the drill bit have on the respective 
frusto-conical formations inter-abutting rocking formations at an 
asymmetric angular position and form a clearance space longitudinally 
adjacent the rocking formations providing lost motion in pivoting about 
the rocking formations between the drill rod and the socket of the drill 
bit. The method includes delivering an impact to the drill bit at a 
predetermined position to cause rocking about the rocking formations to 
break static frictional engagement between the male formation of the drill 
rod and the socket formation of the drill bit.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
With reference to FIG. 1 of the drawings, a drill bit in accordance with 
this invention, generally designated as 10, includes an elongate body 12 
having, at one end which is not shown, drilling formations, i.e., a hard 
insert used to drill earth strata formations. At an opposed end, it has a 
socket 14 which is defined by a frusto-conical wall. In accordance with 
the invention, at a predetermined angular position, there is provided an 
inwardly protruding protrusion 16. The protrusion 16 conveniently has a 
flat surface. The drill bit 10 is generally of molded construction and the 
protrusion 16 is integrally molded as a part of the wall that defines the 
socket 14. 
With reference to FIG. 2, a drill rod in accordance with the invention is 
generally indicated by reference numeral 20. The drill rod 20 has a 
frusto-conical male formation 24 at one end. In accordance with the 
invention, in the frusto-conical male formation 24, there is provided a 
flat depressed surface or face 26 providing a relatively depressed area or 
notch, i.e., an area which lies within a geometrical demarcation 
corresponding to a hypothetical symmetric outline of the male formation. 
With reference to FIG. 3 there is shown a combination, generally designated 
as 30.1, of the drill bit 10 and the drill rod 20 respectively of FIGS. 1 
and 2. It is shown that the drill bit 10, and more specifically, its 
socket 14, is received on or seated on the frusto-conical formation 24 of 
the drill rod 20. The relative orientation is such that the protrusion 
16.1 seats on the depression 26.1 so that the protrusion 16.1 engages the 
depression 26.1. Thus, a positive driving connection between the drill rod 
20 and the drill bit 10 is provided which prevents the drill bit from 
slipping relative to the drill rod in operation. The applicants are of the 
opinion that such positive driving connection is particularly advantageous 
in the case of those drill bit and drill rod combinations which are 
operated predominantly by rotation as opposed to percussion combined with 
rotation. It is thus expected that this invention will find particular 
application in coal mining where drilling is generally or predominantly 
done by way of rotation. 
Still referring to FIG. 3, in accordance with the second aspect of this 
invention, the protrusion 16.1 abuts the depression 26.1 as shown 
respectively at 19.1 and 29.1 to provide rocking formations in accordance 
with the invention. In this embodiment, it is seen that the rocking 
formation is at the smaller diameter end of the frusto-conical male 
formation 24. 
It is shown that the angle 28.1 which the depression 26.1 forms is slightly 
shallower or narrower than the angle 18.1 which the protruding face 16.1 
forms with an axis of the socket. Thus, toward one side of the rocking 
formation 19.1, 29.1, a clearance space is provided which allows lost 
motion, and thus, rocking about the rocking formation 19.1 and 29.1. This 
clearance space extends from the rocking formation to the larger diameter 
end of the frusto-conical male formation 24. 
In use, when the drill bit 10 is seated on the drill rod 20, at the rocking 
formation 19.1 and 29.1, the protruding face 16.1 seats on the depressed 
face 26.1 to provide positive driving connection between the drill rod and 
the drill bit. 
When the drill bit 10 is to be detached or removed from the drill rod 20, 
in accordance with the invention, an impact is delivered to the drill bit 
10, e.g. by means of a hammer, at a position in register with the area or 
maximum clearance i.e. on the body of the drill bit 10 remote from the 
rocking formation 19.1 and at the angular position of the protrusion 16.1. 
Such impact breaks static friction between the walls of the components to 
release the drill bit 10 and to allow it to be removed from the drill rod 
20. 
With reference to FIG. 4, another combination, generally designated as 
30.2, is shown. Many features are similar or even identical and the same 
or like reference numerals are used to refer to the same or like features 
or components. The principal difference between the combination of FIGS. 3 
and 4 is that, in the case of the embodiment of FIG. 4, the rocking 
formation 19.2 and 29.2 is provided at the larger cross-sectional ends of 
the frusto-conical formations and the area of maximum clearance is 
provided at the ends of smaller cross-sectional dimension. 
It is shown that the angle 28.2 which the depression 26.2 forms is slightly 
larger than the angle 18.2 which the protruding face 16.2 forms with an 
axis of the socket. Thus, toward one side of the rocking formation 19.2, 
29.2, a clearance space is provided which allows lost motion, and thus, 
rocking about the rocking formation 19.2 and 29.2. This clearance space 
extends from the rocking formation to the smaller diameter end of the 
frusto-conical male formation 24. 
When the drill bit 10 is to be detached or removed from the drill rod 20, 
in accordance with the invention, an impact is delivered to the drill bit 
10, e.g. by means of a hammer, at a position in register with the area or 
maximum clearance i.e. on the body of the drill bit 10 remote from the 
rocking formation 19.2 and at the angular position of the protrusion 16.2. 
Such impact breaks static friction between the walls of the components to 
release the drill bit 10 and to allow it to be removed from the drill rod 
20. 
With reference to FIG. 5, a third combination, generally designated as 
30.3, is shown, and the same or like reference numerals are again utilized 
to refer to the same or like components or features compared to FIGS. 3 
and 4. The principal difference between the embodiment of FIG. 5 and the 
embodiments of FIGS. 3 and 4 is that the rocking formations 19.3, 29.3 are 
generally midway along the lengths of the frusto-conical portions, i.e., 
intermediate the smaller and larger cross-sectional ends of the 
frusto-conical male formation 24 and the frusto-conical socket, and 
clearance is provided to either side of the rocking formations 19.3, 29.3. 
In order to form the rocking formations 19.3, 29.3 intermediate of the 
larger and smaller diameter ends of the frusto-conical male formation 24, 
the depression has two distinct portions. One portion is axially rearward 
of the rocking formations so as to be nearest to the larger diameter end 
of the frusto-conical male formation 24. The other portion is axially 
forward of the rocking formations so as to be nearest to the smaller 
diameter end of the frusto-conical male formation 24. 
Referring to the axially rearward portion, it is shown that the angle which 
this portion of the depression 26.3 forms is slightly shallower or 
narrower than the angle which the protruding face 16.3 forms with an axis 
of the socket. Thus, toward the axially rearward side of the rocking 
formation 19.3, 29.3, a clearance space is provided which allows lost 
motion, and thus, rocking about the rocking formation 19.3 and 29.3. This 
clearance space extends from the rocking formation to the larger diameter 
end of the frusto-conical male formation 24. 
Referring to the axially forward portion, it is shown that the angle which 
this portion of the depression 26.3 forms is slightly greater than the 
angle which the protruding face 16.3 forms with an axis of the socket. 
Thus, toward the axially forward side of the rocking formation 19.3, 29.3, 
a clearance space is provided which allows lost motion, and thus, rocking 
about the rocking formation 19.3 and 29.3. This clearance space extends 
from the rocking formation to the smaller diameter end of the 
frusto-conical male formation 24. 
When the drill bit 10 is to be detached or removed from the drill rod 20, 
in accordance with the invention, an impact is delivered to the drill bit 
10, e.g. by means of a hammer, at a position in register with any one of 
the two areas of maximum clearance, i.e., on the body of the drill bit 10 
remote from the rocking formation 19.3. Such impact breaks static friction 
between the walls of the components to release the drill bit 10 and to 
allow it to be removed from the drill rod 20. 
The applicant regards the invention as having the advantage that positive 
driving between the drill rod and the drill bit is provided, in 
combination with a feature allowing for easy separation of the drill bit 
from the drill rod. 
Other embodiments of the invention will be apparent to those skilled in the 
art from a consideration of the specification or practice of the invention 
disclosed herein. It is intended that the specification and examples be 
considered as illustrative only, with the true scope and spirit of the 
invention being indicated by the following claims.