Note: Descriptions are shown in the official language in which they were submitted.
Patent Application 9022 -IR RD
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Background of the Invention
1. Field o~ the Invention -
This invention pertains to a thread system and
particularly a thread system for transmitting rotary and
S percussive power.
2. Description of the Prior Art -
In male thread applications employed to transmit
rotary and percussive power, the male threads are subject-
ed to relative motion conditions which can r-esult in
localized heating, thread galling, pitting formation and
ultimate transverence fatigue failure. These applica-
tions include, but are not limited to striking bars,
extensive steel and thread bit heads to shanks. When
striking bars are employed, the striking bar is impacted
on one end by a piston and energy is transmitted to a
drill steel through a coupling connected by a male thread
on the striki~g bar to a male thread Qn a drill steel.
The form and size o~ the thread is .he deptll upon the-
power of the drill, the diameter of the hole to be
drilled, and the steel system selected for a special
application. The male thread on the striking bar is
sub~ected to the most severe conditions, primary and
reflected stress pulses combined with torsion and bending
stress. The form of thread is a compromise between a
connection which can provlde for easy detachment of the
steel system and will remain sufficiently tight to pro-
vide for efficient energy transverence. Thread galling
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and the formation of pitting and stress risers
occur which result in premature fatigue type
transverence failure. It is desired to lessen thread
failure.
Summarv of the Invention
This invention pertains to a thread system
adaptable for transmitting rotary and percussive power
having a rodg a male thread on said rod wherein the
rod contains a plurality of slots and a means for
cooling the thread.
According to a further broad aspect of the
present invention there is provided a thread system
adaptable for transmitting rotary and percussive powerO
The system comprises a rod having a male thread thereon
wherein the rod contains at least six longitudinal slots
formed for the entire length of the male thread and
penetrating below the minor diameter thereof, thereby
forming thread segments wherein the thread segments
will deflect and deform plastically when subjected to
excessive localized for~es. A means is provided for
cooling the thread and comprising a passage through
the center of the rod, and an end surface having at
least one radial groove forming a channel between the
male thread and the passageO
Brief Description of the Drawinqs
Figure 1 is an illustration of a striking bar.
Figure 2 is a side illustration of the
striking bar as viewed along the lines 2-2 in Figure 1.
Description of the Preferred Embodiments
Thread systems adaptable for transmitting a
rotary and percussive power include, but are not
limited to applications such as striking bars, extensive
steel and thread bit heads to shanks. As shown in
Figure 1 a striking bar 10 is illustrated. Striking bar 10
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has a striking face 12 which is impacted by a piston
not shown. Shank 14 of striking bar 10 is supported
by a shank alignment bushing,also not shown~ Striking
bar 10 has a means for connecting to rotational drive~
the means includes spline 16~ Striking bar 10 is
rotated by means of spline 16 for an independent
rotational force. Striking bar 10 has a male thread
18 which is coupled to an unshown drill steel at contact
face 20 through an unshown coupling.
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Patent Application 9022-IR-RD
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According to the present inventi.on, male thread 18
contains a plurality of slots which include longitudinal
slots 22. Suitably, there are at least six (6) longitudi-
nal slots and preferably about twelve (12) longitudinal
slots. The longitudinal slots run from contact face 20
to a thread run-out undercut 24. A means for cooling
thread 18 is also provided. The cooling means includes
a means comprising an air passage 26 running through the
center of striking bar 10 and radial slots 28 as shown in
figure 1 and 2. Air passage 26 as a primary function may-
provide air to a bit for hole cleaning whereln a small
amount of air is divexted Eor cooling. There is at least
one radial slot and suitably about four radial slots.
Longitudinal slots 22 divide thr~ad 18 into segments
and have a rod diameter less than the rod diameter of thread
18 but greater than the rod diameter of thread run-out
undercut 24. Suitably longitudinal slots 22 and radial
slo~s 2~ are 1~8 inches (3.18 ri,mj wide with a ~a~ius Gf
1/16 inch (1.5~ mm) at the base. The general parametric
portion of the thread systems having a cordal segment less
than measured on the mean diameter of the thread of
approximately 2 1/2 times the thread depth. These
proportions result in twelve longitudinal slots.
During operation, striking bar 10 is impacted on
striking face 12 while being rotated by means of spline 16.
Striking bar 10 is retained in contact with the face of
a drill steel through contact face 20 and by a coupling
connecting the drill steel and striking bar 10. The
Patent Application 9022-IR-RD
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stress pulse resulting from the impact on striking face 12
is tramsmitted through s~riking bar 10 by means of contact
face 20 to a drill steel and then through a drill system
to a drill bit where it effects a fracture of a rock. The
combined reflected stress pulse, torque and bending stress
may result in a small relative motion between male
thread 18 and a female thread of the coupling. In a
conventional thread manufacturing, variations of a thread
can result in excessive locaiized forces which lnitiate
localized pitting resulting in galling and pitt~ng of male
thread 18. The pit areas serve as stress risers and can
result in transverence failure.
According to the present invention, the failure of
male thread 18 is minimized since the thread segments ~
formed by the plurality of slots 22 can deflect and deform
plastically. The localized force is thus relieved and
redistributed among all thread segments before catastrophic
galling and pitting can occur. Longitudinal slots 22
provide a design void to accept plastic transformation.
In addition, a small volume of air is blown through
passage 26, across contact face 20 through radial slots 28
and is exhausted through longitudinal slots 22 to atmos-
phere. The air flow through longitudinal slots 22
provides heat exchange with all thread segments and any
localized heating within a specific thread segment is
removed by the air. The flowing air also serves as
thermal barriers between adjacent thread segments. The
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Patent Application 9022-IR-RD
flowing air may also contain a lubricant, such as rock
drill oil. The flowing air through longitudinal slots 22
thus lubricates ~he thread segments with a random level of
oil.
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