Note: Descriptions are shown in the official language in which they were submitted.
W0 96/02729 2 1 9 2 2 0 4 ~ r ' ~
Thread cou~linq
The present invention relates to a thread coupling for
percussive drilling including at least one male thread
5 and one female thread, said male thread being arranged
upon a spigot and said female thread being arranged
within a sleeve, said male and female threads being
cylindrical, an ~t~rn;~l shoulder stop at a free end of
the sleeve, said shoulder stop including contact
10 surfaces being perpendicular to a longitudinal centre
axis of the thread coupling, the spigot at a free end
having an end surface that iæ perpendicular to said
longitudinal centre axis, the sleeve being provided
with an internal stop surface that is perpendicular to
1~ said longitudinal centre axis, i~ an unused thread
coupling there is an initial play between the end
surface of the spigot and the lntf~rn;ll stop surface,
said initial play being eliminated after wearing-in o~
the thread coupling.
A thread coupling of the type defined above is
previously known from SE-B-469 603 (US-A-4,968,068),
said document being incorporatea by reference into the
present application. A problem with such a thread
25 coupling, especially when trape~20idal threads are used,
is that the coupling during use becomes 80 tightened
that it is difficult to unscrew the coupling when one
member of the coupling needs to be exchanged.
3 0 The present invention has the aim to present a thread
coupling of the type mentioned above, said thread
coupling being less tightened than prior art thread
couplings of the type def ined above .
35 The aim of the present invention is realized by a
thread coupling that has been given the characteristics
W096/02729 ~ l 9~2 ~ 4 r~l~h~r~ ~
of the appending claims . Below ~embodiments of the
invention: will be described with reference~to the
enclosed drawings, where Fig. l ~shows a schematic,
partly sectioned view of a thread coupling according to
5 the invention; Fig . 2 shows a view similar to Fig .1 of
an alternative embodiment of the invention; and Fig. 3
shows a view similar to Fig. l of a further alternative
f~mho~; t of the invention.
10 The thread coupling of Fig. l i~cludes a male thread 10
that i8 provided on a spigot 11 which constitutes an
integral part of a male extension member 12 for
percussive drilli~g. At the imler end of the spigot l
the male extension member 12 is provided with a
15 shoulder 13 that has a first plane contact surface 14
directed towards the free end of the spigot 11.: The
first contact surface 14 has an extension perpendicular
to a longitudinal centre axis 15 o~ the male extension
memher 12.
The free end of the spigot 11 has the shape of a plane
end surf ace 16 that has an extension perperidicular to
the ce~tre axis 15.
25 The thread coupli~g also includes a female thread 17
that is provided in a sleeYe 18 which constitutes an
integral part of a female extension member 19. ~t the
f ree end oi- the sleeve 18 a second plane contact
surface 20 is provided, said second contact surface 20
30 having an extension perpepdicular to the longitudinal
centre axis 15 of the f emale extension member 19, said
longitudinal centre axis co1 nf~ n~ with the centre
axis of the male extension member 12. I~side the sleeve
18 the female extensio~ member l9 has a plane bottom
35 surface 21 that has an extension perpendicular to the
longitudinal centre axis 15.
WO 96l02729 2 1 ~ 2 2 0 4
From Fig. 1 it is evident that in the thread coupling
according to the present invention the f irst contact
surface 14 of the male extension member 12 always
contacts the second contact surface 20 of the sleeve
5 18, i.e. so called shoulder stop is es~hli~Pd.
It is also evident from Fig. 1 that between the end
surface 16 of the spigot 11 and the bottom surface 21
inside the sleeve 18 there is an initial play ~ that
10 ~ minirlly iS chogen to be zero (0) but with a positive
manuf acturing tolerance in the magnitude of one ( 1 ) mm .
After a certain time of use, at the most within 20% of
the length of life for the thread coupling, this play
15 will be eliminated due to wearing-in of the thread
coupling and consequently the thread coupli~g according
to the invention will have both shoulder and bottom
stop .
20 From Fig. 1 it is also evident that at the right end of
the thread coupling a thread clearance 22 of the male
extension member 12 and a thread clearance 23 of the
female extension member 19 are arranged, said
clearances 22, 23 having the aim of evening out bending
25 stresses from manufacturing inaccuracies of the contact
surfaces 14, 20 or the threads. In addition the
clearances 22, 23 even out torsion stresses and
stresses f rom shock or tension waves that pass through
the thread coupling.
In the event that the thread coupling according to the
present invention is between a drill rod and a drill
bit it is favourable that the drill bit constitutes the
male extension member 12 while the drill rod
35 constitutes the female extension member 19. The reason
theref ore is that the region o~ the clearance 22 of the
WO96/02729 21922~4 r~l .
male thread lO is the weake6t portion of the thread
coupling according to the present invention, i.e. if
the coupling collapses it is likely that the ~racture
will occur in the region of the clearance 22. Since a
drill bit i6 worn out up to ten time6 fa6ter than a
drill rod it is favourable that the fracture is located
in the drill bit. _ _
A6 i6 indicated in ~ig.1 the male thread 11 has a pitch
angle (Y. Of cour6e the female thread 17 ha6 the same
pitch angle ~. In accordance with the pre6ent invention
the pitch angle ~ i6 greater that 8.5 and le66 than
15 (8.5~ ~l . Preferably the pitch angle~
6hould be greater than 9.5 and less than 11.5
(9.5< ~ c 11.5~. For thread coupling6 without
6houlder-bottom 6top 6uch pitch angle6 are too great
and the thread-coupling would be un6~ ;r;~nt
tigthened, the con6equence being that pitting6 occur
and the length of life of the threads i6 unacceptable
2 0 6hort .
Due to the 6houlder-bottom 6top in the thread coupling
according to the pre6ent inve~tion the 6hock wave i6
tran6mitted 6imultaneou61y through both the 6pigot 11
and the 61eeve 1~. Thi6 means that there i6 very 6mall
relative motions in the axial r~lrPrt;rn between the
male thread 10 of the 6pigot 11 and the female thread
17 of the 61eeve 18. Thus, the thread coupling
acr--r-1;nrj to the present invention will operate
properly at a lower tirjht.~n~n~ level than thread
coupling6 without shoulder-bottom stop . Said lower
tightening level i6 achieved by an increa6e of the
pitch angle ~.
In the ~mho~;m~nt according to Fig.2 two drill rod6 12
and 12" having two 6pigot6 11' and ll", re~pectively,
_ _ . . _ _ _ ,, ... .. .. _ .
~ WO 96/02729 2 1 9 2 2 0 4 P~
are coupled together by a separate coupling sleeve 18'.
In case the spigot 11 ' i9 considered to belong to the
male extension member then the sleeve 18 ' together with
the drill rod 12 " is considered to constitute the
5 f emale extension member . Since there i8 a play
between the end surfaces il6', 16" of the spiyots 11'
and 11" respectively the end surface 16" is considered
to be the bottom surface of the female extension
member. If on the other hand the spigot 11" is
10 considered to belong to the male extension member then
of course a reversed approach must be used. However, in
the appending claims the spigot 11~ is considered to
belong to the male extension member 12 ~ . As in Fig .1
the end surfaces/bottom surfaces 16', 16' ' have an
15 ~t~nqi~n perpendicular to the longitudinal centre axis
15 .
Also in the embodiment according to Fig. 2 both the male
threads 10', 10" and the female threads 17', 17" have
2 o the same pitch angle ~ .
The r~mhor1;r-nt according to Fig.3 ;noll~r1r~ a male
thread 10' ~ ~that is provided on a separate spigot
. In Fig.3 the male thread 10' ' ' is interrupted in
25 the intermediate region of the longitudinal direction
of the spigot 11' ' ' . However, within the scope of the
present invention it is also possible that the male
thread has a continous extension along the entire
length of the spigot 11' ' ' . Since the spigot 11' ' ' is a
30 separate element there are two end surfaces 16' ' ' and
16 ' ~ ~ ~ respectively .
The spigot 11' ' ' is received in two sleeves 18 ' ~ ' and
18 ~ respectively, said sleeves 18 ' ' ', 18 ' ' ' ' being
35 i~tegral with drill tubes 19' ' ' and 19' ' ' '
respectively. The female threads 17' ' ' and 17' ~ ~ ~ are
~?'
WO 96/027Z9 2 i 9 2 2~ 4 r~
located inside the sleeves 18' ' ' and 18' ' ' '
respectively. Both the male thread lQ' ' ' and the female : ~
threads 17' ~ ~ and 17' ~ ~ ~ have a pitch angle ~. '
5 At the free ~ns~ o~ the ~leeves 18' ~ ~ a~d 18' ~ ~ ~ contact
surfaces 20' ' ' and 20' ' ' ' respectively are arranged. ~:
Inside the sleeves 18' ~ ~ and l=a' ~ ~ ~ planar bottom
surfaces 21' ~ ~ and 21' ~ ~ ~ resFectively are arranged.
The end surfaces 16 ' ' ', 16' ' ' ', the contact surfaces ~
2n' ~ ~, 20' ' ~ ~ and the bottom surfaces 21' ' ~, 21' ~ ~ ~ all
have an extension per,oendicular to the=longitudinal
centre axis 15.
The embodiment of Fig.3 fllnct;t~nq according to the
15 principles of the present invention. First there is
shoulder stop est~hl; ~h~d between the contact surfaces
20 ' ' ' and 20' ' ' ' . Then there are two bottom stops
eatablished when after wearing in of the thread
coupling the plays ~ at both ends of the spigot 11'
2 0 are eliminated .
The invention is in no way restricted to the
embodiments described above. Thus the principles of the
invention can be used both for drill rods and drill
25 tubes for percussive drilling and also in a thread
coupling between a shank adapter and the f irst drill
rod. The threads of a thread coupling according to the
present invention preferably have one ent~y but it is
also possible with two entries. The embodiments and
3 0 examples should not be considered given in a
restricting manner but only for examplifying purposes.
Although the present invention primarily relates to
trapezoidal threads, the present invention is not
35 limited to such type of threa~ds. ~ ~
W0 96/027~9 ~ 1 9 2 2 g 4' r~
Also in other respects the invention can be varied
f reely within the scope of the appending claims .
