Note: Descriptions are shown in the official language in which they were submitted.
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The present invention relates to improvements
in pipe connectors.
According to the present inventio~ there is
provided a pipe connector comprising a tubular pin
member having a frusto-conical outer peripheral surface,
a tubular box member for receiving and enga~eable with
the pin member and having a frusto-conical inner
peripheral surface corresponding to the frusto-conical
surface of the pin member and which overlies the frusto-
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conical surface of the pin member when the members areengaged, and annular projection and groove means provided
in the frusto-conical surfaces of the pin member and the
box member and inter-engageable to axially lock the pin
member and the box member together, the projection and
~ groove means comprising annular projections in one of the
~ frusto-conical surfaces and annular grooves in the other
of the frusto-conical surfaces the projections having
~. planar crest surfaces, and the projections and grooves
;: being axially spaced apart along the frusto-conical
surfaces, extendin~ in radial planes, and being arranged
so that, on assembly of the pin member and the box member,
initial metal-to-metal contact will be made between the
: crest surface of a respective one of the projections of
one of the frusto-conical surfaces and a part of the other
~; of the frusto-conical surfaces between adjacent grooves,
` wherein the radial dimens.ions of the projections and
grooves are such that the expansion of the box member
and/or contraction of the pin member resulting from
forcing the projections into the corresponding grooves
during engagement of the members does not exceed the
elastic limit of the material of the box member and/or the
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. pin membe~.
; The present invention will be more fully
understood from the following description of an embodiment
thereof, given by way of example only, with reference to
the accompanying drawings.
In the drawings:
Figure 1 is an axial section through an embodi-
ment of a pipe connector in accordance with the present
invention and showing the pin and box members assembled;
Figures 2 and 3 are enlarged sections of the
pin and box members of Figure 1 respectively;
Figures 4 and 5 are enlarged sections showing
the pin and box members of Figure 1 during assembly and
when assembled;
' Figure 6 is an axial section through the
.~ connector of Figure 1 showing means for applying an axial
: assembling force thereto; and
Figure 7 is a plan view of the force apply means
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of Figure 6.
As shown in the drawings, the pipe connector
comprises a tubular pin member 1 for connection, e.g. by
welding, to the end of a pipe 2, and a tubular box member 3
for connection, e.g~ by welding, to the end of a pipe 4
to be connected to pipe 2. The pin and box members are
telescopically engageable and have corresponding frusto-
conical outer and inner peripheral surfaces 5, 6 respectively
which overlie one another when the pin member 1 is fully
inserted into the box member 2.
To axially lock the pin member relative to the
box member when the members are engaged, the box member has
in its frusto-conical surface 6 a plurality of circumferentially
extending annular grooves 7a, 7b...7~, 7h, each groove
extending in a radial plane, having a planar root surface
8a parallel to surface 6, radially extending end surfaces
~; 8b, 8c and being spaced by a surface lGa, lOb
lOg, lOh from the adjacent groove. The root surfaces 8a
lie on a frusto-conical surface having the same conicity
a5 surface 6. The pin member has axially spaced circumfer-
entially extending annular projections or teeth lla, llb...
llg, llh corresponding to the grooves 7 and having planar
crest surfaces 9a parallel to surface 5, and radially extend-
ing end surfaces 9b, 9c. The grooves 7 and teeth 11 are
relatively dimensioned and shaped to facilitate assembly of
the pin and box members, to resist axial forces tending to
pull the members apart, and so that there is metal~to-metal
contact between the end face 8b of each groove and the corres- ¦
ponding end ~ace 9b of each tooth resisting axial forces tend-
~ 30 ing to pull the members apart when the members are fully
; engaged. The teeth and grooves ~ay, as shown extend over sub-
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stantially the entire extent of the surfaces 5, 6 but may
extend over a lesser extent of the surface.
~ The box member may, as shown be provided with a
; radial passage 12 communicating with an axially extending
groove or recess 13 intersecting some of the grooves 7
centrally of the groove region. The passage 12 is adapted for
i~ connection to a source of liquid, e.g. oil, under pressure,
- e.g. at about 5000 to 7000 p.s.i. for pin and box members
made of high tensile steel.
The joint is designed to be assembled as follows.
Initially the pin member is pushed into the box member until
metal-to-metal contact is obtained between parts of the frusto-
conical surfaces 5, 6. The conicity and the tooth and groove
lengths of the pin and box members are arranged so that initial
- metal-to-metal contact is obtained between the crest surface
of each tooth, e.g. sur~ace 9a of tooth llg, on the pin abutt-
ing that surface, e.g. surface 10g, immediately before the
respective groove, e.g. 7~, in which the tooth is to be
engaged~ Once metal-to-metal contact has been made, an
axial force is applied between the pin and box members to
; progressively bring the members together and engage the keeth
) in the respective grooves. On application of the axial force,
the box member expands and/or the pin member contracts a
su~ficient amount to allow each tooth e.g. tooth llg, to slide
over the surface, e.g. surface 10g, into the groove, e.g.
groove 7g. The tooth and groove depth is arranged so that in
so doing, the elastic limit of the material of the pin and
box members is not exceeded.
A caliper type jack 14 (Figure 6 and 7) may be
used to apply the axial force to the members. The caliper
jack consists of an upper plate 15 and a lower plate 16
each of which is split diametrically and hinged at 17 to
permit each plate to be engaged around a respective one of
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the melnbcrs. A p11lra:Lity of hydraulic jacks lo are
arran~ed to act bctween the platcs, the jacks,beins
angular]y spaced apart around the axis of thc caliper jack.
t'The platcs 15, 16 en~ase in srooves :L9, 20 provided in
the pin and box members respectively.
~,,Durins application of the axial force, it is
found advantageous to apply liquid under pressure to the
region of overlap between the pin and box members. It is
for this reason that the passage 12 and recess 13 are
providcd. The liquid flows from the passage lZ to the
recess 13 and then into those groovcs 7 with which the
recess comm~micates. ~lo~q beyond these grooves 7 is
initially prevented by the metal-to-metal contact between
the teeth ll and surfaces lO. The pressure of the liquid
is set at a level sufficient to aid expansion of the box
member and/or contraction of the pin member as the members
are brought together under the axial force. It is found
that in effect the liquid lubricates the contacting
,surfaces of the pin and box membor which then fcrm a
hydrostatic bearins so that metal-to~ ctal contact is
lost. While there is consequently leakage of the liquid,
the leakage is not sufficient to render the application
of the liquid ineffective. The lubrication of the contacting
surfaces of the pin and box member reduces the possibility
,~ 25 of damage to the toothed and grooved surfaces of the pin
;~ and box member as they are forced together.
ln -the I)referrccl embodimcnt of the connector,
1;he tolerarcos of thc surfaces 5, 6 of the pin and box
melllbeJ-s arc minin1ised and the box is dimcnsioncd so that thc
~in is a s1lrink fi,t in the box wil:h tl~e end faces ~ of t11c
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grooves 7 in metal-to-metal contact with the corresponding
end faces 9b of the teeth 11 and with radially extending
surfaces 24, 25 in abutment. With this arrangement, it is
found essential to ensure that no liquid is trapped in any
of the grooves 7 when the pin and box mernbers are fully
engaged. Should any liquid be trapped, the corresponding
tooth will be unable to engage fully in its groove and there
will then be a risk of the connector coming apart. To
avoid this possibility, the recess 13 is extended to and
is in cornmunication with the two grooves 7b and 7~ adjacent
each end groove 7a and 7h so that the liquid in the grooves
7b to 7g can be drained through the passage 12. Any
liquid remaining the end grooves 7a and 7h can escape
around the end of the pin member and box member respectively.
Where the pin member is not a shrink fit in the box member,
it is merely necessary to ensure that all fluid can be
drained from between the overlying surfaces of the pin and
box members and the precise extend of the recess is not so
critical but clearly it must be sufficient to aid in
expansion and/or contaction of the box member and pin
member espectively.
If it is required that the assembled connector
be able to be disassembled, the passage 12 and recess 13
can be provided and used for this purpose. Liquid under
pressure is then applied to the passage 12 and flows along
' the recess 13 and circumferentially in the clearances which
are left between the end face 9 of each recess and the
corresponding end face of each tooth for those grooves 7
which are in communication with the recess 13. The axial
extent of penetxation of the liquid is initially limited
by the metal-to-metal contact between the teeth and grooves
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at T,he CII~S o tlle recess 13. At the sallle time an axial
disen~a~in~ force is apl)]-ied to the pin and bo~ members,
e.g. usin~ 1he cal~per jack 1ll~so as to maintain metal-to-metal
contact between the end face 8~of each sroovc and the
corrcsponding end face~of the tooth. As in the case where
liquid under pressure is used in assembling the pin and
bo~ members, the liquid acts to expand the box member and/or
contract the pin melnber to free the teeth from the grooves.
~owever in disassembly, the applied axial force ~aintains
the end faces 8Aof the grooves in contact with the
corresponding end faces~of the teeth to prevent substantial
leakage of the liquid until the teeth llave been disen~aged
from the grooves and rest on the surfaces 10 between the
srooves. Further slight application of a~ial force will
;~ 15 bring the pin member back to a position relative to the
box member as shown in Figure 4 corresponding to initial
~- metal-to-metal contact during assembly~
Seals may be provided in one or both of the
surfaces 5, 6 of the p:in and box memb~ts at the ends of
these surfaces to assist prevention of leakage of liquid
froln between the members during assembly and disassembly
and in use. If such seals are provided, one ormore of
the teeth and grooves at the ends of the members may be
omitted. }lowever, ir the pin and box members are suitably
rclatively dimensioned, sealing by tne-tal-to-metal contact
between the p-in and box members may be soLely relied Oll
and no otller seals provided. As showll an 0 ring seal 21 is
proviclod in tllc surface Or thc pin ~ ad;jaccnt thc cnd
B tooth ]la to providc additional sealins whei~ the couplins is
i n use.
3 ~ ere tl~c boY n~em1er is dinlcllsioned rclativc to thc
pin melllber -to provide a Ch~ k f-t ~-ith tl-c pin ~ntmber, tllc
cx )~n f
comlector ~ill to all e~:tc~& translllit torque.
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Should scparate torque transm-ission means be required
an inwardly projcctinS pin may be provided at the inner
end c)f tho frusto conica]. surface of the box member for
engasement in a recess provided in the leadins edge of the
pin member, the end Sroove 7a and tOOt}l lla being omitted~
In a prefcrred embodiment, ~he pin and box members
are made of high tensile steel and have external and
in.ternal diameters of about 28". The conicity of the frusto-
conical surfaces is 2 , each tooth hu., a height of 0.0~o"
and a length at its base of 0.~". Each groove has a
depth of o.o4llll and a length at the surface of 0.o4~. l3ight
teeth and grooves are provided in each frusto-conical
surface and are spaced 1.5" apart in the axial direction.
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The end face 8~of each groove and the corres~onding face~of
~~5 each tooth has a taper of 12 to a plane perpendicular to
~ the axis of the pin and box members and the face~ of each
~ groove and the corresponding face~of each tooth has a taper
of 60 . The former taper is determined by the tolerances
of manuf~cture and is the ansle requ:ircd to ensure a ti.Sht
~hc O~D~OSl!c~ fi~r~qccs ~S~ i' !;
fit betweenloppoEod Eurfnocs, as showll,at the innor end
of the pin member and the free end of the box member, or
at the free end of the pin member and the inner end of the
box mcmber, for pile drivins.
It will be appreciated that by usinS a d:ifferent
ang].e for thc conici*y oi` the frusto-conical surfaces of
the pin and box members, and different materials for the
and numbers
pin and box n~embers, the fore~oing dilllensions/of 1;hc tceth
und grooves may be varicd.
It will bc furthcr apprcciated that w}lilo the
3~ above dc~cri.bed connector has boerl described i.n terms of
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: teeth provided on the pin member and grooves provided in
the box member, this is exactly equivalent to the provision
of grooves in the pin member and teeth in the box member.
There is thus provided a pipe connector which
has a simple construction, is easy to assemble and does not
rely on relatively movable parts to maintain interengagement
between the pin and box members.
The above described pipe connector is particularly
designed and adapted for use in connecting pipes and other
tubular structures for use in the drilling and/or completion
of all-shore ~il anl/or gas wells.
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