Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
211 6~ fiI
Tu~e Conduit Connection and Method of Producing
the Same from Polyolefins
The invention relates to a method of producing a tube con-
duit connection in which method a tube end of a tube made of
polyolefin, is expanded and placed onto a conneckor member, as
well as a tube conduit connection thus produced.
10
In a known method of this type as published in German Pub-
lished Patent Application No. P 38 17 442.1, there is described
such tube conduit connection by means of, for example, a
shrink-on sleeve which bridges the connector members of two
:15 tubes. The shrink-on sleeve may be made of, for example, a
thermo-elastic material like cross-linked polyolefin. The
shrink-on sleeve is connected to the connector members in that
the cross-linked polyolefin, after being heated above the
crystallite melting point, can be deformed in the heated con-
;20 dition and pushed with expansion onto the connector members inthe heated condition. In the same manner, the tube end of a
tube made of cross-linked polyolefin also can be pushed onto a
c~nnector member, for example, a T-piece.
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From European Published Patent Application No. 0 102 919
there is also known a tube conduit connection made of a
connector member, which also may be a tube end, and a tube
end. The tube end is firmly and sealingly connected to an end
portion of the connector member or the tube ~end by heating
above the crystallite melting point and self-reconversion. The
tube_e~d has~an internal diameter which is smaller than the
outer diameter of the connector member or the tube.
Carrying out this method and producing the aforementioned
tube conduit connection results in certain difficulties in
practicebecause the cross-linked polyolefin must be heated to
relatively high temperatures, for example, above 135C in the
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case of cross-linked poly ethylene, and has sufficiently ready
deformability only at this temperature. Therefore, it is
decisive that the concerned parts are connected to each other
within a brief time period such that there is no cooling below
the crystallite melting temperature.
It i8 the object of the invention to provide a method of
producing a tube conduit connection of the initially mentioned
type and which method permits producing a secure tube conduit
connection under normal, i.e. environmental temperatures. It
is also an object of the invention to provide a tube conduit
connection which can be produced under environmental
conditions and constitutes a secure sealing connection.
According to the invention and with regard to the method,
the object is achieved in that the end of the tube which has
an internal diameter smaller than the external diameter of the
connecting member, is reversibly expanded at environmental
temperature with the assistance of an expanding mandrel to an
internal diameter which~is greater than the external diameter
of the connecting member,~and, after removal of the expanding
mandrel, the still expanded end of the tube and the connecting
member~ aré telescoped onto~each other, whereby the connecting
member and the tube~end are firmly ~and sealingly inter-
aonnected~ due~ to the self-reconversion of the reversibly
expanded-~tube end.
-Regarding th2 tube~ conduit ~connection, this object is
ac~ieved in that the~-tube end, which has been mechanically
; 30 expanded at -environmental ~temperature and ~which is self-
; récon~ve~tib~at the ~environmental temperature! is firmly andséalingiy connected to the end portion of the connecting
member.~
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The invention is based on the surprising recognition that
: polynlefing, in particular medium density, high density or
cross-linked polyolef~ins, have sufficiently extensive,
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reversible deformability even in the cold and partially
crystalline condition, i.e. in a condition not heated above
the crystallite melting point. This means that the polyolefin
can be deformed or shaped under mechanical action, however, in
S its deformed condition, tends to reassume the original shape.
Upon application of sufficiently strong forces, for example,
by means of an expanding mandrel of conventional construction
for expanding tubes, it is, therefore, possible to reversibly
expand the tube ends of tubes made of polyolefins. Under the
conditions prevailing at environmental
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21~6~61
temperature, the self-reconversion to the original condition,
i.e. the original tube width, proceeds at relatively low speed
so that the expanding mandrel can be removed from the expanded
tube end and the still expanded tube end can be telescoped
onto the respectively desired connector member. On the other
hand, the speed of self-reconversion is sufficiently high so
that there do not arise any undue waiting periods.
When compared to other materials, polyolefins have the
advantage that the expansion as far as still existing after
connection to the connector member, does not result in stress
cracks.
The inventive method thus offers a particularly advan-
tageous possibility of connecting tubes which are made of
polyolefins, especially tubes made of medium density, high
density or cross-linked polyolefins, with a respectively
desired connector member~ without~the expense of heat energy.
When carryi~ng out this~method, there is obtained a particular-
ly f~irm and seal-ing,~specifically~gas-tight connection~due to
the~ self~-reconversi~on~of;~the ~expanded tube end~. During such
self-reconversion,; the~ polyolefin~adapts to surface struc-
i25~ tures which are~eventually~present at the connector member. As
'~ ~examples~for~;such~;~surface~structures which increase the bon-
ding 'gtrength,~'there- may~be~cons~idered beads,~lutes, grooves
or~Xnurlings~whiah~are~ ngaged~by~the 'reconverted polyolefin.
; In~connection~with the'precedingly~described method further
securiDg~of the-~produced tube~conduit connections is possible,
if required.~This~ purpose~is served~by tube clamps of conven-
tional'type~ However~ it~is~also possible to attach a tension
ring to~the-tube~end~of the~ tube~which is made of polyolefin.
In 'the~e~ent that such tension;ring~is~also made~of reversibly
deformable material,~ the~tension ring may be~ attached to the
tube end from the start. It is, however, also possible to push
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211~&1
a tension ring which is made of a material, for example, metal
which is not or only little deformable, onto the tube-sided
end of the tube conduit connection using known hydraulic
means, after the tube conduit connection has been produced.
Exemplary embodiments of tube conduit connections produced
in accordance with the inventive method are illustrated in the
drawings and will be explained and described hereinbelow in
detail with reference to the reference numerals. There are
shown in
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Figure 1 a sectional view of a tube conduit connection
produced from a connector member and a tube end
applied thereto according to the inventive method;
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Figure 2 a sectional view of a tube conduit connection as -
shown in Figure 1 and containing a tension ring;
Figure 3 a sectional view of the inventive tube conduit
connection formed between two tube ends.
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In the sectional view of Figure 1, there will be recognised
Z5 a connector member 1 which~ may constitute, for example, a
-s~raight tube~piece, an angle tube or any other connector for
connecting two tubes~,~ however, also a triple connector piece
~like a~T-piece. This~connector member~1 is made of a material
like~metal, glass, ceramic, plastic or any other material
selected with~the~view of the intended purpose of use. At each
- ~ ~ j;UnCt-10~ ~place ;the~connector member l is provided with a sur-
-face structure~for~ incréasing~the~ bonding strength. In the
illustrated exemplary embodiment, this surface structure is
formed by a thickened end ;portion 2 which tapers towards the
end. Instead, there may be provided;one or more beads, flutes
or grooves or also knurlings or the like.
2li6~6l .
The illustration of Figure 1 shows a tube 3 made of poly-
olefin, preferably medium density or high density, particu-
larly cross-linked polyolefin. The internal diameter of the
tube 3 is smaller than the external diameter of the connector
member 1; as illustrated, the internal diameter may be sub-
stantially equal to the internal diameter of the connector
member 1 whereby there can be prevented the formation of flow
resistance due to constrictions or deposits formed at the con-
strictions from the medium flowing through the connector mem-
ber 1 and the tube 3. For producing the tube connection, the
tube end 4 i5 expanded at environmental temperature, using,
for example~ a conventional expanding mandrel, to an extent
such that the internal diameter of the tube end 4 is at least
as wide as the external diameter of the connector member 1 in
the area of the thickened end portion 2. After being pushed
beyond the thickened end portion 2, the tube end 4 is subject
to self-reconversion to the original dimensions. As a conse-
quence, the tube~end 4, as illustrated, adapts to the external
profile of the connector member 1. Since the tube end 4 origi-
nally~had an internal ~diameter which is smaller than the ex-
~ternal diameter~of the connector momber 1, the tube end 4tightly engage8~along;its~1ength the~end~portion 2 of the con-
nector member 1.~ There is thus formod in~ the ond a relatively
large-area, very~tight connèction between the tube end 4 and
the eonn-ctor;mombor~
Piguré ~2 ~shows a ~furthor- ombodiment of tho aforedescribed
tube conduit,connection and correponding members therein are
~3~ pro~ided with-~the~same~reférenco~numorals~. In this embodiment,
a~tengion ring~S~is provided~as ~additional socuring means for
producing~-a sealing;~connoction-~between~the tube end 4 and the
connector~mémber~ This~ tension~ring 5~preferably is made of
~: the 8amæ material as~ tho~tubo 3.~I~n~the~ilIustrated exemplary
embodiment, the tube~3; as wé11 as ;the tension ring 5 are made
of cross-linked poly~ethylone.~ Tho intornal diameter of the
tension r~ing 5 is c losely adapted to ~tho~external diameter of
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211~.~1 " '''
the tube 3 and is pushed onto the tube end 4 prior to making
the tube conduit connection. During the subsequent expanding
operation, the tension ring 5 is temporarily expanded con-
jointly with the tube end 4 such that the expanded tube end ~
is placed onto the end portion 2 of the connector member 1 to-
gether with the applied tension ring 5. Subsequent self-recon-
version, then, results in the sealing connection between the
tube end 4 and the end portion 2 of the connector member 1 in
the aforedescribed manner, whereby also the tension ring 5
contracts and thus additionally presses the tube end 4 against
the end portion 2 in the area of the tension ring 5.
Figure 3 shows a tube conduit connection formed between two
tube ends. Both the tubes may consist of the same or different
materials; preferably, the tubes are made of cross-linked
polyolefin and serve as conducting tubes for corrosive media.
As an example there are mentioned industrial, however, par-
ticularly domestic waste waters which require especially cor-
rosion resistant tube materials and with respect to which
tubes made of cross-linked polyolefin have proven useful in
practice.
In the illustrated exemplary embodiment, the two tubes have
the same internal and external diameters. This, however, is
not significant since the same tube conduit connection can
also be produced between tubes of different diameters, if de-
sired, provided that the differences in the internal diameters
do not result in undue flow resistance and deposits. A first
tube 10 has a first tube end 11; a second tube 12 has a second
tube end 13. I~t will be seen that the internal diameter of the
secon-d ~tube end 13 is expanded and this expanded second tube
end 13 is pushed onto the first tube end 11 of the first tube
10. This expansion is carried out using, for example, a con-
ventional expanding mandrel at environmental temperature, as
in the previous exemplary embodiments, and is subject to the
described self-reconversion due to which the expanded tube end
- 13 tends to reassume its original shape. The large-area tight
2116~1
engagement between the two tube ends 11 and 13 produces, also
in this case, a sealed tube conduit connection which, due to
the corrosion resistance of the material against the aforemen-
tioned waste water, will not leak even after long-time use.
Also in this case, as in the exemplary embodiment illu-
strated in Figure 2, the connection can be additionally
secured by means of a tension ring; however, it must be ob-
served in such case that no undue deformation of the first
tube end 11 i8 produced under the compressive pressure exerted
by such tension ring. Such deformation may present a flow
resistance to the throughflowing waste water or may give rise
to deposits formed from the waste water in the region of the
connection area. Instead of the tension ring, a bonding agent
may be employed, if desired, for additionaIly securing the
connection area.
Tubes which are made of cross-linked polyolefin, therefore,
are used in waste water technology also for this reason,
because in this~manner~secure, self-seal~ing connections can be
readily made~between~tw~o ~smooth tubes~. Additionally, there is
obtained~the~;further~advantage~that the tubes 10 and~13, which
~are ~prodùced~;in~a;continuous~process,~ can also be placed or
laid~a~ continuous~tubes~without there~being required specific
~ 25 angle tubes or'other'~-connécting ~mémbers in order to place or
^~ lay~the~-'tubes -in~accordance~with a predetermined pattern or
course~.'Th~èréfore,~connections~between *ubes must only be made
;at''the'-i'n ~ '-''and'ou'tl'et'~'locations.~
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