CA2116561A1

CA2116561A1 - Pipe joint and process for producing pipe joints made of polyolefin

Info

Publication number: CA2116561A1
Application number: CA002116561A
Authority: CA
Inventors: Friedrich Imgram
Original assignee: Individual
Current assignee: WIRSBO PEX GmbH
Priority date: 1991-08-31
Filing date: 1992-08-21
Publication date: 1993-03-18
Also published as: CZ32294A3; NZ244134A; ES2081406T3; SK21594A3; JPH06509994A; KR940702257A; ZA926585B; PT100823B; FI940864A0; HU215296B; SK282175B6; FI940864A; DK0530387T4; IL102958A; IL102958A0; NO940672D0; EP0530387A1; HK100096A; AU669665B2; HUT69886A

Abstract

An end (13) of a pipe (12) made of polyolefin is cold-deformed, i.e. at the ambient temperature, by means of a spreading mandrel.
After the spreading mandrel is removed, the enlarged pipe end (13) and a desired connecting piece or the end (11) of another pipe (10) are plugged onto each other. The polyolefin pipe end (13) is then deformed back to the original shape and forms by self-redeformation a solid and gas-tight connection with the connecting piece or the end (11) of the other pipe (10).

Description

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.

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 2~ fi ~

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.~
" --The invention is based on the surprising recognition that : polynlefing, in particular medium density, high density or cross-linked polyolef~ins, have sufficiently extensive, ~: , 2I16;&1 - 2~

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 , , : , 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 : .
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 :

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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Claims

1. Method of producing a tube conduit connection in which method a tube end (4) of a tube (3) made of polyolefin, is expanded and placed onto a connector member (1), characterised in that the end (4) of the tube (3) which has an internal diameter smaller than the external diame-ter of the connector member (1), is reversibly expanded at environmental temperature with the assistance of an expan-ding mandrel to an internal diameter which is greater than the external diameter of the connector member (1), and that, after removal of the expanding mandrel, the still expanded end (4) of the tube (3) and the connector member (1) are telescoped onto each other, whereby the connector member (1) is firmly and sealingly connected to the tube end (4) due; to the self-reconversion of the reversibly expanded tube end (4).

2. Method according to claim 1, characterised in that an end portion (2) of the connector member (1) is provided with a surface structure for increasing the engagement surface at the tube end (4).

3. Method according to claim 1 or 2, characterised in that the connection is additionally secured by means of a tube clamp.

4. Method according to claim 1 or 2, characterised in that the connection is secured by means of a tension ring (5).

5. Method according to claim 4, characterised in that the tension ring (5) is made of a material which is expandable at environmental temperature and self-reconvertible and which is reversibly expanded conjointly with the tube end (4).

6. Method according to claim 4, characterised in that the tension ring is made of a material which is not or only little deformable, and hydraulically pushed onto the tube end surrounding the connector member after making the connection.

7. Tube conduit connection made of a connector member (1) and a tube end (4) which is mechanically expanded and firmly and sealingly connected to an end portion (2) of the connector member (1) by self-reconversion, the tube (3) having an internal diameter which is smaller than the external diameter of the connector member (1), characterised in that the tube end (4) which is mechanically expanded at environmental temperature and self-reconverted at environmental temperature, is firmly and sealingly connected to the end portion (2) of the connector member (1).

8. Tube conduit connection according to claim 7, characterised in that the end portion (2) of the connector member (1) is provided with a surface structure for increasing the engagement surface with the tube end (4).

9. Tube conduit connection according to claim 7 or 8, characterised by a tension ring (5) which is applied to the tube end (4) and which is made of a material which is expandable and self-reconvertible at environmental temperature.

10. Tube conduit connection according to any one of claims 7 to 9, characterised in that the tube (3) is selected from a medium density, high density or cross-linked polyolefin.

11. Tube conduit connection made of a first tube end (11) of a first tube (10) and a mechanically expanded, self-reconvertible second tube end (13) of a self-reconvertible tube (12), said second tube end being firmly and sealingly connected with the first tube end (11), characterised in that the second tube end (13) which is mechanically expanded at environmental temperature and self-reconvertible at environmental temperature, is firmly and sealingly connected with the first tube end (11).

12. Tube conduit connection according to claim 11, characterised in that the first tube end (11) of the first tube (10) is provided with a surface structure for increasing the engagement surface with the second tube end (13).

13. Tube conduit connection according to claim 11 or 12, characterised in that the connection is secured by means of a tension ring.

14. Tube conduit connection according to claim 13, characterised in that the tension ring is made of a material which is expandable and self-reconvertible at environmental temperature.

15. Tube conduit connection according to any one of claims 11 to 14, characterised in that the first and second tube (10,12) are made of medium density, high density or cross-linked polyolefin.