Note: Descriptions are shown in the official language in which they were submitted.
~l~v~
~_
The invention relates to a plastic connecting
piece (such as a sleeve or a T-coneection saddl~) inten-
ded for joining axially or transversely, and by heat-
welding, twa pipes, in particular in the gas industry,
the invention relating more particularly to the.improve-
ment of the connection terminals of the electrically
conducting resistance element with which said connecting
device is equipped.
Such a device, which includes, for the heat-welded
ZO joining of two polyethylene ~ipes, an electrical heating
resistance element consisting of a coiled electrically
conducting wire embedded in the thickness of the piece in
the vicinity of its internal welding surface, is already
known from publications EP-A-0,149,410 or LTS-A-4,684,417.
The welding operation is then carried out by
placing opposite each other the pieces to be welded and
by connecting the coiled electrical wire to an electrical
source (such as a rectified source of alternating cur-
rent) which. by the Joule effect, will heat up the
resistance element and cause the softening until melting
of the plastic surrounding the pieces. ensuring welding
under pressure.
Fox the electrical connection of the resistance
element, its two wire ends are usually each welded to a
connection terminal each often emerging into a well or a
cavity, so ~s to be able to constitute two pins which
will be able to be plugged in, inside the said w~lls, t~
remavable complementary sockets.
Still within the same field, other types elf
resistance element can b~ used.
Thus, publication FR-A-2,654,978 provides the use
of a single-wise net or of a grid which can be produced
from a stretched metal plate.
However. the e~eternal electrical conaxaction of
this net or of this grid rennaix~a the same as the solution
mentioned hegeinabove. In, the first case (single-wire
net). the two ends of the wine era drawn out in order to
ba welded to the aforementioned pins. In the second case
(stretched grid). it is advised to use two conducting
2~C3j:~2
_ 2
plates fixed at two opposite ends of the grid, and two
conducting joint cables welded on one aide to the said
plates and on the other side to the two aforementioned
pine.
However, problems of reliability of the welded
joints may then occur. There i~ also the r3sk~that the
fusion zone of the plastic body can end up damaging these
joints. at the moment of the welding.
Furthermore, especially in the case of the use of
a monofilar net. all this implies lengthy and tricky
implementation operations.
Anather solution is provided in ,A.pplication
EP-A-0,2°78,553. In this application, the connection
terminals are applied to a connection piece in which a
resistance element in the form of. a coiled wire is
embedded. These terminals each consist of two complement-
ary pieces which are fitted into each other after having
been inserted into the cavities provided for this purpose
in the connecting piece. The two parts of the one same
terminal, which are subjected to two opposed direction
forces, are thus suitable for gripping a thin thickness
of plastic where the resistance element passes and. once
°'clipped together", then establish an electrical contact
with this resistance element. However, the use of such
terminals necessitates producing tapped holes in the
piece in ordsr to ins~rt therein the two complementary
components of the terminals. ~n the other hand the
fitting of these components one into the other could lead
(if the fitting forces are..not very precisely applied).
to a detrimental deformation of the connecting piece.
Taking this into account, the object of the
invention is especially to provide a connecting piece
whose connection terminals ensure a connection which is
reliable and is carried out very rapidly by a simple
operation, the electrical joint obtained with the resis-
tance element being particularly firm mechanically,
without appreciable risk of this resistance element '
tearing or of the puce becoming damaged.
Thus it has been imagined to have recourse to a
CA 02105122 2004-03-26
3
riveted joint.
of course, the use of rivets is known :Ln mechanical
engineering. It is also known, from EP-A-0,010,055, to use
a rivet as an electric socket. In this application, a blind
rivet is fixed to an electrically conducting solid metal. sheet
in order to establish an electrical contact r~rith this metal
sheet. This rivet is installed in a known manner by virtue
of a pair of tongs exerting on a single side a traction force
on the male component of the r~.vet, the female component being
14 held pressed ags.inst the metal sheet.
However, EP-A-0,010,055 does not relate to the field of
electro-welding.
This document therefore does not take into account the
problems specific to electro-weldable thermoplastic pieces and
especially the questions:
a)-of mechanical and thermal. stresses which the
resistance element and its joint have to withstand during the
welding;
b) -of installation of the said terminals within the piece
itself.
With regard to point a), nothing indicates that the
riveted joint of EP-A-0,010,055 could be suitable for an
electro-weldable device, the more So as document
EP-A-0,278,553 invites the use of two-piece electrical
terminals, therefore certainly being able, at least slightly,
to act one with respect to the other and with respect to the
resistance element, if the mechanical stresses due to heating
during the welding are too great. It will also be noted that
the rivet of EP-A-0, 07.0, OS5 is fixed to a solid plate, and is
therefore relatively rigid, whereas the terminals of
EPA-0,278,553 are fixed to a coiJ.ed wire.
E~.~rthermore, as regards point b) , if, based on
EP-A-0,2?8,553, it is sought to install. instead of terminals
hav~.ng fittable components, the rivet described in
EP-A~o,010,055, by conventional application, from one side,
of a force an its male component (the female component being
CA 02105122 2004-03-26
4
pressed against the thin layer of plastic enclosing 'the
resistance element), this would certainly run the risk of a
disastrous deformation of this layer, or indeed of the wire
resistance element.
Now, going precisely counter to the teaching that the
person skilled in the art would be able to draw from
EP-A-0,278,553 and EP-A--0,010,OSS, the invention precisely
provides the use of a rivet (and more precisely of its female
Component) as an electrical connector for supplying the
resistance element of a joint piece for the heat-welded
joining especially of polyethylene pipes_
According to vne aspect of the present invention, there
is provided a connecting device for connecting two pipes
therebetween, said pipes being at least partly made of a heat-
weldable thermoplastic material, said device comprising a body
made of a heat-weldable thermoplastic material including.
-a resistance element fox heating said thermoplastic
material of the body, and welding it with the thermoplastic
material of the pipes; and
-connection terminals electrically connected to said
resistance element and extending through said device body so
a~s to emerge outwardly on an outer surface thereof, each
terminal comprising a tubular rivet body made of an
electrically conductive material, so as to be an electrical
connector, said tubular rivet body comprising first and second
tubular parts and an integral collar ther2between, the second
part extending through an opening zn the resistance element
and having its distal portion compacted to corm a flange, the
resistance element being held between the flange and the
3Q collar,
In practice, the female body of the rivet will ensure its
connection function by means of its shaft which will be able
to act as a pin. In addition, the connecting device, which
is the subject of the present invention, will be able to
constitute an electro-weldable sleeve for the substantially
coaxial joining of two pipes by heat-welding. This piece will
CA 02105122 2004-03-26
also be able to constitute an electro-weldable branch
connector far the transverse joining of the pipes.
Advantageously, and as indicated above, the invention is
most particularly applicable if the resistance i5 in the form
5 of a monofilar meshed net, which is particularly sensitive to
the stresses which can be induced during the welding.
Another problem which arises is therefore that of the
electrical contact to be established with this particular type
of resistance element under optimum conditions of
effectiveness and in conjunction with the' problems of
mechanical stresses mentioned previously.
Hence, a preferred embodiment involves assoc~.ating with
each.rivet component engaged through a mesh of the resistance
element, means far tearing the covering layer of the said wire
at the location of the riveting of the terminal, thus ensuring
the electr~.cal contact, the said terminals furthermore being,
with the resistance element, partly embedded, by moulding, in
the body of the piece. In practice, and preferably, the
adopted tearing means will extend around this mesh facing the
flange of the terminal. For this purpose, and depending on the
size ag the meshes of the net, it will be possible in
particular tv use two washers for each rivet, gripping the net
tightly between them, one of these washers (which can most
particularly be of the "toothed" type).
Finally, taking into account the above, according to a
second aspect of the invention there is provided a method of
manufacturing a connecting device for Connecting two pipes
therebetween, said pipes being at least partly made of a
heat-weldable thermoplastic material, said device comprising
a body made of a heat-weldable thermoplastic material having
a resistance element for heating said thermoplastic material
of the body, to weld the thermoplastic material of the pipes
and connection terminals, each connection terminal having a
tubular rivet body comprising first and second tubular parts
and an integral collar therebetween, said method comprising
the steps of:
CA 02105122 2004-03-26
~~1
- riveting each of the connection terminals to the
resistance element so that the second tubular part of each
connection terminal extends through an opening in the
resistance element and has its distal portion compacted to
form a flange, the resistance element being held between the
flange and the collar; and
-over-molding the body of the connecting device onto said
connection terminals so that the first tubular part of each
connection terminal emerges into an opened cavity of said
device body, said cavity opening on an external surface of the
device body.
It will be noted that such a manufacturing method has the
advantage of being simple to implement, the reliability of the
terminals/resistance-element electrical connection virtually
preventing any risk of rupture of this connection, during the
overmoulding especially. Furthermore, the fixing of the
terminals to the resistance element before overmoulding the
assembly makes it possible to avoid the possible risks of
deformation of the piece which are connected, on installing
the terminals on the already-formed body, with its resistance
element.
Other characteristics and advantages of the invention
will again appear from the more detailed description which
follows, given with reference to the_.
210'3 ~~
- 6 -
attached drawings which show, in a non-limiting fashion,
embodiment and utilization examples of the invention.
Thus, in these figures:
- Figure 1 shows, in exploded view, the two
pieces which can form the basis of the ~1~ctrical connec
tion rivet of the inventions
- Figure 2 shows the installation of the rivet of
Figur~ 1 for the electrical connection of a conducting
piece;
- Figure 3 shows the entire Figure 2 once the
rivet has been riveted;
~ Figur~ 4 shows the rivet of Figure l, to which
has been added two washers, the rivet being in this ease
arranged in the position ready to grip a net portion
tightly;
- Figure 5 shows a possible embodiment detail of
the wire constituting the n8t illustrated in Figure
according to the detail V of this same figure;
- Figure 6 shows the entire Figure 4 once the
connection piece has been riveted;
- Figure 7 shows a possible conformation of
monofilar n~t which can be used in particular on a heat-
weldable connecting sleeve;
- Figure 8 is a view of the .net of Figure 7 in
th~ direction of the arrow VIII of this same Figure 7t
- Figure 9 shows an embodimerat detail of the net,
at the location of the r~ference IX of Figure 70
- Figure 7.0 repres~nts. in central longitudinal
section, an ~lectro-weldabl~ connecting sleeve equipp~d
with the rivetslnet assembly;
- Figure 11 represents another possible embodi-
ment of such a net having the appearance of a ring or a
crown:
- and Figure 12 is a central longitudinal s~c-
tional view of a T-connection saddle ec;uipped with the
net in the form of a. rosett~ of Figure 11, h~r~ reprs-
sented in a cut-away view.
First of all, Figure 1 shows an ass~mbly piece of
the "blind" rivet type~which will therefor~ bs used as an
CA 02105122 2004-03-26
7
electrical connection terminal.
The device, identified in its entirety by 1, comprises
an "ejectable" male rivet stud 2 and an elongate female body
5. It will be noticed that this stud 2 has a shank 3 and a
~ridex~ed part forming the head at one end. R frangible neck
portion ~, near the head 9, divided the shank 3 into a
proximal portion and a distal portion.
The stud 2 is said to be "ejectable" in that its shank
3 breaks off at the location of the preformed rupture neck 7
and is separated from the head 9 and the body 5, once the
latter has been riveted, the stud then being ejected from the
riveting apparatus.
Regarding the body 5, this is penetrated by an axial
passage 11 of intermediate cross--section ~i between the
cross-section ~ of the shank and that d of the head 9 so
that only the said shank can be inserted therein.
In addition to this, the body 5 has, at an intermediate
location along its axial length, an external. normal collar 13
delimiting a lower tubular section 5a (the longer section) and
an upper tubular section Sb (the shorter section) , coaxial one
with respect to the other.
Preferably, (and in fact conventionally), the two parts
of the piece 1, stud and body, will be produced from metal,
such as alum~.niurn typically, being thus electrically
conducting and relatively malleable under a force without
rupturing.
By Way of embodiment example, the stud 2 will be able to
have a length of approximately 40 millimeters with a shank 3
cross-section of the order of 1 millimeter and a head
cross-section (_d~) of the order of 2 millimeters. As regards
the tubular body 5, this will be able to have a length of
approximately 25 millimeters with a cross-section of the lower
section Sa of the order of 35 to 40 millimeters and a
cross-section of the upp~r section 5b of the order of 25 to
30 millimeters, each section being able to have a length of
approximately 15 and 8 millimeters, respectively,
CA 02105122 2004-03-26
Figure 2 shows the piece 1 engaged in an orif~.ce 15 made
through an electrically conducting piece 17, such as a metal
plate which is to be supplied with electric power via a
connection terminal, a role which the piece 1 will play once
the ls.tter has been riveted to this plate.
In order to fix the piece 1. the diameter of the orifice
will be less than the diameter d, (see Figure 1) of the
collar 13 which has been placed just beneath the plate 17, the
orifice 15 of which is only penetrated by the upper tubular
10 section 5b.
The shank 3 of stud 2 has been installed through the body
5 in such a way that its head 9 emerges on the side of the
upper section 5b.
Once the piece 1 has been thus arranged, it will suffice,
15 in order to fix it, to use a conventional pair of riveting
tongs available commercially, such as a pair of tongs of the
"FACOM" trade mark (registered trade rnark), model "GESIPR NT
X".
Undex the action of the jaws of this pair of tongs which
will exert an axial traction force on the shank 3 in the
direction of the arrow 19 of Figure 2, the head 9 will exert
a, compressive force on the section 5b which, made from a
plastically deformable material, will be squashed from its
free upper end in order to form a flange identified by 5'b in
Figure 3, the cross-section of this flange then being greater
than the cross-section of the orifice 15, thus keepir~g, by
means of this riveting operation, the plate 17 between the
flange formed and the collar 13.
During this operation, and as indicated hereinabove, the
shank 3 will break off at the location of its preformed
rupture neck 7, the distal or lower shank part being ejected
from one side, the remaining proximal or upper poxtion of this
shank and the head 9 being ejected from the other.
In this manner, thexe now only remains, fixed to the
plate, a single electrically conducting body 5 whose
cylindrical hollow shaft 5a will be able to be used as a pin
CA 02105122 2004-03-26
9
for the connection to an associated socket, such as, for
example. one of the two sockets 2I, 23 illustrated in Figures
and 12.
Figure 4 and the following figures illustrate the
5 applicat~.on of the connection terminal of the invention to the
electrical connection of a conducting piece produced in the
form of a cloth or of a meshed net.
Such a net used on an electro-weldable connect3.ng piece
is in particular described in the publication FR-A-2,654,978
10 (corx~espanding Unwed States Patent US-A-5,141, 580) . For any
complementary information concerning this net, it will be
poss~.ble to refer to these publications, to which the reader
is directed for referez~ca.
Thus, Figure 4 represents a net portion having interlaced
sections, the net having the particular feature of being
preferably produced from a single electrically conducting wire
21 (i.e., ensuring electrical continuity from one end to the
other of the network).
The structure of this wire has been recalled in Figure
5, from which it is possible to show that the said wire can
in particular consist of a conducting cable 23 (for example
made of copper) of a few tenths of a millimeter in diameter
coated with a layer or with a film 2S, for example based on
polyesteximide, and electrically insulating at least up to a
Z5 predetermined temperature (approximately 250°C).
Figure 4 shows the shank 3 inserted into the internal
passage 11 of the body 5, in such a way that the head 9
emerges from the side of the section 5b which penetrates one
of the meshes of the net, For good integrity of the assembly,
two larger-diameter metal washers 2', 29 have been added, one
above the net and the other beneath it.
After the riveting has been performed, the net or the
corresponding meshed fariric will thus be encountered again,
as shown in Figure 6, held tightly between the two washers 27,
29 the flange 5tb holding it a17. tightly together. between it
and the collar 13.
CA 02105122 2004-03-26
911
10
20
30
rf the wire of the meshing used is of the type of that of
Figure 5, it will therefore be necessary to provide, on the
ri~ret, rupture means for tearzng, during .
~,~.Q~~.~~
the riveting, the skin ~5 at this location of the placing
of the rivet, so as thus to ensure the electrical con-
tact.
These tearing means could, for example, consist
of sgrrations made on the '°upper'° surface 13a (see
Figure 4) of the collar 13.
FIowever, in this case, it has b~en preferred to
use as the washer ~9 a toothed washer which is to ensure
the same effect. Thus, these tearing means extend around
the mesh penetrated by the terminal, that is to say
substantially perpendicular to the shaft 5, between the
mesh in c~aestion and the collar 13, facing the flang~ 5'b
(or indeed its sid~).
Let us now turn our attention to Figures 7 to 9,
in order to describe briefly the usg, on an electro
weldable plastic sleev~, of such a meshed net thus
connected to the connection terminal 5 of Figure 6,
towards each of th$ opposite ends of its wire.
Figures 7 and 8 show the tubular shape, in the
form of a cylinder of substantially circular cross-,
section, of the net 31 whose two opposite ends of the
wire constituting it have been identified by 21a and 21b.
E'igure 9 illustrat~s dial;rammatically the manner
in which the °°St°°-shop~d loops of the ware 21
are mutually
25~ interlaced in oxder t0 cOnstitutl9 the meshes of the net,
which net is ~naountered agaia arrang~d inside the
electro-weldable connecting sleeve 33 in Figure 10.
Except for this resistanc~ element in the form of
a n~t 31, which is here arranged with its cylinder axis
31a substantially coincident with the axis 35 of the wide
central cylindrical orifice 37 which penetrates right
through the sleeve, the letter has, locally, on two
opposite sides of its external perimeter. two cavities or
wells 39. 41. which are open to the outside and, in this
39 case, are substantially p~rpendicular to the axis 35.
Into each of these cavities egesrges tho free end of one
of the two shafts 5a of a conn~ction terminal 5 in
accordance with the~inv~ntion. of tours~. each terminal
5 has been riv~ted b~forehand to the resistive net with
~~~~~ 2
- 1, -
interposition of the washer 27 and of the toothed washer
29.
Thus arranged, the two shafts 5a will be able to
constitute two electrical connecting pins, which are
connectable, if care has been taken to give them a
suitable length and diameter, with two conventional
connecting sockets. such as the sockets 21 and 23, which
are themselves each connected to their conducting supply
cabl~, respectively 43 and 45.
Figure 10 also shows the two thermowaldable
plastic pipes 47, 49 intended to b~ joined together via
the sleeve 33. Tn this cas~, these pipes have been
arranged coaxially so that their two ends facing each
other are inserted quite tightly inside the orifice 37 of
the sleeve.
Let us now turn our attention to Figures 11 and
12 in order to show another application of the invention.
First of all, it will b~ possible to notice in
Figure 19. that the shape of the conducting net. refer
enced in this case by 51, is in t:he form of a flanened
ring.
Such a °'resiative ring" can especially be of the
type of that described in lFxench Patent Application FR-A-
92/04415 filed by the present Applicant on 10th April
3992. Tn other words, the component 51 can be produced
from the meshed cylindrical structure of Figures 7 axxd 9
from which a section will have been cut, which section
will have been squashed on itself and flattened so as to
constitute a double-thickness circular ring.
It is this ring 51. having a single resistive wire
which is encountered again in Figure 12.
This figure more generally shows an electro-
weldable branch connector 53 for the transverse connect-
ing of a pipe 55 with another pipe (not shown).
Ian this case. the piece 53 whose body is produced
from a heat-meltable plastic (such as polyethylene), as
was the body of the sleeve~33. has a part 57 in the foray
of a saddle with yin internal surface 59 forming a
cylinder part of semicircular cross-section, so as to be
2~.8~~~ ~~
- 12 -
able to straddle substantially coaxially the pipe 55.
In the vicinity of this internal surface 59, and
embedded in its plastic body, the piece 53 encloses the
resistiv8 ring 51 which has, of course, a curvature
corresponding substantially to that of the saddle 57, the
central orifice 61 of this resistive element 5l~surround-
ing, at some distance, the passage 63 of the shaft 65,
which stands up substantially half way along th~ branch
connector, perpendicular to the axis of the pipe 55. Tn
practice, and as is known per as, the passage 63 is
intended to b~ prolonged by a coaxial orifice 67 enabling
the pipe 55 to communicate transversQly with anoth~r pipe
which will be installed and correctly connected to the
projecting shaft 65.
As before, and substantially in th~ region of thg
two ends of its constitu~nt wire, the resis~tiv~ ring 51
is connected to the then-riveted corn~ction terminals 5
preferably with their washers 27, 29.
~s in figure 10, the two terminals 5 stand up in
order to emerge into two transwersa external wells 69,
71, each being thus connectabl~ to the removable sockets
21, 23.
In practice, the manufacture of the two pieces
33, 53 will be easy to implement. In order to do this. it
will suffice, after having chosen the moat suitable
resistance element (such as the :resistive cylinder 31 fQr
th~ sl~ev~ 33 and the r~sistivE~ ring 51 for the trans-
verse T-connection connectar 53), to fix the two
connection terminals 5 bar riveting, taking care to
arrange them at th~ two locations making it possible to
ensure a current flow such that it runs, from one of the
terminals, at least into most of the said resistance
element, b~sfor~ reaching the second terminal.
Once this crimping operation has been completed,
the resistance slam~nt will then be placed, with its
terminals, in a moulding machin~. known per se, and ont~
these terminals will be overmoulded. by injection, the
plastic body of the~connecting piece. During this opera
tion. the wells 39, 41 or 69. 71 will be produced with,
~~.~W~
- 13 -
panetratin~ through them, the shafts 5a (of cross-section
markedly smaller than that of the said wells).
Tt will them suffice to allow the piece to cool
until it is completely solidified.
