Note: Descriptions are shown in the official language in which they were submitted.
CA 02268598 1999-04-06
The invention concerns a motor vehicle tank of plastic material.
Particularly for reasons of combating environmental pollution, there
is a need for the evaporation losses of fuel disposed in the tank system of
a motor vehicle to be kept at as low a level as possible. Accordingly, when
manufacturing a tank from a material which is permeable in relation to the
fuels which are usually employed, for example polyethylene, it has long been
the usual practice for the tanks to be subjected to a particular treatment.
for example by fluorination, with the aim of noticeably reducing the level
of permeability of the tank wall. Another possible way of attaining this end
involves making the wall of the tank of a multi-layer or laminate structure
and including a barrier layer for example of polyamide which is impermeable
in relation to the fuel to be contained in the tank.
As time has gone past however the regulations relating to the
admissible level of evaporation losses have become so strict that even the
evaporation losses which occur at tank connections, for example for valves.
conduits and the like, have become significant in terms of keeping the
losses within the permitted limits.
One way of moving towards that aim is to mount a valve internally to
the wal 1 of a motor vehi cl a tank usi ng a connecti ng ni ppl a whi ch
compri ses
polyamide and which is surrounded on the outside by a casing or sheathing of
polyethylene. The latter can be applied by means of injection molding.
Polyamide and other plastic materials which afford little permeability in
relation to fuels cannot be welded to polyolefins, for example polyethylene.
Therefore, the operation of fixing the valve to the nipple on the tank which
consists of polyethylene is implemented by making a welded connection
between the sheathing of the nipple and the external surface of the tank
wall. A valve housing projects into the interior of the tank through the
opening in the tank wall, without however affording a fluid-tight closure
for the openi ng outsi de the va 1 ve housi ng . The consequence of thi s i s
that
liquid fuel and fuel vapors can pass into the space which is defined by the
sheathing of the nipple and the region of the tank wall, which surrounds the
opening. As the sheathing which consists of polyethylene is permeable in
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CA 02268598 1999-04-06
relation to the fuel, substantial evaporation losses through that region of
the nipple sheathing are inevitable. Furthermore, with that arrangement, the
core of the nipple of polyamide is provided with ribs extending therearound,
which engage into corresponding recesses in the sheathing of the nipple, in
order thereby to provide a positively locking connection and sealing
integrity as between the core and the sheathing.
The present invention aims to provide a motor vehicle tank of plastic
material which affords a reduced level of evaporation losses attributable to
the presence of a pipe connecting portion, such as to comply with the
relevant regulations. and which has a connecting portion comprising a pipe
portion surrounded by a sheathing, wherein a firm strong connection between
the pipe portion and the sheathing is guaranteed under substantially all
operating conditions which normally occur in a practical context.
The invention seeks to provide enhanced sealing integrity, including
more particularly in respect of evaporation losses, in relation to a
connection between the tank body and a connecting or mounting portion
carried thereon.
In accordance with the present invention there is provided a motor
vehi cl a tank of pl asti c materi al i ncl udi ng : a tank wal 1 , an openi
ng i n the
tank wall, a connecting means mounted to the tank wall at the opening for
communication with the opening and comprising a pipe portion of a plastic
material with low permeability for fuel and a sheathing enclosing the pipe
portion and comprising a different plastic material adapted to be connected
to the tank wall, the sheathing having a first end towards the tank and at
said first end extending at a spacing from said pipe portion and being
joined to the outside surface of the tank wall, wherein at its said first
end the pipe portion of the connecting means has a part which projects
beyond said sheathing and extends into said opening, and means sealing the
tank wall region delimiting the opening with respect to the outside
peripheral surface of said projecting part of said pipe portion.
Embodiments of the present i nventi on wi 11 now be descri bed by way of
example with reference to the accompanying drawing in which:
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Figure 1 shows a plan view of a part of a motor vehicle tank with a
pipe connection mounted thereon,
Figure 2 is a view in section taken along line II-II in Figure 1.
Figure 3 is a view corresponding to Figure 2 of a second embodiment of
the invention, and
Figure 4 is a view corresponding to Figure 2 of a third embodiment of
the invention.
Referring firstly to Figures 1 and 2, reference numeral 10 denotes the
wall of a motor vehicle tank 12, the wall 10 being provided with an opening
14 which is generally produced in the wall 10 of the tank 12 after
manufacture of the tank 12 and to which a connection generally indicated at
16 is connected. The connection 16 has a pipe or tube portion 18, referred
to herei nafter as the pi pe porti on , whi ch forms the actua 1 condui t or
duct
formi ng a communi cati on between the i nteri or and the exteri or of the
tank .
and which comprises a plastic material which is not only virtually
impermeable in relation to fuel but is also relatively rigid in terms of
shape . The pl a sti c materi a 1 may be for exampl a pol yami de . The pi pe
port i on
18 is enclosed by a sheathing indicated at 20, which at the two ends of the
substantially right-angled connection 16, is shorter than the pipe portion
18.
It will be noted at this point that, in all the embodiments
illustrated by way of example herein, the connection 16 is of a right-angled
configuration although that is not an essential aspect of the invention.
Thus, the connection 16 may also be of a linear or straight configuration or
it may be curved or bent at a different angle or it may be of some other
configuration.
As can be seen in particular from Figure 2, the pipe portion 18 has a
section 24 which extends perpendicularly to the tank wall 10 and thus
substantially parallel to the longitudinal axis, indicated at 22, of the
opening 14 through the tank wall 10. The section 24 has a part 26 which
projects with respect to the sheathing 20 and extends through the opening 14
into the interior of the tank 12. The annular end region of the sheathing
20, which is towards the tank 12, forms a foot 23 which serves for securing
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CA 02268598 1999-04-06
the connection 16 to the outside surface of the wall 10 of the tank 12. That
is generally implemented by means of a welding operation as the sheathing 20
comprises a material which can be welded at any event to the material
forming the outside surface of the tank 12. Normally this will be the above-
mentioned material polyethylene. In this arrangement, the annular end region
23 is disposed at a radial spacing from the adjoining part of the pipe
portion 18 so that there is an annular space 21 defined between the pipe
portion 18 and the end region 23 of the sheathing 20.
In the embodiment shown in Figures 1 and 2 the arrangement is such
that the outside diameter of the pipe portion 18 in the region of the
opening 14 is matched to the diameter of the opening 14 in such a way that
the peripheral surface of the part 26 bears against the wall region of the
tank wall 10, that defines the opening 14, and thus provides a fluid-tight
closure at that location.
It will be seen that the above-described design configuration prevents
fluid from passing into the annular space 21 which at the outside is
delimited only by the end region 23 of the sheathing 20, said end ,region 23
being disposed at a spacing from the part 26 of the core-forming pipe
portion 18, that projects beyond the end of the sheathing 20. This is
important for the reason that, as already mentioned, the sheathing 20
generally comprises a plastic material, for example polyethylene, which on
the one hand is weldable to the tank wall 10 but which on the other hand is
permeable in relation to fuel to be contained in the tank 12. The
possibility of fuel diffusing through the tank wall 10 in substantial
quant i ti es does not need to be taken i nto consi derati on as ei ther the
tank
wall has been suitably treated at its inward side, for example by means of
fluorination, or it is of a multi-layer or laminate structure, in which case
at least one of the layers thereof is substantially impermeable to the fuel.
The pipe portion 18 in any case comprises a material, for example polyamide,
which is impermeable or only negligibly permeable in relation to the fuel
and thus forms a barrier to resist the ingress of fuel in gaseous form into
the annular space 21.
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CA 02268598 1999-04-06
The section 24 of the connection 16, which extends perpendicularly to
the tank wall 10, is provided in the region of the sheathing 20 with strip-
shaped or bar-shaped projections 32 which extend therearound in a rib-like
configuration and between which engages the material of the sheathing 20
which is generally applied around the pipe portion 18 by means of an
injection molding procedure. That provides a positively locking connection
between the pipe portion 18 and the sheathing 20, which in addition acts in
the manner of a labyrinth seal and prevents fuel in the liquid or gaseous
phase, which may possibly nonetheless still penetrate between the pipe
portion 18 and the sheathing 20, from passing the region provided with the
ribs or projections 32, towards the free end 34 of the connection 16.
In the illustrated configuration, reference 36 denotes a radial rib
which is at the end of the array of projections or ribs 32, that is towards
the tank 12 . The ri b 36 i s addi ti ona l ly provi ded wi th an extensi on
porti on
38 which is bent over substantially through 90° to extend towards the
tank 12
and which thus forms an annular sleeve portion which extends substantially
coaxially with respect to the longitudinal axis 22 of the opening 14 and the
section 24 of the connection 16. The extension portion 38 defines a kind of
undercut configuration as indicated at 40, into which plastic material
passes when the sheathing 20 is produced around the pipe portion 18, thereby
further improving the sealing action as between the pipe portion 18 and the
sheathing 20. That also applies in particular if, in the event of the
materi al formi ng the sheathi ng 20 swel 1 i ng under the acti on of fuel ,
there
is an increase in the volume of the sheathing 20 radially with respect to
the longitudinal axis 22, in the region of the undercut configuration 40.
That would further enhance the sealing integrity between the pipe portion 18
and the sheathing 20.
The pipe portion 18 also has at the other end indicated at 34 of the
connection 16 an end part 33 which also projects beyond the sheathing 20. At
a spacing from the above-mentioned free end 34, at a step or shoulder 35,
the pi pe porti on 18 i s a 1 so provi ded wi th a ki nd of undercut conf i
gurati on
as indicated at 42 which extends substantially parallel to the longitudinal
axis 44 of the angled part 46 of the pipe portion 18, and accommodates the
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CA 02268598 1999-04-06
end of the sheathing 20. This configuration also affords an improvement in
sealing integrity, besides producing a positively locking connection between
the pipe portion 18 and the sheathing 20. In the event of swelling of the
plastic material forming the sheathing 20, the pressure, produced thereby.
of the materi a 1 formi ng the sheathi ng 20 agai nst the pi pe porti on 18
whi ch
involves a substantially higher level of rigidity, also improves the sealing
action at this location. Moreover, the above-described configuration also
provides, at the free end 34 of the connection 16, that the fuel which flows
through the connection 16 does not come into contact with the sheathing.
At its angled part 46. the connection 16 is provided in the region of
the sheathing 20 with a groove 48 which extends around the angled part 46 on
the outside peripheral surface thereof, for receiving a seal illustrated in
the form of an 0-ring 50. The ring 50 provides an additional sealing effect
between the outside surface of the connection 16, or more specifically the
sheathi ng 20 thereof , and an end porti on 52 of a duct or conduit whi ch i s
connected to the free end of the connection 16 for forming the communication
with the interior of the tank 12. That conduit is mounted to the connection
16 i n some sui tabl a fashi on , for exampl a by means of a cl amp or cl i p
( not
shown). The sealing ring 50 is intended to ensure that fuel vapors which may
possibly escape outwardly along the separation surface between the pipe
portion 18 and the sheathing 20 cannot issue into the atmosphere. On the
contrary, by virtue of the barrier action formed by the sealing ring 50,
such vapors are to be discharged into the conduit as indicated at 52, which
is connected to the connection 16.
In the embodiment shown in Figures 1 and 2 the end part 33 of the tube
portion 18 is provided on the outside with sealing and/or holding rings of a
sawtooth configuration, for the connection of the conduit 52 to the
connecti on 16 . The fact that the end part 33 i s di rectly communi Gated wi
th
the condui t 52 whi ch i s not permeabl a i n rel ati on to fuel a 1 so provi
des i n
this region that only very small amounts of fuel can escape to the exterior
by a diffusion effect. Furthermore, the more rigid material of the pipe
portion 18 forms a supporting core for a clip or clamp or the like which is
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CA 02268598 1999-04-06
possibly used to fix the conduit 52 to the connection 16 by being clamped
therearound, thereby to hold the conduit 52 on the connection 16.
Reference will now be made to Figure 3 showing a second embodiment of
the present invention which is the same as that shown in Figures 1 and 2 in
respect of all its essential features and details, so that the same parts
wi 11 al so be denoted by the same references as those used i n Fi gures 1 and
2, but increased in each case by 100 in Figure 3. The difference in the
Figure 3 embodiment is that the opening 114 in the wall 110 of the tank 112
is sealed with respect to the end part 126 of the pipe portion 118 by a
sealing ring 160 which is disposed in the annular space 121 and which bears
against the part 126. The sealing ring 160 is subjected to a compressive
loading by a part of the sheathing 120, that is to say more specifically by
the end surface 162 thereof, which is set back somewhat in the upward
direction in Figure 3 with respect to the foot 123, thereby ensuring that
the sealing ring 160 bears against both the outside peripheral surface of
the part 126 of the pipe portion 118, the outside surface 164 of the tank
wall 110, and against the end face 162 of the sheathing 120. That therefore
provides for sealing integrity in relation to the opening 114 which, in the
embodiment of Figure 3, is not completely closed by the part 126 outside
same. It will be appreciated that it is also possible for the embodiments of
Figures 1 and 2 and Figure 3 to be combined together and thus additionally
also to provide a sealing ring which is advantageously in the form of an 0-
ring, when the opening 14 in Figures 1 and 2 or 114 in Figure 3 in the tank
wall is already closed in fluid-tight relationship by the part 26 or 126 of
the pipe portion 18 or 118 respectively.
A further difference in the Figure 3 embodiment in relation to the
embodiment shown in Figures 1 and 2 is that the end part 113 of the
connection 116 is of a configuration which is required for co-operation with
a form of connector referred to as a quick connector. In this case, formed
on the end part 113 on the outsi de thereof i s a 1 ocki ng ri ng i ndi Gated
at
180 which co-operates with a locking member on the quick connector and
behind which the locking member of the quick connector engages. In the
embodiment shown in Figure 3 the locking ring 180 is mounted on the
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CA 02268598 1999-04-06
sheathing 120 at the outside surface thereof. Sealing integrity within the
quick connector is effected however in the region marked by the dash-dotted
line 182, that is to say in relation to the pipe portion 118 comprising a
material which is not permeable or only slightly permeable in relation to
fuel.
Looking now at Figure 4, shown therein is a further embodiment of the
invention which is also substantially the same as the embodiment of Figures
1 and 2 so that the same components are also denoted by the same references
but increased in each case by 200 in relation to Figures 1 and 2.
Referring therefore to Figure 4, the wall 210 of the tank 212 is shown
at two different positions in respect of height. The part of the wall 210 to
the right of the opening 214 shows the finished welded connection 230
between the tank wall 210 and the sheathing 220, while the part to the left
of the opening 214 shows the position of the parts which co-operate in that
si tuati on , bei ng therefore the wal 1 210 and the foot 223 , i n the posi
ti ons
immediately before the welded connection is formed. For the purposes of
making the welded connection, the regions indicated in darkened form at 268
and 270 respectively are generally heated and plasticised in the course of
the procedure which is referred to as surface-to-surface welding, whereupon
the two parts are then pressed against each other to produce the welded
connection indicated at 230. In regard to the embodiment of Figure 4, the
i nventi on provi des i n thi s respect that a part of the pl asti ci sed
materi a 1
in the regions 268 and 270 of the sheathing 220 and the tank wall 210 is
displaced in such a way that, at the end of the operation for producing the
welded connection 230, the annular space 221 is entirely or substantially
filled by displaced material as indicated at 272, at any event to such an
extent that the displaced material 272 closes off the opening 214 in the
tank wall 210. In this respect, there is no need for the amount of
plasticised material to be accurately matched to the volume of the annular
space 221 as, when the parts which are to be joined together are pressed
against each other, superfluous plasticised material can be displaced to the
exterior from the region between the foot 223 and the outside surface 264 of
the tank wall 210. It will be appreciated that in this case also it is
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possible, using the arrangement shown in Figures 1 and 2, for the opening
214 to be completely closed off by the end part 226, by virtue of suitable
dimensioning of the diameter of the opening 214 and the outside diameter of
the part 226. Alternatively but also additionally, it would also be possible
to provide a sealing ring as indicated at 160 in the embodiment of Figure 3.
in which case the displaced plastic material 272, at the peripheral surface
of the part 226, forms an abutment for the sealing ring or a portion
delimiting a seating for same.
The embodiment of Figure 4 also provides that the end part 233 is
designed for connection to a quick connector, but in this case the locking
ring 280 is carried by the pipe portion 218 or more specifically the region
233 thereof which extends beyond the sheathing 220. In this case also the
dash-dotted line 282, corresponding to the line 182 in Figure 3. indicates
the regi on i n wh i ch sea 1 i ng i ntegri ty i s effected i n rel at i on to
the qui ck
connector.
It will be seen from the foregoing description that the configuration
in accordance with the invention, in terms of sealing integrity for the
opening in the tank wall, provides that fuel in the form of liquid and/or
gas in the region of that opening can only issue through the internal free
cross-section of the connection 16, 116, 216, or the pipe portion 18. 118.
218 thereof, whereas fuel cannot escape through the opening outside the
condui t or passage whi ch i s defi ned by the connecti on 16 . 116. 216 . As
the
plastic material, for example polyamide, which forms the pipe portion 18,
118, 218 constituting the core of the connection 16, 116, 216 has only a
negl i gi bl a 1 evel of permeabi 1 i ty i n rel ati on to fuel and the wa 11
10 . 110 .
210 of the tank is also only very slightly permeable in relation to fuel,
either by virtue of a suitable treatment applied to the tank, for example by
means of fluorination, or by the provision of a barrier layer in the wall
structure 10. 110, 210 of the tank, the amount of gaseous fuel which passes
into the space defined by the sheathing 20, 120. 220 on the exterior thereof
i s so sl i ght that the evaporati on 1 osses whi ch escape to the exteri or
as a
result are negligible. That improvement has been achieved using simple means
as producti on of the connecti on 16. 116. 216 and preparati on or processi ng
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of the tank to produce the opening 14, 114. 214 therein and possibly
arranging a seal at that location do not require any additional significant
complication or expenditure. That is important for the reason that fuel
tanks of this kind are articles which are produced in very large numbers,
and the cost factor is therefore an important aspect.
It will be appreciated that the above-described embodiments have been
set forth solely by way of example and illustration of the principles of the
invention and that various other modifications and alterations may be made
therein without thereby departing from the spirit and scope of the
invention.
