Fuel tank with opening closed by removable holding cover and sealing ring

A fuel tank for a motor vehicle has a connecting portion which extends around an opening in the tank wall which is closed by a holding cover, with the interposition of a sealing ring. The connection between the connecting portion and the holding cover is made by a fixing means urging the holding cover towards the connecting portion. The sealing ring is disposed in a groove in the connecting portion or the holding cover and the cross-sections of the groove and the sealing ring are so selected that, in its operative position of closing the opening, the holding cover is supported directly by the end surface of the connecting portion, bearing against that end surface.

FIELD OF THE INVENTION
 The invention concerns a fuel tank, for example of thermoplastic material,
 for installation in a motor vehicle.
 BACKGROUND OF THE INVENTION
 One form of fuel tank comprising a thermoplastic material, for installation
 in a motor vehicle, comprises a connecting portion extending around an
 opening in the tank wall, with the opening being closed by a holding cover
 which is fitted on to the connecting portion and held thereon by a fixing
 means for urging the holding cover in a direction towards the connecting
 portion. The holding cover is provided for holding for example conduits or
 hoses, filling level indicator means, a pump or the like. A sealing ring
 which may be in the form of an O-ring is interposed between the holding
 cover and the connecting portion to which the holding cover is secured. In
 a fuel tank of that general design configuration, as is to be found in
 German patent specification No 42 40 629, the arrangement is such that the
 holding cover lies exclusively on the resilient sealing ring in order in
 that way to be able to apply contact pressing forces of different
 magnitudes and compensate for any manufacturing tolerances that may be
 present. In that arrangement the resilient sealing ring is a structural
 component of the connection between the tank and the holding cover. That
 however suffers from the disadvantage that the sealing ring is required to
 perform two functions, namely a sealing function on the one hand and on
 the other hand the function of a structural member for the transmission of
 forces, with the result that a variation in the position of the sealing
 ring, which can be caused for example by swelling or creep movement of the
 material forming it, as may occur for example due to the action of fuel
 thereon, may possibly also at the same time result in the configuration of
 the connection being affected.
 Reference may also be made to German laid-open application (DE-OS) No 31 35
 982 disclosing a fuel tank of thermoplastic material for motor vehicles,
 with a filling connection portion or filler neck, and a connecting support
 which is mounted thereto, for receiving the closure cap of the filler. In
 that case a sealing ring is arranged between the filler neck and the
 connecting support portion which is supported against a contact surface of
 the filler neck by way of the elastic sealing ring. In this case also the
 aim of the invention is to make use of the elasticity of the sealing ring
 to compensate for tolerances which may be caused by virtue of dimensional
 fluctuations and different coefficients of expansion so that this design
 also essentially suffers from the disadvantages already described above in
 connection with the fuel tank of German specification No 42 40 629.
 SUMMARY OF THE INVENTION
 An object of the present invention is to provide a fuel tank for a motor
 vehicle, which eliminates the disadvantages of the aboved-discussed tanks.
 Another object of the present invention is to provide a fuel tank for a
 motor vehicle having a sealing ring between a connecting portion and a
 holding cover thereon, wherein the sealing ring does not have to perform
 any function as a structural member in order thereby to ensure that any
 effects on the sealing ring such as those of swelling or creep of the
 material forming same cannot adversely affect the connection between the
 fuel tank and the holding cover and thus the effectiveness of that
 connection.
 Still another object of the present invention is to provide a fuel tank for
 installation in a motor vehicle having a connecting portion and a holding
 cover for fitting thereon and for carrying for example conduits, filling
 level indicators and/or pumps or like accessories, in which a sealing ring
 is operatively disposed between the connecting portion and the holding
 cover, wherein the components can be readily assembled in a simplified
 operating procedure.
 In accordance with the principles of the present invention the foregoing
 and other objects are achieved by a fuel tank which more particularly for
 example comprises thermoplastic material for installation in a motor
 vehicle. The fuel tank comprises a tank body having a tank wall, with an
 opening in the tank wall. A connecting portion extends around the opening
 for receiving a holding cover which is adapted to close the connecting
 portion and the opening therein. The holding cover is provided for holding
 accessory components, for example conduits, filling level indicators,
 pumps and the like. A sealing ring is operatively interposed between the
 connecting portion and the holding cover and is preferably in the form of
 an O-ring. A fixing means is operative to urge the holding cover towards
 the connecting portion to hold the holding cover thereon. The sealing ring
 is arranged in a groove in the connecting portion or the holding cover,
 with the cross-section of the groove and the sealing ring being so
 selected that, in its operative position of closing the opening in the
 tank wall, the holding cover is supported directly by the outwardly facing
 end surface of the connecting portion, in a condition of bearing against
 that end surface.
 As will be seen from embodiments of the invention which are described in
 greater detail hereinafter, to achieve the required sealing effect between
 the connecting portion and the holding cover, it will be necessary for the
 sealing ring, in the condition of not being loaded by the holding cover,
 to project towards the respective other part of the assembly, that is to
 say, when the groove is provided in the connecting portion on the fuel
 tank, then the sealing ring is required to project towards the holding
 cover, while when the groove is provided in the holding cover, the sealing
 ring must project towards the connecting portion. The depth of the groove
 or the depth of penetration into the groove of the undeformed sealing ring
 is thus to be so selected that it is less than the diameter or
 corresponding outside dimension of the sealing ring. In that connection
 however the cross-section of the groove must be of such a size that it can
 completely accommodate the sealing ring which is subjected to a pressure
 loading by the co-operation of the connecting portion and the holding
 cover, with corresponding cross-sectional deformation of the sealing ring,
 in order thereby to provide that on the one hand a condition of adequate
 sealing integrity is guaranteed while on the other hand the sealing ring
 does not represent a component of the load-bearing structure of the
 connecting configuration afforded by the connecting portion and the
 holding cover.
 The fixing means for securing the holding cover in its operative position
 can be in the form of a clamping ring. It is however also possible to
 position on the connecting portion, a holding ring of a push-in closure
 arrangement in the manner of a bayonet closure arrangement, the holding
 ring co-operating with a clamp ring which engages over the holding cover
 at its peripheral edge and urges it towards the end surface of the
 connecting portion on the tank wall.
 Another possible design configuration provides that the connecting portion
 is provided on its outside with a screwthread, on to which can be screwed
 a union nut, an edge region thereof engaging over the edge region of the
 holding cover.
 At any event it should be possible for the holding ring which for example
 can carry accessory components such as filling level indicators, delivery
 conduits or hoses, pump devices or the like which are arranged in or which
 lead into the fuel tank, to be mounted to the fuel tank in a given
 orientation in respect of its peripheral position and to be connected in
 that position to the fuel tank in order thus to ensure that the components
 which are mounted on the holding cover or connected thereto are in a
 defined arrangement relative to the tank. That can be achieved in the
 usual manner by the provision on the connecting portion, the fixing means
 and the holding cover, of means which produce a positively locking
 engagement therebetween and which permit the co-operating parts of the
 assembly to be fitted or installed only in predetermined positions
 relative to each other in order thereby to ensure that a fuel pump, a
 filling level indicator and other devices and components assume within the
 fuel tank a given position which can be readily reproduced again, even
 after the connection between the holding cover and the fuel tank has been
 disconnected, when that connection is restored.
 Further objects, features and advantages of the invention will be apparent
 from the following description of preferred embodiments thereof.

DESCRIPTION OF PREFERRED EMBODIMENTS
 Referring firstly to FIG. 1, shown therein is a part of a fuel tank 10
 which (in particular for example) comprises thermoplastic material and
 which is intended for installation in a motor vehicle. The tank 10 has a
 tank body with a wall of which part is shown in FIG. 1, carrying an
 outwardly projecting connecting portion 12 which extends around and
 defines an opening 14 through the tank wall. A fuel tank of that kind is
 generally produced by a blow molding procedure from suitable thermoplastic
 material, with the connecting portion 12 initially being closed at its
 free end. The opening 14 is normally produced by a particular cutting
 operation.
 The opening 14 and the connecting portion 12 therearound are closed by a
 holding cover 16 which usually comprises a different material from the
 fuel tank 10. The holding cover 16 may comprise a metal material, but it
 may possibly also be made from a plastic material which differs from the
 plastic material of the fuel tank 10, by virtue of being of greater
 hardness. Blow-molded fuel tanks of plastic material are generally made
 from a polyolefin.
 In the embodiments illustrated in the drawing the holding cover 16 serves
 to held various accessory components and is illustrated as carrying
 conduit portions 18, by means of which a connection is made between the
 interior of the fuel tank 10 and the outside atmosphere. Those conduit
 portions 18 may be parts of delivery conduits or hoses or other devices
 which are arranged within the fuel tank 10 and which require junctions
 disposed outside the fuel tank 10.
 In the embodiment illustrated in FIGS. 1 and 2, the connection between the
 holding cover 16 and the connecting portion 12 of the fuel tank 10 is made
 by means of a two-part clamping ring 20. The two parts of the clamping
 ring 20 are indicated at 20a and 20b in FIG. 3, from which it will be seen
 that each part 20a, 20b constitutes, substantially a respective half of
 the clamping ring 20. The two parts 20a, 20b of the clamping ring 20 can
 be connected together and braced together by way of a hook-type connection
 as indicated at 22, which permits a pivotal movement between the two parts
 20a, 20b, and a screwthreaded bolt 24 with nut 25, the bolt 24 and nut 25
 being positioned at 180.degree. displacement relative to the hook
 connection 22. It will be seen from FIG. 1 that the profile of the
 clamping ring 20 is such that it defines two limbs which spread apart
 somewhat in a radially inward direction from the outer edge of the
 clamping ring 20, while the edge region 26 of the holding cover 16, which
 co-operates with the limbs of the clamping ring 20, is correspondingly
 bevelled or inclined so that, when the screw connection of the bolt 24 and
 the nut 25 is tightened, a force component extending substantially
 parallel to the axis of the connecting portion 12 takes effect, by which
 the holding cover 12 is urged against the outwardly facing end surface 28
 of the connecting portion 12. It will be seen from FIGS. 1 and 2 that the
 connecting portion 12 has an outwardly projecting flange-like rim portion
 29 to stiffen the outwardly facing end surface 28 and to increase the area
 thereof.
 At its end surface the connecting portion 12 is provided with a
 peripherally extending groove 30 therein, the cross-section of which
 uniformly decreases or tapers from the end surface 28 towards the bottom
 of the groove 30. The groove 30 serves to receive a sealing ring 34 whose
 cross-sectional dimensions, in relation to the depth of the groove 30, are
 so selected that on the one hand, in the non-loaded condition thereof, the
 sealing ring 34 projects upwardly somewhat beyond the end surface 28, as
 shown in FIG. 2, while on the other hand the cross-section of the sealing
 ring 34 is not greater than that of the groove 30 so that, in the
 operative position of the components as shown in FIG. 1, in which the
 holding cover 16 lies on and bears against the end surface 28 of the
 connecting portion 12, the sealing ring 34 is completely accommodated in
 the groove 30. The cross-section of the groove 30 may be somewhat larger
 than that of the sealing ring 34. The important consideration is that, due
 to the holding cover 16 being seated on and in contact with the end
 surface 28, the sealing ring 34 experiences elastic deformation and thus a
 prestressing effect which is adequate to produce a condition of sealing
 integrity which is such as to satisfy all requirements arising in
 practical operation. On the other hand the elastic deformation that the
 sealing ring 34 experiences under the effect of the holding cover bearing
 thereagainst when fitted on to the end surface 28 of the connecting
 portion 12 is too slight that it could involve a significant transmission
 of forces, as the holding cover 16 bears with its edge region over a
 surface area thereof against the end surface 28 of the connecting portion
 12. With this arrangement therefore the sealing ring 34 is not a part of
 the load-bearing structure of the connection between the connecting
 portion 12 and the holding cover 16.
 Referring now to FIG. 4, the embodiment illustrated therein is Identical in
 terms of the basic arrangement of its essential parts to the embodiment
 shown in FIGS. 1 through 3 so that the same components are also denoted by
 the same references but increased in FIG. 4 in each case by 100.
 In the FIG. 4 embodiment the holding cover 116 is fixed on the connecting
 portion 112 using a clamp ring 136 which is provided in an outer edge
 region thereof with projection portions 138 co-operable with a holding
 ring 40 which is fixedly mounted on the connecting portion 112 on the
 outside thereof. The clamp ring 136 and the holding ring 140 co-operate in
 the usual fashion in the manner of a bayonet closure. The projecting
 portions 138 of the clamp ring 136, in the course of a rotary movement of
 the latter, are brought into engagement with the guide surface 142 of the
 respective holding portion 144 on the holding ring 140, in which case, by
 virtue of suitable inclination of the guide surfaces 142 in the peripheral
 direction, the co-operating parts are clamped together in the course of
 the rotary movement in the usual way. The rotary movement can be produced
 using a suitable tool, for the engagement of which openings 146 are
 provided in the clamp ring.
 A further difference in the FIG. 4 embodiment, in comparison with the
 embodiment of FIGS. 1 through 3, is that the groove 130 for accommodating
 the sealing ring 134 is provided in the holding cover 136. In other
 respects the conditions already set forth in connection with the
 embodiment of FIGS. 1 through 3 also apply here so that in this case also
 the edge region of the holding cover 116 bears directly against the end
 surface 128 of the connecting portion 112 and the sealing ring 134 is not
 a part of the load-bearing structure of the connection between the
 connecting portion 112 and the holding cover 116.
 It will be appreciated that in regard to this construction, as for all
 other embodiments described herein, the invention permits a simple
 connection to be quickly made between the fuel tank and the holding cover,
 and that connection on the one hand remains operative over a prolonged
 period of time while on the other hand if required, for example in the
 event of repair, it can be quickly released and also restored.
 Referring now to FIG. 5 the embodiment illustrated therein is the same in
 terms of its essential parts to that shown in FIGS. 1 through 3 so that
 identical components are denoted by the same references but increased by
 200. One difference here is that the sealing ring 234 in the FIG. 5
 embodiment is arranged in a groove 230 at the end surface of the
 connecting portion 212. In this construction also, similarly to FIG. 4
 embodiment, the sealing ring could be arranged in the holding cover 216,
 as conversely in the FIG. 4 embodiment the groove for the sealing ring
 could be in the end surface of the connecting portion. In many cases
 arranging the groove for receiving the sealing ring in the connecting
 portion on the fuel tank will be preferable as the connecting portion must
 in any case be of the minimum thickness required for the purposes of
 affording an adequate degree of rigidity, whereas when the groove is
 arranged in the holding cover, it may under some circumstances possibly be
 necessary, for that purpose, for the holding cover to be thicker at least
 in the region having the groove, than would otherwise be necessary if no
 groove were provided there.
 A further difference between the embodiment of FIGS. 1 through 3 and the
 FIG. 5 embodiment is that the FIG. 5 construction additionally has a
 fitting ring 248 which embraces the connecting portion 212 on the outside
 and engages under the flange-like outer rim portion 229 thereof. That
 fitting ring 248 which is produced separately and is divided or is
 otherwise suitably designed in such a way that it can be bent open in
 order to be passed around the connecting portion 212 only serves to
 simplify the configuration of the holding ring 240 for the bayonet
 closure. It will be noted that FIG. 4 shows that adaptation of the holding
 ring 140 to the external profiling of the connecting portion 112 requires
 a plurality of shaping procedures which to a certain extent are expensive.
 Admittedly, the divided fitting ring 28 also has to be adapted, in terms
 of its internal definition, to the external profile of the connecting
 portion 212. That however does not involve an increase in expenditure when
 manufacturing the fitting ring 248 for example by means of an injection
 molding process. On the other hand, the fitting ring 248 can be of such a
 definition on its outside that it is substantially flat-surfaced and
 accordingly only involves a low level of shaping expenditure for the
 holding ring 240 which can be provided at the side towards the body of the
 fuel tank 210 with an inwardly bent-over flange portion 250. The flange
 portion 250 engages under the fitting ring 248 so that the holding ring
 240 is connected to the fitting ring 248 in positively locking engagement
 therewith. The fitting ring 248 is of L-shaped cross-section, wherein the
 limb 252 of the fitting ring 248, which engages behind the flange-like rim
 229 of the connecting portion 212, produces an effective positively
 locking engagement between the fitting ring 248 and the connecting portion
 212 so that the holding ring 240 is at any event held in its operative
 position in spite of the absence of direct contact with the connecting
 portion 212.
 The use of a fitting ring 248 of that kind will depend on whether it is
 more expensive to produce such a fitting ring or to use a holding ring
 which, like that shown in FIG. 4, must involve a plurality of shaping
 steps. The fitting ring is advantageously made from a plastic material
 which is harder than the plastic material constituting the fuel tank.
 To secure the clamp ring 236 in the clamping position on the projection
 portions 238 the clamp ring 236 has projections 254 which, at the end of
 its rotary movement that provides the firm connection between the holding
 cover 216 and the fuel tank 210, engage into corresponding openings on the
 holding ring 240 and in that way provide for an additional positively
 locking engagement which can only be disengaged by applying a minimum
 force acting in the opposite direction to the rotary movement for making
 the connection. Such projections 254 and the above-mentioned openings for
 receiving same may obviously also be provided in the embodiment shown in
 FIG. 4.
 Reference will now be made to FIG. 6 showing an embodiment in which those
 parts that are identical to those of the embodiment of FIGS. 1 through 3
 are denoted by the same references but increased by 300. Here the
 connection between the holding cover 316 and the connecting portion 312 of
 the fuel tank 310 is made by means of a union or cap nut 356 which is
 screwed on to a male screwthreaded ring 358 which is arranged on the
 connecting portion 312 on the outside thereof and extending therearound,
 and which is of a similar configuration to the fitting ring 248 of the
 embodiment of FIG. 5. The limb 352 of the screwthreaded ring 358 engages
 behind the flange-like outer rim 329 of the connecting portion 312, which
 is provided in its end surface with the groove 330 for receiving the
 sealing ring 334. The screwthreaded ring 358 is also of a divided design
 in such a way that it can be bent open somewhat in order to pass it over
 the connecting portion 312 and move it into the operative position shown
 in FIG. 6. The screwthreaded ring 358 and the union nut 356 can be made
 from plastic material which however should be harder than the material of
 the fuel tank 10. As a departure from the other embodiments described
 above the construction shown in FIG. 6 is provided with a groove 330 which
 is approximately rectangular in cross-sectional configuration.
 It will be appreciated that the above-described embodiments of the
 invention have been set forth solely by way of example and illustration of
 the principles thereof and that various other modifications and
 alterations may be made therein without thereby departing from the spirit
 and scope of the present invention.