Abstract:
A bleed valve which is intended for the fuel tank of a vehicle has a housing, a floating body disposed in such a manner as to be able to move in the longitudinal direction. A rim of an outlet orifice forms a valve seat for a sealing element which is supported by a support disc, wherein the support disc is articulated in a cardanic manner on the floating body. The sealing element is disposed in such a manner as to be able to move according to the movement of the floating body between a position which closes the outlet orifice and a position which opens same, wherein as a result of the said articulation of the support disc on the floating body positional changes, e.g. inclined positions, which are caused by the drive operation of the vehicle do not impair the sealing function.

Description:
FIELD OF THE INVENTION 
   The invention relates to a bleed valve, for example, for use in a fuel tank of a vehicle. 
   BACKGROUND 
   Bleed valves of this type are normally configured for vertical installation into the wall of the fuel tank of a vehicle and are intended to provide a continuous connection between the inner chamber of the tank above a fuel level and the outside environment, so that in the open position, air is able to escape from the tank during the filling procedure and air can flow into the tank as fuel is consumed, in order to prevent a vacuum from building up. In the event that the tank is overfilled or that the position of the valve is substantially deviates from its usually topside position on the tank, the last condition indicating that an accident has occurred or that the vehicle has overturned, creating a risk that fuel may leak out in an uncontrolled manner, the valve should be switched to its closed position. Therefore, in dependence upon the operating state of the tank or the vehicle, a device for automatically switching the valve should be configured in a reliable manner between an open position and a closed position. In particular, characteristic vehicle movements based on the drive operation of the vehicle are also to be taken into consideration for the operation of the valve. 
   A valve of this type is disclosed e.g. in DE 696 01 135. A floating body which cooperates with an elongate, strip-like, flexible membrane is disposed inside a cylindrical housing which on the base-side comprises inlet orifices and on the topside comprises an outlet orifice. The floating body can move axially inside the housing between an open and a closed position of the valve and is supported on the base-side by a spring. The movement of the floating body inside the housing and thus the switching position of the valve is thus determined quantitatively by the lifting force, which acts upon the floating body and is dependent upon the fuel level, by a mass force and by the force of the spring. On its side facing towards the floating body the outlet orifice which is configured in an elongate or slit-like manner forms with its rim a valve seat for the membrane which is fixed in the closed position of the valve between the valve seat, which extends in an inclined manner with respect to the axis of the housing, and a counter surface (the counter surface is also called a bearing surface as used in U.S. Pat. No. 5,738,132 which is related to and an English version of DE 696 01 135) of the floating body which extends in parallel with the valve seat. The membrane is secured merely at one end to the floating body. By reason of the inclined orientation of the valve seat and of the counter surface relative to the axis of the housing and thus the movement direction of the floating body, the opening procedure of the valve is characterised by the fact that the membrane becomes gradually detached from the valve seat. 
   U.S. Pat. No. 6,240,950 discloses a bleed valve for a fuel tank, in which a floating body is disposed in a housing and supports on its topside a cylindrical attachment, from the planar topside of which a guide mandrel protrudes axially parallel with the axis of the housing with a conical transition region positioned therebetween. The guide mandrel passes through a central orifice of a sealing element which is supported on a support disc, on which a guide sleeve is integrally formed on the underside and engages around the outer side of the cylindrical attachment. On the free end of the guide sleeve an annular projection is integrally formed on the inner side and in cooperation with an annular projection integrally formed on the outer side on the upper end of the projection defines the axial displacement capability of the support disc and thus of the sealing element. The housing is connected via inlet orifices to the inner chamber of the tank, so that according to the fluid level the floating body which is spring loaded on the underside is caused to float and furthermore until the sealing element lies against a valve seat which extends perpendicular to the longitudinal axis of the housing and issues into an outlet orifice. Although the connection of the support disc to the central attachment of the floating body ensures that the sealing element is able to move in a virtually cardanic manner with respect to the floating body, the sealing element and the valve seat normally extend, however, in parallel with each other by reason of the arrangement of the annular projections of the guide sleeve and the attachment which is concentric with respect to the longitudinal axis of the housing and this can render it more difficult for the sealing element to become detached from the valve seat. 
   U.S. Pat. No. 4,753,262 discloses a further bleed valve for the fuel tank of a vehicle, in which a floating body which is supported on the base-side by a spring is disposed in such a manner as to be able to move axially in a cylindrical housing which is provided with base-side inlet orifices. The housing is provided with a topside outlet orifice, of which the side facing towards the floating body forms a circular ring-shaped valve seat which is operatively connected to the membrane. Located on the topside of the floating body is a retaining element which forms a cage for the membrane and which is characterised by fingers which are disposed distributed uniformly in the peripheral direction and whose free ends the membrane is partially overlapped in the radial direction. In the axial direction of the housing the fingers comprise different lengths which are dimensioned with the proviso that in the event of a downwardly directed movement of the floating body which causes the outlet orifice to be revealed, the opening procedure begins at the point on the periphery of the outlet orifice which is allocated to the axially shortest finger so as to establish in turn an opening procedure which starts gradually. The valve seat extends similar manner to a counter surface of the floating body perpendicularly with respect to the axis of the housing. 
   Against this background, it is the object of the invention to provide a bleed valve of the generic type defined in the introduction such that an improved guiding effect is exerted upon the sealing element both during the opening movement and closing movement of the valve, in particular taking into account positional changes of the valve which result from the drive operation. In the case of a bleed valve of this type, this object is achieved by the use of a sealing element disposed on and connected to a support disc which has a facing side forming a counter surface for the sealing element, the support disc being articulated in a cardanic manner on a floating body. 
   Accordingly, it is essential to the invention that in contrast to the prior art set forth in the introduction, it is not a surface which is structurally connected in a fixed manner to the floating body but rather the side of a support disc which faces towards the sealing element and for its part is articulated in a cardanic manner with respect to the floating body which acts as the counter surface for the sealing element. This means that positional changes, in particular inclined positions which result from the driving operation, can be compensated for in a defined frame, so that the sealing function is not impaired. In terms of material, the support disc will regularly differ in view of its function from the sealing element and consist of a less elastic material, preferably synthetic material, which is relatively harder in comparison with the sealing element. In contrast, the sealing element is subjected to a support effect which stabilises its configuration and accordingly can consist of a relatively softer material which is adapted to fulfil a sealing function. These measures lead to improved guidance of the sealing element whilst at the same time improving the integrity of the seal. 
   An opening procedure according to a non-uniform detachment of the sealing element from the valve seat which commences at a point on the periphery of the valve seat and progresses from this point is advantageous in order to reduce the expenditure of energy during opening and release of the valve and thus to improve its reliability. A cardanic articulation of the support disc is provided whilst at the same time taking into account the detachment of the sealing element which commences at a point on the periphery of the valve seat during opening of the valve. Therefore, one of the two pivot axes is characterised by an inclined position with respect to the axis of the housing. The other pivot axis extends perpendicularly with respect to the axis of the housing. In the event of a non-cylindrical housing the same applies in relation to the longitudinal extension thereof. 
   The housing and the floating body which is located therein can comprise a structure which is rotationally symmetrical in relation to a central axis, so that the floating body moves between the open and closed position of the valve generally in the direction of the axis of the housing. However, a configuration of the housing and of the floating body which differs from the rotationally symmetrical shape is equally possible. The valve seat extends in a radial manner in relation to the axis of the housing, as well as perpendicularly with respect to the longitudinal extension of the housing. Thus the valve seat can be disposed correspondingly in a plane extending perpendicular to the axis of the housing or to the longitudinal extension thereof. 
   To improve the guiding effect exerted upon the movement of the support disc the support disc is pivotably articulated on the floating body about two mutually perpendicular pivot axes. These features on the whole improve the reproducibility of the movements of the support disc, the integrity of the sealing effect and the smoothness of the movements. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be explained in detail hereinafter with reference to the exemplified embodiment which is illustrated by way of example in the drawings, in which: 
       FIG. 1  shows an exploded view of the essential components of the bleed valve in accordance with the invention; 
       FIG. 2  shows an axial sectional view of the bleed valve of  FIG. 1  in the open position; 
       FIG. 3  shows an axial sectional view of the bleed valve of  FIG. 1  in the closed position; 
       FIG. 4  shows an axial sectional view of the bleed valve of  FIG. 1  at the commencement of a new opening procedure; 
       FIG. 5  shows a plan view of the floating body in accordance with a viewing direction V-V of  FIG. 1 ; and 
       FIG. 6  shows a sectional view and partial view of the installation state of the bleed valve. 
   

   DETAILED DESCRIPTION 
   Reference will be initially made hereinafter to  FIGS. 1 to 2  and  5  of the drawings. As shown therein, the bleed valve consists of a cylindrical housing  1  which is closed off on the topside  1 ″ by means of a preferably detachably inserted cover  2 , and of a generally likewise cylindrical floating body  3  which is disposed in the housing  1  in such a manner as to be able to move in the direction of the longitudinal axis  5  thereof. 
   The floating body  3  can be guided in a non-rotatable manner inside the housing  1  in relation to the axis thereof by virtue of means which are known per se and are effective in a positive-locking manner. The housing  1  is provided on the topside with two mutually adjacent inlet orifices  4  and an outlet orifice  6  which extends in a coaxial manner with respect to the axis  5  is located in the cover  2 . The outlet orifice terminates on the outer side in a connecting piece  7  which is intended for the connection of an output line. 
   The floating body  3  is supported in a manner known per se on the underside by way of a spring ( 32 ), on the base  1 ′ of the housing  1 , the mode of operation of the spring will be explained hereinafter. The floating body is provided with an annular-cylindrical chamber  8  which is open towards the underside  3 ′ of the floating body and extends substantially coaxially with respect to the axis  5 , wherein the spring is supported on the closed chamber base  9  of the chamber. 
   The topside  3 ″ of the floating body  3  is characterised by a ring-like arrangement of identically configured support fingers  10  which extends substantially coaxially with respect to the longitudinal axis  5 . The support fingers are integrally formed with the floating body  3  at uniform peripherally spaced intervals and protrude from the otherwise planar topside, which is radial in relation to the axis  5 , of the floating body. The reference numeral  11  designates an approximately conically-shaped guide mandrel which is located in a central position inside the ring-like arrangement and protrudes from the topside  3 ″ and whose significance will be explained hereinafter. In the illustrated exemplified embodiment, the guide mandrel extends a shorter distance axially in the direction towards the topside  1 ″ than the support fingers  10  (see  FIG. 2 ). 
   The reference numeral  12  designates a support disc which in the peripheral region forms an annular step which is adjoined by an annular flange  13 . The support disc  12  comprises a central circular opening  14 , into which protrudes a cylindrical projection  16  which is formed integrally with a sealing disc  15  and by means of which the sealing disc is releasably connected to support disc  12 . The sealing disc  15  overlies the support disc  12  on its side facing away from the floating body  3 , i.e., the support disc has a counter surface  12 ′ for bearing against the sealing disc (see  FIG. 2 ). The annular step of the support disc  12  encompasses the outer side of the arrangement of support fingers  10  and as a result thereof is subjected to a substantially axially directed guiding movement. A guiding or centring effect is also exerted by virtue of the guide mandrel  11  which protrudes into the open end  16 ″ of the projection  16  facing towards the guide mandrel. The projection  16  also forms a continuous connection  16 ′ (a fluid conduit) between its open end  16 ″ facing towards the guide mandrel  11  and its open end  16 ′″ facing towards the valve seat  19 . The reference numerals  17 ,  17 ′ designate two angular retainer elements which are attached in a mutually diametrically opposed manner to the floating body  3 , each having an abutment section  17 ″ extending over the annular flange  13 , and which are intended to engage the top of the annular flange  13  as seen in  FIG. 4  to lock in place a pivot axis  30  of the support disk  13  and thus the sealing disc  12  at an incline as further discussed below. The axial lengths of the retainer elements are different in dimension as shown. This means that the potential movements of the support disc  12  with respect to the two retainer elements  17 ,  17 ′ accordingly will be different. In each case, according to the dimensions of the two retainer elements  17 ,  17 ′ the entire system consisting of a support disc and sealing disc  12 ,  15  is subjected to an approximately cardanic suspension or mobility on or with respect to the floating body. Put another way, when the valve is in the fully closed position as shown in  FIG. 3 , the support disc and sealing disc  12 ,  15 , can pivot about the mandrel  11  generally in any direction relative to the floating body  3 , i.e., pivotally move about two mutually perpendicular pivot axes  30  and  31  as shown in  FIG. 5 . The pivot axis  30  passes through the retainer elements  17 ,  17 ′ as shown. However, when the valve starts to open, i.e., as the float moves downwardly as illustrated in  FIG. 4 , the abutment section  17 ″ of the shorter retainer element  17  engages the support disk  12  before the longer retainer element  17 ′ does, thereby causing the pivot axis  30  to move to and be locked into an inclined pivot axis position  11 ′ relative to the longitudinal axis  5 . On the other hand, the other pivot axis  31  which is not affected by the retainer elements  17 ,  17 ′ can remain perpendicular to the axis  5  and thus is not inclined. As used herein, a non-inclined pivot axis  30 ,  31  would be perpendicular to the longitudinal axis  5 , while an inclined pivot axis  30  ( 11 ′) would not be perpendicular to the longitudinal axis  5 . Thus, when the pivot axis  30  is inclined as shown by  11 ′, this pivot axis causes the support disc and sealing disc  12 ,  15  to be in the inclined position having a longitudinal axis  5 ′ relative to the housing longitudinal axis  5 . This allows the left side of the sealing disk  15  to pull away from the valve seat  19  before the right side as shown in  FIG. 4  and as further described below. 
   The outlet orifice  6  is characterised by a comparatively short tubular element  18  which extends coaxially with respect to the axis  5  and protrudes into the housing  1  and whose free end  19 ′ forms a valve seat  19  for the sealing disc  15 . 
   As shown in detail in  FIG. 6 , a bleed valve of this type is intended for installation into the topside wall  20  of the fuel tank  21  of a vehicle. The fuel tank is filled to a permissible level  22 , so that in the type of installation shown where the housing  1  is located almost completely inside the tank, the inlet orifices  4  communicate merely with the head space  23  above the fluid. Other types of assembly of the bleed valve, in which the housing is located substantially outside the tank, are equally possible, wherein the inlet orifices have to be placed in different positions accordingly. However, this will be not be discussed further hereinafter. 
   As is known per se, the position of the floating body  3  inside the bleed valve, which is oriented vertically in the installed condition, is determined according to the forces which act upon the floating body, namely a resilient force which acts upon its underside  3 ′, a lifting force in dependence upon the fluid level inside the housing  1  and a mass force, wherein the spring in conjunction with the material of the floating body  3  is selected with the proviso that in the open position of the valve as illustrated in  FIG. 2  which is normally characterised by the absence of a lifting force, the resilient force is overcome by the mass force of the floating body  3  including the parts which are connected thereto and the floating body  3  sinks to the base  1 ′ of the housing  1 . In this case, a continuous connection (ventilation flow path) is established between the inlet orifices  4  and the outlet orifice  6 , so that it is possible to ventilate and similarly bleed the tank substantially without any hindrance. The sealing disc  15  in this position thus does not have any contact with the valve seat and the support disc  12  lies on the underside on the guide mandrel  11  which at the same time exerts a centring effect upon the sealing disc or the support disc. A radial guiding effect is also exerted by the support fingers  10 , the radial outer sides of which are disposed at a small spacing with respect to the radial inner side of the annular step of the support disc  12 . 
   Reference will also be made hereinafter to the  FIGS. 3 ,  4  of the drawings, in which functional elements which correspond to those illustrated in  FIGS. 1 ,  2 ,  5  or  6  are designated with like reference numerals so as to obviate any repetition of the description in this respect. 
   The closed state of the bleed valve as illustrated in  FIG. 3  is characterised by virtue of the fact that e.g. under the influence of a lifting force which is effective in addition to the resilient force and the mass forces, the floating body  3  has moved inside the housing  1  upwardly in the direction of the cover  2 , so that the sealing disc  15  lies against the valve seat  19 . The stabilising effect of the support disc  12  provides a reliable and reproducible sealing effect. At the same time, in this position the projection  16  is urged into sealing abutment against the guide mandrel  11 . The retainer elements  17 ,  17 ′ do not function when the valve is in this position. 
   The closed state of the bleed valve can occur as a result of the tank being overfilled or in the event of an orientation of the position of the axis of the valve which deviates substantially from the vertical orientation and which can be instigated by corresponding vehicle movements, in particular swinging movements, the negotiation of turns with a change in orientation, but also as a result of an accident, e.g. a vehicle overturning. 
   The cardanic suspension of the sealing disc  15  serves to provide a uniform sealing effect, to an extent dependent upon the different dimensions of the retainer elements  17 ,  17 ′, along the valve seat  19  and the guide mandrel  11  even when the valve is in an inclined position, since any offset of the axes of the floating body  3  and of the housing  1  can be compensated for. 
   The state illustrated in  FIG. 4  where the valve starts to open anew following on from a closed state is characterised by the fact that the sealing disc  15  becomes gradually detached from the valve seat  19 , wherein the detachment procedure is initiated as a result of the movement of the floating body  3  in the direction towards the base  1 ′ of the housing  1  by virtue of the retainer element  17  which in axial terms is relatively shorter, and correspondingly the valve begins to open at a point on the periphery of the valve seat, so that the sealing disc  15  assumes a temporary inclined position with respect to the axis  5 . The expenditure of energy required for the detachment can be kept low in this manner, i.e., it is easier to unseat the sealing disc from the valve seat. 
   Furthermore, the detachment procedure also initially causes the projection  16  to lift off from the guide mandrel  11 , with the consequence that starting from the inlet orifices  4  a continuous connection  16 ′ is established via the projection  16  to the outlet orifice, thus further facilitating the detachment procedure. 
   A bleed valve of this type, in particular its housing, can be disposed in the wall of the fuel tank, in this case it can form a supporting structure on the outer side or can even protrude at least partially into the tank. As an alternative to this wall attachment, it is also possible to use a particular holding device, in which the housing is received and which provides a connection to the outlet orifice, wherein this holding device is held on a pump unit or another component or is disposed together with an independent line system on the inner side of the tank. 
   As a result, a structural element intended for use in a fuel tank is provided with the bleed valve in accordance with the invention and is characterised by a simple structural design and satisfies all operational requirements in a reliable and reproducible manner.