Patent Application
20070034271
The present invention relates to a residual pressure valve having a valve body and a valve seat, the valve seat being formed by a flexible tubular piece which is fixed in a housing, consists of an elastomer and surrounds the valve body under elastic prestress, and the valve body being formed by an axially symmetrical control element.
Residual pressure valves, which are known in various types of design, are normally used if a pressure container or a line under pressure is not to be emptied completely. It is therefore possible to prevent, for example, another medium, such as ambient air, penetrating into a container containing a specific fluid or into the corresponding line. During the use of residual pressure valves, safety requirements, aspects of the cleanest possible refilling or corrosion-preventative considerations can play a part. It is characteristic of residual pressure valves that they open as a function of reaching a specific response pressure or, respectively, close, in particular when the pressure falls below a minimum limiting pressure. For instance, such a pressure for the case of rupture of a line in an air suspension system is about 5 bar.
A valve of the general type discussed above is described by EP-A-0 800 032. That patent describes a valve for central lubricating systems, which is arranged as a shut-off valve between a pump output from a pump unit and an operating unit and comprises an input line, an output line, an inner flexible elastomer tube, an axially asymmetrical shut-off element, in particular a ball, and clamping connections. In this case, the clamping connections can be covered with a shrinkable tube, so that a type of housing is produced. As a result of the arrangement provided of the input line and the output line in their relationship with the inner flexible elastomer tube, the shut-off element is an inner flexible elastomer tube between the input line and the output line, in each case the clamping connector squeezing the inner flexible elastomer tube in such a way that the input line and the output line are sealed off via the flexible elastomer tube. The pressure difference between the pressure of the lubricant pump and a contact stress of the inner flexible elastomer tube on the shut-off element affects the opening and closing of the shut-off valve, in that the inner flexible elastomer tube forms a sleeve between the clamping connectors and allows a quantity of lubricant assigned to the pressure difference to pass through. In this way, the shut-off element forms a tribological arrangement with the inner flexible elastomer tube and the lubricant. In this case, the valve additionally has an outer flexible elastomer tube and a passage notch arranged at one end of the end face of the output line and is formed in such a way that, as a result of the pressure of the lubricant pump, the sum of the contact stress of the outer flexible elastomer tube and the inner flexible elastomer tube on the shut-off element is overcome and an annular gap is formed, it firstly being possible for the lubricant to be delivered directly via the passage notch into the output line leading to the frictional point but, secondly, at a pressure of the lubricant pump which is lower than that necessary for opening the annular gap, the shut-off valve remains closed. The inner flexible elastomer tube is in this case chosen with regard to the type of lubricant, while the outer flexible elastomer tube should have fatigue-free, predefined characteristic elasticity values. The free mobility of the ball when forming the annular chamber under the action of the pressure of the lubricant pump in this case represents an uncertainty factor with regard to the precise fulfillment of the function of the valve.
The present invention is based on the object of providing a residual pressure valve of the type discussed previously, in particular with a suitability for air suspension systems, which is distinguished by low cost construction and mounting and by an ability to respond to pressure which is precise and presettable.
According to the invention, the object is achieved in that the control element has a cylindrical, barrel-like or biconical basic shape, a hollow space being formed in each case starting from each of its axial ends, which is in each case connected via at least one channel, in particular a channel oriented radially, to an annular control chamber, which is arranged in the outer surface of the control element and is separated from the respective other control chamber by a radial intermediate wall resting on the flexible tubular piece. As a result of the annular shape of the control chamber, these elements can easily be fabricated, specifically by means of a turning operation. In addition, the annular shape permits a uniform circumferential application of pressure.
If a medium under filling pressure flows through the residual pressure valve according to the invention from a filling side, then it passes through the hollow space arranged on the filling side, in particular an axial bore through the radially oriented channel, into the first control chamber, which is larger, as compared with the other. In this case, larger is to be understood to mean that the area of the flexible tube enclosing the control chamber, that is the effective pressure area with respect to the flexible tubular piece, is greater than the enclosing area of the flexible tube or effective pressure area of the second control chamber on the residual pressure side. The enclosing area of the flexible tube is in this case acted on with a filling pressure which acts against the flexible tubular piece. The latter thus advantageously not only performs the function of the valve seat but also the function of a spring. In this case, firstly, the cost of construction is kept low and, secondly, the valve body does not need to carry out any movements in order to open or close the valve. Below a predeterminable response pressure, the area of the flexible tube enclosing the control chamber on the filling side blocks the flow of the fluid.
Additionally, in a preferred embodiment of this invention, provision can advantageously be made for a predetermined prestress to be set with the aid of a spring surrounding the flexible tubular piece circumferentially, in particular a spring band or a clamp-like spring, by which means higher precision and stability can be achieved. The pressure therefore acts not only against the flexible tubular piece but also against a spring. By means of the diameter of the flexible tubular piece and the diameter of the control element in the region of the intermediate wall, which can be matched to each other while taking account of the modulus of elasticity of the flexible tube material, and also the characteristic of the spring, the prestress and therefore the response pressure of the valve can advantageously be varied. The arrangement of a spring on the circumference of the flexible tubular piece can also be advantageous, irrespective of the specific formation of the control chambers or the other components, so that this feature is independently a subject of the invention in conjunction with the previously described residual pressure valve.
Since the pressure exerts a higher force on the flexible tube than the spring, the flexible tube is expanded radially by the application of pressure and opens toward the second, preferably smaller, control chamber on the residual pressure side. In the process, the flexible tubular piece is lifted off the radial intermediate wall. Once the filling pressure is reached, the pressure source switches off. The control chamber on the filling side is depressurized, the flexible tubular piece returns to the initial position. However, the residual pressure in the control chamber on the residual pressure side cannot open the valve in turn, i.e. lift the flexible tubular piece off the intermediate wall, since the pressurized area of the flexible tube is smaller than the area of the flexible tube of the control chamber on the filling side. The relation between the sizes of the areas of the flexible tube enclosing the control chambers and their absolute values can thus likewise be used according to the invention for adjusting the response behavior of the valve.
As far as the shaping of the control element which is optimal for its function and mounting is concerned, this can preferably have oppositely convergent conical end regions for mounting and can in each case be provided with a cylindrical and/or conical step-like turned portion at its axial ends, which are used for fixing during mounting and for mounting inspection and security.
The ends of the flexible tubular piece can be fixed to the control element and in a similar way also to the housing, in particular via retaining elements such as annular grooves, on annular retaining beads of the flexible tubular piece and via retaining elements of the control element which act in a form-fitting and/or force-fitting manner and are preferably arranged on the conical end regions of the latter, and are clamped between the control element and the housing.
The housing in which the ends of the flexible tube are fixed can advantageously comprise two parts, such as two housing halves, which can be connected to each other in a form-fitting and/or force-fitting manner, in particular in a plug-in manner, but additionally or alternatively also by means of latching, screw fixing and/or flanging. The flexible tubular piece can in this way be mounted in the housing so as to be secured against rotation and free of torsion.
In order that no overpressure is produced in the event of a leak, an unpressurized housing chamber surrounding the flexible tubular piece can be vented from the outside through vent openings, so that fluid which is liberated can escape from the housing.
As a result of the retention of the control element in the flexible tubular piece, carried out under prestress, the flexible tubular piece experiences widening in some regions. In order that the ends of the flexible tubular piece remain unaffected by this widening, the flexible tubular piece can have a minimum length matched to the diameter of the control element.
Further advantageous configuration features of the invention are contained in the subclaims and the following description.
In the following text, the invention is to be explained in more detail by using two preferred exemplary embodiments.
In the drawing figures, identical and mutually corresponding parts are always provided with the same designations, so that they are generally also described only once.
The housing 3 comprises in particular at least two housing parts 3a, 3b, which are illustrated as individual parts in
As
The flexible tubular piece 2 can be provided with a friction reducing layer, for example of PTFE lubricating varnish, for the purpose of improved mounting and for reliable operation. This friction reducing layer can be applied to one side or else to both sides.
As can be gathered from
When a medium under filling pressure flows into the residual pressure valve according to the invention from the filling side (side of the housing part 3b or the end 1B of the control element), it passes through the hollow space 1H2 arranged on the filling side, through the radially oriented channels K1B, K2B, K3B (cf.
In this case, the response pressure is set less by the predetermined prestress of the flexible tubular piece 2 than with the aid of the spring clip 4 surrounding the flexible tubular piece 2 circumferentially. The fluid pressure therefore acts against the prestress produced by the flexible tubular piece 2 and primarily against the comparatively higher prestress from the spring force of the spring clip 4.
When the pressure of the fluid in chamber SB reaches the response pressure, the flexible tubular piece 2 is expanded radially by the pressurization in such a way that a section A3 of the flexible tubular piece 2 which is located between the two sections A1, A2 located on the control chambers SA, SB, which initially rests on the intermediate wall ZW, lifts off the wall ZW. As a result, a flow path to the control chamber SA on the residual pressure side is opened for the fluid. Once the filling pressure is reached, the pressure source switches off. The control chamber SB becomes unpressurized, the flexible tubular piece 2, in particular its section A3, returns into the initial position. In particular as a result of the flattened or rounded shape of the tip ZWS of the intermediate wall ZW, in the quiescent state, the section A3 rests closely and in a tightly sealing manner on the outer contour of the control element 1 without any risk of damage. The residual pressure obtained in the control chamber SA on the residual pressure side, for example at a level of up to 6 bar, is now not able to open the valve in turn, that is to say to lift the flexible tubular piece off the intermediate wall ZW in its section A3, since the pressurized area of the flexible tube in the corresponding section A1 is too small for this purpose.
The control element 1 has oppositely convergent conical end regions K1, K2 for its mounting. In addition, in order to mount the control element 1, in particular as an axial termination of its conical end region K1 at its end 1A on the residual pressure side, a step-like turned portion ST is provided.
The flexible tubular piece 2 can advantageously be mounted in the housing 3 so as to be secure against rotation and free of torsion, the ends 2A, 2B of the flexible tubular piece 2 being fixed to the control element 1 in particular via retaining elements HR1, such as annular grooves, which are formed on annular retaining beads 2W on the flexible tubular piece 2, and via corresponding formfitting and/or force-fitting retaining elements HS1 of the control element 1, which are preferably arranged on its conical end regions K1, K2. Furthermore, in addition to the clamping of the flexible tubular piece 2 already mentioned above, provision can be made for the ends 2A, 2B of the flexible tubular piece 2 to be fixed to the housing 3 in particular via retaining elements HR2, such as annular grooves, which are likewise formed on the annular retaining beads 2W of the flexible tubular piece 2, and corresponding form-fitting and/or force-fitting retaining elements HS3 of the housing 3, such as circumferential protrusions (see in particular
The spring clip 4 can be designed in different forms, as
The housing 3, comprising the housing parts 3a and 3b, can further be designed to the effect that a leakage path is provided as a vent opening in the surfaces 3e, 3f, 3g, see
Furthermore, according to the invention, provision can be made for filters H to be arranged at the axial ends of the hollow spaces 1H1 and 1H2, see
The overall view shown in
The second embodiment of the invention, illustrated in
In this case, the flexible tubular piece 2 is formed as a shaped flexible tube, see
The flexible tubular piece 2 is clamped in a form-fitting and force-fitting manner with its end regions and the sealing beads 23 between the housing parts 3a, 3b of the housing 3 and the control element 1. On both sides of its control chambers SA, SB, the control element 1 has a cylindrical section 11, whose external diameter is smaller than the external diameter DK of the intermediate wall ZW. In its outer end walls 12 running radially, annular grooves 13 which have the shape of a part circle in cross section are formed, which accommodate the sealing sections 25 of the sealing beads 23, so that the sealing function of an O ring results in this region. The end walls 12 are each adjoined by the step-like cylindrical turned portions ST, which have a smaller external diameter than the sections 11, which project into corresponding cylindrical sections of bores in the housing parts 3a, 3b, so that the sealing beads 23 are encapsulated.
Overall, by means of the sealing beads 23 in conjunction with the adaptation of the shapes of the contours of control element 1 and housing 3, the result is an optimized sealing and retaining function of the control valve according to the invention.
A modified embodiment of a flexible tubular piece 2 in relation to that according to
As the possible differences in the embodiments illustrated already show, the valve according to the invention, with its advantageously compact design, which is simple to fabricate and saves material and is also easy to mount, and with its secure and precise function, is not restricted to the exemplary embodiments described but also comprises all the equivalent embodiments in the sense of the invention. For example, it would be possible to use an ellipsoid of rotation instead of the control element 1 illustrated without departing from the scope of the invention. The ends 3E1, 3E2 of the housing 3 can if required be provided with connecting means for a latching means, in a departure from the embodiments illustrated. Retaining arms, at least two, preferably three, for the respective other housing part could be formed on at least one housing part 3a, 3b, preferably on both housing parts 3a, 3b. The housing 3, as illustrated, can also comprise an unpressurized housing chamber 6 surrounding the flexible tubular piece 2 and the spring clip 4, which housing is vented from outside via vent openings (not shown). As a result, in the event of leakage, the formation of a hazardous overpressure in the housing 3 is avoided.
It is therefore intended that the foregoing detailed description be regarded as illustrative rather than limiting, and that it be understood that it is the following claims, including all equivalents, that are intended to define the spirit and scope of this invention.
| Number | Date | Country | Kind |
|---|---|---|---|
| DE202004012793.8 | Aug 2004 | DE | national |
