Abstract:
A valve device, in particular a double stop-check valve, preferably of the two-way valve type, has at least three fluid connections ( 1, 2, 3 ) provided in a valve housing ( 51 ). Two valve elements ( 65, 67 ) can slide in the valve housing ( 51 ). One control device ( 71 ) controls the valve elements ( 65, 67 ). At least one of the valve elements ( 65, 67 ) forms, together with parts ( 59/61 ) of the valve housing ( 51 ), a seat leak-tight closure part for the associated fluid connections ( 1, 2, 3 ).

Description:
FIELD OF THE INVENTION 
     The invention relates to a valve device, in particular an unlockable double check valve, preferably of the two-way valve type. The valve device has at least three fluid connections in a valve housing. At least two valve elements are displaceable in the valve housing. At least one control device controls the respective valve elements. 
     BACKGROUND OF THE INVENTION 
     Valve devices of this type are state of the art. Such valve devices are used as two-way valves in hydraulic and pneumatic circuits, in which a logical OR link of pressure signals is required. Two-way valves have two inlet connections and one outlet connection on the valve housing. The two-way valve has two defined switch positions. In each switch position, an inlet connection to the assigned valve element is always closed and the other inlet connection is opened, so that fluid can reach the outlet connection from the opened fluid connection. If both fluid inlets are pressurized, in the case of a conventionally designed two-way valve, the respective valve element opens the inlet connection conveying the higher pressure, while the other inlet connection having a lower level of pressure is closed. In another design, as a reverse two-way valve, the respective valve element closes the inlet connection conveying the higher pressure, while the fluid connection conveying the lower pressure is opened toward the outlet connection. 
     In the case of a two-way valve formed as a double check valve, which has two valve elements, each of which is assigned to a fluid connection  1  and a fluid connection  2  forming an inlet connection. A control device in the form of a connecting element is provided between the valve elements, which connecting element couples the valve elements with one another during their movements between opened and closed positions. In the prior art, the valve elements are formed by switching balls, so that each check valve is formed by a ball valve. 
     SUMMARY OF THE INVENTION 
     An object of the invention is to provide an improved valve arrangement of the aforementioned type, which features particularly advantageous operating behavior. 
     According to the invention, this object is basically achieved by a valve device having, as a significant characteristic of the invention, at least one of the valve elements, together with parts of the valve housing, that forms a seat leak-tight closure part for the assigned fluid connection point. The replacement of the switching ball of a conventional ball valve with a seat leak-tight closure part that cooperates with assigned housing parts avoids the problems associated therewith encountered in the prior art. Forming the respective valve element with a seat leak-tight closure part allows a two-way valve to be implemented, in which all connections are non-leaking in the unactuated switch position and, in particular, a positively overlapped valve arrangement can be implemented. 
     In particularly advantageous exemplary embodiments, by contrast with the prior art, in which the valve elements of the double check valve are coupled with one another by a connecting element of the control device during their movements, the control device is designed such that it allows the valve elements to be controlled independently of one another. This independent control removes the serious disadvantage of the conventional valve arrangements, namely that in a respective opening process all three connections are briefly connected to one another. In the phase between the opening operation of a valve element and the closing operation of the other valve element in the prior art, a fluid short circuit is generated. With independently occurring activation of the valve elements, the switching operation can be configured such that the valve element assigned to the fluid connection to be opened performs its opening movement independent of the other valve element that remains in the closed position. 
     In an advantageous embodiment, the control device can have a rod-shaped control element that is displaceable in the valve housing in the direction of travel of the valve elements. During the displacement of the control element in the one or other direction of travel, the one or the other valve element can be carried along, independently of the respective other valve element. 
     In particularly advantageous exemplary embodiments, valve elements in the form of conical pistons are provided with a conical sealing surface that, in cooperation with an assigned sealing edge of the valve housing, forms a seat leak-tight closure. Thanks to the valve cone design, a fully leak-free closure can be implemented. 
     The arrangement may be obtained in a particularly advantageously manner, where the conical pistons are pretensioned in a closed position by an energy storage, preferably by a spring in each case. In a closed position, the one conical piston seals a first fluid connection assigned to it, and the other conical piston seals a second fluid connection assigned to it, in a leak-free manner in each case, against a third fluid connection, which adjoins both sealing edges. 
     In a particularly advantageous design of the control device, the rod-shaped control element has effective piston surfaces opposite one another. To the first piston surface, the pressure of the first fluid connection can be applied, and to the second piston surface pressure of the second fluid connection can be applied. The switching movements of the conical pistons serving as valve elements are thus not effected by direct pressure actuation from the associated fluid connection. Rather, as a result of mechanical control by the rod-shaped control element moved by pressure applied to its piston surfaces. This advantageously allows an independent and, in each case, optimized damping to be provided for the switching movements of each conical piston, by forming various choke positions in the connecting lines leading to the piston surfaces of the rod-shaped control element. Implementing an independent, individual damping for each conical piston in the switching operations is then possible. 
     When the valve device is designed as a standard two-way valve, the effective piston surfaces of the rod-shaped control element are connected with the fluid connection  1  or the fluid connection  2  in such a way that the control element is moved by the pressure of the fluid connection conveying the respective higher pressure, in a direction in which it moves the conical piston associated with the fluid connection of higher pressure out of the closed position and leaves the conical piston associated with the fluid connection of the lower pressure in the closed position. In the same way, the arrangement can, when designed as a reverse control valve, be such that the effective piston surfaces of the rod-shaped control element are connected to the fluid connections in such a way that the rod-shaped control element is moved, by the pressure of the fluid connection conveying the respective higher pressure, in a direction in which it moves the conical piston associated with the fluid connection of the lower pressure out of the closed position and leaves the conical piston associated with the fluid connection of the higher pressure in the closed position. 
     In particularly advantageous exemplary embodiments, the control element has the form of a round rod, which engages both conical pistons coaxially. Bore holes, starting from the end-side piston surfaces and extending along the displacement axis in the rod, form ducts for the fluid connection of the piston surfaces with the respective associated fluid connection  1  or  2 . This arrangement has the particular advantage that, by replacing the rod serving as the control element, an otherwise identically constructed valve device can be formed as a standard two-way valve or as a reverse two-way valve, by providing rods with different bore holes that form a corresponding duct course for the connection of the piston surfaces with the desired fluid connection. 
     To implement the desired decoupling of the opening and closing movements of the conical pistons in a simple manner, a predefined no-load stroke of the control element can be provided for the carrying along of the conical pistons by the rod-shaped control element. 
     For an adaptation of the switching behavior to application-specific requirements, the effective piston surfaces of the rod-shaped control element can have different sized effective piston surfaces. In addition, the arrangement can advantageously be such that each conical piston has a piston surface that, when the pressure of the respective associated fluid connection is applied to it, increases the spring force acting on the conical piston. The non-leaking seat leak-tight closure is facilitated by the correspondingly increased sealing force. With an advantageous design of the conicity of the conical piston below the seat, the opening behavior can be positively influenced by the stroke, e.g. in the form of a dampened opening. 
     The valve concept according to the invention not only ensures the described seat leak-tightness, it creates a positively overlapped valve concept at the same time. During the switching of the valve together with associated valve elements, no fluid connection exists between at least two of the at least three employed fluid connections of the valve housing. Thanks to the positive overlapping, the connections can be switched independently of one another and, as described above, dampened accordingly. The seat leak-tightness alluded to additionally results in improved energy efficiency in operation of the valve device. Using the solution according to the invention for a reverse-operation valve in the manner described above has proven to be particularly advantageous. 
     Other objects, advantages and salient features of the present invention will become apparent from the following detailed description, which, taken in conjunction with the drawings, discloses preferred embodiments of the present invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Referring to the drawings that form a part of this disclosure: 
         FIG. 1  is a schematic diagram of a hydraulic circuit for an exemplary application for two-way valves; 
         FIG. 2  is a side view in section, which is enlarged and depicted schematically simplified compared to an actual valve device, of a valve device according to a first exemplary embodiment of the invention in the form of a double check valve forming a reverse two-way valve; 
         FIG. 3  is a side view in section, which is enlarged and schematically simplified compared to an actual valve device, of a valve device according to a second exemplary embodiment of the invention in the form of a standard two-way valve; and 
         FIGS. 4 and 5  are side views in section of valve devices according to third and fourth exemplary embodiments, respectively, of the invention in the form of reverse two-way valves. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Of the multitude of possible applications for two-way valves,  FIG. 1  shows, by way of an example, the use of a standard two-way valve  11  in a closed hydraulic circuit  13  for controlling a working cylinder  15 . The hydraulic circuit  13  has a hydraulic pump  17  driven by an electric motor, which hydraulic pump builds up hydraulic pressure in a first line  19  or a second line  21  depending on the direction of rotational drive. Of the three fluid connections of the two-way valve  11 , a first fluid connection  7  serving as an inlet connection is connected to the line  19 , and a second fluid connection  8  serving as a second inlet connection is connected to the line  21 . A third fluid connection  9  is an outlet connection and is connected both to a controlled openable check valve  23  and to a controlled openable check valve  25 . The check valves  23 ,  25  have inlet connections  27  and  29 , respectively, which are connected to the line  19  and the line  21 , respectively. The respective inlet connection  27 ,  29  can be opened against the closing force of a respective spring  31  and  33  by the pressure signal at the third fluid connection  9  of the two-way valve  11 , to connect an outlet connection  35  or  37  of the respective check valve  23 ,  25  to the piston chamber  39  or the rod chamber  41  of the working cylinder  15 . In this arrangement, both check valves  23  and  25  supplying the working cylinder  15  can be opened from the fluid connection  9  of the two-way valve  11 , irrespective of which of the lines  19  or  21  forms the pressure line or return line, depending on the direction of rotation of the pump  17 . By selecting the drive of the pump  17 , the operation of the working cylinder  15  can then be controlled. In the manner conventional for such hydraulic circuits, a pressure-maintaining and energy recovery unit having a hydraulic accumulator  43  and a directional valve  45  is inserted between the lines  19  and  21 , respectively. The directional valve  45  is a reverse two-way valve with a closed central position. Its first inlet connection  1  and its second inlet connection  2  are connected to the line  19  and to the line  21 , respectively. The outlet connection  3  is connected to the hydraulic accumulator  43 . 
       FIG. 2  shows a first exemplary embodiment of the valve device according to the invention in the form of a double check valve, which forms a reverse two-way valve. The associated valve housing  51  has an inner workspace, which extends in the form of a stepped bore hole along an actuation displacement axis. Due to the formed steps, the workspace is divided into sections of different diameters. A fluid chamber  53  offset to the left of the central area is connected to the fluid connection  1  as an inlet connection of the housing  51 . A fluid chamber  55  offset to the right of the central area is connected to the fluid connection  2  as a second inlet connection of the housing  51 . A third or central fluid chamber  57  lying between them is connected to the fluid connection  3  as the outlet connection of the housing  51 . The central fluid chamber  57  has a lesser diameter compared with the other fluid chambers  53 ,  55 . The step of the valve housing  51  located at the transition from central fluid chamber  57  to the respective adjoining fluid chambers  53  and  55  in each case forms a sealing edge  59  and  61  for forming a seat leak-tight closure in cooperation with a conical surface  63 , which is formed as a sealing surface on an associated conical piston in each case. In front of sealing edges  59 ,  61  are a first conical piston  65  assigned to the first fluid chamber  53  connected to the fluid connection  1  and a second conical piston  67  assigned to the fluid chamber  55  connected to the fluid connection  2 . In the unactuated state depicted in  FIG. 2 , the left-side conical piston  65  forms, in cooperation with the sealing edge  59 , a seat leak-tight closure part, while the conical piston  67  lying on the right-side forms, in cooperation with the sealing edge  61 , a seat leak-tight closure part. In this state, all fluid connections  1 ,  2  and  3  are closed. 
     The conical pistons  65 ,  67  forming the valve elements of a double check valve are pretensioned in the closed position depicted in  FIG. 2  by a respective pressure springs  69 . Each spring  69  is supported on the surface of the conical pistons  65 ,  67  opposite the conical surface  63 . For movements of the conical pistons  65 ,  67  out of the closed position as a result of pressure signals at the fluid connection  1  or fluid connection  2 , a control device is provided having a control element that can be moved along the displacement axis. This control device is formed by a round control rod  71 , which is displaceably guided in the housing  51 , and which has at each of the end sides a respective piston surface  73  and  75  that can be pressurized by fluid. The rod  71  engages the conical pistons  65 ,  67  coaxially forming an inner guide, which allows a relative movement of the rod  71  and which is sealed by a respective sealing element  77  in the case of each conical piston  65 ,  67 . The rod  71  has a carrying device between the pistons  65 ,  67 , formed by two radial projections  79 . One of projections  79  is located in proximity to an adjacent conical piston  65 ,  67 . In movements of the rod  71  in the one or the other direction of displacement, the one or the other conical piston  65  or  67 , upon completion of a short no-load stroke, which is determined by the amount of distance of the projections  79  from the adjacent conical piston  65 ,  67 , is carried along and raised against the action of the respective assigned pressure spring  69  from the sealing edge  59  or  61 , in order to connect the fluid connection  1  or the fluid connection  2  to the fluid connection  3  as an outlet connection. 
     As already mentioned, the example of  FIG. 2  is constructed as a reverse two-way valve. This construction means that, in the case of a pressure signal at the fluid connection  1 , its connection to the fluid connection  3  resulting from the abutment of the conical surface  63  of the conical piston  65  with the sealing edge  59  is closed, while the conical surface  63  of the other conical piston  57  is raised from the sealing edge  61 , in order to connect the fluid connection  2  to the fluid connection  3 . This opening movement of the conical piston  67  takes place by a displacement movement of the rod  71 , during which the assigned projection  79  serving as a carrier contacts the conical piston  67  and moves the conical piston  67  against the force of the pressure spring  69  towards the right in  FIG. 2 . This movement of the rod  61  takes place by pressurizing the piston surface  73  with the pressure of the fluid connection  1 . For this purpose, a diagonal bore hole  81  is formed in the conical piston  65 , starting from the fluid chamber  53 , which diagonal bore hole leads to the chamber surrounding the pressure spring  69 . As additional connecting ducts to the piston surface  73 , a bore hole  83  is formed in the rod  71 , starting from the end thereof and extending along the displacement axis, together with a transverse bore hole  85 . 
     For the reverse switching operation, during which the higher pressure signal is applied at the fluid connection  2 , the other conical piston  67  likewise has a diagonal bore hole  81  to supply the piston surface  75  located at the right side end of the rod  71  with the pressure of the fluid connection  2  via a longitudinal bore hole  83  and a transverse bore hole  85  of the rod  71 . Accordingly, the rod  71  moves to the left in  FIG. 2  for correspondingly carrying the conical piston  65  along out of the closed position, so that the fluid connection  1  is opened. During the respective switching operations, the conical piston  65  or  67  not carried along by the displacement movements of the rod  71  remains in the closed position. 
     For an independent damping of the switching operations for each valve side, i.e. for the movements of the conical piston  65  and of the conical piston  67 , choke points can be inserted via orifices into the respective assigned diagonal bore holes  81  and the transverse bore holes  85  of the rod  71 , which choke points are not depicted in the drawings. 
     The second exemplary embodiment depicted in  FIG. 3 , which is constructed as a standard two-way valve, differs from the example of  FIG. 2  merely by a different design of the ducts that extend in the rod  71  for the connection of the piston surfaces  73  and  75  to the fluid connections  1  and  2 . For this purpose, the rod  71 , starting from each piston surface  73  and  75 , has a respective longitudinal bore hole  87  and  89 , which extend parallel to one another. The first longitudinal bore hole  87  connects the piston surface  73  via a transverse bore hole  91  to the chamber of the conical piston  67  surrounding the spring  69 . The other or second longitudinal bore hole  89  connects the piston surface  75  via a transverse bore hole  91  to the chamber of the conical piston  65  surrounding the spring  69 . Aside from the reversed switching behavior compared with  FIG. 2 , the functionality corresponds to the example of  FIG. 2 . Choke points may also be formed in the diagonal bore holes  81 . For a change of the operating behavior (standard/reverse), in the case of an otherwise identical valve design, replacement of the rod  71  having the respective required bore holes is sufficient. 
     The third exemplary embodiment of  FIG. 4  is constructed, like the example of  FIG. 2 , as a reverse two-way valve, with the difference compared with  FIG. 2  being that the connections of the piston surfaces  73  and  75  of the rod  71  to the fluid connections  1  and  2  are not formed via bore holes of the rod  71 . Rather these connections are formed by connecting lines  93  and  95  guided or extending in the valve housing  51 , starting from the fluid connection  1  or from the fluid connection  2 . The sides of the conical pistons  65 ,  67 , which the respective pressure spring  69  adjoins, are thus not required as control pressure conveying pressure chambers providing a pressure compensation for the conical pistons  65 ,  67 . To this end, a continuous longitudinal duct  97  is formed in each conical piston  65 ,  67 . By contrast with the examples of  FIGS. 2 and 3 , the sealing does not take place by means of sealing elements  77  between the conical pistons  65 ,  67  and the housing  51 , but rather by f sealing elements  78  between the rod  71  and the housing  51 . If diagonal bore holes  81  are not included in the conical pistons  65 ,  67 , a choking may be provided by way of an orifice in the line  93  and/or  95 . 
     The fourth exemplary embodiment of  FIG. 5  corresponds to the exemplary embodiment of  FIG. 4 , except that a rod section  99  with an enlarged diameter is provided on the rod  71  on an end part located on the right side in the drawing. Thus, in the exemplary embodiment of  FIG. 5 , the piston surface  75  has a larger effective area than the piston surface  73  of the other end. This surface area difference, according to the selection of the sizes of the piston surfaces  73 ,  75 , permits adapting the switching behavior to respective application-specific requirements. 
     In the schematically simplified depictions of  FIGS. 2 through 5 , with respect to the valve housing  51 , only the details functionally cooperating with the conical pistons  65 ,  67 , such as the location of the fluid connections  1 ,  2 ,  3  and the assigned edges  59 ,  61 , are depicted in detail. Because the rest of the structural design of the housing  51  can correspond to the prior art, details regarding the same are omitted for the sake of clarity. For the mounting of the movable functional parts, the housing  51  can be designed in multiple parts, which is depicted as one piece in the simplified depiction. 
     While various embodiments have been chosen to illustrate the invention, it will be understood by those skilled in the art that various changes and modifications can be made therein without departing from the scope of the invention as defined in the claims.