Abstract:
A directional poppet valve ( 10 ) has valve pistons ( 16 - 22 ) arranged in a valve housing ( 12 ) for controlling a plurality of fluid connections (A, B, P, T). The positions of each valve pistons ( 16 - 22 ) in the valve housing ( 12 ) can be changed by at least one actuating device. The fluid connections (A, B, P, T) are connected to one another or separated from one another alternately depending on the position of the valve pistons ( 16 - 22 ). The valve pistons ( 16 - 22 ) are arranged inline along at least one axis (R), consecutively and/or at least such as to partially interengage, in the valve housing ( 12 ).

Description:
FIELD OF THE INVENTION 
     The invention relates to a directional poppet valve, comprising valve pistons disposed in a valve housing for controlling a plurality of fluid connections. The positions of each of the valve pistons in the valve housing can be changed by means of at least one actuation device. The fluid connections are alternately connected with one another or separated from one another depending on the placements of the valve pistons. 
     BACKGROUND OF THE INVENTION 
     Directional poppet valves are known in different structural designs. In known directional valves, the poppet valve cartridge cannot be fully force balanced, which results in a loss of performance and the need for increased actuation forces. Sometimes the structural design of the known directional poppet valves is so costly and prone to failure that complicated actuation mechanisms and a complicated drilling path in the block must be implemented for the actuation. In addition, a defined opening of control edges as well as a positive or negative overlap of control edges is only possible with great difficulty or is not possible at all. In addition, in known directional poppet valves, the fluid pressures must be selected such that the pump pressure in the supply connection exceeds the consumer load pressure in the respective utility connection, and this load pressure in turn must exceed the tank pressure in the tank connection. 
     SUMMARY OF THE INVENTION 
     An object of the invention is to provide an improved directional poppet valve that is as force balanced as possible, that can be actuated in a simple manner and with low actuation forces, and that has improved control functions. 
     This object is basically achieved by a directional poppet valve having piston valves disposed in an inline construction, one after the other along at least one axis and/or in the valve housing such that they at least partially interengage. 
     According to the invention, two or more valve pistons are disposed in the piston chamber, which chamber extends along the at least one axis in the valve housing. The valve pistons may be moved or displaced along the respective axis. The respective actuation device provided for this purpose may be designed for electric actuation, for example as an electromagnet or as a step or linear motor, respectively, or may be designed for mechanical actuation or for manual actuation. In addition, the directional poppet valve according to the invention may be operated by proportional and/or switching magnets, or in other words, the respective valve piston may be actuated in such manner. 
     The arrangement of the valve pistons according to the invention makes possible a simple production and a compact design of the directional poppet valve according to the invention. An at least partial interengagement of each of a plurality, typically two valve pistons, allows the installation space, or more precisely the piston chamber provided in the valve housing, to be designed such that it is smaller in comparison with conventional solutions. Depending on the intended use of the directional poppet valve according to the invention, this valve may be designed as a 3/2-directional poppet valve, as a 4/2-directional poppet valve or as a 4/3-directional poppet valve for example. Due to the comparatively short adjustment or actuating travel of the respective valve piston, the respective, for example three or four, fluid connections corresponding to the desired switch positions may be connected to one another such that they can carry fluid, or may be separated from one another such in a fluid-tight manner. 
     In a preferred embodiment of the directional poppet valve according to the invention, the piston valves interengage in pairs. Preferably, each piston is disposed between two seats, and can be moved relative to one another by a respective resetting device, preferably in the direction of one respective seat. The advantage of this embodiment lies in the fact that, when viewed in the direction of the axis, the piston valves can be disposed in a short piston chamber in a space-saving manner. The resetting device allows the piston valves to be moved towards and apart from one another, so that in the non-actuated state, i.e., without the application of an actuation force by the respective actuation device, the piston valves abut the respective seats thereof. The resetting device allows the contact force, or the contact pressure, respectively, to be specified for the respective valve piston at the respective seat. 
     The piston valves and/or the associated seats are each formed such that they are essentially rotationally symmetrical to the axis. The valve pistons may each be designed as conical pistons. This shape provides the advantage of a particularly cost-effective implementation of the directional poppet valve according to the invention. Especially preferably, the seat for the respective valve piston may be formed as an annular surface that is disposed transverse, preferably perpendicular, to the axis. With that annular surface, the dedicated end face of the respective valve piston allocated thereto may be in contact, typically with a contact force applied by the respective resetting device. 
     At least one tank connection, at least one supply connection and at least one utility or consumer load connection may be provided as valve connections. The fluid connections are connected to the piston chamber encompassing the valve pistons in a fluid-conveying manner, and are typically each designed as at least one through bore in the valve housing. The fluid connections of the through bores are advantageously disposed such that they extend radially to the axis, which ensures a simple structural design and simple fabrication of the directional poppet valve according to the invention. 
     In an additional preferred embodiment of the directional poppet valve according to the invention, the respective actuation device comprises an actuation rod, which acts on at least one valve piston, and/or which at least partially passes through this valve piston. A particularly simple and compact design results when the at least one actuation rod extends along, or parallel to, the axis, so that complicated constructive actuation mechanisms may be omitted. The actuation force is transferred to the respective valve pistons by the respective actuation rod. These valve pistons are moved linearly, accordingly, in the selected direction along the axis. In the case of an actuation of this kind, the corresponding valve piston or pistons is or are spaced away from the respective seat and the corresponding fluid connection is opened. In so doing, the reset force, which is exerted by the respective resetting device on the respective valve piston for movement in the direction of the respective seat, must typically be overcome. Once the actuation is complete, the valve piston is guided back to, and placed in contact with, the respective seat by the reset force exerted by the resetting device, which is typically designed as a spring element. 
     The respective actuation rod is advantageously guided in the respective valve piston. At least one actuator, which actuates at least one valve piston, is disposed on the respective actuation rod. That design of the directional poppet valve according to the invention is especially advantageous when a plurality of, for example, two valve pistons are actuated by a shared actuation rod. In the case of two valve pistons, which interengage as a pair, the actuation rod is typically guided through both valve pistons and has a first or front actuator and a second or rear actuator. Depending on the direction of movement of the actuation rod relative to the valve piston, each actuator abuts a first or front side respectively, or a second or rear side, respectively, of the pair, or of the respective valve piston. The actuators are fixedly attached to the actuation rod or connected thereto respectively, so that an actuation force can be transferred from the actuation rod to the respective valve piston by the actuator. 
     In an additional preferred embodiment of the invention, the actuation rods associated with the respective valve pistons are disposed in the valve housing such that they at least partially interengage. Especially preferred, a first actuator and a third actuator may be provided on an actuation rod to space first and third valve pistons away from a first or third seat, respectively. A second actuator and a fourth actuator may be provided on another actuation rod oriented in the opposing direction to space the second piston rod and the fourth piston rod away from a second seat or fourth seat, respectively. A first utility connection may be provided between the facing first and second seats for the first and second valve pistons, which interengage as a pair. A second utility connection may be provided between the facing third and fourth seats for the third and fourth valve pistons, which interengage as a pair. A supply connection or a tank connection may be provided between the second seat and the third seat. A tank connection or a supply connection, respectively, may be provided between the first seat or fourth seat, respectively, and the respective end of the valve housing. 
     In this embodiment, the actuation rods for a plurality of valve pistons are coupled with or to one another, respectively, such that two valve pistons are each moved or displaced upon the movement of the corresponding actuation rod, and a corresponding switch position of the directional valve is adjusted. Thus, with the actuation of the one actuation rod, a fluid connection from the supply connection to the second utility connection and an additional fluid connection from the first utility connection to the tank connection are opened. Accordingly, with the actuation of the other actuation rod, a fluid connection from the supply connection to the first utility connection and an additional fluid connection from the second utility connection to the tank connection are opened. The tank connection and supply connection may then be exchanged with one another. In a comparable arrangement, three and more utility connections may be connected to tank and supply connections. Actuation rods, which act on the valve pistons associated with the respective fluid connections or fluid ports, are then used. 
     According to the invention, various disclosed features may each be implemented individually or in any combination with one another. 
     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 a preferred embodiment of the present invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Referring to the drawings that form a part of this disclosure and that are schematic and not to scale: 
         FIG. 1  is a side view in section of a directional poppet valve according to an exemplary embodiment of the invention; and 
         FIG. 2  a circuit diagram the directional poppet valve of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  shows a section of a directional poppet valve  10  having a valve housing  12 . In the piston chamber  14  of a valve housing  12  a first valve piston  16 , a second valve piston  18 , a third valve piston  20  and a fourth valve piston  22  are disposed. The piston chamber  14 , having an elongated design, extends in the direction of an axis R, which simultaneously represents a rotational axis for the respective valve piston  16 ,  18 ,  20 ,  22 . The four valve pistons  16 ,  18 ,  20 ,  22  are disposed in an inline construction along the axis R. The first and the second piston valves  16 ,  18  as well as the third and the fourth piston valves  20 ,  22  are each disposed such that they interengage in pairs. The two pairs of in each case two valve pistons  16 ,  18 ;  20 ,  22  are sequentially disposed along the axis R in the piston chamber  14 . 
     A seat  17 ,  19 ,  21 ,  23  is assigned to each valve piston  16 ,  18 ,  20 ,  22 . Each seat  17 - 23  is formed as an annular surface that is rotationally symmetrical to the axis R, and delimits the front end of the respective receiving section of the piston chamber  14  to receive the one pair, comprising the first and second valve pistons  16 ,  18 , or the other pair, comprising the third and fourth valve pistons  20 ,  22 , respectively. In the non-actuated state shown, the valve pistons  16 ,  18 ,  20 ,  22  each abut the respective seat  17 ,  19 ,  21 ,  23 . The contact force needed therefor is applied in each case by a resetting device  34 A,  34 B, each of which is disposed within the valve pistons  16 ,  18 ;  20 ,  22 , which interengage in pairs, and guides these valve pistons towards and away from one another to the respective valve seat  17 ,  19 ;  21 ,  23 . An annular sealing device  36 A,  36 B is disposed between the valve pistons  16 ,  18 ;  20 ,  22  that are connected to one another in pairs. 
     Two actuation rods  24 A,  24 B are provided for the movement of the valve pistons  16 - 22 , which actuation rods are disposed along the axis R in the piston chamber  14 , and which interengage with one another in the region of the piston chamber  14 . The two actuation rods  24 A,  24 B are each part of an actuation device (not otherwise shown), which each exert an actuation force F A , F B  on the respective actuation rod  24 A,  24 B. The actuation force is oriented in one respective direction. To transfer the actuation forces F A , F B  from the actuation rods  24 A,  24 B to the respective piston  16 ,  18 ,  20 ,  22 , actuators  26 ,  28 ,  30 ,  32  are provided on the two actuation rods  24 A,  24 B. The front end of each of these actuators each act on the respective valve piston  16 ,  18 ,  20 ,  22 , to space these pistons away from the respective valve seat  17 ,  19 ,  21 ,  23 . In the embodiment shown in  FIG. 1 , the two pairs of valve pistons  16 ,  18 ;  20 ,  22  are disposed symmetrically to the (not shown) center plane of the piston chamber  14  or of the valve housing  12 , respectively. By an actuation force F A  directed towards the right in  FIG. 1 , the first valve piston  16  can be spaced apart from the first seat  17  by a first actuator  26 , and the third valve piston  20  can be spaced apart from the third valve seat  21  by the third actuator  30 . Accordingly, with an opposing actuation force F B  directed towards the left in  FIG. 1 , the second valve piston  18  can be spaced apart from the second seat  16  by the second actuator  28 , and the fourth valve piston  22  can be spaced apart from the fourth seat  23  by the fourth actuator  32 . The first and third actuators  26 ,  30  are disposed on the one actuation rod  24 A shown on the left in  FIG. 1 . The second and fourth actuators  28 ,  32  are disposed on the other actuation rod  24 B shown on the right in  FIG. 1 . 
     A tank connection T, a first utility connection A, a supply connection P, a second fluid connection B, and in turn, a tank connection T, are formed sequentially in the valve housing  12  along the piston chamber  14 , from left to right in  FIG. 1 . The first tank connection T and the first fluid connection A are controlled by the one pair comprising the first and second valve pistons  16 ,  18 , and accordingly, the second utility connection B and the second tank connection T are controlled by the other pair comprising the third and fourth valve pistons  20 ,  22 . The supply connection P, which is centrally disposed between the two pairs, is controlled by the adjacent second and third valve pistons  18 ,  20 . In the non-actuated state, shown in  FIG. 1 , of the corresponding switch position of the directional poppet valve  10 , respectively, all of the valve pistons  10 ,  18 ,  20 ,  22  abut the respective seat  17 - 23 , whereby the fluid connections A-T are separated from one another in as fluid-tight a manner as possible. Due to the symmetrical, uniform design of the valve pistons  16 ,  18 ,  20 ,  22 , of the valve seats  17 ,  19 ,  21 ,  23  as well as of the resetting devices  34 A,  34 B or of the respective reset force, the valve arrangement in a non-actuated state is force balanced. The non-actuated switch position of the directional poppet valve  10  is shown in the center of the circuit symbol from  FIG. 2 . 
     In the case of an actuation or movement of the one actuation rod  24 A, shown on the left in  FIG. 1 , which movement corresponds to an actuation force F A , the first and third valve pistons  16 ,  20  are spaced apart from the first or third seat  17 ,  21 , respectively. Accordingly, a fluid connection from the first utility connection A to the tank connection T as well as an additional fluid connection from the supply connection P to the second utility connection B are opened. By actuating or moving the one actuation rod  24 A, the resetting devices  34 A,  34 B are further compressed, whereby the respective contact pressure of the second and fourth valve pistons  18 ,  22  at the second or the forth seat  19 ,  23  is increased accordingly. A fluid connection from the supply connection P to the first utility connection A, as well as an additional fluid connection from the second utility connection B to the tank connection T remains blocked. The switch position of the directional poppet valve  10  that can be reached by an actuation force F A  is illustrated on the left in  FIG. 2 . At the end of the application of an actuation force F A , the two, first and third, valve pistons  16 ,  20  are guided back by the resetting devices  23 A,  34 B and abut the first or third seat  17 ,  21 . Accordingly, in addition to the actuators  26 ,  28 ,  30 ,  32 , the actuation rods  24 A,  24 B return to their respective placement or position in the non-actuated state. 
     In the case of an actuation or movement of the other actuation rod  24 B shown on the right in  FIG. 1 , the second and fourth valve pistons  18 ,  22  are spaced apart from the second and fourth seat  19 ,  23 . Accordingly, a fluid connection from the supply connection P to the first utility connection A, and an additional fluid connection from the second utility connection B to the tank connection T, are opened. By actuating the other actuation rod  24 B, the resetting devices or resetters  34 A,  34 B are compressed and consequently the respective contact pressure of the first and third valve pistons  16 ,  20  at the first or third seats  17 ,  21 , respectively, are increased. Also, the corresponding fluid connections, from the first utility connection A to the tank connection T, as well as from the supply connection P to the second utility connection B, are blocked. The switch position of the directional poppet valve  10 , corresponding to the actuation of the other actuation rod  24 B with the other actuation force F B , is shown on the right in  FIG. 2 . As can be readily observed in  FIG. 2 , the directional poppet valve  10  is a 4/3-directional poppet valve having three switch positions for fluid connections between four fluid connections A, B, P, T. At the end of the application of the other actuation force F B , the two, second and fourth, valve pistons  18 ,  22  are guided back by the resetting devices  34 A,  34 B and abut the second and fourth seat  19 ,  23 . Accordingly, in addition to the actuators  26 ,  28 ,  30 ,  32 , the actuation rods  24 A,  24 B return to their respective placement or position in the non-actuated state. 
     The directional poppet valve  10  shown in  FIG. 1  is a directly controlled valve. A pilot-controlled design of the directional poppet valve  10  according to the invention is also possible. The fluid pressure available at the supply connection P is typically present in the interior of the valve pistons  16 ,  18 ,  20 ,  22 , which interengage in pairs, of the interengaging or meshing actuation rods  24 A,  24 B respectively, and of the actuation devices (not otherwise shown). Depending on the position of the actuators  26 ,  28 ,  30 ,  32 , a positive or negative overlap of the control edges may be achieved. In addition, a tolerance compensation may be achieved by the actuators  26 ,  28 ,  30 ,  32  such that in a non-actuated state or in other words, in the central position, all valve pistons  16 ,  18 ,  20 ,  22  abut the respective seats  17 ,  19 ,  21 ,  23  and block the corresponding fluid connections. Depending on the requirements, additional sealing devices may be formed on the valve pistons  16 ,  18 ,  20 ,  22 . In the embodiment shown, the one actuation rod  24 A encompasses the other actuation rod  24 B up to the end of the rod  25 A on the opposing end of the piston chamber  14 . Accordingly, the other actuation rod  24 B extends into the one actuation rod  24 A, wherein the corresponding end of the rod is not shown in  FIG. 1 . 
     While one embodiment has 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.