Patent Publication Number: US-2012025115-A1

Title: Electromechanically actuated membrane valve for branching ducts of sprinkling and/or weed control systems

Description:
The present invention relates to an electromechanically actuated membrane valve, particularly for branching ducts of a fluid of sprinkling and/or weed control systems and the like. 
     BACKGROUND OF THE INVENTION 
     In the field of agriculture and, in particular, with regard to sprinkling techniques, it is known to use sprinkler machines designed to accurately distribute irrigation liquids over the ground, such as fertilizers, fluids for herbicide treatments, anticryptogamics, insecticides, pesticides, water and other liquids. 
     More precisely, sprinkler machines of the known type, which are generally fixed or pulled by a tractor that travels over the crop to be sprinkled, are basically constituted by a chassis supporting a tank filled with the fluid to be sprinkled and associated with a pumping assembly that supplies one or more sprinkler bars used to distribute the fluid. 
     Going further into detail, sprinkler bars of the known type, which can be of the horizontal type for herbaceous crops, vertical or arched for arboreal crops, are constituted by a supporting structure associated with the above-mentioned supporting chassis to which pipes for conveying the fluid to be sprinkled are fixed. 
     More specifically, the conveyance pipes, which are supplied by the pumping assembly by way of suitable valves for controlling and adjusting the flow, have a plurality of branching assemblies and assemblies for dispensing the fluid, each of which is provided with a respective shut-off valve with the functions of stopping and/or allowing the passage of fluid inside the branching assembly and, if the passage is to be stopped, of preventing dripping of the fluid. 
     Each branching assembly is constituted by an external duct and by an internal duct, which are mutually coaxial, between which an interspace is formed with the external duct connected, at one end, to the conveyance pipe from which it receives the fluid, whereas the internal duct is connected to means of dispensing the fluid constituted, for example, by one or more atomizer nozzles. 
     At the opposite end the two ducts, external and internal, are connected to each other and associated with a shut-off valve that is basically constituted by a blocking element alternately adapted to assume an open configuration, in which the fluid passes from the external duct to the internal duct and arrives at the atomizer nozzles, and a closed configuration, in which the two ducts are isolated from each other so that the fluid does not reach the nozzles. 
     Among the shut-off valves of the known type are spring-loaded valves, the function of which is substantially anti-drip, that are constituted by a disk-like membrane kept pressed against the ends of the ducts, internal and external, by a preloaded compression spring. 
     The fluid introduced into the interspace between the two ducts exerts a pressure on the membrane that is such as to overcome the resistance of the spring and thus move away the membrane, connecting the external duct with the internal duct. In this case we have valves that are directly actuated by the fluid. 
     Alternatively, pneumatically actuated piston valves are known, of the type that are normally open or normally closed, constituted by a cylinder inside which is a piston accommodated so that it can slide, in a straight and alternating motion, fitted at the head with a plug of the internal duct of the branching assembly. 
     In more detail, under the action of a flow of compressed air, the piston is caused to slide alternately between the open configuration, in which the plug is extracted from the internal duct which thus communicates with the external duct, and the closed configuration, in which the plug is protracted into the internal duct thus blocking it and preventing the passage of the fluid coming from the external duct. 
     Furthermore, pneumatically-actuated membrane valves are known of the type that is usually open or usually closed, that are constituted by a cylinder inside which a piston is mounted, so that it is able to slide in a straight and alternating motion, the head of which pushes a disk-like membrane to close the ends of the ducts, external and internal, of the branching assembly. 
     In this way, a flow of compressed air moves the piston between the open configuration, in which the membrane is spaced and the two ducts, internal and external, are connected, and the closed configuration, in which the membrane is kept pressed against the two ducts thus preventing their connection. 
     Membrane valves that are normally open, of the type described above, have a reaction spring that, in the absence of a flow of air, keeps the piston in the open configuration of the branching assembly, and air is introduced to bring it to the closed configuration. 
     Conversely, membrane valves that are normally closed have a reaction spring which, in the absence of a flow of air, keeps the piston in the closed configuration of the branching assembly, and air is introduced to bring it to the open configuration. 
     Finally, a third type of valve involves an actuation of the electromechanical type, for enabling a more instantaneous control of the opening and closing of the valve, in which for example, the plug of the valve is commanded to close and open by a solenoid. 
     These electromechanically actuated valves comprise a valve body, inside which an actuator is slidably associated, provided with a membrane plug for the duct for dispensing the fluid. 
     The actuator, generally of the metal type, is moved between an open configuration and a closed configuration of the duct by a solenoid, which, electrically excited, generates a magnetic field that is such as to attract the actuator and thus move it along the directional axis of action thereof. 
     For overcoming the drawback of having to provide metal actuators, with the constructive limitations that such materials involve, for reducing a further drawback deriving from the fact that the solenoids conventionally used are often not sufficient to move the actuator if high pressure levels are necessary for the dispensed fluid, solenoid valves of the known type have been developed which comprise a pressure plate having a first and a second hole with the actuator configured in such a way as to selectively block the first or the second hole. 
     Moreover, in solenoid valves of the known type a spring is provided that is adapted to move the plate away from the actuator so that the actuator uncovers the second hole thus allowing the fluid to pass through it. The closing of the first hole, which occurs at the same time as the opening of the second hole, prevents the fluid from expanding in the valve body. 
     With this contrivance, the pressure of the fluid is balanced on one side and on the other side of the plate thus allowing a decrease of the pressure exerted on the blocking element. 
     Electromechanically actuated valves of the known type are not devoid of drawbacks among which there is the fact that they are particularly complex, in that they are a combination of a plurality of constructive elements that are difficult to assemble, and in that they involve complicated calibration steps. 
     Moreover, a further drawback of electromechanically actuated valves of the known type consists in the fact that the need to have a through hole in the sealing element, i.e. the membrane, while on the one hand allowing the decreasing of the force that the solenoid has to exert to close the duct, on the other hand compromises the resistance of the membrane, thus drastically decreasing its useful lifetime and preventing the separation of the elements in motion and the elements responsible for the motion from the fluid to be dispensed, a fact that inevitably prejudices the operation and reliability of the valve over time. 
     Other valves of the known type involve the substitution of the membrane by a gasket ring, for example of the O-ring type, associated with the piston and protruding circumferentially therefrom, that blocks the duct by internally interfering therewith. 
     This solution, however, has the drawback of not ensuring a perfect seal and a separation of the elements in motion, i.e. the piston, and the elements responsible for the motion, i.e. the linear actuator, springs and others, from the fluid to be dispensed due to the absence of the membrane. 
     SUMMARY OF THE INVENTION 
     The aim of the present invention is to eliminate the above-mentioned drawbacks in the background art by providing an electromechanically actuated membrane valve, particularly for branching ducts of a fluid of sprinkling and/or weed control systems and the like, that makes it possible to ensure long-lasting and high efficiency of the sealing elements and, at the same time, a decrease in the force exerted to move the elements adapted to closing/opening the branching duct. 
     Within this aim, an object of the invention is to provide an electromechanically actuated membrane valve that enables considerable savings in terms of electricity absorbed for the operation thereof, especially in dispensing systems in which it is necessary to have a high number of valves, independent of each other and individually controlled. 
     Another object of the invention is to ensure, with the varying of the flows and pressures in play in the branched fluids, a force exerted to move the elements for the closing/opening of the branching duct that is substantially contained and relatively constant or, at the most, variable within a substantially limited range of force values. 
     A further object of the invention is to provide a valve that has low encumbrances, is easy to wire and assemble and is easily adapted to the applications in use and, therefore, universally usable. 
     Another object of the present invention is to provide an electromechanically actuated membrane valve, particularly for branching ducts of a fluid of sprinkling and/or weed control systems and the like, that has a simple structure, is easy and practical to implement, safe to use and effective in operation, and relatively low-cost. 
     This aim and these and other objects are all achieved by an electromechanically actuated membrane valve, particularly for branching ducts of a fluid of sprinkling and/or weed control systems and the like, comprising a hollow valve body which can be associated with an end portion of a branching duct of a fluid or the like and contains in its interior a piston adapted to interact with a disk-like membrane for blocking said end portion of said branching duct, said piston being movable with respect to said valve body between an open configuration and a closed configuration of said valve and said branching duct comprising an internal duct and an external duct which are mutually coaxial, characterized in that it comprises means for reducing the passage section of at least one of said internal duct and said external duct, which are associated with said valve body and adapted to interact with said disk-like membrane on the side opposite to said piston for the hermetic isolation of said external duct with respect to said internal duct and vice versa. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Further characteristics and advantages of the present invention will become more apparent from the description of two preferred, but not exclusive, embodiments of an electromechanically actuated membrane valve, particularly for branching ducts of a fluid of sprinkling and/or weed control systems and the like, illustrated for the purposes of non-limiting example in the accompanying drawings wherein: 
         FIG. 1  is a sectional side elevation view of a first embodiment of an electromechanically actuated membrane valve, particularly for branching ducts of a fluid of sprinkling and/or weed control systems and the like, according to the invention, in the closed configuration thereof; 
         FIG. 2  is an enlarged-scale view of a detail of the electromechanically actuated membrane valve shown in  FIG. 1 ; 
         FIG. 3  is an enlarged-scale view of a detail of the electromechanically actuated membrane valve shown in  FIG. 1  in the open configuration thereof; 
         FIG. 4  is a sectional side elevation view of a second embodiment of an electromechanically actuated membrane valve, particularly for branching ducts of a fluid of sprinkling and/or weed control systems and the like, according to the invention, in the open configuration thereof; 
         FIG. 5  is an enlarged-scale view of a detail of the electromechanically actuated membrane valve shown in  FIG. 4  in the closed configuration thereof; 
         FIG. 6  is an enlarged-scale view of a detail of the electromechanically actuated membrane valve shown in  FIG. 4  in the closed configuration thereof after a lowering of pressure of the intercepted fluid. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     With reference to the figures, an electromechanically actuated membrane valve, particularly for branching ducts of a fluid of sprinkling and/or weed control systems and the like, generally designated in the two embodiments proposed with the reference numerals  1   a  and  1   b , comprises an outer shell  5  accommodating inside it a hollow valve body  2  that is substantially cylindrical in shape with a circular base, associable with an end portion  3  of a branching duct  4  of a fluid of a sprinkling and/or weed control system or the like. 
     More precisely, the valve body  2  is associated with a threaded ferrule  6  that can be engaged on the end portion  3  of the branching duct  4  and has a threading complementary to that of the threaded ferrule  6 . 
     Moreover, the branching duct  4 , shown in the accompanying figures, is of the type that has an external duct  7  annular in cross-section and an internal duct  8  that is circular in cross-section. 
     The external duct  7  and the internal duct  8 , which are mutually coaxial with the latter inside the former, form, respectively, the supply duct and the drainage duct of the valves  1   a  and  1   b  and both converge in a communication chamber  9  formed inside the valve body  2 . 
     More precisely, the communication chamber  9  is delimited in an upper region by a disk-like membrane  10  interacting with a piston  11   a  or  11   b  contained inside the valve body  2  and movable with respect to it between two positions corresponding, respectively, to the closed configuration of the valves  1   a  and  1   b , in which the disk-like membrane  10  prevents communication between the external duct  7  and the internal duct  8 , and an open configuration of the valves  1   a  and  1   b , in which the external duct  7  and the internal duct  8  are in communication with each other. 
     As mentioned previously, the valves  1   a  and  1   b  are of the electromechanically actuated type and each comprises at least one electromechanical actuator  12 , which can be of the stepped motor type or of any other type of drive means belonging to the state of the art and designed to actuate electromechanical actuators, arranged inside the valve body  2  for moving the pistons  11   a  and  11   b  between the closed configuration and the open configuration of the valves  1   a  and  1   b.    
     More specifically, the movable element  13  of the electromechanical actuator  12  is directly connected to the piston  11   a  or  11   b  by means of a threaded coupling and, interposed between the piston  11   a  or  11   b  and a resting surface  14  formed by at least one of the electromechanical actuator  12  and the valve body  2 , first elastic means  15  are provided, consisting for example in a first helical spring, which operate, as will be described in detail hereinafter, to move the piston  11  away from the resting surface  14  so as to promote the movement of the piston  11   a  or  11   b  from the open configuration of the valve  1   a  or  1   b  to the closed configuration of the valve  1   a  or  1   b.    
     With reference to the second embodiment, shown in  FIGS. 4 to 6 , as will be better described hereinafter, for preventing unwanted dripping of the fluid intercepted by the valve  1   b , the piston  11   b  is provided by a first part  22  associated with the movable element  13  of the electromechanical actuator  12  and a second part  23  designed to engage the disk-like membrane  10 . 
     Advantageously, the first part  22  and the second part  23  are mutually associated by a mating of the snap-acting type with second elastic means  24  interposed consisting, for example, in a preloaded second helical spring adapted to send the second part  23  into contact with the disk-like membrane  10  thus closing the valve  1   b  after a lowering of the pressure of the fluid coming from the external duct  7  below a preset value of, for example, 0.5 bar. 
     Moreover, in both of the embodiments proposed, an aeration system is provided consisting in at least one venting hole  25 , preferably two on opposite sides, of small diameter, formed radially in the valve body  2  and adapted to put the inner chamber between the seal of the pistons  11   a  and  11   b  and the disk-like membrane  10  into communication with the outside, in such a way as to allow the escape of the pressurized air which the continuous movement of the two seals tends to create, thus preventing the pressurized air from compromising the linear movement of the disk-like membrane  10  or leading to the malfunctioning of the valves  1   a  and  1   b.    
     As concerns the control of the electromechanical actuator  12 , it is entrusted to means  16  of management and control of the electronic type which consist, for example, in an electronic card  17  associated with the valve body  2  and contained inside the outer shell  5 . 
     According to the invention, the valves  1   a  and  1   b  comprise means  18  of reducing the passage section of at least one of the internal duct  8  and the external duct  7 , which are associated with the valve body  2  and are adapted to interact with the disk-like membrane  10  on the side opposite to the piston  11  for the hermetic isolation of the external duct  7  from the internal duct  8  and vice versa. 
     Advantageously, these reduction means  18  comprise at least one perforated bushing  19  which can be inserted coaxially into the internal duct  8  and forms a service duct  20  the inside diameter of which is smaller than the inside diameter of the internal duct  8 . 
     Naturally, for ensuring a correct airtight seal of the valves  1   a  and  1   b , among the various elements that make it up there are seal elements  21 , such as O-rings and/or the like. 
     Operation of the electromechanically actuated membrane valves  1   a  and  1   b , particularly for branching ducts of a fluid of sprinkling and/or weed control systems and the like, is described below. 
     Depending on the type of electromechanical actuator  12  used, i.e. depending on whether in the inactive configuration the movable element  13  is extracted from the body of the electromechanical actuator  12  or accommodated therein, the valve  1  can be of the type that is normally closed or normally open. 
     Thus starting from the closed configuration of the valves  1   a  and  1   b  in which the disk-like membrane  10 , which is made of a rubber-like and elastically deformable material, is deformed under the action of the piston  11   a  or  11   b  to isolate the external duct  7  from the internal duct  8  and vice versa, the passage to the open configuration thereof occurs by way of the action of the electromechanical actuator  12  which, by making its movable element  13  retract, makes the piston  11   a  or  11   b  perform a translational movement away from the perforated bushing  19  thus allowing the disk-like membrane  10  to return to its initial, geometry thus uncovering the communication chamber  9  of the valve, with a consequent passage of fluid from the external duct  7  to the internal duct  8  by passing through the service duct  20 . 
     With regard to the first embodiment only, given the use for which the valve  1   a  is designed, in order to prevent unwanted dripping of the fluid, it is preferable, in the absence of electricity, for the movable element  13  to be arrangeable in its extracted position by the electromechanical actuator  12  so as to switch the valve  1   a  to its closed configuration, i.e. send the piston  11   a  into abutment with the perforated bushing  19  with the disk-like membrane  10  interposed between the two. 
     The anti-drip system just described can be implemented if the electromechanical actuator  12  is not of the stepped motor type. In fact, if an electromechanical actuator  12  of the stepped motor type is used, the movement of the movable element  13  of the electromechanical actuator  12  is made possible only by electrically actuating the electromechanical actuator  12 . 
     Differently, in the second embodiment, notwithstanding the use of stepped motors to provide the electromechanical actuator  12  in the valve  1   b , for preventing unwanted dripping of the fluid, even with the valve  1   b  switched to its open configuration as shown in  FIG. 6 , following a lowering of pressure, the second part  23  of the piston  11   b , under the thrust of the second elastic means  24 , overcomes the pressure exerted by the fluid and sends the disk-like membrane  10  into abutment against the perforated bushing  19  thus closing the valve  1   b.    
     Moreover, in both of the embodiments proposed, for further ensuring the state of closure of the valves  1   a  and  1   b , the movement of the pistons  11   a  and  11   b  is assisted by or, in a variation of the valves  1   a  and  1   b , for example if a solenoid motor is used, can be exclusively caused by the action of the first elastic means  15 . 
     In practice it has been found that the electromechanically actuated membrane valve, particularly for branching ducts of a fluid of sprinkling and/or weed control systems and the like, according to the present invention, fully achieves the set aim and objects in that it makes it possible to resolve the drawbacks of the known art by reducing the area of the membrane upon which the pressure of the fluid acts and therefore the thrust required of the electromechanical actuator and, consequently, the corresponding electrical absorption, while keeping to the standard sizing of the ducts. 
     Another advantage of the valve, according to the present invention, consists in that the first elastic means with which the valve is provided act in the direction of closure of the plug, thus further reducing the effort required. In the open state the thrust of the fluid cooperates with the action of the electromechanical actuator to compress the first elastic means. 
     A further advantage of the valve, according to the present invention, consists in that the geometry of the valve is such as to form a double end of travel for the piston: in closing to determine the squashing point of the membrane and prevent wear thereof, and in opening to have control over the point of arrest of the piston and to update the zero position of the stepped motors by means of the internal electronics. 
     Another advantage of the valve, according to the present invention, consists in that it provides an anti-drip system that enters into operation the moment when the pressure of the fluid to be intercepted falls below a threshold value. 
     The electromechanically actuated membrane valves, particularly for branching ducts of a fluid of sprinkling and/or weed control systems and the like, thus conceived, are susceptible of numerous modifications and variations, all of which are within the scope of the appended claims. 
     Moreover, all the details may be substituted by other, technically equivalent elements. 
     In practice the materials employed, provided they are compatible with the specific use, and the contingent dimensions and shapes, may be any according to requirements and to the state of the art. 
     The disclosures in Italian Patent Application No. MO2010A000218 from which this application claims priority are incorporated herein by reference.