Abstract:
A flexible diaphragm for an irrigation system includes a core layer and at least one protective layer formed on the core layer. The core layer may have specific chemical and physical properties, and the protective layer may be formed of specific materials.

Description:
RELATED APPLICATIONS 
       [0001]    The present application claims priority to U.S. Provisional Application No. 60/950,748, filed Jul. 19, 2007, whose contents are incorporated by reference in their entirety. 
     
    
     BACKGROUND 
       [0002]    The present disclosure relates to diaphragms and in particular to diaphragms used in irrigation systems. 
         [0003]    An example of such a diaphragm can be found in U.S. Pat. No. 6,568,607 which describes a drip irrigation emitter with a diaphragm that is assembled inside a conduit. An increase of water pressure in the conduit deforms the diaphragm which in turn affects the flow of water available for dispersion through exist holes in the conduit. 
         [0004]    Water used for irrigation may contain substances like chlorine chloramines, organic contaminants and/or surface active agents which may damage such diaphragms. 
       SUMMARY 
       [0005]    In one aspect, the present invention is directed to a flexible diaphragm for an irrigation system. The flexible diaphragm includes a core layer and at least one protective layer formed on the core layer. 
     
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         [0006]    Exemplary embodiments are illustrated in referenced figures. It is intended that the embodiments and figures disclosed herein are to be considered illustrative, rather than restrictive. The disclosure, however, both as to organization and method of operation, together with objects, features, and advantages thereof, may best be understood by reference to the following detailed description when read with the accompanying figures, in which: 
           [0007]      FIG. 1  shows a cross sectional view of a drip irrigation emitter incorporating a diaphragm in accordance with the present disclosure; 
           [0008]      FIG. 2  shows an enlarged cross sectional view of the diaphragm; and 
           [0009]      FIG. 3  shows a block diagram of a method for forming the diaphragm. 
       
    
    
       [0010]    It will be appreciated that for simplicity and clarity of illustration, elements shown in the figures have not necessarily been drawn to scale. For example, the dimensions of some of the elements may be exaggerated relative to other elements for clarity. Further, where considered appropriate, reference numerals may be repeated within the figures to indicate like elements. 
       DETAILED DESCRIPTION 
       [0011]    The contents of aforementioned U.S. Pat. No. 6,568,607 are incorporated by reference to the extent necessary to understand the present invention. 
         [0012]    Attention is first drawn to  FIG. 1 . A drip irrigation emitter  10  has an inlet  12 , an outlet  14  and a flow path  16  therebetween. A flexible diaphragm  18  which is located in the drip emitter  10  communicates with fluid passing via the flow path  16  to regulate the flow of fluid exiting the emitter  10  via the outlet  14 . As seen in  FIG. 1 , the flexible diaphragm  18  is optionally positioned within the emitter  10  between the inlet  12  and the outlet  14  such that a fluid passing through the emitter  10  is forced to bear against the flexible diaphragm  18 . The drip emitter  10  may be integrally or releasably attached to a conduit (not shown) in such a way that its inlet  12  is in fluid communication with the fluid passing through the conduit. Optionally, the emitter  10  is integrally bonded to the conduit. 
         [0013]    It should be noted that the drip irrigation emitter  10  is only one example of an irrigation element that may utilize the diaphragm  18  in accordance with the present disclosure. Other non-limiting examples may include sprinklers, anti-drip valves or pressure regulators. In addition it is noted that the diaphragm  18  in accordance with the present disclosure may be utilized for functions other than regulating fluid flow. For example, the diaphragm  18  in accordance with the present disclosure may be used to seal a portion of an irrigation element. 
         [0014]    Attention is draw to  FIG. 2 . The diaphragm  18  has a core layer  20  that is encompassed between external protective layers  22  that contact the fluid in the irrigation element  10 . The core layer  20  is a polymer and/or compounds thereof, having a shore A hardness as measured at 20-25 degrees Celsius of between 30 to 85 and a thickness of between 100 micron to 5 millimeter. The core layer  20  is characterized by 2 percent secant flexural modulus, according to ASTM D790, of about 0.1 to 100 Mpa. 
         [0015]    The core layer  20  may be formed from silicone, polyurethane, ethylene-propylene copolymers and terpolymers, ethylene-alpha olefin copolymers and terpolymers, ethylene-vinyl acetate, ethylene-acrylic (or methacrylic) ester copolymers and terpolymers, polysulfide, nitrile rubber, butadiene rubber, chlorinated rubber, natural rubber, SBR rubber, Styrene-butadiene-styrene (SBS), styrene-ethylene/butylene-styrene (SEBS), polyisoprene rubber (IR), thermoplastic vulcanizates (TPV), thermoplastic olefins (TPO), ionomer, polyether-block amide (PEBA), polyester, and any mixture thereof. In addition, the core  20  layer may comprise fillers, extenders, nano-size particles including nano-clays, plasticizers, processing aids, pigments, stabilizers, antioxidants, antiozonats, carbon black, oils, plasticizers and reinforcing particles and fibers. The polymer may be thermoplastic or cross-linked (thermoset). 
         [0016]    The protective layers  22  are optionally deposited or applied on the core layer  20  using methods such as sputtering, Sol-gel, co-extrusion, melt coating, solvent-borne coating, 100% solid coatings, water borne coating, Chemical-vapor-deposition (CVD), or Physical-vapor-deposition (PVD). Optionally, the protective layer  22  is deposited on the core layer  20  using a plasma assisted deposition (referred to hereinafter as PAD) method. The plasma is generated by direct or alternate current. The plasma acts to implant its deposited compounds into the core layer  20  chains to thus form adhesion between the protective and core layers  20 ,  22 . 
         [0017]    Attention is drawn to  FIG. 3 . In the PAD method the following steps are optionally followed. A carrier inert gas such as Argon or Nitrogen is mixed with a gaseous compound such as FREON™ or Silicon tetra chloride, a monomer such as styrene, an ethylene or tetra ethoxy silane, or an oligomer such as silicone oil, that is a precursor for the protective layer. The precursor may be solid, liquid or gas at ambient pressure and temperature and may be selected in a non limiting example from silicone halides such as silicone tetra chloride, silicone alkoxides such as tetra ethoxy silane (TES), and titanium halides and alkoxides, zirconium halides and alkoxides, aluminum halides and alkoxides, fluorine atom containing molecules such as tetra fluoro carbon, FREON™. Optionally, the carrier and precursor are heated prior to mixing, during mixing or after mixing; in order to avoid phase separation. 
         [0018]    The mixture is then transferred to an excitation module (referred to hereinafter as EXTM). The EXTM which is provided with electrical power activates and transforms the mixture into reactive-plasma which is then forced out of the EXTM through a slot or nozzle toward the core layer  18 . The combination of reactive compounds in the reactive-plasma and the chemical nature of the compounds provide a dense, impermeable and optionally pin-hole free layer which is characterized by good adhesion to the core layer  20 . The layer is usually cross linked by a process known in the art as plasma-polymerization which provides the layer with its chemical resistance and impermeability. 
         [0019]    It is noted that the protective layer  22  has a thickness of up to 500 micron. In a protective layer  22  formed by a plasma based production method, the thickness is typically smaller and may reach a magnitude of several microns. 
         [0020]    In the plasma based production methods, the protective layer  22  is a combination of a layer derived from the plasma ingredients and a hybrid layer which consists partly of the reactive-plasma and the core layer  20 . The protective layer  22  therefore is characterized as having a higher concentration of atoms selected from silicon, titanium, aluminum, zirconium, fluorine, chlorine and combinations thereof, relative to the concentration of the same atoms in the middle of the core layer  20 . 
         [0021]    Once the diaphragm  18  is formed, to form the emitter  10  seen in  FIG. 1 , one provides a first portion in which the inlet  12  is formed, a second portion in which the outlet  14  is formed, places the diaphragm  18  between the two portions, and press fits or otherwise joins the two portions such that the diaphragm  18  is captured between the two portions. 
         [0022]    The inventors have performed theoretical studies of the efficiency of the protective layer  22  to protect the core layer  20  of the diaphragm  18  from substances that may be found in fluid used in irrigation. The studies indicate that the permeability or sensitivity of a core layer  20  that is deposited by a protective layer  22  to chlorine ions is between 0.01 to 80 percent of the permeability or sensitivity of a similar core layer  20  without a protective layer  22  to similar ions, as measured at 20-25 degrees Celsius in aqueous medium. The studies in addition indicate that the permeability or sensitivity of a core layer  20  that is deposited by a protective layer  22  to iso-octane is between 0.01 to 80 percent of the permeability or sensitivity of a similar core layer  20  without a protective layer  22  to iso-octane, as measured at 20-25 degrees Celsius. 
         [0023]    In the description and claims of the present application, each of the verbs, “comprise” “include” and “have”, and conjugates thereof, are used to indicate that the object or objects of the verb are not necessarily a complete listing of members, components, elements or parts of the subject or subjects of the verb. 
         [0024]    Although the present embodiment has been described to a certain degree of particularity, it should be understood that various alterations and modifications could be made without departing from the scope of the disclosure as hereinafter claimed.