Abstract:
A pre-manufactured fiberglass reinforced plastic (“FRP”) tank may be fitted with one or more conical internal diffuser plates (also termed nozzle plate, filtration plate, or chamber separator plate). To insert the diffuser plate into the FRP tank, a plastic liner is cut perpendicular to the axis of the tank and along the tank sidewall so as to allow complete access to the inside of the tank. The cut results in two opposing and substantially equal surfaces that mate with weld grooves on the diffuser plate. The first opposing face is welded to the mating weld groove on one side of the diffuser plate while the other opposing face is welded to the mating weld groove on the other side of the diffuser plate. The weld creates a hermetic seal between the interior of the tank and the exterior along both welds. The FRP tank may be cut a second time, or more times, to install additional diffuser plates as required. Each diffuser plate has a wall section that now becomes an extension of the tank sidewall and completes the liner. One or more riser tubes can be installed through central openings in the diffuser plate(s) to provide for ingress and egress of liquid from the FRP tank.

Description:
RELATED APPLICATIONS 
       [0001]    In addition to the patent applications cited herein, each of which is incorporated herein by reference, this patent application is related to and claims priority to U.S. Provisional Patent Application No. 61/312,398, filed on Mar. 10, 2010, entitled “Water Treatment Pressure Vessel Having Internal Conical Distributor Plates,” the entire disclosure of which is incorporated herein by reference. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention relates generally to a fiberglass reinforced plastic (“FRP”) pressure vessel made with a plastic liner and having internal diffuser plates. The invention is generally used for residential and commercial water treatment, water conditioning, and filtration of fluids. 
       BACKGROUND OF THE INVENTION 
       [0003]    FRP vessels have long been the standard means for water containment in water treatment, conditioning and filtration applications. FRP tanks are manufactured by several methods with the primary method being termed as “blow mold and wind” methodology. This is the process by which a plastic bottle or liner is blow molded to the required size and configuration and then reinforced for pressure capability by fiberglass filament winding. The continuous strand fiberglass is impregnated with an epoxy resin that serves as the binder between the fiberglass and the tank. The fiberglass is wound around the exterior of the tanks in a controlled method. The amount and pattern by which the fiberglass is applied determines the ultimate performance of the pressure vessels in terms of strength and durability. 
         [0004]    Other less utilized techniques for making a FRP pressure vessel center around the various methods for making the plastic liner. They include rotational molding, split shell injection molding, and the welding of injection molded end caps to an extruded sidewall. In all cases, the final plastic bottle is wound with fiberglass to achieve the strength requirements. 
         [0005]    The plastic bottle needed for use in the intended applications may have numerous openings. At a minimum, the tank will have one axial opening for the attachment of control valves or other connections for getting fluid in and out of the tank. The size of that opening can vary but in all cases it is smaller than the diameter of the tank. The size of the opening restricts access into the tank thereby limiting the installation of features and accessories. 
         [0006]    One of the most desirable accessories is what is called a diffuser plate. Other names associated with a diffuser plate may be nozzle plate, filtration plate, or chamber separator plate. FRP tanks not having an internal diffuser plate have what is called a filter basket in its place. The purpose of the filter basket is to separate the clean fluid from the solid filter media. The filter basket comes in many designs but generally is small so it can be installed in the center of the bottom of the FRP tank. The filter basket is attached to a riser tube, which is a connection between the control valve and the filter basket. All water injected into or drawn from the FRP tank travels through the filter basket and the riser tube. During the cycling of a water softener, water travels through the filter media to perform the softening or cleaning process required. 
         [0007]    With the market introduction in 2002 of a tank construction method by which injection molded end caps are welded to an extruded sidewall tube, the industry has started to demand FRP tanks with internal features and accessories. There is a need in the art for more efficient and/or better internal features of a FRP tank. 
       BRIEF DESCRIPTION OF THE INVENTION 
       [0008]    In one embodiment, the present invention provides a pressure vessel or tank that includes a plastic liner with at least one axial opening, is typically reinforced with continuous strand fiberglass, and has at least one conical internal diffuser plate. The plastic liner may be made of any thermoplastic material suitable for use in potable water applications. 
         [0009]    In another embodiment, the present invention provides a tank, such as an FRP tank, with a conical internal diffuser plate (also termed nozzle plate, filtration plate, or chamber separator plate). To insert the diffuser plate into the tank, a plastic liner is cut perpendicular to the axis of the tank and along the tank sidewall so as to allow complete access to the inside of the tank. The cut results in two opposing and equal surfaces that mate with weld grooves on the diffuser plate. The weld grooves may each be in a substantially U-shaped configuration with inner and outer weld walls and a connecting bottom, or any other similar shape for guiding and connecting opposing face walls. The first opposing face is welded to the mating weld groove on one side of the diffuser plate while the other opposing face is welded to the other side of the diffuser plate. The weld creates a hermetic seal between the interior of the tank and the exterior along both welds. The diffuser plate has a wall section that now becomes an extension of the tank sidewall and completes the liner. As a result, the tank liner is divided into two separate chambers and the top chamber can be filled with filter media. 
         [0010]    In a further embodiment, the present invention provides a tank with multiple conical internal diffuser plates. As an example of a method to produce a tank with two conical diffuser plates, a plastic liner that already has an internal diffuser plate installed as described above again is cut perpendicular to the axis in any location along the sidewall of the tank. The cut results in two opposing and equal surfaces that mate with weld grooves on the diffuser plate. The first opposing face is welded to the mating weld groove on one side of the diffuser plate while the other opposing face is welded to the other side of the diffuser plate. The weld creates a hermetic seal between the interior of the tank and the exterior along both welds. The diffuser plate has a wall section that now becomes an extension of the tank sidewall and completes the liner. As a result, the tank liner is divided into three separate chambers. The top chamber can be filled with one filter media and the middle chamber can be filled with another filter media. One can envision that the present invention also provides tanks with more than one or two conical internal diffuser plates, such as three, four, five, or however many conical diffuser plates are required for the function of the tank. 
         [0011]    The present invention provides a conically shaped diffuser plate with slotted openings radiating from the diffuser plate center and molded into the diffuser plate. The spacing and amount of slotted openings can be graduated with the greater amount of openings located towards the outside circumference of the diffuser plate. Having the spacing and amount of slotted openings graduated with the greater amount of openings located towards the outside circumference of the diffuser plate facilitates fluid migration to the outer rings due to the greater passage openings towards the outside of the tank. In a preferred embodiment, the slotted openings may have a maximum gap of approximately 0.010 inches. The conical shaped diffuser plate may have ribbing to add sufficient strength for supporting filtering media. The conically shaped diffuser plate may have tapered wall guides that position the plastic liner wall into the weld groove. 
         [0012]    The present invention provides a means for attaching a riser tube extension when a second diffuser plate is installed into a plastic liner. This diffuser adapter or pipe fitting male adapter may be constructed of plastic or any other kind of material allowing it to function in aiding the installation of a second diffuser plate. The second diffuser plate is installed in the same manner as the first diffuser plate and is located higher in the tank than the first diffuser plate. The second diffuser plate is similar to the first installed diffuser plate with the exception of the centrally located opening. The opening on the second diffuser plate is larger than the first diffuser plate. When using the second diffuser plate, the riser tube with the pipe fitting male adapter is attached to the first diffuser plate and may be shorter than the position of the second diffuser plate, alternatively the lower riser tube may extend through and above the position of the second diffuser plate. Installation of the lower riser tube may be completed after the cut for the second diffuser plate is made and prior to the welding of the second diffuser plate, alternatively, the lower riser tube may be installed after the installation of the second diffuser plate, e.g., after the welding of the second diffuser plate. A second upper riser tube assembly is made using a threaded diffuser adapter that has a mating thread to the thread in the second diffuser. The diffuser adapter may be glued to the upper riser tube and then attached to the second diffuser plate. A mating pocket on the bottom of the diffuser adapter engages the lower riser tube creating a complete passage from the control valve to the bottom chamber. 
         [0013]    In another aspect, the present invention provides methods for installing into the plastic liner at least one diffuser plate generally located towards the bottom of the tank. The plastic liner is cut perpendicular to the axis of the tank and along the tank sidewall so as to allow complete access to the inside of the tank. The cut results in two opposing and equal surfaces that mate with weld grooves on the diffuser plate. The first opposing face is welded to the mating weld groove on one side of the diffuser plate while the other opposing face is welded to the other side of the diffuser plate. The weld creates a hermetic seal between the interior of the tank and the exterior along both welds. The diffuser plate has a wall section that now becomes an extension of the tank sidewall and completes the liner. As a result, the tank liner is divided into two separate chambers with the ability to fill the top chamber with filter media. These methods can be employed with conical shaped diffuser plates as well as diffuser plates with other shapes. For example, a flat bottomed diffuser plate can also be inserted into a FRP tank using the methods of the present invention. 
         [0014]    The present invention also provides methods for attaching the riser tube to a centrally located opening in the diffuser plate. A standard plastic male pipe fitting adapter is glued to the riser tube and then threaded into the corresponding threads located in the central opening of the diffuser plate. The riser tube is generally long enough to extend to the opening of the tank and mate with a control valve. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0015]      FIG. 1  illustrates an external view of an FRP tank; 
           [0016]      FIG. 2  illustrates an FRP tank cut perpendicular to its axis and two exposed opposing faces of each side of the cut; 
           [0017]      FIG. 3  illustrates a conical-shaped diffuser plate and the integral weld groove; 
           [0018]      FIG. 4  illustrates a conical-shaped diffuser plate inserted into the FRP tank and welded in place; 
           [0019]      FIG. 5  illustrates an FRP tank with the outer weld guide removed; 
           [0020]      FIG. 6  illustrates an FRP tank with an inserted diffuser plate and riser tube; 
           [0021]      FIG. 7  illustrates an FRP tank with a second cut to install a second conical diffuser plate and riser tube; 
           [0022]      FIG. 8  illustrates an FRP tank with a second conical diffuser plate installed; 
           [0023]      FIG. 9  illustrates an FRP tank with the outer weld guide removed from a second conical diffuser plate; 
           [0024]      FIG. 10  illustrates an FRP tank with two conical diffuser plates and an integrated riser tube; 
           [0025]      FIG. 11  illustrates an FRP tank with installed diffuser plate and riser tube and filter media; and 
           [0026]      FIG. 12  illustrates an FRP tank with multiple installed diffuser plates, a riser tube and multiple filter media. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0027]    The present invention relates to achieving a cost effective and improved method for installing internal diffuser plates into a tank, such as an FRP tank. In order to install diffuser plates into a plastic liner, there must be access inside the plastic liner prior to applying the continuous strand fiberglass reinforcement. One way to achieve this in the prior art is by fabricating the plastic liner in segments such as the molding of end caps, extruding a pipe-like sidewall and welding the components together to form a liner. This method requires significant investment in equipment and tooling to fabricate the numerous sizes and has a higher cost to manufacture than other alternatives. 
         [0028]    Another way to install diffuser plates into a plastic liner in the prior art is to mold the bottle shaped liner as one piece and, using complex processes, mold the diffuser plate into the solid bottle during the molding process. This method requires extremely complex equipment and set-up operations that interrupt synchronous production operation. Additionally, the ability to locate the diffuser plate on demand is compromised as is the ability to add multiple diffuser plates. Manufacturing flexibility is limited because manufacturing equipment must be dedicated to making either type of tank, thus causing difficult production scheduling issues, increased delivery lead-times, and the carrying of inventory. 
         [0029]    Recognizing the shortcomings of the prior art, the improved methods of the present invention allow the ability to take pre-molded plastic liners that are readily available and in production, and modify them as needed to meet customer demand. Pulling a liner out of the standard production process and customizing it according to a customer&#39;s demands is more efficient than setting up manufacturing equipment for each customized version. Having the ability to cut the pre-existing plastic liner at any position on the tank gives maximum flexibility to the manufacturing process. Interruptions are eliminated because operations can build FRP products with a diffuser plate and an infinite number of variables on demand and at the lowest cost. 
         [0030]    Another cost effective feature of the present invention is that by having the diffuser plate located on the sidewall portion of the tank, there is a significant reduction in diffuser plate tooling expense. Locating the bottom diffuser plate in the lower dome portion requires a plate that is a size smaller than the outer diameter of a FRP tank. Making a FRP tank with both a bottom and an upper diffuser plate would require the fabrication of two different plate diameters thus requiring two different tooling sets. The present invention allows the use of one basic plate with a different center opening. 
         [0031]    Another purpose of the present invention is to offer a diffuser plate that is less susceptible to manufacturing defects and long-term material strength and fatigue issues. The attachment of a diffuser plate to the inside wall of a plastic liner puts significant stress and fatigue loads onto the welded connection. The filter media that the diffuser plate must support is extremely heavy and an inside wall weld is placed in shear load. This heavy load, coupled with the fact that FRP tanks expand and contract significantly during cycling, makes the weld susceptible to failure. 
         [0032]    The present invention uses the diffuser plate as an extension of the sidewall when welded to the opposing faces of the cut plastic liners. Axial loads on the weld and the actual diffuser plate are reduced since the plate is integrated into the tank sidewall. Additionally, if a diffuser plate with a conical shape is used for the methods of the present invention, the conical shape of the diffuser plate acts as a flexible membrane to absorb any expansion and contraction loads during tank cycling. Conversely, flat plates of the prior art see high stress loads on the plate itself and the inside weld during tank cycling making the plate and weld susceptible to plastic fatigue. Additionally, having a diffuser plate with a conical shape maximizes tank volume by extending into the dome area of the tank, thus using the available tank space more efficiently. Prior art flat plates leave excess space under the plate which wastes tank capacity, and in the end may result in the need for a larger tank. 
         [0033]    Another purpose of the present invention is to offer a simplified process for filling and servicing a tank utilizing multiple diffuser plates. When filling a standard single diffuser plate FRP tank, the open end of the riser tube is simply plugged and the media is poured into the tank. In order to fill the lower chamber of a multi-plate FRP tank, the filtering media needs to go through the center of the upper plate. Therefore, the filter media intended to fill the lower chamber has to bypass the upper plate. In prior art FRP tanks that have a flat plate, simply pouring the filter media into the top opening would not work because the filter media would be caught on the upper plate. One way to avoid this problem is to insert a special tube to circumvent the upper plate and funnel the filter media to the lower chamber. The present invention provides a solution to this problem by using a conical shaped diffuser plate which acts as a funnel to assure that all filter media is in the lower chamber. In this case, no additional tools or special equipment are required. 
         [0034]    Additionally, capping off the center opening of the upper diffuser plate is necessary in a multi-plate FRP tank. Having a threaded adapter that is directly attached to the upper riser tube allows ease of closure and ease of connection to the lower riser tube without any special equipment or tools. This is in contrast to prior art multi-plate FRP tanks where the center cap is of a snap fit design, requiring a special tool to install or remove the cap for future servicing. 
         [0035]    Still another purpose of the present invention is to improve the efficiency of a water treatment system by increasing the effectiveness of the filtering media. In water treatment applications that use a traditional riser tube basket as the means for dispersing the fluid flow, there can be a dead zone of water flow through the filter media. This is because in general, fluid will flow to the path of least resistance, such as from high pressure to low pressure. Specifically, a water column inside a tall FRP tank, such as that of the prior art, has the lowest resistance to water flow towards the center of the column. As water exits the riser tube basket, it immediately seeks low pressure towards the center of the tank. As the fluid flows in either an upward or downward direction, it gravitates to the center of the tank until it reaches a balanced pressure. Fluid starting at the bottom will gradually flow outward as it approaches an equal pressure towards the surface. In reverse flow, fluid will equally disperse on the surface and gravitate inward to the low pressure point of the riser basket. The present invention, which employs a diffuser plate having a conical shape, spreads the dispersion of the fluid across the tank diameter so that a greater amount of filtering media is utilized. Further, the graduated slots in the diffuser plate of the present invention levels out the pressure at the face of the diffuser plate so that fluid flows uniformly through the diffuser plate. Additionally, the conical shape of the diffuser plate helps move the outbound fluid higher in the filter media so that it will remain towards the outer wall of the tank and be less susceptible to seeking the low pressure center column. 
         [0036]    Turning to  FIG. 1 , this represents a horizontal exterior view of a cylindrical tank  10 , such as an FRP tank. The tank  10  may be a pre-manufactured tank suitable for any filtration purpose. By way of example, the tank may be a tank used in a water filtration apparatus such as a water softener used in homes or businesses to filter out minerals and other undesirable chemicals from a ground water source and supply the filtered water to occupants and tenants of the home or business. 
         [0037]    Turning to  FIG. 2 , this represents a horizontal exterior view of a cylindrical tank  10  that has been cut to accommodate the insertion of an item to the interior of the tank  10 . The cut is made at a 90-degree angle  12  to the central axis  14  of the tank  10 , extending through the entire tank  10 . When complete, the cut separates a desired portion of the tank  10  completely and produces a first opposing face  16  and second opposing face  18  of the side wall of the tank  10 . The first opposing face  16  and second opposing face  18  are substantially mirror image sections of the same cut and may provide highly secure weld points when reconstructing the tank  10 . 
         [0038]    Turning to  FIG. 3 , this represents a conical shaped diffuser plate  30  to be inserted in a tank  10 . The conical shaped diffuser plate  30  having a weld guide  32  with a first weld groove  34  and a second weld groove  36  for attachment to the sidewall of the tank. The conical shaped diffuser plate  30  has a centrally located opening  38  having a threaded portion. The conical shaped diffuser plate  30  typically has radiating slots that increase in frequency towards the outer perimeter of the diffuser plate  30 . The first weld groove  34  and the second weld groove  36  are on opposing sides of the weld guide  32  and may be used to position the opposing faces of the tank portions into the weld grooves to form first and second weld joints. It is envisioned that the first and second weld grooves  34 ,  36  of the weld guide  32  may be in a substantially U-shaped configuration with inner and outer weld walls and a connecting bottom for guiding and securing of the opposing face cuts, as depicted in  FIG. 3 . In an alternative embodiment, the weld grooves may only comprise the inner weld wall and bottom (and not the outer weld wall) for guiding and securing of the opposing face cuts. Other configurations of the weld grooves are also envisioned. 
         [0039]    Turning to  FIG. 4 , this represents an exemplary positioning of the conical shaped diffuser plate  30  when it has been welded within the tank  10 . The conical shaped diffuser plate  30  is positioned between the first opposing face  16  and the second opposing face  18  cuts. The centered opening in the diffuser plate  30  is aligned with the central axis of the tank  10  with the weld grooves on the diffuser plate  30  aligned with the opposing face cuts. With the opposing face cuts aligned with the weld grooves, a first weld joint secures the first opposing face to the diffuser plate and a second weld joint secures the second opposing face to the diffuser plate such that the tank sections are securely connected to the diffuser plate with the weld guide of the diffuser plate forming a portion of the exterior wall of the tank  10 . 
         [0040]    Turning to  FIG. 5 , this represents an exemplary view of the tank  10  with the conical shaped diffuser plate  30  fully welded into position within the tank  10 . The weld guide  32  has been completely incorporated into the sidewall  50  of the tank  10 , forming a smooth, strong weld junction between the wall of the tank  10  and the conical shaped diffuser plate  30 . The outer portion of the weld guide  32  that extends past the exterior wall of the tank  10  can be removed, preserving the smooth exterior of the tank (in an alternative embodiment, only the inner weld wall and bottom are present initially, so any outer weld wall and outer portion does not need to be removed). The conical shaped diffuser plate  30  serves as an extension of the sidewall when welded to the opposing faces of the cut tank  10 . Axial loads on the weld and the actual conical shaped diffuser plate  30  are reduced since the plate is integrated into the tank  10  sidewall. Additionally, if a diffuser plate with a conical shape is used as in this exemplary configuration, the conical shape of the diffuser plate acts as a flexible membrane to absorb any expansion and contraction loads of the tank sidewall during tank cycling. 
         [0041]    Turning to  FIG. 6 , this represents an exemplary view of the tank  10  with a riser tube  60  inserted into the conical shaped diffuser plate  30  through the use of plastic pipe fitting adaptor  62 . The riser tube  60  performs the connection between the control valve and the conical shaped diffuser plate  30 . All liquid injected into or drawn from the tank  10  travels through the conical shaped diffuser plate  30  and the riser tube  60 . The conical shaped diffuser plate  30  thus provides the separation between a filter medium in the tank and the liquid being filtered. 
         [0042]    Turning to  FIG. 7 , this represents an exemplary view of the preparation for the installation of an additional equipment item in the tank  10  into which a first conical shaped diffuser plate  30  and riser tube  60  have been installed. A second cut of the FRP tank  10 , once again at 90 degrees to the central axis of the FRP tank  10 , has been performed, separating the tank into two portions each with an opposing face ( 70 ,  72 ) of the cut. The riser tube  60  has been shortened and forms the bottom riser tube  62  (as shown in  FIG. 8 ) upon the installation of additional equipment. 
         [0043]    Turning to  FIG. 8 , this represents the installation of a second conical shaped diffuser plate  80  in the tank  10 . The installation of the second conical shaped diffuser plate  80  is performed by first aligning the bottom weld groove of the weld guide of the second conical shaped diffuser plate  80  with the opposing cut face of the bottom portion  82  of the tank  10 . The second conical shaped diffuser plate  80  is then welded to the bottom portion  82  of the tank  10 . 
         [0044]    Turning to  FIG. 9 , this represents the attachment of the top portion  84  of the tank  10 . The opposing cut face of the top portion  84  is aligned with and inserted into the top weld groove of the weld guide and then welded to the top portion  84  of the tank  10 . Once again, the weld guide may extend beyond the sidewall of the tank  10 . The extended portion of the weld guide may be removed to produce a smooth exterior wall  86 , with the second conical shaped diffuser plate  80  securely connected to the tank  10 . 
         [0045]    Turning to  FIG. 10 , this represents the completion of the installation of the second conical shaped diffuser plate  80 . With the weld complete and holding the second conical shaped diffuser plate  80  securely in place, an upper riser tube  90  is installed to allow the flow of liquid into and out of the tank  10 . The upper riser tube  90  is inserted through an opening in the center of the second conical shaped diffuser plate and attached to the bottom riser tube  62  through the use of a diffuser adaptor  92  that connects the upper riser tube  90  to the bottom riser tube  62  with a waterproof seal. The second conical shaped diffuser plate  80  central opening is also adapted to permit the flow of filter media from the upper chamber formed by the installation of the second conical shaped diffuser plate  80 , into the bottom, or lower, chamber that has the first conical shaped diffuser plate  30  as the base of the lower chamber. The conical shape of the diffuser plate permits filter media poured into the top of the tank  10  to flow down the sloped sides of the diffuser plate, through the adapted central opening of the diffuser plate, and down into the lower chamber. The filter media intended for the lower chamber may be poured into the tank prior to the installation of the upper riser tube  90 . Capping off the center opening of the upper diffuser plate is necessary in a multi-plate tank  10 . Having a threaded adapter that is directly attached to the upper riser tube allows ease of closure and ease of connection to the lower riser tube  62  without any special equipment or tools. In this example, a tank  10  having two chambers, each with potentially a different filter medium installed may be easily manufactured and assembled. 
         [0046]    Turning now to  FIG. 11 , this figure presents an exemplary view of a tank  10  having a single conical shaped diffuser plate  30  and configured and prepped for use as a water softener. The filter media  110  is emplaced within the tank  10  and directly supported by the conical shaped diffuser plate  30 . The riser tube  60  transports the liquid  112 , in this example the liquid is water, from the bottom of the tank below the conical shaped diffuser plate  30  and out of the tank for use in a home or business (after filtration). In this system, no gravel is required in the bottom of the tank. 
         [0047]    Turning now to  FIG. 12 , this figure presents an exemplary view of a tank  10  having a first conical shaped diffuser plate  30  and a second conical shaped diffuser plate  80  installed within the tank  10  to provide a dual filtration system. In this example, the tank  10  has a first layer of filter media  110  in the lower chamber and a second layer of filter media  114  in the upper chamber. The first layer of filter media  110  is supported by the first conical shaped diffuser plate  30  and the second layer of filter media  114  is supported by the second conical shaped diffuser plate  80 , providing for at least a two stage filtration of the liquid  112  introduced into the tank  10 . Once again, the riser tube  60  transports the filtered liquid  112  out of the tank for use in a home or business (after filtration). 
       CONCLUDING REMARKS 
       [0048]    The foregoing detailed description of embodiments refers to the accompanying drawings, which illustrate specific embodiments of the invention. Other embodiments having different structures and operations do not depart from the scope of the present invention. The term “the invention” or the like is used with reference to certain specific examples of the many alternative aspects or embodiments of the applicant&#39;s invention set forth in this specification, and neither its use nor its absence is intended to limit the scope of the applicant&#39;s invention or the scope of the claims. This specification is divided into sections for the convenience of the reader only. Headings should not be construed as limiting of the scope of the invention. The definitions are intended as a part of the description of the invention. It will be understood that various details of the present invention may be changed without departing from the scope of the present invention. Furthermore, the foregoing description is for the purpose of illustration only, and not for the purpose of limitation.