Abstract:
A submerged sensor head is protected from fouling by marine organisms by positioning the sensor head in a submerged hollow enclosure. Openings are formed in the hollow enclosure to admit water but filters are positioned in the openings so that only filtered water may enter the enclosure. The filters remove biologically active marine organisms from the water and have sufficient surface area to enable free flow of water into the hollow enclosure.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority from U.S. provisional application Ser. No. 60/319,102, entitled: “Apparatus and Method for Protecting Toroidal Conductivity Sensors”, filed Jan. 28, 2002. 
    
    
     BACKGROUND OF INVENTION 
     1. Field of the Invention 
     This invention relates, generally, to salinity measurements in near shore or estuarine environments. More particularly, it relates to means and methods for protecting toroidal conductivity sensors from biological growth thereon that causes a slow decrease in conductivity readings. 
     2. Description of the Prior Art 
     Non-toroidal salinity sensors are particularly susceptible to the deleterious effects of biological growth on the sensors, due in part to the exposed electrodes found in such sensors. The application of anti-foulant chemicals does little to stem the problem, especially in the biologically active lower latitudes. 
     Toroidal salinity sensors are more resistant to such fouling, but organisms nonetheless grow slowly upon them and eventually cause them to produce erroneous readings. Significantly, the fouling occurs so slowly that the decrease in conductivity falls too gradually to be noticed until the readings are clearly bad. Thus, many months may pass where a sensor is fouled and generating inaccurate readings without the knowledge of those collecting data from it. 
     What is needed, then, is a salinity sensor that is not subject to fouling by biologically active organisms. 
     However, in view of the prior art considered as a whole at the time the present invention was made, it was not obvious to those of ordinary skill in the pertinent art how the identified need could be fulfilled. 
     SUMMARY OF INVENTION 
     The long-standing but heretofore unfulfilled need for a method and apparatus that protect a toroidal conductivity sensor from fouling is now met by a new, useful, and nonobvious invention. The steps of the method include enclosing the sensor in a hollow enclosure and providing at least one opening in the hollow enclosure to enable water to flow into the hollow enclosure so that the sensor is immersed therein. Biologically active marine organisms are filtered from the water as it flows through the at least one opening to inhibit growth of marine organisms on the sensor. Accordingly, the sensor does not lose its sensitivity due to marine organisms growing thereon. 
     The structure of the novel apparatus that protects a submerged sensor head from fouling by biologically active marine organisms includes an enclosure having a hollow interior for housing the sensor head. At least one opening is formed in the enclosure to admit water into the hollow interior. A filter is disposed in the at least one opening for removing marine organisms from water admitted into the hollow enclosure. Accordingly, the sensor head is submerged in water that is substantially free of marine organisms. 
     More particularly, the enclosure includes a tubular base made of a straight pipe, an end cap having a tubular part that ensleeves a first end of the tubular base, and a closure means formed integrally with the tubular part. A first plurality of openings is formed in a preselected part of the end cap and a first plurality of filter means is positioned within each opening of the first plurality of openings. 
     A coupler has a tubular part that ensleeves a second end of the straight pipe and further includes a diameter-reducing part formed integrally with the tubular part of the coupler. The diameter-reducing part has a frusto-conical configuration. A second plurality of openings is formed in a preselected part of the coupler and a second plurality of filter means is positioned within each opening of the second plurality of openings. 
     An annular neck extends from the diameter-reducing part. A sensor means includes an elongate base and a sensor head is mounted to a first end of the elongate base. The annular neck is adapted to receive the elongate base therethrough so that the sensor head is positioned within the hollow enclosure. 
     A clamping means maintains the elongate base against sliding displacement relative to the annular neck so that the sensor head has a fixed position within the hollow enclosure. The clamping means includes a pipe that is split axially to accommodate the elongate base of the sensor means. The elongate base is slideably received within the axially split pipe, and the clamping means further including an annular band adapted to be positioned in overlying relation to the axially split pipe and tightened. 
     An important object of this invention is to protect a submerged toroidal conductivity sensor from fouling by marine organisms. 
     A more specific object is to immerse the sensor in a housing to protect it from marine organisms while ensuring that sea water within the hollow interior of the housing has the same conductivity as sea water external to the housing so that the sensor makes true measurements. 
     Another object is to filter biologically active marine organisms from the sea water that is within the hollow interior of the enclosure. 
     Another object is to position a toroidal conductivity sensor in sufficient spaced apart relation to metallic or other electrically conductive materials so that such materials do not interfere with measurements made by the sensor. 
     These and other important objects, advantages, and features of the invention will become clear as this description proceeds. 
     The invention accordingly comprises the features of construction, combination of elements, and arrangement of parts that will be exemplified in the description set forth hereinafter and the scope of the invention will be indicated in the claims. 
    
    
     BRIEF DESCRIPTION OF DRAWINGS 
     For a fuller understanding of the nature and objects of the invention, reference should be made to the following detailed description, taken in connection with the accompanying drawings, in which: 
     FIG. 1 is an exploded elevational view of the novel enclosure; and 
     FIG. 2 is an elevational view of the enclosure in its assembled configuration and including the toroidal sensor housed therewithin. 
    
    
     DETAILED DESCRIPTION 
     Referring to FIG. 1, it will there be seen that the reference numeral  10  denotes an illustrative embodiment of the present invention as a whole. 
     Enclosure  10  includes a tubular base  12  made of a straight PVC pipe having a diameter of about four inches (4″). 
     A lower or first end of base  12  is ensleeved by tubular part  14  of end cap  16 . Closure means  18  is formed integrally with said tubular part  14 . 
     An upper or second end of base  12  is ensleeved by PVC coupler  20 . Specifically, coupler  20  includes a first tubular part  22  that ensleeves tubular base . Diameter-reducing part  24  is formed integrally with tubular part  22  and has a frusto-conical configuration so that it reduces the diameter of tubular part  22  to about two inches (2″). Annular neck  26  extends upwardly relative to part  24 . 
     A first plurality of equidistantly and circumferentially spaced filters, collectively denoted  28 , is mounted to frusto-conical wall  24  in registration with a first plurality of openings formed in said wall. There are four filters  28  in the illustrated embodiment, only three of which are visible, but four is not a critical number. A second plurality of filters, collectively denoted  30 , is mounted on end cap in registration with a second plurality of openings formed in said end cap in the illustrated embodiment, one of the filters  30  is mounted at the center of end cap  18 , on the longitudinal axis of symmetry of said end cap, and six additional filters are equidistantly and circumferentially spaced about the perimeter of said end cap. The depicted number and placement of filters  28  and  30  is exemplary and not critical. 
     Filters  28  and  30  are preferably sintered bronze filters because that material inhibits biological growth and therefore such filters are slow to become clogged. Due to the metallic structure of the filters, it is important to space them apart from the sensor head to avoid false readings. An important feature of this invention is that the sensor head is positioned a maximum distance from the filters, within the limitations of the size of the hollow enclosure. 
     The surface area of each filter  28  or  30  is preferably sufficiently large to enable free passage of water therethrough. This ensures that the water in the enclosure is the same as the water outside it, with the exception that the water within the enclosure is substantially free of marine organisms. 
     Set screw  32  screwthreadedly engages an internally threaded radial bore formed in neck  26 . A two inch (2″) in diameter PVC pipe  34  is split axially and lower end  34   a  thereof is slideably received within neck  26 . Set screw  32  bears against said lower end  34   a  when said set screw is advanced, thereby securing pipe  34  to neck  26 . 
     When the novel structure is assembled, a toroidal sensor, not depicted in FIG. 1, is slideably received within pipe  34  and hose clamp  36  is tightened around split part  34   b  of pipe  34  to secure said toroidal sensor against longitudinal displacement. 
     Set screw  38  serves to join together four inch (4″) PVC pipe  12  and tubular part  22 , and set screw  40  joins said PVC pipe  12  and tubular part  14 . Adhesives may also be employed, either as an auxiliary holding means or in lieu of said set screws. 
     As depicted in FIG. 2, toroidal sensor  50  includes an elongate base  52 , neck  54 , and sensor head  56 . 
     Hose clamp  36  and set screws  32 ,  38 , and  40  are eliminated from FIG. 2 to simplify the drawing. Such fastening means are also relatively unimportant because many different fastening means can be employed in lieu thereof or in conjunction therewith. 
     Significantly, sensor head  56  is positioned in the center of enclosure  10 . Accordingly, it is not in physical contact with any part of said enclosure  10 . No metal part or other conductor that could interfere with the measurements made by sensor head  56  is in close proximity thereto, thereby attaining an important object of the invention. 
     The large surface area of filters  28  and  30  enables free water flow into enclosure  10 , thereby ensuring that water in the enclosure has the same conductivity as water external to said enclosure, thereby attaining another important object of the invention. 
     The enclosure prevents marine growth from attaching to sensor head  56 , thereby attaining yet another object of the invention. The organisms that attach to the sensor heads of the prior art are filtered out of the water within enclosure  10  by filters  28  and  30 . 
     Base  52  of toroidal sensor  50  is attachable to a tide gauge or any other underwater structure by any suitable means. 
     Enclosure  10  could be built in many different ways, all of which are obvious to those of ordinary skill in the mechanical arts in view of this disclosure and its teachings relating to the efficacy of enclosing sensor head  56  within a filtered, substantially organism-free submerged environment. 
     Any sensor head requiring protection from marine organisms may be housed in the novel enclosure, i.e., the invention is not limited to the protection of toroidal conductivity sensors. 
     Without restriction to any particular apparatus, the novel method for inhibiting growth of marine organisms on a submerged sensor includes the steps of enclosing the sensor in a hollow enclosure, providing a plurality of openings in the hollow enclosure to enable water to flow into the hollow enclosure so that the sensor is immersed therein, and filtering biologically active marine organisms from the water as the water flows through the plurality of openings to inhibit growth of the marine organisms on the sensor. 
     It will thus be seen that the objects set forth above, and those made apparent from the foregoing description, are efficiently attained, since certain changes may be made in the above construction without departing from the scope of the invention, it is intended that all matters contained in the foregoing description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense. 
     It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described, and all statements of the scope of the invention that, as a matter of language, might be said to fall therebetween. 
     Now that the invention has been described,