Abstract:
A waterproof enclosure primarily for radio frequency transmitters used in an automatic meter reading (fixed or mobile) system is described. In one example embodiment, the enclosure includes a base unit, cover that is press-fit into the base unit and a collar that has interlocking ends that compressively secure the base and cover together. The enclosure assembly further includes a seal member or O-ring that is interposed between bearing surfaces of the lid and base to promote a waterproof seal.

Description:
RELATED APPLICATION  
       [0001]     This application claims the benefit of U.S. Provisional Application No. 60/500,533, filed Sep. 5, 2003. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The invention relates generally to contaminant-proof enclosures and more particularly, relates to a waterproof enclosure for electrical and electronic components.  
       BACKGROUND OF THE INVENTION  
       [0003]     In many applications, electrical circuitry and other delicate instrumentation together with the end connections between electrical wires or cables are required to operate under ambient conditions where they can be exposed to contaminants such as moisture, chemicals, fire, gases and the like. These contaminants can degrade the components to an extent that they can malfunction. In particular, electrical end connections require shielding from moisture and other ambient conditions to prevent shorts, sparking and disconnections. Typically, components such as electrical circuitry and other electrical elements include the electrical endpoint connections in sealed enclosures, which are designed to prevent the permeation of water and other contaminants into the enclosure. However, the better the seal the more expensive the enclosure.  
         [0004]     The prior art contains several approaches for constructing and using such enclosures. U.S. Pat. No. 5,825,303 discloses a sealed housing and method of sealing for apparatus in meter pit enclosures. The &#39;303 invention appears to teach a sealed housing for a transponder unit in a utility meter pit enclosure. The sealed housing has an appropriately sized tube in which transponder electronics carried by a circuit board and an antenna are inserted from the bottom and fitted into guide structures and then a body of epoxy adhesive/sealant is used to fill the cavity of the tube and encapsulate the electronics and antenna within the tube. The epoxy sealant seals and forms a recessed lower end of the tube, which, in use, appears to be immersible in water within a subsurface pit enclosure. A method of assembling and sealing the unit is also disclosed.  
         [0005]     U.S. Pat. No. 5,796,041 appears to disclose a waterproof protective cover comprising an upper casing member and a lower casing member that are obtained by cutting a box-like casing molded out of insulating resin materials into two halves in a longitudinal direction of the casing. A sidewall on the left sides of the casing member and a sidewall on the right side of the casing member are pivotably connected by means of hinges in the longitudinal direction of the casing. Thus, these upper and lower casing members can be put together and opened.  
         [0006]     U.S. Pat. No. 5,151,239 appears to teaches an enclosure having a conductive, threaded wire engaging inner surface disposed within a housing and filled with a sealing compound. A flexure cover closes off the enclosure. U.S. Pat. Nos. 6,433,275 and 5,239,129 also appears to teach alternate constructions of a waterproof enclosure.  
         [0007]     The various prior art enclosures appear to teach a sealing compound filling the enclosure and encapsulating the parts to be protected. Moreover, some of the two-part enclosures utilize a hinged connection between the two parts of the enclosure. A hinged connection generally does not provide a uniform pressure between the two mating parts of the enclosure so as to create a waterproof enclosure without auxiliary sealing means.  
         [0008]     Accordingly, there is a need for an endpoint transmitter enclosure or receptacle that is reliable and can be manufactured at a low cost. An enclosure that addresses the aforementioned problems, as well as other related problems, is therefore desirable.  
       SUMMARY OF THE INVENTION  
       [0009]     Various embodiments of the invention are directed to addressing various needs in connection with providing waterproof enclosures for radio frequency transmitters used in an automatic meter reading (fixed or mobile) system.  
         [0010]     In one example embodiment of the invention, an economical and reliable water endpoint enclosure is described for housing electrical circuit elements and associated wiring/cable connections. In operation, such an enclosure may be located in a harsh environment where it is susceptible to moisture and other contaminants permeating into the space where the electrical interconnections are housed. The enclosure of the invention provides a relatively large sealed cavity for housing the components that are sought to be protected from the ambient environment. It is amenable to tool-less disassembly whereby unobstructed access can be gained to the components housed within it. The enclosure can be easily resealed and the quality of the seal maintained by using the snap-fitting lock collars to clamp the two portions of the enclosure housing together. The invention also provides an enclosure where a separate conduit operates as the point of entry/exit of wiring or cable into the sealed cavity where the electrical elements and associated endpoint connections are housed. This entry/exit point is moisture-isolated from the ambient environment by means of a sealant thus substantially eliminating the possibility of water ingress through the cable. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]     The invention may be more completely understood in consideration of the following detailed description of various embodiments of the invention in connection with the accompanying drawings, in which:  
         [0012]      FIG. 1  illustrates an assembly of an exemplary embodiment of a water endpoint enclosure of the invention.  
         [0013]      FIG. 2  is an exploded perspective view of a water endpoint enclosure of the invention.  
         [0014]      FIG. 3  is an illustration of an embodiment of a base unit of the enclosure according to the invention.  
         [0015]      FIG. 4  illustrates an embodiment of a lid or cover of the enclosure of the invention.  
         [0016]      FIGS. 5A and 5B  illustrate a pair of molded collars or rings.  
         [0017]      FIG. 6  illustrates the mounting bracket of the water endpoint enclosure of the invention. 
     
    
       [0018]     While the invention is amenable to various modifications and alternative forms, specifics thereof have been shown by way of example in the drawings and will be described in detail. It should be understood, however, that the intention is not to limit the invention to the particular embodiments described. On the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims.  
       DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0019]     The invention is generally directed to a waterproof enclosure for a radio frequency transmitter used for transmitting data, collected from meter modules, to at least a first tiered receiver or transceiver, wherein the transceiver is assigned by a central utility to a designated area. While the invention is not necessarily limited to such an application, the invention will be better appreciated using a discussion of example embodiments in such a specific context.  
         [0020]     While the invention is described in reference to a water endpoint enclosure  100 , illustrated in  FIG. 1 , it is contemplated that the benefits of the invention accrue to alternative types and configurations of water endpoint enclosures. Therefore, in the description that follows, reference to a specific water endpoint enclosure is for exemplary purposes only, and is not intended to restrict or limit the practice of the invention to any particular water endpoint enclosure, such as water endpoint enclosure  100 .  
         [0021]     Discussion of the invention will now be made with specific reference to the drawing figures.  FIG. 1  illustrates an assembly of an exemplary embodiment of a water endpoint enclosure assembly  100  of the invention and  FIG. 2  is an exploded perspective view of the assembly depicted in  FIG. 1 . As shown in  FIGS. 1 and 2 , water endpoint enclosure  100  has a modular construction and includes a base unit  200  and a lid or cover  300  which can be press-fit into base unit  200  to define a sealed enclosure  290 . A flexible ring or plurality of interconnected lock collars  500 A,  500 B are disposed along the periphery of the base unit  200  and lid  300  to clamp them together and improve the seal between them. At least one collar  500 A,  500 B can be provided with a mounting tab  800  adapted for releasable attachment to a universal mounting bracket  900 .  
         [0022]     In one embodiment of the water endpoint enclosure, exemplified in  FIG. 3 , base unit  200  is a generally cylindrical molded structure with a closed end  210  having a first or interior surface  215  and an open or distal end  220 . An annular or base unit sidewall  225  having an inner surface  230  and an exterior surface  234  depends outward and away from surface  215  to extend between closed end  210  and open end  220  so as to include a relatively large cavity  235  of internal diameter  237  (not shown) which can protectively encase electrical devices and connecting electrical cabling  240  (not shown) therein. The term “annular” herein is not limited to a circular ring, but rather pertains any cylindrical geometry whereby the surface can be described as generated by a straight line intersecting and moving along a closed plane curve, while remaining parallel to a second fixed straight line that is not on or parallel to the plane of the closed plane curve. First surface  215  may have fins, bosses and other structural elements  245  abutting from surface  215  and into cavity  235  to constitute anchoring means for electrical devices and connecting electrical cabling  240  housed within cavity  235 . Annular wall  225  is provided with at least one aperture  260 . In the embodiment illustrated in  FIG. 3 , aperture  260  is in fluid communication with a tubular conduit  264  which is integrally molded with the base unit and disposed along outer surface  234  of annular wall  225  so that an end  266  of conduit  264  communicates with the external ambient environment. A plurality of wall structures  268  with coterminous edges  269  forms a contiguous barrier that extends outwardly from first surface  215  of closed end  210  and cooperates with a portion of side wall  272  containing aperture  260  to form an internal potting well  270  enclosing a cavity  274  in fluid communication with tubular conduit  264  through aperture  260 . In a region proximate open end  220  of annular wall  225 , cavity  235  increases in diameter to form a radial inset  224  bounded by an outer perimeter  226  and an upward facing lateral or bearing surface  252 . At open end  220 , the annular wall extends radially outward to form a circumferential base unit flange  248  having a surface  250  and an outer radial perimeter  251 .  
         [0023]      FIG. 4  illustrates an embodiment of lid  300  of the invention that fits with base unit  200 . As shown in the figure, lid  300  in this particular embodiment is disk shaped with a first lid or cover surface  310 . An annular wall  305  with an external surface  308  and external diameter  311  (not shown) depends outwardly from first lid surface  310 . Also disposed adjacent first lid surface  310  is an annular channel or cover flange portion  307  having a sealing surface portion  336  and a lid-bearing surface  314  with perimeter  316 . Portion  336  extends between lid-bearing surface  314  and external surface  308  of annular wall  305  and forms a radial sealing surface which is adapted to seat a weatherproofing means in the form of an annular sealing o-ring  333  (not shown) which is slidingly received on external surface  308  of annular wall  305 . External surface  308  of annular wall  305  is shaped and dimensioned to be press-fit within cavity  235  such that at least a portion of inner surface  230  of annular wall  225  is in frictional contact with at least a second portion of outer surface  308  of annular wall  305  and annular surface  336  is in sealing engagement with bearing surface  252  through the intermediation of annular sealing o-ring  333  interposed between the surfaces. O-ring  333  operates to prevent moisture and other contaminants from entering into an enclosure  360  defined by cavity  235  bounded by lid  300 . The radial sealing surface ensures constant compression of o-ring  333  so that it forms a uniform seal all the way around thus avoiding moisture permeation at points of non-uniform sealing. In this embodiment, a substantial portion of base-unit flange surface  250  is also engaged with a substantial portion of lid-bearing surface  314  to comprise a connection or seal joint  254  (not shown) thereby limiting the magnitude of pressure loading that can be imposed on annular sealing o-ring  333 .  
         [0024]      FIGS. 5A and 5B  illustrate a pair of semicircular molded lock collars or channel sections  500 A and  500 B each having a u-shaped cross-section  510  that combine to form a flexible ring. Each lock collar has a first end formed into a barb  520 A, and a barb  520 B with at least one tapered surface  525 A and  525 B and a second end formed into a receptacle  530 A and  530 B, respectively, adapted to slidingly receive each barb  520 A and  520 B. Lock collars  500 A and  500 B are circumferentially positioned about seal joint  254  in a diametrically opposed relationship with each other (as shown in  FIGS. 1 and 2 ) such that a substantial peripheral area of flange  248  and a substantial peripheral area of annular region  307  is disposed in captured relationship within u-shaped cross-section  510  of molded collars  500 A and  500 B. Barb  520 A ( 520 B) of lock collar  500 A ( 500 B) is inserted and snap-fitted into receptacle  530 B ( 530 A) of lock collar  520 B ( 520 A) so that lock collar  500 A ( 500 B) is releasably attached to lock collar  500 B ( 500 A) and opposing lock collars  500 A and  500 B form a continuous loop or band around the periphery of seal joint  254 . Lock collars  500 A,  500 B are adapted in structure and dimension to cause surface  314  to be drawn up against surface  250  so that the two surfaces are sufficiently in a clamped and sealed engagement at seal-joint  254 . This sealing and joining method resists the incursion of moisture from the ambient atmosphere into enclosure  290  through seal-joint  254 .  
         [0025]      FIGS. 1, 5B  and  6  exemplify a mounting tab  800  and a universal mounting bracket  900  means through which the water endpoint enclosure, in this embodiment, is mounted to an external structure. At least one of lock collars  500 A and  500 B is provided with mounting tab  800  molded with a plurality of protrusions  820  and slots  830 , the protrusions and slots adapted to releasably engage with a universal mounting bracket  900  at a plurality of locations  950 . Each of said plurality of locations  950  are adapted to releasably secure a corresponding protrusion  820  or slot  830  on mounting tab  800  so that the water endpoint meter can be supported in a plurality of orientations from a plurality of structures to which mounting bracket  900  can be attached. The points of attachment of mounting bracket  900  may include but are not limited to a vertical wall via screw holes  952 , a horizontal surface and a pole with a band/strap via holes  954 . This provides a variety of mounting options for the water endpoint enclosure.  
         [0026]     In operation, the electrical cables are threaded into enclosure  290  through conduit  264  and via cavity  274  enclosed by potting well  270 . A viscous, insulative sealant  920  (not shown) is used to fill cavity  274  and at least a portion of conduit  264  to form a potted water barrier thereby substantially sealing enclosure  290  against moisture wicking up the cable. Typically a silicone or polyurethane based sealant, epoxies, a potting compound, greases, or any other waterproofing compound may be utilized to fill cavity  274 . Lid  300  is press fit onto base unit  200 , while collars  500 A and  500 B are adjusted around seal-joint interface  254  between base unit  200  and lid  300  so that at least a peripheral portion of both components are captured within the groove formed by the u-shaped cross-section of the collars. The barb at the end of a first collar is inserted and snap-fit into the receptacle of the second collar which disposes the collars in a continuous loop around the periphery of the base-unit and lid seal-joint. The circumferential extent of the collar is sized to cause a clamping action on the base-unit and lid when the collars are placed in the above-described configuration. The collars can be released and the base-unit and lid separated so that the electrical components and endpoint connections within the base-unit are accessible for repair or replacement.  
         [0027]     In this embodiment, base unit  200  and lid  300  are unitary moldings formed of electrically nonconductive and moisture resistant materials such as polyurethane. Collars  500 A and  500 B are molded from an insulative and somewhat chemically inert material such as plastic. In a related embodiment, base unit and the lid can be cast from a metallic material, such as aluminum or stainless steel, so long as the base unit includes a bearing surface (such as surface  252 ) and the lid includes a corresponding wall (such as wall  305 ) and an o-ring interposed between the two fitting members.  
         [0028]     While the particular water endpoint enclosure, shown and disclosed in detail above, is fully capable of obtaining the objects and providing the advantages stated, it is to be understood that it is merely illustrative of the presently preferred embodiments of the invention and various other modifications and changes with which the invention can be practiced and which are within the scope of the description provided herein will be readily apparent to those of ordinary skill in the art.