Abstract:
A light fixture for use in low voltage outdoor lighting systems that comprises a cowl, a lamp, a socket positioned within the cowl for holding the lamp and a collar positioned within the cowl. The collar comprises an inner aperture having a diameter large enough to receive a base of the lamp and a perimeter that the follows the contours of the inner surface of the cowl. The collar seals the socket and the inner portions of the cowl from the elements. Further, the collar is coated for protection from the elements. The light fixture can be attached to a standard sized pipe thread.

Description:
FIELD OF THE INVENTION 
     The invention relates to a light fixture for use in low voltage outdoor lighting systems and more specifically to a down light fixture which is less susceptible to the effects of oxidation and corrosion. 
     BACKGROUND OF THE INVENTION 
     Environmental lighting, particularly outdoor lighting, is well known in commercial or public settings, such as parks and schools. Such lighting is also popular in residential applications, both to enhance the appearance and safety of the outdoor area and for security, to illuminate dark areas around a building or in a yard which may provide hiding places and unobserved entry points for intruders. 
     Landscape and outdoor lighting systems include one or more lighting fixtures which are connected to either a 12 V transformer or a standard 120 VAC line. Some lighting fixtures enclose a halogen or conventional bulb within a housing, and include a reflector assembly having a lens or window. These fixtures may be used for highlighting features such as trees or statues., i.e., up-lighting, or for path lighting. Other fixtures, used almost exclusively in down-lighting applications, may be open, with the lamp inserted into a socket within a shell or cowl that has its open end directed toward the ground. These fixtures tend to be used in larger quantities within a lighting system since they are typically less expensive than the closed fixtures and are capable of washing large expanses of open area with glare-free light, e.g., pathways, driveways, patios, and for perimeter lighting. 
     The open fixtures often have a cowl shaped in the form of a bell, half-shell, cone, tulip, or other bell-shaped flower that surrounds the lamp except for the lower end of the cowl from which the light emanates. In addition to preventing escape of light in an upward direction, the inner surface of the cowl acts as a reflector to optimize the amount of light directed toward the desired target area. However, because it is open to the elements, the inner surface of the cowl can become coated with a layer of dust and dirt following repeated exposure to moisture, enhancing corrosion and diminishing the reflectivity of the surface. Further, if the cowl is formed from an uncoated metal such as copper or brass, as commonly used in higher end fixtures, the inner surface of the cowl oxidizes, reducing reflectivity. 
     One method that has been used to overcome or minimize the effects of build-up and/or oxidation is to treat the inner surface of the cowl by coating it with a white paint or powder coating to produce a porcelain-like white finish, the latter providing a superior finish that is far more durable. However, in most cases, where only the inner surface is to be coated, the rest of the cowl must be masked or otherwise protected to prevent overspray from depositing on the outer surface. Then, after the masking step, the outer surface must be hand buffed to remove any residual markings and to ensure uniformity of the finish, thus introducing additional steps into the manufacturing process that result in the product being more costly. 
     It would be desirable to provide a light fixture that is attractive, easy to manufacture and provides a reflective surface that is not easily degraded by corrosion or oxidation. The problems and deficiencies are clearly felt in the art and are solved by the present invention in the manner described below. 
     SUMMARY OF THE INVENTION 
     It is an advantage of the present invention to provide a light fixture which has a cowl with a high quality reflective inner surface without requiring additional manufacturing steps to protect the exterior finish. 
     It is a further advantage of the present invention to provide a light fixture with improved resistance to degradation by corrosion and oxidation of the materials of which the fixture is made. 
     Another advantage of the present invention is to provide a light fixture which protects the lamp base and socket against exposure to the elements and intrusion by foreign objects. 
     In an exemplary embodiment, the light fixture comprises a spring-blased socket and a lamp retained within a base portion of a cowl disposed at an end of a goose-necked stem through which are passed wires for providing electrical connection between the socket and a power supply. The cowl is generally bell-shaped with a cylindrical base and a flared skirt, but may be any shape having a cavity for retaining the lamp and socket and an open and perhaps partially flared bottom. A collar having a profile closely matching at least a portion of the inner profile of the cowl has an opening at its center through which the base of the lamp passes. The collar, which in the preferred embodiment is formed from aluminum, is coated with a reflective (white) coating and is dimensioned so that light emitted from the lamp is reflected outward away from the fixture. The preferred coating is powder coating. A resilient O-ring is disposed around the base portion of the lamp so that when the lamp base is fastened within the socket, the O-ring presses against the collar, pressing it against the inner surface of the cowl. A metal connector formed preferably from brass can be used to connect the cowl to the stem to reinforce the joint. The stem typically has a threaded fitting at its distal end allowing connection to a riser pipe or ground spike. 
     The collar provides a reflector which will not degrade even as the material of which the cowl is made oxidizes and, while it is not completely watertight, it provides a barrier to entry of moisture, debris, spiders and insects that often collect within the inner cavities of open ended light fixtures. In an alternate embodiment the outer edges of the collar can have a resilient bead formed from silicone or a similar material so that the bead is compressed between the collar and inner surface of the cowl to enhance the fixture&#39;s moisture resistance. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Understanding of the present invention will be facilitated by consideration of the following detailed description of a preferred embodiment of the present invention taken in conjunction with the accompanying drawings, in which like numerals refer to like parts and in which: 
     FIG. 1 is a side elevation of the light fixture attached to a spike mount; 
     FIG. 2 is a cross-sectional view of the fixture head taken along line A—A. of FIG. 1; and 
     FIG. 3 is a perspective view of the interior of the cowl. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     As illustrated in FIG. 1, the lighting fixture  2  includes a cowl  4 , a head fitting  6 , a stem  8  and a base fitting  10  for attachment to ground spike  12 . In the preferred embodiment of the invention, cowl  4  is formed from solid copper. The solid copper is intended to oxidize to a verde color and thus is preferably uncoated. Alternate materials may be used, including brass, bronze, stainless steel, coated or anodized aluminum, plastic or polymer. Cowl  4  is generally bell shaped with a crown portion  14  which is generally cylindrical and a skirt portion  16  which flares out from the crown portion  14  and may be formed by machining, die casting, molding, or any other procedure appropriate for the selected materials. Other shapes may be substituted as long as a sufficient recess is provided to enclose the lamp and socket sufficiently to prevent direct viewing of the lamp from above the fixture. For example, tulip or other bell-like flower shapes, pyramids, half-shells, such as a scallop shell, or cones may be used. The shapes are not limited to rounded or symmetrical shapes. 
     Referring to FIG. 2, head fitting  6  can be cylindrical in shape or a frustum (as shown) and encircles the proximal end of stem  8  to provide a firm connection between cowl  4  and stem  8 . A set screw  9  inserted through a threaded bore perpendicular to stem  8  holds the pieces together. Stem  8 , shown formed as a goose-neck, and head fitting  6  are hollow to permit wiring to be connected to the lamp socket for connection to a power supply. In the preferred embodiment, head fitting  6  is brass while stem  8  is copper. Base fitting  10 , which encircles the distal end of stem  8 , has a standard thread pattern, e.g., ½″ NPS male thread, at its lower portion for mating with a corresponding opening in ground spike  12 . Wires are fed up from the ground spike  12  through base fitting  10  and into stem  8 . Alternate mounting means for securing the fixture in place are known to those in the art. 
     Referring to FIG. 2, retained within cowl  4  are the socket  20 , lamp  22 , collar  24  and O-ring  26 . Socket  20 , preferably formed from brass, has a spring  28  disposed within its base which creates an outward bias against the contact  30  that provides electrical connection to lamp  22 . Lamp  22  is typically an incandescent bulb which is commercially available in a wide range of wattage ratings. Socket  20  may also be formed from plastic or other appropriate materials. Base  32  of lamp  22  has a conventional bayonet mounting which is commonly used in low voltage lighting fixtures. The bayonet pins  34  mate with corresponding right angle slots in socket  20 . The bias created by spring  28  causes lamp  22  to be held firmly in place once the bayonet pins  34  are inserted into the slots and lamp  22  is rotated to trap the pins within the slots. Alternatively, a conventional screw-type connection or an interference fit connection can be used to hold lamp  22  within socket  20 . 
     Before lamp  22  is inserted into socket  22 , O-ring  26 , with an inner diameter that closely fits the outer diameter of lamp base  32 , is slid over lamp base  32  up to the uppermost portion of base  32 . O-ring  26  is preferably a silicone or other heat tolerant material. Then, collar  24 , which has an opening  36  at its center which is larger than the outer diameter of lamp base  32 , including the bayonet pins  34 , but smaller than the outer diameter of O-ring  26 , is slid over the base  32 . Collar  24 , shown in more detail in FIG. 3, is preferably formed from aluminum or aluminum alloy which has been shaped into a parabolic configuration and powder coated with white, silver or other light color on all surfaces, creating a porcelain-like finish that is very durable and corrosion resistant. In the preferred embodiment, a polyester powder coat is used for its superior durability, corrosion resistance and UV protection, however, other forms of powder coating, or a hard white, silver or other light color enamel paint, may also be used. To provide the highest quality finish on collar  24 , it may be treated using a three part process which involves, after shaping the reflector, 1) acid etching the aluminum for optimal adhesion; 2) using chromate conversion to seal the aluminum surface to prevent pitting and blistering; and 3) powder coating. If cowl  4  is not rounded or symmetrical in shape, the shape of collar  24  should be adapted to conform to the profile of the cowl. 
     When base  32  is inserted into socket  22  and locked in place, the opposing forces of spring  28  and the lamp  22  apply pressure against O-ring  26 , pressing collar  24  against the inner surface  38  of cowl  4 . In the prior art, the cavity created by crown portion  14  is usually open to the elements. Because this area is open in prior art fixtures, the socket, which in many less expensive products is plastic, will decompose in time, causing the socket to crack and break when the lamps are changed. Further, spiders and insects often make their homes in the protected area of the cowl  4 , which can make the act of changing a lamp  22  an unpleasant experience for some persons and can cause the fixture to malfunction. 
     To further protect socket  22 , lamp base  32  and the electrical connections to socket  22 , it may be desirable to form a bead of silicone sealant or other resilient material around the upper (inside) edge of collar  24 , for instance at  25 , to press against the inner surface  38  of cowl  4 , to create an even better seal against moisture intrusion. Alternatively, a second O-ring can be placed between the two surfaces to provide the same function. If an O-ring is used, it may be desirable to form a small channel or lip on the upper edge of collar  24  to hold the O-ring in place. 
     The light fixture of the present invention overcomes several disadvantages of the prior art dealing with corrosion and oxidation of the fixtures which result in decreased light output. Further, the light fixture is easy to manufacture, and is constructed in such a way that the components are readily replaceable without requiring spot welding or permanent fasteners, thus making it more economical all-around relative to existing light fixtures of similar design. Still further, the inventive light fixture is configured so as to reduce the opportunity for moisture, dirt and insect intrusion into the fixture which can interfere with operation and/or shorten the lifetime of the fixture. 
     Obviously, other embodiments and modifications of the present invention will occur readily to those of ordinary skill in the art in view of these teachings. Therefore, this invention is to be limited only by the following claims which include all such other embodiments and modifications when viewed in conjunction with the above specification and accompanying drawings.