Patent Publication Number: US-6902200-B1

Title: Contaminant-resistant pivot joint for outdoor lighting fixture

Description:
RELATED APPLICATIONS 
   This is a continuation of application Ser. No. 09/536,676, filed Mar. 28, 2000, now abandoned. 

   FIELD OF THE INVENTION 
   Environmental lighting, particularly outdoor lighting, is well known in commercial or public settings, such as parks and schools. Such lighting has also become increasingly popular for use in private residences, both to enhance the appearance and safety of the outdoor area and for security by eliminating hiding place and unobserved entry points for intruders. 
   Landscape and outdoor lighting systems generally include one or more lighting fixtures which are connected to either a 12 V transformer or a standard 120 VAC line. The lighting fixtures generally include a housing, a reflector assembly having a halogen or conventional bulb, and a lens or window. Many configurations are known, each of which provides a different lighting effect. 
   One of the more popular and versatile lighting fixtures utilizes a cylindrical housing attached to a pivoting knuckle joint that allows the light to be directed at variable angles. The knuckle joint may be attached to a mounting bracket for attachment to structures, or placement of the fixtures can be as simple as sticking a tapered spike into the ground, so that no structures need to be modified to retain the fixture. Further, the use of a spike allows the fixtures to be placed within planters and lawn areas, and next to trees, away from structures. 
   Directability of the lighting fixture is important and much of this directability relies upon the pivoting knuckle joints. While the pivoting joints provide significant adaptability in the aiming of the light, they constitute the weakest point in the fixture. The fixtures are subject to impact from gardening tools and equipment as well as persons inadvertently running into or kicking the fixture. Exposure to various environmental conditions including temperature extremes, moisture and corrosive fertilizers and insecticides can weaken the joints and cause them to be easily broken. An example of a typical outdoor lighting fixture is provided in U.S. Pat. No. 4,464,707 of Forrest, where the joint comprises two pieces which remain pivotally engaged using opposingly toothed notches. A significant disadvantage of this particular configuration is that when the fixture is exposed to the elements, the toothed notches become fouled by dirt and corrosion and the two parts of the joint can no longer remain engaged. Furthermore, the adjustment is incremental, limited by the sizes and number of notches. 
   Other outdoor lighting fixture configurations, such as those disclosed in U.S. Pat. Nos. 4,626,975 and 5,713,662, provide examples of the pivot joint structures which may be more susceptible to wear and corrosion from prolonged exposure to the outdoor environment, or may not be sufficiently strong to withstand the punishment to which a ground-mounted lighting fixture can be subjected. In the lighting fixture disclosed in U.S. Pat. No. 4,626,975, the pivot joint is a relatively small structure attached to a much larger lamp housing, with a significant amount of surface area between the two hinged portions, thus providing locations where contaminants can collect to accelerate corrosion and cause the structure to seize up, preventing movement. In U.S. Pat. No. 5,713,662, the pivoting joint of the outdoor lighting fixture has at least four locations in the hinge where spaces between opposing surfaces can collect contaminants to eventually jam the joint to prevent movement. 
   It would be desirable to provide a sturdy joint for environmental lighting fixtures that allows the light angle to be adjusted over a wide range while minimizing the presence of components that can result in premature failure of the fixture due to weather, wear, dirt and corrosion. 
   SUMMARY OF THE INVENTION 
   It is an advantage of the present invention to provide a pivot joint for use in an outdoor lighting system that minimizes the space within which contaminants can collect. 
   It is another advantage of the present invention to provide a pivot joint for outdoor lighting systems with a wide range of adjustability. Another advantage of the present invention is to provide a pivot joint for outdoor lighting systems that can be adjusted and locked into position using a single fastener. 
   In an exemplary embodiment, the pivoting knuckle joint comprises a base knuckle, a top knuckle and a fastener for locking the base and top knuckles in position. Each of the base knuckle and top knuckle has a generally cylindrical body with a domed top, a portion of which is cut-away to form a flattened face, and circular cavity formed in the flattened face with a tapered ferrule formed in and extending from the cavity. The ferrule of one of the knuckles has a smaller diameter than the other, so that the smaller ferrule fits within the larger ferrule, forming a pivot point. The relative diameters of the ferrules are adapted to closely fit such that friction is generated when one knuckle is pivoted relative to the other, thus creating a taper lock which can hold the joint in position when one ferrule is fully seated in the other. In the preferred embodiment, the smaller ferrule has an internal thread formed therein for receiving a locking screw inserted through the body of the knuckle with the larger ferrule to hold the two knuckles together and, thus, permitting the position of the joint to be locked in place after adjustment. O-ring seats are formed around the perimeter of each cavity for receiving an O-ring to seal the interior of the joint against moisture and other contaminants and to provide additional frictional resistance to rotation of the joint. A bore is formed extending through the body of each knuckle exiting within the cavity on one end and through the distal end of the knuckle joint on the other end to provide a by-way for an electrically-conductive wire to be fed through the joint to provide voltage to the lamp. The distal end of the base joint has external threads formed thereon for attachment to a mounting device such as a spike or pole. The distal end of the top joint is adapted to connect to a housing containing a lamp and appropriate lenses and reflectors, and may include a recess and a plurality of threaded bores for receiving fastening screws. 

   
     BRIEF DESCRIPTIONS OF THE DRAWINGS 
     For a more complete understanding of the present invention, reference is now made to the following detailed description of the embodiments illustrated in the accompanying drawings, wherein: 
       FIG. 1  is a perspective view of the complete knuckle joint; 
       FIG. 2  is a perspective view of the top portion of the joint; 
       FIG. 3  is a perspective view of the base portion of the joint; 
       FIG. 4  is a bottom end view of the base portion; 
       FIG. 5  is a side view of the joint as mounted to a support means; 
       FIG. 6  is an enlarged sectional view taken on line  6 — 6  of  FIG. 1 ; and 
       FIG. 7  is a sectional view of the present invention taken on line  7 — 7  of  FIG. 6 . 
   

   DESCRIPTION OF PREFERRED EMBODIMENTS 
   Referring to  FIG. 1 , the knuckle joint assembly is formed by the combination of base knuckle  102 , top knuckle  104 , and locking screw  134 . Base knuckle  102  has a proximal end  150  corresponding to the pivot point and a distal end  152  which provides means for attaching to a support or other like structure such as a spike which may be driven into the ground, a pole or wall mount (not shown). A conduit for passing electrical wiring from a voltage supply to a lamp extends through the joint assembly, beginning at bore  116  at distal end  152  and exiting through the distal end  156  of top knuckle  102 . In the preferred embodiment, base knuckle  102  and top knuckle  104  are formed from brass by CNC machining of a cylindrical bar, or by other machining or forming techniques known in the art. Other corrosion resistant materials may be used as well, including stainless steel, aluminum, copper, ceramic, or high temperature plastics or composites, by machining, die casting or molding where appropriate. A rock tumbler or finishing vibrator can be used to remove any marks left after machining. Exterior finishes may be used to enhance the aesthetics and/or durability of the joint, including painting, powder coating, electroplating and anodizing. In instances where the components are to be coated, allowances must be made in the machine manufacture of the joint assembly to compensate for any thickness the coating adds to the measurable dimensions of the joint. Locking screw  134  is disposed within screw seat  136  of base knuckle  102  to secure base knuckle  102  and top knuckle  104  together. 
   The components of the knuckle joint assembly are more clearly illustrated in  FIGS. 2 and 3 , which show perspective views of the uncoupled top knuckle  104  and base knuckle  102 , respectively. As shown in  FIG. 2 , base knuckle  102  comprises a generally cylindrical body having a proximal end  150  with a domed shaped and a distal end  152 , where the cylindrical body is effectively cut in half lengthwise to define flattened face  108  in a recessed area on its inner side. Flattened face  108  is distally terminated by pivot stop  112 , a peaked structure with its apex aligned with a longitudinal plane bisecting flattened face  108 . Where the knuckles are formed by machining, pivot stop  112  is the portion of the cylindrical body that remains after material is removed to define face  108 . It should be noted that the shape of the knuckle is not limited to a cylindrical body, but may also be rectangular or some other body that has polygonal cross-section, as long as a portion of the body is cut-away to define flattened face  108 . The angled faces  158  and  160  of pivot stop  112  determine the range of movement of the joint. In the preferred embodiment, the angled faces  158  and  160  are selected to be on the order of 30°, providing a total range of rotation of about 240°. Axially extending from distal end  152  is externally threaded portion  114  for threadably securing the knuckle joint assembly to an appropriate support which is partially represented by dashed lines in  FIG. 5 . As will be readily apparent to those of skill in the art, other fastening means may be utilized, and the described externally threaded connection of the preferred embodiment is not intended to be limiting. Bore  116  traverses threaded portion  114  through the body of base knuckle  102 , exiting through vertical face  108  to provide a conduit for electrical wiring running from a voltage source to a lamp mounted on the knuckle joint assembly. 
   A circular cavity  132  is formed in vertical face  108  of base knuckle  102 . Extending concentrically from cavity  132  is a tapered male ferrule  122  which has a decreasing diameter as it extends from cavity  132 . Ferrule  132  is internally threaded with threads  129  for mating with locking screw  134  which holds the two knuckles together once the angle has been adjusted. An O-ring seat  126  encircles the perimeter of cavity  132  and defines half of a channel that, when the joint is assembled, provides a means for retaining an O-ring  125  ( FIG. 3 ). O-ring  125  helps to seal the joint against moisture intrusion, but more importantly, provides a surface within the joint that creates some frictional resistance against rotation of top knuckle  104  relative to base knuckle  102  to prevent uncontrolled slippage while still permitting the joint to be adjusted. 
   Illustrated in  FIG. 3 , top knuckle  104  has a proximal end  154  corresponding to the pivoting end of the knuckle and a distal end  156  corresponding to the attachment point for a lamp, hood and lens (not shown). Top knuckle  104  is formed in a similar manner to base knuckle  102 , in the preferred embodiment, with flattened face  106  formed by cutting a domed cylindrical body in half up to a point where face  106  is distally terminated by pivot stop  110 . As noted above, the body shape is not limited to a cylinder, and those of skill in the art will recognize that the shape may be chosen for aesthetic purposes as long as a recessed flattened face  106  can be formed on its inner side to cooperate with face  108  of base knuckle  102 . Pivot stop  11  has angled faces  162 ,  164  intersecting at an apex which limit the rotation of base knuckle  102  to a total range of about 240 when faces  162  and  164  have an angle on the order of 30 relative to a line perpendicular to a longitudinal centerline bisecting flattened face  106 . Referring briefly to  FIG. 4 , a recess  115  is formed in distal end  156  of top knuckle  104  for receiving a lamp base or socket (not shown) which can be attached using threaded bores  138  and  140 . The dimensions of recess  115  can be adapted to different applications by modifying the length and width of top knuckle  104 , including making recess  115  large enough to retain a lamp and socket within the recess, thus making the joint itself the light fixture, with a lens or other light transmissive cover disposed over the opening to enclose the lamp within the recess. Bore  118  extends from recess  115  through the body of top knuckle  104 , exiting through face  106  to provide a conduit for electrical wiring between the lamp and the voltage supply. 
   Circular cavity  130  is formed in vertical face  106  of top knuckle  104 . Extending concentrically from cavity  130  is a tapered female ferrule  120  which has a decreasing outer diameter/increasing inner diameter as it extends from cavity  130 . The inner diameter of ferrule  120  is slightly larger than the outer diameter of ferrule  122  of base knuckle  102  so that ferrule  122  will closely fit within ferrule  120  when the knuckles are joined to create a taper lock that will provide frictional resistance to rotation of the join. It should be noted that relative positions of the male and female ferrules can be reversed, i.e., that the female ferrule can be in base knuckle  102  and the male ferrule can be in top knuckle  104 . When one ferrule is fully seated within the other ferrule, the friction between the two opposing ferrule surfaces creates a taper lock  172  (shown in  FIG. 7 ) which, alone, should be sufficient to resist any change in the angle of the joint. Nonetheless, locking screw  134  is provided to keep the two knuckles together with the two ferrules in frictional contact, thus ensuring that taper lock  172  is not inadvertently disrupted by pulling one knuckle away from the other, thus separating the ferrules enough to allow essentially free rotation of the joint. Locking screw passage  128  runs through ferrule  120  and exits the side of top knuckle  104  are countersunk screw seat  136 , which is shown in  FIG. 1  with locking screw  134  in place. As with base knuckle  102 , an O-ring seat encircles the perimeter of cavity  130 , defining the other half of the channel that, when the joint is assembled, provides a means for retaining an O-ring  125 , which is shown in place in the O-ring seat in  FIG. 3 . O-ring  125  can be formed from rubber, plastic, silicone, polymer or other resilient material. 
   Locking screw  134  traverses locking screw passage  128  extending through ferrule  120  of top knuckle  104  where it can be mated with screw threads  129  in ferrule  122  of base knuckle  102 . It is the combined function of the taper lock  172 , locking screw  134  and O-ring  125  that provide means for adjustable securing the pivoting knuckle assembly once the desired angle has been selected by the user. When locking screw  134  is tightened within screw threads  129 , tension is increased within the taper lock  172  formed by ferrules  120  and  122  to prevent the knuckle assembly from being rotated. Tightening of screw  134  also increases the compression of O-ring  125 , creating further resistance to rotation of the knuckle assembly. O-ring  125  also functions to prevent the intrusion of moisture and dirt within the internal cavities of the joint. Rotating locking screw  134  in a counter clock-wise direction decreases the tension on taper lock  172  thereby allowing the pivotal rotation of the knuckle joint. 
   As illustrated in  FIG. 5 , a lighting fixture, exemplified by lamp base plate  170 , can be secured to the knuckle joint assembly by mounting screws which mate with threaded mounting bores  138 ,  140  of base knuckle  102 . The lighting fixture/knuckle joint assembly can be attached to a support ground spike or like structure by mating threaded portion  114  of base knuckle  102  to a complimentary internally threaded portion of a support such as a ground spike that can be pushed into the ground, a pole or other appropriate mounting. 
   As illustrated in  FIGS. 6 and 7 , the union of base knuckle  102  and top knuckle  104  forms the pivotally adjustable knuckle joint of the present invention. The taper lock  172  formed by the cooperation between ferrules  120  and  122  provides means for axially rotating the knuckle joint assembly as well as providing means for maintaining the selected orientation of the joint assembly when combined with locking screw  134 . O-ring seats  124 ,  126  are machined to form an annular seat for retaining the resilient O-ring  125  when the top and base knuckles are joined. Additionally, O-ring  125  creates additional resistance between the relative rotation of base knuckle  102  and top knuckle  104 . 
   The joining of base knuckle  102  and top knuckle  104  to form the pivotally adjustable knuckle joint also creates a conduit from the distal end  152  of base knuckle  102  to the distal end  156  of top knuckle  104  through which an electrical wire  144  can pass from a voltage source outside of the fixture to the lamp inside the fixture. Bore  116  extends from the distal end  152  of base knuckle  102  and exits in cavity  132 , where wire  144  follows the internal curvature of the combined cavities  130  and  132 . Bore  118  extends from cavity  130  through top knuckle  104 , exiting through distal end  156  to be connected to a lamp base (not shown). The smooth, unobstructed passageway comprising formed by combined cavity  130 ,  132  permits wire  144  to traverse the interior of the unit knuckle joint without binding or chafing while still allowing the knuckle joint to be pivotally adjustable. In one exemplary embodiment, for installation using a ground spike, wire  144  would continue from distal end  156  through an opening in the ground spike, then continues to termination at the transformer or other power supply. In an alternate embodiment, threaded portion  114  of top knuckle  104  is attached to a tubular post (not shown) or other form of support which is then, in turn, connected to the ground spike. Wire  144  would pass from the knuckle joint assembly, through the entire length of the tubular post, through the opening in the ground spike and then continue to termination at the power source. 
   The pivotally adjustable knuckle joint assembly of the present invention provides a robust mounting with a wide range of directional control for a lighting fixture. The pivotal joint construction provides simple one screw adjustment for the variable directability of the affixed lighting component with the entire joint designed to resist the effects of prolonged environmental exposure. The configuration of the present invention is aesthetically pleasing with clean lines and is constructed with a focus on simplicity and durability. 
   Other embodiments of the present invention may occur 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 other such embodiments and modifications when viewed in conjunction with the above specification and accompanying drawings.