Patent Publication Number: US-2016235224-A1

Title: Heavy-Duty Plastic Picture Hanger Having Dual-Hooks And Hook-Above-Nail Arrangements

Description:
BACKGROUND OF THE INVENTION 
     Now day, user commonly uses a pair of metal hangers to hang a large picture frame on wall. Before hanging the picture frame, user needs to adopt a leveling tool (i.e. spirit level) to mark a horizontal line on wall, and then anchor the metal hangers along the horizontal line. After hanging the picture frame, user needs to take time and effort to adjust picture frame to a level and balance position. This is because picture frame can&#39;t be hung in level and balance if its weight center (i.e. center line) is not positioned nearby the center location between hangers. 
     There is one major drawback of metal hanger of prior art. It typically has a nail-above-hook arrangement, in which, a lateral projectile is provided directly above hook for guiding nail into wall in incline position. When user is holding picture frame above hanger in an attempt to hang the picture frame, he needs to maneuver the metal wire of picture frame to bypass the lateral projectile while sliding picture frame against wall in downward direction. Afterward, he needs to maneuver the metal wire into the hook that is immediately below the lateral projectile. Many users consider such maneuver task troublesome and user-unfriendly. 
     Using metal hanger in lieu of plastic hanger also has two obvious disadvantages: (1). Metal hanger has higher material and manufacturing costs. (2). Metal hanger is vulnerable to corrosion, particularly, metal-to-metal contact corrosion between the metal body of hanger and the metal wire of picture frame. Unfortunately, plastic hangers of prior art characteristically have limited load capacity due to the inherent low-shear/bending-strength plastic material characteristics. 
     The motivated concept of present invention is to improve structural design of plastic hanger, and provide a plastic hanger that not only has dual-hooks and hook-above-nail arrangements, but also has a load capacity equivalent to that of metal hangers. The above hanger becomes more user friendly because: 
     (1). There is no need to adopt a leveling tool (i.e. spirit level). (2). There is no need to mark a horizontal line on wall for installing hangers. (3). Troublesome maneuver task for engaging metal wire of picture frame into hook is eliminated. (4). Adjusting picture frame in a level and balance position takes less effort and time. This is because hanger is provided with a marking along the vertical centerline of hanger, and user can visualize it as a target while aligning the weight center (i.e. center line) of picture frame to the center location between hangers (i.e. dual-hooks). In prior art, when a pair of hangers are installed and separated at a distance on wall, user can&#39;t visualize the center location between hangers unless he takes time and effort to take measurement and mark it on wall. 
     By conducting extensive mechanics analyses and load testing of prototypes, author of present invention is able to achieve the structural design of hanger of present invention that has both dual-hooks and hook-above-nail arrangements, and offers a 50 lb. (or 70 lb.) weight load capacity with two (or three) nails anchoring hanger onto drywall, that is equivalent to the load capacity of a single-hook-dual-nails metal hanger of prior art, or the load capacity of a pair of single-hook-single-nail metal hangers of prior art. Some important design features of hanger of present invention are discussed in detail in later section. 
     In U.S. Pat. No. 5,178,355, Herzig discloses a hanger with hook-above-nail arrangement. Herzig&#39;s hanger has a vertical lower body, an inclined upper body, and an inclined nail hole penetrating upper body along the longitudinal center line of upper body. Top surface of upper body is divided into a rear inclined top surface for hanging a metal wire of picture frame, and a front horizontal top surface for supporting a small L-shaped metal frame of picture frame. 
     Herzig&#39;s hanger has a major drawback that metal wire of picture can easily fall off from top surface of upper body. Herzig&#39;s hanger is lack of all the design features of hanger of present invention as discussed in later section. An ordinary designer may modify Herzig&#39;s hanger to eliminate the above drawback, but he can&#39;t possible modify Herzig&#39;s hanger to achieve a load capacity equivalent to that of hanger of present invention. This is due to the fact that, in order to achieve load capacity of hanger of present invention, ratio of “the height of nail exit above bottom edge of lower body” to “the lateral width of open top surface” needs to be equal to or greater than 530%. This design feature of hanger of present invention is based on mechanical analyses and load testing, and can&#39;t possibly be comprehended or suggested by an ordinary designer without conducting mechanics analyses and load testing. 
     We may argue that load capacity of Herzig&#39;s hanger can be increased by proportionally enlarging its size without modifying its structural design. In this case (without implementing all the design features of hanger of present invention), the enlarged Herzig&#39;s hanger can&#39;t possibly achieve a structural strength equivalent to that of hanger of present invention, so that the enlarged Herzig&#39;s hanger can&#39;t possibly achieve a load capacity equivalent to that of hanger of present invention. Also in this case, overall width of Herzig&#39;s hanger will increase proportionally, and thus create a large gap between wall surface and rear surface of picture frame while hanging the picture frame on wall. This is not acceptable because we all know that overall width of hanger needs to be restricted in order to eliminate or minimize such a gap. 
     In U.S. Pat. No. 7,216,841, Dodig discloses a hanger with dual-hooks arrangement. In first embodiment, hanger has a nail-above-hook arrangement. In second embodiment, hanger has a hook-above-nail arrangement. Dodig&#39;s hanger is inherent with low shear/bending strength plastic material characteristics. Without implementing all the design features of hanger of present invention, Dodig&#39;s hanger is deemed to be a light-duty hanger for hanging a small picture frame. 
     SUMMARY OF THE INVENTION 
     Objective of present invention is to provide a plastic hanger that has both dual-hooks and hook-above-nail arrangements, and offers a load capacity equivalent to that of a pair of single-hook-single-nail metal hangers, or a single-hook-dual-nails metal hanger. 
     Another objective of present invention is to provide such a plastic hanger with a minimum overall width that minimizes the gap between wall surface and rear surface of picture frame while hanging picture frame onto wall. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective and exploded view of the first preferred embodiment of hanger of present invention. 
         FIG. 2  is a cross sectional view of  FIG. 1 . 
         FIG. 3  is a perspective view of the second preferred embodiment of hanger of present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective and exploded view of the first preferred embodiment of hanger of present invention, in which, hanger  1  comprises of a base plate  2 , and a pair of identical left and right lateral projectile  3  and  4  integrally connected to base plate  2 . 
     In  FIG. 1 , base plate  2  is divided into a left rectangular section  5 , a central rectangular section  6 , and a right rectangular section  7 , in which, left section  5  has a height, width or surface area identical to that of right section  7 , but smaller than that of central section  6 . Central section  6  is divided into an upper portion  8  above the height of left or right section, and a lower portion  9  below the height of left or right section. 
     Left lateral projectile  3  or right lateral projectile  4  is integrally connected to left section  5  or right section  7  of base plate  2  to form a hanger body  10  as shown in  FIG. 2 . In  FIG. 2 , hanger body  10  comprises of a lower body  11 , a transition body  12  projecting upwardly and forwardly from lower body  11 , and an upper body  13  projecting upwardly from the front portion of transition body  12 . 
     Lower body  11  has a bottom surface  14 , a vertical rear surface  15  emerging from the bottom edge  16  of lower body  11 , and a vertical front surface  17 . Rear surface  15  is flush to a vertical rear surface  18  of transition body  12 . The combined rear surfaces  15  and  18  have a height, width or surface area identical to that of left or right section of base plate  2 . 
     Transition body  12  has an inclined bottom surface  19  sloping upwardly and forwardly from the adjacent front surface  17  of lower body  11 , a substantially vertical front surface  20 , and an inclined open top surface  21  sloping upwardly and forwardly from rear surface  18 . Inclined open top surface  21  is flush to top surface  22  of left or right section of base plate  2 . 
     Transition body  12  has an inclined nail hole  23  that penetrates across the upper portion of transition body  12  from front surface  20  to rear surface  18 . Inclined nail hole  23  has an incline angle identical to that of open top surface  21 . Inclined nail hole  23  has a nail hole exit  24  located immediately below open top surface  21 . 
     Upper body  13  has a top surface  25 , a rear vertical surface  26  emerging from the open top surface  21  of transition body  12 , a rear inclined surface  27  projecting upwardly and outwardly from rear vertical surface  26 , and a substantially vertical front surface  28  flush to front surface  20  of transition body  12 . 
     Hanger  1  of present invention as described above also has the following important design features: 
     (1). An indent  29  is provided at the top surface of upper portion  8  of base plate  2  that serves as a visible marking of the vertical centerline of base plate  2 . Lower portion  9  of central section  6  of base plate  2  has a slightly greater base plate thickness than that of upper portion  8 . Lower portion  9  has an inclined top surface  30  emerging outwardly and downwardly from front surface of upper portion  8 . Inclined top surface  30  is at the same height of the top surface  22  of left or right section of base plate  2 , and thus serves as a visible marking of the elevation of open top surface  21  where metal wire of picture frame is loaded upon. The above design features allows user to precisely anchor hanger  1  at desired location on wall. Increasing base plate thickness in lower portion  9  of central section  6  of base plate  2  is also necessary in order to increase the structural strength of hanger  1 . 
     (2). Functionally speaking, upper body  13  forms a front leg of an U hook, open top surface  21  of transition body  12  forms an internal side of bottom closed end of U hook, and the upper portion  8  of central section  6  of base plate  2  forms a common rear leg of U hooks. 
     In order to assure that metal wire of picture frame is securely retained by U hook without possibility of accidentally falling off from U hook or breaking apart the front leg (i.e. upper body  13 ), upper body  13  has a height equal to twice of the lateral width of open top surface  21 , and a lateral width equal to the lateral width of open top surface  21 . Lateral width of open top surface  21  is determined by a horizontal distance between the rear vertical surface  26  of upper body  13  and the rear surface  18  of transition body  12 . 
     (3). In order to maximize shear strength of hanger  1 , bottom surface  14  of lower body  11  has a lateral wall thickness equal to the lateral width of open top surface  21  of transition body  12 , so that shear stress under loading condition can be distributed in the entire vertical cross section of lower body  11 . 
     (4). Functionally speaking, lower body  11  serves as a bending moment resistant cantilever under loading condition. The design feature ( 3 ) above assures that lateral thickness throughout lower body  11  is no less than the lateral width of open top surface  21  of transition body  12 , and thus maximizes bending strength of hanger  1 . 
     (5). Functionally speaking, transition body  12  serves as a nail anchor body. Transition body  12  adjacent to nail hole exit  24  and below nail hole  23  is subject to maximum bending stress, and thus needs to be reinforced with greater lateral and vertical wall thicknesses. Accordingly, transition body  12  below nail hole  23  envelopes a circular boundary around nail hole exit  24 , which has a radius equal to or greater than 160% of the lateral width of open top surface  21 . 
     Due to the consideration that front surface  20  of transition body  12  serves as a nail striking surface, the front portion of transition body  12  has a vertical wall thickness below nail hole  23  that is equal to the lateral width of open top surface  21 . 
     (6). Based on mechanics analyses, maximum load capacity of a wall hanger is determined by the weight load that causes the anchored nail in wall to rotate to a nail pullout angle, and thus causes nail to be pulled out of wall. Before weight load approaches maximum load capacity (as defined above), load capacity of a hook-above-nail hanger is proportional to the vertical distance between the nail exit point and the bottom edge of hanger. 
     Accordingly, in order to maximize load capacity of hanger  1  of present invention, nail hole exit  24  is at a predetermined height above the bottom edge  16  of lower body  11 , and ratio of “the predetermined height of nail hole exit  24 ” to “the lateral width of open top surface  21  of transition body  11 ” is about 530%. As confirmed by load testing, at the above ratio, hanger  1  of present invention achieves a 50 lb. weight load capacity when it is anchored to a drywall with two 3d penny size finish nails. 
     (7). Based on mechanics analyses, the incline angle of anchored nail in wall does not affect nail pullout angle, nor does it affect load capacity of hanger. Furthermore, in order to maximize load capacity of a hook-above-nail hanger, the vertical distance between the load landing point (i.e. the internal bottom closed end of U hook) and the nail exit point needs to be minimized. By specifying the incline angle of open top surface  21  identical to that of nail hole  23 , such a vertical distance is therefore minimized. Based on the geometry of hanger  1  of present invention, the vertical and lateral wall thickness surrounding nail hole exit  24  can be maximized by decreasing incline angle of nail hole  23 . When two hangers have an identical size, the hanger with smaller incline angle has a greater nail exit height above the bottom edge of hanger, and thus has a greater load capacity. But inclined angle of nail hole  23  needs to be at least some degrees above a horizontal plane to prevent nail from being accidentally pulled out of wall by external force. Accordingly, inclined angle of nail hole  23  is determined at 15 degree that is significantly less than typical 30 to 45 degree incline angle of conventional metal hanger. 
     (8). Hanger body  10  ( FIG. 2 ) has an overall width determined by the greatest lateral wall thickness in transition body  12 , and ratio of “the lateral width of open top surface  21  of transition body  12 ” to “the overall width of hanger body  10 ” is about 50%. This is due to the consideration that overall width of hanger body  10  needs to be sufficiently small to minimize the gap between wall and the top rear surface of picture frame while hanging the picture frame, but the lateral width of top opening of U hook or the lateral width of open top surface  21  needs to be sufficiently large to allow metal wire of picture frame to be easily caught by U hook while engaging metal wire of picture frame into U hook. 
     It is understood that some modifications to hanger  1  can be done to enhance the appearance of hanger  1  without affecting its shear/bending strength or load capacity. For example, front surface  17  of lower body  11 , inclined bottom surface  19  and front surface  20  of transition body  12 , and front surface  28  of upper body  13  can be integrated into a continuously curved front surface. For another example, bottom surface  14  can be an inclined surface rather than a horizontal surface. These modifications are considered within the scope of present invention. 
       FIG. 3  is a perspective view of the second preferred embodiment of hanger of present invention, in which, hanger  31  comprises of a base plate  32  resemble to base plate  2  of first preferred embodiment, a pair of identical left and right lateral projectiles  33  and  34  resemble to left and right lateral projectiles  3  and  4  of first preferred embodiment, and a third central lateral projectile  35 . 
     As similar to base plate  2  of first preferred embodiment, central section  36  of base plate  32  is divided into an upper portion  37  and a lower portion  38 . Third lateral projectile  35  is integrally connected to the lower portion  38  along the centerline of base plate  32 . Third lateral projectile  35  has an inclined nail hole  39  that penetrates across third lateral projectile  35  from inclined top surface  40  to rear surface (not shown), and continuously penetrates across base plate  32 . 
     Hanger  31  of second preferred embodiment offers two advantages over hanger  1  of first preferred embodiment. First, as confirmed by load testing, hanger  31  offers a greater load capacity at 70 lb. as hanger  31  being anchored to drywall with three 3d penny size finish nails. Second, user can install hanger  31  onto wall at desired location by anchoring the first nail through nail hole  39  of third central lateral projectile  35 , so that he can adjust hanger  31  to a level position and subsequently anchor the second and third nails without holding hanger  31  by hand. Hanger  1  requires user to hold hanger  1  by hand at all time while installing hanger  1  onto wall.