Abstract:
A sliding patio door locking rod is designed to keep the view of the outside free of obstruction in both its vertical/inoperative position and its horizontal/operative position. Magnetic retainers hold the rod in position vertically or horizontally. A shortened version of the rod allows the door to slide open slightly to permit ventilation from outside.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates generally to home security. More particularly, it relates to a sliding door locking rod.  
       BACKGROUND OF THE INVENTION  
       [0002]     A variety of devices have been invented to serve as a secondary lock on a sliding glass patio door; that is, a door having an outer framed panel which is fixed in position and an inner framed panel which slides horizontally along tracks mounted at the top and bottom of the door frame to open or close the door. The security rod of Cohen and Evans (U.S. Pat. No. 3,328,920) includes a one-piece rod that pivots between a disengaged and an engaged position. In its disengaged position, the rod is held vertically against the door frame within a “pair of inwardly flared fingers . . . formed to provide a pinching damp”. The rod pivots about a point at its hinged end into its horizontal engaged position. When the rod is engaged, its free end (i.e., the end opposite from the pivot axis) snaps into a bracket on a side edge of the sliding panel to hold the rod horizontal. Perhaps because of the relative novelty of sliding glass patio doors at the time of the Cohen and Evans invention-the patent application was filed in 1965—the device (now known as a “charlie bar”) was mounted about mid-way up the door. The idea was to make the rod dearly visible across the panel, helping to prevent people from “thinking the space was open” and getting injured by colliding with the transparent door. Evans (U.S. Pat. No. 4,135,376) added an apparatus to lock the rod in its horizontal position.  
         [0003]     The device of Zins (U.S. Pat. No. 4.272,113) addresses the situation where the sliding panel is the outer one. The invention of Tierney (U.S. Pat. No. 4,073,522) employs a rod split into left and right halves pivotally hinged where they join together, so that the locking rod changes from its engaged to its stored position by bending upward at its middle. The rod when operational lies horizontally along the bottom of the door frame in the track of the (inner) sliding door. McCartney (U.S. Pat. No. 5,685,582) notes possible problems with the Tierney apparatus encountering mechanical fouling caused by gradual accumulation of dirt in its central pivoting mechanism because of its position at the bottom of the door. McCartney uses a split rod similar to that of Tierney, but mostly elevated above the door track.  
         [0004]     Like the Cohen security rod, the devices of Allenbaugh (U.S. Pat. No. 5,193,865), Brown (U.S. Pat. No. 6,382,689) and Walsh (U.S. Pat. No. 3,821,884) all obstruct the view through the door when they are in their operative positions. McCartney&#39;s locking bar obstructs the view in all its configurations. Tierney&#39;s invention appears inobtrusive in both its operative and inoperative positions, but is relatively complex and, according to McCartney, may malfunction due to accumulated dirt.  
       SUMMARY OF THE INVENTION  
       [0005]     Sliding patio doors have become commonplace, and in many households the possibility of people inadvertently crashing into them is not of particular concern. The locking rod of the present invention provides a completely unobstructed view through the patio door in both operative and inoperative positions, as well as mechanical reliability.  
         [0006]     The locking rod is a single piece, pivotally connected at the base of the door frame. It can swing from a vertical inoperative position to a horizontal operative position. In the preferred embodiment, the rod has an essentially rectangular cross-section. The pivot axis is essentially at the line where the horizontal and vertical parts of the door frame intersect at the right edge of the fixed glass panel (assuming, without loss of generality, that the right panel is fixed and the left panel slides rightward to open and leftward to dose). When the rod is in the horizontal position, it lies flat in the bottom track of the sliding glass door, where it is below the top of the frame of the sliding panel, and thus will not obstruct the view through the panel at all. Because the rod is a single piece, it avoids any problem of dirt accumulating and fouling a complex folding mechanism. In the preferred embodiment of the invention, when the rod is horizontal, its end abuts the sliding panel, preventing it from being opened.  
         [0007]     The rod is held in its vertical/inoperative position magnetically, a simpler and less visible approach than the bracket of Cohen and Evans. In the preferred embodiment, the rod is recessed into the door frame when in its vertical position, and in any case does not obstruct the view through the glass. The rod may have a rectangular cross-section, allowing it to blend in with the door frame. The rod is all but invisible if both it and the door frame are constructed of similar material, such as the same species of wood identically finished. The pivoting capability is provided by an unobtrusive butt hinge coupling the rod to the door frame, whose flanges can themselves be recessed into both members. Because of its simplicity and dosed construction, the butt hinge will not foul, only occasionally requiring lubrication.  
         [0008]     The need for a second bracket as in Cohen to hold the free end of the horizontal rod is also eliminated because the rod lies in the sliding door track. However, to make the rod somewhat less likely to be dislodged from its horizontal position, the end of the rod in the preferred embodiment can be secured magnetically when horizontal.  
         [0009]     In another embodiment of the invention, to provide ventilation, the rod is shorter by some distance D (typically several centimeters) than the full distance from its pivot point to the right frame of the dosed sliding panel, so that the sliding panel can open by a corresponding length D when the rod is horizontal. With this configuration, it is somewhat more likely that the operational locking rod  200  could get dislodged, so magnetic retention of the rod in its horizontal position becomes a more important consideration. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]      FIG. 1  is an isometric drawing showing the two panels of a sliding patio door system, and how the locking rod of the present invention changes position by rotating about its pivot axis.  
         [0011]      FIG. 2  is a front view of the locking rod of the present invention held magnetically in its vertical/inoperative position by a vertical retainer.  
         [0012]      FIG. 3  is an isometric drawing of the butt hinge about which the locking rod rotates, recessed into the rod and the door frame near the bottom of the outside edge of the fixed panel.  
         [0013]      FIG. 4  is a top cross-sectional view showing the locking rod in its horizontal/operative position, abutting the sliding panel.  
         [0014]      FIG. 5  is a top cross-sectional view showing an alternate embodiment of the invention having a shortened rod to allow the sliding door to open slightly to provide ventilation. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0015]      FIG. 1  shows the type of sliding door system  100  contemplated by the present invention. Coordinate directions  105  are provided in this and all other drawings to assist in providing orientation. The door system  100  consists of two panels  110 , a fixed panel  115  and a sliding panel  120 . The sliding panel  120  is moved horizontally within two tracks  140  attached to the door frame  135 , a top track  145  (not shown) and a bottom track  150 . In the figure, the sliding panel  120  is the left panel, and has a movement direction  160  rightward to open and leftward to dose. The reverse arrangement is also common. Typically, each panel  110  consists of a glass pane  125 , within its own panel frame  130 . The sliding panel  120  is the inner panel  110 , and the fixed panel  115  is the outer panel  110 . The locking rod  200  pivots about pivotally mounted at the right end of the bottom track  150 , so that the rod  200  can be rotated counterclockwise to move from its vertical position  230  to its horizontal position  240 . The rotation axis  260  is provided in the preferred embodiment by a butt hinge, attached to the locking rod  200  and to the right door frame member  155 . The locking rod  200  is held magnetically in its vertical position by a vertical retainer  400 . In the preferred embodiment, a locking rod magnet  420  in the locking rod  200  is attracted to a magnet or plate including some ferromagnetic material in the vertical retainer  400 . According to the American Heritage Dictionary, “ferromagnetic” is defined as “[o]f or characteristic of substances such as iron, nickel, or cobalt and various alloys that exhibit extremely high magnetic permeability, a characteristic saturation point, and magnetic hysteresis.” Note that a ferromagnetic material is not necessarily a magnet, and need not contain iron.  
         [0016]      FIG. 2  shows details of the locking rod magnet  420  in contact with the ferromagnetic vertical retainer  400  within the right door frame member  155  when the locking rod  200  is in its vertical position  230 . A variation of this where only one of the vertical retainer  400  and the adjacent part of locking rod  200  is a magnet, and the other contains ferromagnetic material (e.g., iron or steel), is well within the scope of the present invention.  
         [0017]     In the preferred embodiment shown in  FIG. 3 , one flange  310  of a butt hinge  300  is attached to the right door frame member  155 , and the other flange  310 , to the locking rod  200 . The flanges  310  may be recessed into the right door frame member  155  and the locking rod  200 , respectively, allowing the locking rod  200  to fold flat about the knuckle  320  of the butt hinge  300 .  
         [0018]      FIG. 4  shows the locking rod  200  in its horizontal position  240 , in the bottom track  150  where it is engaged and abutting the sliding panel  120 . In the preferred embodiment, a magnetic configuration, analogous to the one used to hold the locking rod  200  in its vertical position  230 , is employed to hold the locking rod  200  more securely in its horizontal position  240 . A horizontal retainer  500  containing ferromagnetic material is located either within the track or immediately adjacent to the track in the frame of the fixed panel  115 . A matching area of ferromagnetic material is contained in the locking rod  200 . In the preferred embodiment, the horizontal retainer  500  is a horizontal retainer plate  510 , which is a plate magnet mounted on (or recessed into) the fixed panel frame. The same locking rod magnet  420  that couples the locking rod  200  to the vertical retainer plate  410  in the vertical position  230  also might also be used to couple it to the horizontal retainer plate  510  in the horizontal position  240 ; alternately, separate magnets can be used. In another alternate embodiment, no magnetic retention is used when the locking rod  200  is horizontal.  
         [0019]      FIG. 5  shows a second alternate embodiment of the present invention, in which the locking rod  200  has been shortened by a distance D  520  (typically several centimeters but in all cases at least one centimeter) so that even when the locking rod  200  is in its operative horizontal position, the sliding door can be opened by the same amount D  520  to provide ventilation. Obviously, this approach relinquishes a certain amount of security in exchange for the fresh air. In this configuration, including the optional horizontal retainer  500  becomes more important because the locking rod  200  when horizontal can more easily become dislodged by the door, perhaps in combination with a foreign object in the bottom track  150 , as the door is moved from its dosed to its partially open position.  
         [0020]     The present invention is not to be limited to all of the above details, as modifications and variations may be made without departing from the intent or scope of the invention. For example, different types of magnets could be used in the vertical position  230 . Consequently, the invention should not be limited by the specifics of the above description, but rather be limited only by the following claims and equivalent constructions.