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RELATED PATENTS 
     U.S. Pat. No. 5,934,020 has the same sole inventor as the instant application (patent) and is hereby incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to locking mechanisms for window guard systems. Window guards cover windows and prevent unauthorized access amongst other things. 
     2. Description of the Prior Art 
     U.S. Pat. No. 5,934,020 issued to McCracken describes a window guard and lock. The instant invention has a new and unique locking system which would discourage unwanted entry, yet permit a person in the home the ability to disengage the locking system and egress from the structure, home of building. The new window guard system incorporates improvements mainly in the locking mechanism. The structural and physical differences of the new window guard system will be made apparent from the following description thereof. 
     SUMMARY OF THE INVENTION 
     The present invention is a locking mechanism for a window guard system. A window is covered by the window guard. Many window guards are permanently affixed, and in case of emergency, exiting through a window so protected would not be possible. The invention herein contemplates a locking mechanism accessible to a person inside the home, building or structure. This locking mechanism may be opened by such a person, permitting the window guard to be opened from within the home. The window guard opens by rotating the main body of the window guard about a set of J-shaped pins located on a first side. For the record, the term home includes a building, a structure, an apartment, a domicile, a basement, an attic or any other window to which the window guard is affixed thereto. 
     The window guard is mounted about the exterior of a window. The window guard is designed to prevent any access from the outside to the inside through the window. Provisions are made to secure the window guard to the frame surrounding the window. These securing means are of sufficient quality to deter the removal of the window guard from the outside of the window short of extraordinary means. 
     However, the window guard may be opened from the inside by an authorized person. This may be done to effect an emergency egress, such as in the case of a fire. It may also be done to more easily clean the window. Additionally, sometimes it may be desirable to have the window opened with the window guard not impairing the view. For these and other reasons, it is desirable to have the capability to open the window guard. 
     The window guard has a three lock mechanism which is employed to secure the window guard in a secure and locked position. The three lock mechanism is mounted on the interior of the second portion of the locking plate. The left side of the first extension bracket is received in an opening defined by the three lock mechanism and the interior of the third portion of the locking plate. 
     The three lock mechanism basically comprises a rectangular channel with an upper portion and a lower portion. The channel is secured to the locking plate on the inside of the window guard. The upper portion of the channel is open and the lower portion of the channel is closed. A first end plate is provided at the intersection of the upper portion and the lower portion. At the rear of the first end plate is a first slot or groove. At the top of the upper portion of the channel is a second end plate, parallel to the first end plate. At the rear of the second end plate is a second slot or groove, in a direct linear relation with the first slot or groove. 
     A first locking element resides in the channel. It is adapted to slide up and down in the channel and resides in the first slot or groove. The top portion of the first locking element is the grasping portion which is integral with and perpendicular to the remainder of the first locking element. The grasping portion is a rectangular plate designed to rest atop the first end plate. The grasping portion may be grasped and slidingly moved in the upper portion of the channel from the first end plate to the second end plate. The lower portion of the first locking element is generally an elongated rectangle. It has a slot which runs down the center of the lower portion. When the first locking element is slid from one position to another, the slot travels upward and downward as well. On the slot is an arcuate cutout. The arcuate cutout is located in the closed lower portion of the channel. In the front of the closed lower portion of the channel and in the rear of the closed lower portion of the channel is an aperture, each aperture in direct linear alignment. These two apertures are also in direct alignment with an aperture located on the first extension bracket. These three apertures in linear alignment are designed to receive a key there through, securing the first extension bracket in the locking plate. 
     The second slot or groove is designed to receive an elongated rectangular element there through which would rest atop the grasping element of the first locking element. This may be termed the second locking element. It disables the ability of the first locking element to slide in the upper open portion of the channel as well as the lower closed portion of the channel. 
     When the second locking element is removed, the first locking element can slide up and down between the boundaries established by the upper portion of the open channel. There is one position when the arcuate cutout on the slot is in alignment with the aperture on the front of the closed channel, the rear of the closed channel and the first extension bracket. The key fits through all of these apertures and secures the first extension bracket to the locking plate. The key has a portion which extends through the front of the lower portion of the channel. The key further includes a portion which fits in the slot of the first locking element, which permits the first locking element to slide freely up and down. The key cannot be withdrawn until the first locking element slides to the precise position where the arcuate cutout is in alignment with the other apertures. The first locking element cannot slide at all when the second locking element is engaged. The key may be considered the third locking element. The third locking element includes other provisions to prevent it from being casually removed, these other provisions will be discussed in the detailed description of the invention. 
     At this point, after opening, actuating or deactivating the three locking elements comprising the locking mechanism, the window guard may be pivotally opened by rotation about the hinge members. As discussed, the locking mechanism must be opened in a specific order in order to open the window guard. Once the window guard has been opened, one may egress the building or clean the window or window guard assembly. By simply reversing the process, the window guard may be secured about the outside portion of the window. 
     The metallic and inter fitting elements of this invention may be protected against oxidation by appropriate treatment of anti-rust compositions. 
     The above brief description sets forth rather broadly the more important features of the present invention in order that the detailed description thereof that follows may be better understood, and in order that the present contributions to the art may be better appreciated. There are, of course, additional features of the invention that will be described hereinafter and which will form the subject matter of the claims appended hereto. 
     In this respect, before explaining the invention in detail, it is to be understood that the invention is not limited in its application to the details of the construction and to the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced and carried out in various ways. Also, it is to be understood, that the phraseology and terminology employed herein are for the purpose of description and should not be regarded as limiting. 
     As such, those skilled in the art will appreciate that the conception, upon which this disclosure is based, may readily be utilized as a basis for designing other structures, methods, and systems for carrying out the several purposes of the present invention. It is important, therefore, that the claims be regarded as including such equivalent constructions insofar as they do not depart from the spirit and scope of the present invention. 
     It is therefore an object of the present invention to provide a window guard which may be opened from the inside of the home, once the window has been opened, permitting emergency egress from the building. 
     It is therefore an object of the present invention to provide a window guard which may be opened from inside of the home once the window has been opened, to permit the cleaning, repair or replacement of the window. 
     It is an object of the present invention to provide a locking mechanism which must be unlocked before the window guard may be opened. 
     It is an object of the present invention to provide a locking mechanism with three separate locking subassemblies. 
     It is an object of the present invention to provide a window guard which is easy to install about a window on its window frame, using removal resistant fasteners or other means to mount the locking plate on the first side and the hinges on the second side to prevent their removal. 
     It is an object of the present invention to provide a window guard which has a pleasant appearance, but which at the same time prevents access to the locking mechanism from outside the window. 
     It is an object of the present invention to provide a window guard which is of strong and durable construction and discourages illegal entry. 
     These together with still other objects of the invention, along with the various features of novelty which characterize the invention, are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and the specific objects attained by its uses, reference should be made to the accompanying drawings and descriptive matter in which there are illustrated preferred embodiments of the invention. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be better understood and the above objects as well as objects other than those set forth above will become more apparent after a study of the following detailed description thereof. Such description makes reference to the annexed drawings wherein: 
     FIG. 1 is a view of the locking mechanism and the window guard system as seen from inside the home. 
     FIG. 2 is a view of the locking mechanism and the a window guard system as seen from outside the home. 
     FIG. 3 is a side view of the locking mechanism  15  shown in FIG.  1 . 
     FIG. 4 is a top view of the locking mechanism as shown in FIG.  3 . 
     FIG. 5 is a bottom view of the locking mechanism as shown in FIG.  3 . 
     FIG. 6 is a partial view showing the locking mechanism and the first extension bracket. 
     FIG. 7 is a front view of the locking mechanism. 
     FIG. 8 is a cutaway view of the locking mechanism showing the key in the secured location. 
     FIG. 9 is a cutaway view of the locking mechanism showing the internal arrangement to permit the removal of the key. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     With reference now to the drawings, a locking mechanism for a window guard system embodying the principles and concepts of the present invention will be described. 
     Turning initially to FIGS. 1 and 2 a view of the locking mechanism for a window guard system  10  is shown. FIG. 1 is a view from inside the home looking out. FIG. 2 is a view from outside the home looking in. 
     The locking mechanism for a window guard system  10  is mounted on the outside of window frame  12 . To access the window guard locking mechanism  15  from the inside, the window  22  must be open. One is not able to access the window guard locking mechanism  15  from the outside. 
     The window frame includes a first side  14 , a second side  16 , a bottom side  18 , and a top side  20 . 
     The second side  16  of the window frame  12  includes a top hinge  24  with a top J-shaped element  26  and a bottom hinge  28  with a bottom J-shaped element  30 . The hinges ( 24 ,  28 ) are mounted in a linear fashion, one over the other, the top (first) hinge  24  proximal the top of the second side  16  of the window frame  12  and the bottom (second) hinge  28  proximal the bottom of the second side  16  of the window frame  12 . The hinges ( 24 ,  28 ) would be secured to the outside window frame  12  by a first plurality of mechanical fasteners  25 . These mechanical fasteners  25  may be chosen to be any of a variety of screws, nails or the like. It would be preferable if the mechanical fasteners  25  would be of the type which would resist removal once they are inserted. 
     A first extension bracket  48  generally has an elongated C-shaped configuration. The first extension bracket  48  has a left side  54 , a top side  50  and a bottom side  52 . The left side  54  is intermediate the top side  50  and the bottom side  52 . A handle  53  is located on the first extension bracket  48  on the left side  54 . The handle  53  is located proximal the midpoint of the length of the left side  54 . The first extension bracket  48  has a first side  47  and a second side  49 . The handle  53  is secured to the first side  47 . The extension bracket  48  further has a third side  46  and a fourth side  51 . The third key or pin receiving aperture  100  is located on the fourth side  51 . This secures the first extension bracket  48  to the locking mechanism in an area proximal the locking plate  40 . The slot  154 , the second key receiving aperture  146  and the first key or pin receiving aperture  140 , and the key or pin  170  will be described in further detail in the description of the locking mechanism. 
     A second extension bracket  32  generally has an elongated C-shaped configuration. The second extension bracket  32  has a first side  38 , a top side  34  and a bottom side  36 . The first side  38  of the second extension bracket  32  is intermediate the top side  34  and the bottom side  36 . Further, the top side  34  is perpendicular to the top end of the first side  38  and the bottom side  36  is perpendicular to the bottom end of the first side  38 . The first side  38  has a first hollow cylindrical element  27  and a second hollow cylindrical element  29  secured thereon. The top J-shaped element  26  is slidingly engaged in the first hollow cylindrical element  27 . The bottom J-shaped element  30  is slidingly engaged in the second hollow cylindrical element  29 . This permits the second extension bracket  32  and all it attached to, to have the capability to rotate or pivot about the J-shaped elements ( 26 ,  30 ) when the locking mechanism is disabled. 
     A locking plate  40  is secured to the first side  14  of the outside window frame  12 . The locking plate  40  would be secured to the first side  14  of the outside window frame  12  by a second plurality of mechanical fasteners  33 . These mechanical fasteners  33  may be chosen to be any of a variety of screws, nails or the like. It would be preferable if the mechanical fasteners  33  would be of the type which would resist removal once they are inserted. The first plurality of mechanical fasteners  25  and the second plurality of mechanical fasteners  33  may be chosen to be the same or to be different. If the fastener types were different it may offer greater resistance to tampering or the like. 
     The locking plate  40  is a single piece of metal with a first bend  60  and a second bend  62  in it. The first portion  42  is secured to the first side  14  of the outside window frame as described in the previous paragraph. The second portion  44  is perpendicular to the first portion  42  about the first bend  60 . The first portion  42  and the second portion  44  are the same length (ie: they traverse from the top side  20  of the outside window frame  12  to the bottom side  18  of the outside window frame  12 ) and are about the same width. The third portion  46  of the locking plate  40  is perpendicular to the second portion  44  of the locking plate  40  about a second bend  62 . The third portion  46  of the locking plate  40  is parallel to the first portion  42  of the locking plate  40 . The first portion  42  of the locking plate  40  and the third portion  46  of the locking plate  40  although parallel extend in exactly the opposite direction from each other and the second portion  44  from the first bend  60  and the second bend  62  respectively. This arrangement can be seen in FIG. 4 when viewing the locking plate  40  from the top. At the bottom of the intersection of second portion  44  and the third portion  46  is a plate  45 . Plate  45  is horizontal, forming a bottom. The bottom side  52  of the first extension bracket  48  can slide on to and off of plate  45  when the locking mechanism  15  is completely released. 
     The main guard  80  has a first side  86 , a second side  88 , a top side  82  and a bottom side  84 . The central area of the main guard  80  has a protective configuration. The protective configuration may be bars forming a lattice, bars disposed closely in a horizontal relationship, bars disposed closely in a vertical relationship, bars disposed closely in any of a plurality of angular dispositions, bars forming an ornamental device which prevents entry (such as that shown in the Figures of U.S. Pat. No. 5,934,264), or another arrangement for preventing access to the window from the outdoor. Closely is defined as close enough together to protect the window and the access thereto from the outside of the home. The central area of the main guard  80  is shown forming a lattice in FIGS. 1 &amp; 2. 
     The main guard top side  82  has a first aperture  90  on the first side and the main guard top side  82  has a second aperture  92  on its second side. 
     The main guard bottom side  84  has a third aperture  94  on the first side and the main guard bottom side  84  has a fourth aperture  96  on its second side. 
     The first extension bracket top side  50  slidingly interfits in the first aperture  90 . The first extension bracket bottom side  52  slidingly interfits in the second aperture  92 . This permits the first extension bracket  48  to be slid to any of a variety of positions within the apertures ( 90 ,  92 ) located on the main guard first side  86 . This allows the window guard to be adapted to fit any of a variety of windows as well. 
     The second extension bracket top side  34  interfits in the third aperture  94 . The second extension bracket bottom side  36  interfits in the fourth aperture  96 . The permits the second extension bracket  32  to be slid to any of a variety of positions within the apertures ( 94 ,  96 ) located on the main guard second side  88 . 
     Now turning to the rest of the figures, the locking mechanism  15  and its function and relation to the rest of the invention is shown. Inside the left or first side of the window frame  14  is the locking plate  40 . The locking plate  40  has the locking mechanism  15  secured thereto. The locking mechanism  15  is secured to the interior of the locking plate  40 , which is only accessible from the inside once the window  22  is open. The locking mechanism  15  is secured to the locking plate  40  somewhere about the midpoint between the top and bottom of the locking plate  40 . The locking mechanism  15  would be secured to the second portion  44  of the locking plate  40 . The locking mechanism  15  is secured to the second portion  44  of the locking plate  40  by any of a variety of means including mechanical fasteners or welding. This description of the orientation of the locking mechanism  15  with respect to the locking plate  40  on the window guard  10  will be better seen in the figures. The locking mechanism  15  includes several subassemblies which gives the mechanism three individual locking devices which must be disabled before the window guard can open by pivoting on the J-shaped elements ( 26 ,  30 ) located on the pair of hinges ( 24 ,  28 ). 
     The locking mechanism  15  is a generally rectangular channel with a top side  110 , a first side  114 , a second side  116 , a front side  118 , a back side  120  and a bottom side  112 . The channel  122  has an upper portion  124  and a lower portion  126 . The upper portion  124  is open, ie the upper portion  124  does not have a front side. The lower portion  126  is closed, we: the lower portion does have a front side  118 . The upper portion  124  is separated from the lower portion  126  by a first end plate  128  which is parallel to both the top side  110  and the bottom side  112 . The top side  110  has a first groove  130  proximal the back side  120 . The first end plate  128  has a second groove  132  proximal the back side  120 . The first groove  130  is in linear alignment with the second groove  132 . The first groove  130  and the second groove  132  extend generally from the first side  116  to the second side  114 . 
     The front side  118  of the channel  122  has a first opening  140  generally centrally located thereon. The first opening  140  has a lower circular opening  142  with a first larger diameter mated with an upper circular  144  opening with a second smaller diameter giving the first opening the appearance of a “Figure 8”. The back side  120  of the channel  122  has a second opening  146  generally centrally located thereon, the second opening  146  has a circular opening with a first larger diameter identical to and in direct linear relation to the first opening first larger diameter. 
     An elongated first tongue  150  is slidably received in the second groove  132 , the first tongue  150  having a second end plate  152  which is perpendicular to the remainder of the first tongue  150  and when not acted upon rests atop the first end plate  128 . The elongated first tongue  150 , when the second end plate  152  is at rest atop the first end plate  128 , substantially transits the lower portion  126  of the channel  122 . The elongated first tongue  150  has a slot  154  which is centrally located on the first tongue  150  and has a length equal to about that of the lower portion  126  of the channel  122 . An arcuate cutout  156  is located at a precise position along the slot  154 . Although the figures do not give exact dimensions, they give approximate dimensions, which will give one a sense of the length of the slot  154 , the location of the arcuate cutout  156  and the proportion of the upper portion  124  of the channel  122  to the lower portion  126  of the channel  122 . The second end plate  152  may be grasped and moved in a sliding fashion until it intersects the top side  110  of the channel  122 . Therefore, the first tongue  150  may slide the length of the upper portion  124  of the channel  122 , having the effect of moving the slot  154  and thus the arcuate cutout  156  located thereon the same length in the lower portion  126  of the enclosed channel  122 . 
     An elongated second tongue  160  is slidably received in the first groove  130 . The second tongue  160  has a top  162 , top portion  164 , a bottom portion  166  and a bottom  168 . The bottom  168  of the second tongue  160 , when inserted fully through the first groove  130  rests atop the second end plate  152 . This has the action of locking the first tongue  150  in place, forcing the second end plate  152  to maintain its position in contact with the first end plate  128 . When inserted, the bottom portion  166  of the second tongue  160  is in the upper portion  124  of the channel  122 , and the top portion  164  of the second tongue  160  is above the top side  110  of the locking mechanism  15 . The top  162  of the second tongue  160  has a grasping element  162  designed to be grasped for removal and insertion through the first groove  130  and the upper portion  124  of the channel  122 . 
     The locking mechanism also includes a key  170 . The key  170  is an elongated generally cylindrical shaft with a first diameter, it includes a bulb  172  on a top portion  174  and a cutout portion  176  along the shaft  178 . The key  170  is inserted through the front side  118  “figure 8” opening  140 , passes through the arcuate cutout  156  on a precise position on the slot  154  of the first tongue  150 , passes through the second opening  146  on the back side  120  and then passes into the final opening  180  on the first extension bracket  48 . This secures the first extension bracket  48  in place with the bottom side  52  or the first extension bracket  48  resting on the horizontal plate  45 , located on the bottom of the locking plate  40 . The cutout portion  176  of the key  170  rests in the slot  154  and permits the second tongue  160  to slide up and down about the key  170 . The bulb  172  on the top portion  174  of the key  178  resides in the area  182  intermediate the slot  154  of the first tongue  150  and the front side  118 . As mentioned, the first tongue  150  may slide up and down after the second tongue  160  has been removed. When the second tongue  160  has been removed, the first tongue  150  is lifted to a certain point. This is the point where the arcuate cutout  156  is located on the slot  154  on the first tongue  150 . This point is designated as the “sweet spot”  200 . This permits the key  170  to slide through the slot  154  because the cutout portion  176  is riot longer retained in the slot  154 . The key  170  is pulled back and rotated to align the bulb  172  with “figure 8” opening ( 140 ,  142 ,  144 ) and to remove key  172  in its entirety when the bulb portion when properly aligned with the “figure 8” opening  140 . At this point, the first extension bracket  48  may be slid toward the main guard, releasing the bracket  48  from the locking plate  40 . And then the entire window guard  10  may pivot open about the second side  16 . The entire window guard  10  may be pulled vertically upward and taken off of the J-shaped elements completely ( 26 ,  30 ). One may do this to install storm windows, clean the windows thoroughly or just to enjoy the view. 
     It is apparent from the above that the present invention accomplishes all of the objectives set forth by providing a new and improved window guard system with a locking mechanism which permits a user to open the window guard while maintaining the security of the structure. 
     With respect to the above description, it should be realized that the optimum dimensional relationships for the parts of the invention, to include variations in size, materials, shape, form, function and manner of operation, assembly and use, are deemed readily apparent and obvious to those skilled in the art, and therefore, all relationships equivalent to those illustrated in the drawings and described in the specification are intended to be encompassed only by the scope of appended claims. 
     While the present invention has been shown in the drawings and fully described above with particularity and detail in connection with what is presently  20  deemed to be the invention, it will be apparent to those of ordinary skill in the art that many modifications thereof may be made without departing from the principles and concepts set forth herein. Hence, the proper scope of the present invention should be determined only by the broadest interpretation of the appended claims so as to encompass all such modifications and equivalents.

Summary:
A locking mechanism for a window guard system is disclosed. The window guard is mounted about the exterior of a window to its frame. The window guard is designed to be have the capability to be opened from the inside. A locking mechanism with three lock subassemblies is provided. A first locking element includes a sliding rod which immobilizes the second lock. The second locking element includes a position dependent sliding member which secures the third lock. The third lock is a pin which must be appropriately rotated in order to be removed when the second locking element is slid to a specific position. At this point, after opening the three locks comprising the locking mechanism, the window guard may be opened by pushing on the now released side causing rotation about the hinge members on the other side. The locking mechanism must be opened in a specific order in order to open the window guard. Once the window guard has been opened, one may egress the building or clean the window or window guard assembly.