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This application claims the benefit of U.S. Provisional Application No. 60/416,378, filed Oct. 5 2002. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention pertains to counterbalanced movable or removable closures, more particularly to an interlocking jamb mounted locking shoe and sash mounted locking pivoted support arm system. 
     2. Description of the Prior Art 
     U.S. Pat. No. 2,796,630 patented Jun. 25, 1957 by G. B. Haas describes a self-locking sash balance in which a plunger from the sash rests upon a first radial side of a tripping lever that is pivotally mounted on a shoe that is biased upward by a balance spring. The second radial side of the tripping lever engages a pivoted detent so that when the plunger applies weight of the sash upon the first radial side, the second radial side presses upward on one side of the detent, rotating the other side of the detent out of biting engagement with a vertical side of the track in which the shoe rides. 
     U.S. Pat. No. 4,799,333 patented Jan. 24, 1989 by Westfall et al. describes a lock shoe system for a take-out window in which a horizontal pin from the sash pushes back a biter knife lever pivotally mounted on the balance shoe so that the knife disengages from the vertical track in which the shoe slides. 
     U.S. Pat. No. 5,189,838 patented Mar. 2, 1993 by N. R. Westfall describes a tilt sash lock shoe system in which an elongated sash pin can be lowered into or lifted vertically from a slot formed by confronting first and second vertical surfaces. The first vertical surface is a wall of the shoe. The second vertical surface is on a pivoted element that has a biting edge on one side of the pivoted element, that is rotated against the window track by upward force of the system&#39;s counter balance spring on the other side of the pivoted element. When the sash is tilted from the vertical with the pin in the shoe, or when the sash is removed from the window, the biting edge presses into the track. When the sash is vertical with an oblong end of the pin in the shoe, the oblong end forces the first and second vertical surfaces apart which rotates the pivoted element so that the biting edge is moved away from the track. 
     U.S. Pat. No. 5,231,795, patented Aug. 3, 1993 by N. R. Westfall describes a shoe designed to be supported by a spring counterbalance system, that is mounted on a jamb for vertical movement on the jamb. A lower outward corner of a sash rests on an inward extending platform extension of the shoe. A horizontally sliding bolt in the shoe is moved inward horizontally into a recess in the lower corner of the sash. Movement of the bolt is by a vertical pin eccentrically mounted on the top of a cylinder that rotates on a vertical axis. The cylinder is turned by a hex keyed hand tool from below the cylinder. In order to remove the sash from the window, the sash is moved down until an upward turned outer end of the bolt is below a downward depending lance that extends outward from the jamb in the direction of the sash. The bolt is slid outward so that when the sash is lifted, the shoe moves up until the outer end of the bolt catches under the lance. The sash, now free of the bolt, is then slid laterally off the platform for removal from the window frame. 
     U.S. Pat. No. 6,041,475 patented Mar. 28, 2000 by M. J. Nidelkoff for a locking counterbalance shoe for tiltably removable sash windows describes a balance shoe in which a first element that is supported by the balance spring contains a second pivoted locking element having a serrated edge that grips the jamb track under the urging of an actuator spring between the first and second elements when there is no sash in the window frame. The second element unlocks from the jamb track when the flat sash pin of a vertical sash rests upon the second element, compressing the actuator spring. When the sash is rotated from vertical, the flat sash pin turns the second element to the locking position wherein the serrated edge grips the jamb track. 
     SUMMARY OF THE INVENTION 
     It is one object of the invention to provide a lock shoe system that locks the shoe to the jamb against upward movement of the shoe. 
     It is another object of the invention that the lock shoe system locks an arm, pivotally mounted on the sash, to the shoe. 
     Other objects and advantages will become apparent to one reading the ensuing description of the invention. 
     A lock shoe system for a window that includes a vertical jamb and a sash mounted in the window for movement up and down alongside the jamb, includes a balance shoe mounted on the jamb for vertical movement on the jamb, a platform on the balance shoe configured for vertical support of an item on the platform when an item is on the platform, and a bracket fixedly mounted on the sash. A first arm mounted on the bracket for rotating about a first axis is configured for transferring lift from a first end of the arm to the bracket, the first end of the first arm being on the platform. A second arm is mounted on the balance shoe for rotating about a second axis. A portion of the second arm spaced from the second axis includes a second end configured for hooking to the jamb at at least one height along the vertical height of the jamb when the second arm is at a first rotary position of the second arm, the portion comprising a third end configured for extending through a first opening in the platform and through a second opening in the first arm when the second arm is at a second rotary position of the second arm. The second arm includes means on the second end for locking the third end in the second opening. The second axis is preferably parallel to the first axis. 
     U.S. Provisional Application Ser. No. 60/416,378, filed Oct. 5, 2002 is hereby incorporated herein in its entirety by reference. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       In order that the invention be more fully comprehended, it will now be described, by way of example, with reference to the accompanying drawings, in which: 
         FIG. 1  is a right side perspective view of a lock shoe system according to the invention showing the sash support arm on the shoe saddle, locked to the shoe. 
         FIG. 2  is a left side perspective view of the assembly of FIG.  1 . 
         FIG. 3  is a right side perspective view from adjacent to the front of the system showing the system locked as in  FIG. 1 , mounted on a jamb and sash of a window. 
         FIG. 4  is a right side perspective view from adjacent to the back of the system showing the locked, mounted system of FIG.  3 . In this view, a spring balance is visible. 
       FIG.  5 . is a right side perspective view of the lock system of  FIG. 1  showing the shoe locked to the jamb against upward movement of the shoe, and the sash support arm disconnected from the shoe. 
         FIG. 6  is a left side perspective view of the assembly of FIG.  5 . 
         FIG. 7  is a is a right side perspective view from adjacent to the front of the system showing the shoe mounted on the jamb, locked to the jamb against upward movement, and the sash support arm and bracket disconnected from the shoe, mounted on a sash that is raised above the saddle of the shoe. 
         FIG. 8  is a right side perspective view from adjacent to the back of the system of FIG.  7 . 
         FIG. 9  is a right side view of the shoe arm. 
         FIG. 10  is a rear view of the shoe arm of  FIG. 9  taken at  10 — 10 . 
         FIG. 11  is a right side view of the spring clip receiver for the shoe arm. 
         FIG. 12  is a front view of the spring clip receiver of FIG.  11 . 
         FIG. 13  is a right side view of the sash support arm. 
         FIG. 14  is a right side perspective view of the sash support arm pivotally mounted on a sash on a pin through a portion of the sash. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Before explaining the invention in detail, it is to be understood that the invention is not limited in its application to the detail of construction and arrangement of parts illustrated in the drawings since the invention is capable of other embodiments and of being practiced or carried out in various ways. It is also to be understood that the phraseology or terminology employed is for the purpose of description only and not of limitation. 
     Referring to  FIGS. 1-4 , and  9 - 13 , shoe  34  of assembly  30  is slidingly mounted on jamb  38 . 
     The shoe is supported vertically by spring balance  40  by way of cross pin  32  in downward open U shaped hooks  36 . 
     Shoe  34  bears part of the weight of sash  46  which travels up and down between two jambs of a window. It is expected that another assembly according to the invention would be mounted on an opposite side of the sash and connected to the jamb adjacent to that side of the sash, also bearing part of the weight of the sash. For the purpose of description of the invention only one assembly on one side of the sash is shown and described. It should be understood that the other assembly preferably would be a duplicate of the one herein described. 
     The present invention will safely support and lock heavy steel and glass sashes such as those found in factories and lofts, as well as lighter wood or plastic sashes. 
     Bracket  50  is mounted on sash  46 , screwed into stile  52  by screws  54  through mounting holes  56 . 
     Sash support arm  60  rotates on pin  62  on axis  64  in pivot holes  66  and  68 . 
     Shoe arm  70  rotates on pin  72  on axis  74 . Pin  72  passes through upward open C-shaped bearings  80 ,  82  in shoe  34 , and downward open C-shaped bearing  86  in shoe arm  70 . 
     Shoe arm  70  is latched by notch  88  and protrusion  92  of arm  70  in spring clip  90  opening  94 . 
     Clip  90  is preferably made of steel. 
     Curved hook  100  of shoe arm  70  extends through opening  104  in platform  110  of the shoe, and into and preferably through opening  112  in arm  60  of bracket  50 . The curve of hook  100  is such that the curve prevents arm  60  from moving axially parallel to axis  64 , laterally normal to axis  64 , and upward or downward from platform  110 . This prevents bracket  50  and the portion of the sash to which bracket  50  is attached from moving outward from the window axially, away from the jamb normal to axis  64 , downward past the platform, or upward past the platform. 
     End  96  of arm  60  extends further from axis  64  than distance  98  of the shortest radius of axis  64  to the surface of bracket  50  so that arm  60  is prevented from rotating up to horizontal by impingement of end  96  against the bracket above the horizontal level of axis  64 , so that lift expressed on end  124  by platform  110  is transferred to axis  64  by arm  60  when arm  60  is prevented from rotation by impingement of end  96  against the bracket. It should be understood that this may comprise a protrusion of the surface of the bracket that prevents rotation of arm  60  so that lift expressed on end  124  by platform  110  is transferred to axis  64  by arm  60  when arm  60  is prevented from rotation by impingement of end  96  against the protrusion. 
     Preferably the top  106  of arm  60  at end  96  extends farther from axis  64  than the bottom of the arm. 
     Sash  46  containing glass  47 , locked to shoe  34  by this configuration moves up and down with the shoe. 
     Preferably the curve of hook  100  is on a radius  102  taken from axis  74 , that is, a portion of the circumference of a circle about axis  74 , shown in FIG.  5 . 
     Spaces  114 ,  116  between end  118  of curved hook  100  and the horizontally  115  and downward  117  facing adjacent surfaces  120  and  121  of the shoe are smaller than the thickness  122  of arm  60  from opening  112  to end  124  that extends into the shoe. 
     Preferably the distance between end  118  of hook  100  and the closest surface of the shoe when hook  100  is in opening  112  and shoe arm  70  is latched in clip  90  is smaller than the thickness  122  of arm  60  such that arm  60  cannot slip past end  118  between end  118  and the closest surface of the shoe to end  118 . 
     Referring to  FIGS. 5-13 , bracket  50  is screwed into the side of the sash at about the lowest part of the sash with arm  60  hanging down, or vertical, from axis  64 . Shoe arm  70  is detached from spring clip  90  by bending the clip away  128  from engagement with notch  88 , and is rotated on axis  74  until end  130  extends into opening  132  in wall  134  of jamb  38 . This rotates curved hook  100  out of opening  112  and vertical opening  104 . 
     Shoe arm  70  hooks in opening  132  by the upward force of the shoe applied to shoe arm  70 . Preferably opening  132  is used for hooking of arm  70  to the jamb. Hooking to the jamb of the arm rotated against the jamb can be to a protrusion on the jamb caught by the arm so long as the protrusion does not interfere with operational sliding of the shoe in the jamb for unlocked vertical movement of the sash. 
     In  FIG. 14 , arm  60  is mounted on pin  62  through holes  142 ,  144  in sash  46 . Arm  60  rotation is limited by impingement of end  96  against wall  148  so that lift expressed on end  124  by platform  110  is transferred to sash  46  by way of arm  60  and pin  62 . 
     Steps for installing the system and sash on a window jamb include: 
     1. Screw bracket  50  into side  136  of sash  46  at approximately the lowest part of the sash with arm  60  hanging down or vertically from pin  62 . 
     2. Detach shoe arm  70  from clip  90 . Preferably shoe arm  70  is shipped with shoe arm  70  locked in clip  90 . 
     3. Mount the shoe  34  on jamb  38  with shoe arm  70  hanging down from pin  72 . 
     4. Mount balance  40  on the jamb. 
     5. Crank the balance to load its internal spring. 
     6. Put rod  140  and cross pin  32  in hooks  36 . 
     7. Slowly let the balance lift the shoe until end  130  of shoe arm  70  which is biased against wall  134  of the jamb by the rotational vector of weight of the shoe arm, catches in opening  132 , hooking in the slot from the upward thrust of the shoe on the shoe arm. 
     8. Mount the sash on the jamb and bring the sash down until arm  60  sits on platform  110 . 
     9. Push the sash down until shoe arm  70  end  130  can be moved out of opening  132 . 
     10. Rotate shoe arm  70 , moving curved hook  100  through openings  104  and  112  until shoe arm  70  snaps into clip  90  opening  94  by way of notch  88  and protrusion  92 . 
     Steps for removing the sash from the window jamb include: 
     1. Move the sash down so that shoe arm  70  is lower than opening  132  in the jamb. 
     2. Release the shoe arm from clip  90  so that the shoe arm rotates under its own weight toward jamb wall  134  so that end  130  rests against the jamb wall and curved hook  100  moves down out of openings  112  and  104  which frees arm  60  from shoe  34 . 
     3. Move the sash up until end  130  moves into opening  132  and hooks there by upward force of the shoe. 
     4. Remove the sash from the jamb. 
     Although the present invention has been described with respect to details of certain embodiments thereof, it is not intended that such details be limitations upon the scope of the invention. It will be obvious to those skilled in the art that various modifications and substitutions may be made without departing from the spirit and scope of the invention as set forth in the following claims. 
     DRAWING DESIGNATORS (INFORMAL LIST) 
     
         
           30  assembly 
           32  cross pin 
           34  shoe 
           36  hooks, downward, U-shaped 
           38  jamb 
           40  spring balance 
           46  sash 
           47  glass 
           50  bracket 
           52  stile 
           54  screw 
           56  mounting hole 
           60  sash support arm 
           62  pin 
           64  axis 
           66  pivot hole 
           68  pivot hole 
           70  shoe arm 
           72  pin 
           74  axis 
           80  bearing, upward open, C-shaped 
           82  bearing, upward open, C-shaped 
           86  bearing, downward open, C-shaped 
           88  notch 
           90  clip, spring 
           92  protrusion 
           94  opening 
           96  end of arm  60   
           98  distance 
           100  curved hook 
           102  radius 
           104  opening 
           106  top 
           110  platform 
           112  opening 
           114  space 
           115  horizontally 
           116  space 
           117  downward 
           118  end 
           120  surface 
           121  surface 
           122  thickness 
           124  end 
           128  away 
           130  end 
           132  opening 
           134  wall of jamb 
           136  side 
           140  rod 
           142  hole 
           144  hole 
           148  wall

Summary:
A window balance shoe includes a downward depending pivoted arm that locks the height of the shoe on the jamb by catching in an opening in the jamb wall, or rotates out of the opening in the jamb wall and extends in a curved arm having a radius from the arm&#39;s pivot, through a hole that is through a horizontal platform on the shoe and through a hole in an arm supported by the platform, that pivots on and supports a bracket that is attached to the sash.