Abstract:
A threaded follower mounted on a spiral rod is attached to the first end of a torsion spring, the second end of the torsion spring being connected to a window sash, one end of the spiral rod being attached to a window frame by a gear box that prevents rotation of the spiral rod unless the gear box receives externally provided rotational force by which it then rotates the spiral rod.

Description:
[0001]    This application claims the benefit of U. S. Provisional Application S/N 60/274,594 filed Mar. 10, 2001. 
     
    
     
       BACKGROUND OF THE INVENTION  
         [0002]    1. Field of the Invention  
           [0003]    The invention relates to window balances, more specifically to preloading of a window balance that comprises a torsion spring and a tension spring.  
           [0004]    2. Description of the Prior Art  
           [0005]    U.S. Pat. No. 5,152,032 patented Oct. 6, 1992 by Davis et al. describes a tension plus torsion balance. In this tension plus torsion balance the torsion spring is turned at one end of the spring by a follower. The follower is rotated by a spiral rod that is threadably engaged with the follower so that moving the spiral rod longitudinally through the follower rotates the follower. The spiral rod is moved longitudinally by a window sash as the sash is lifted and lowered, by a first eyelet at one end of the rod that is attached to the window sash.  
           [0006]    In order to provide a predetermined baseline lifting force to be transmitted back to the sash, the torsion spring is preloaded by gripping a second eyelet adjacent to the first eyelet when the first eyelet is not attached to the sash, and twisting the rod until the desired force is obtained, then while holding the rod at that rotational position, attaching the rod to the sash by the first eyelet. U.S. Pat. No. 5,152,032 is hereby incorporated by reference.  
           [0007]    In M. H. Gregg et al. , U.S. Pat. No. 2,890,480 patented Jun. 16, 1959 the sash is lifted and the preload adjustment is made by moving a first driver of a dog-tooth clutch that is in axial alignment with the spiral rod, past a lock pin and into the second driver of the dog tooth that is attached to the end of the spiral rod, and turning the first driver.  
           [0008]    In Larson et al., U.S. Pat. No. 2,825,089 patented Mar. 4, 1958 a slotted head for a screw driver is mounted in axial alignment on the end of the spiral rod. The head is journaled in a laterally oriented slot, pulled to one end of the slot against a ratchet pawl by a convolute spring. Increase in minimum lifting force is made by turning the screw as the pawl enters successive notches around the head. Decrease in minimum lifting force is made by moving the head laterally in the slot against the urging of the convolute spring until the notched periphery of the screw head is drawn away from the paw, and reversing the direction of the screw.  
         SUMMARY OF THE INVENTION  
         [0009]    It is one object of the invention to provide a window balance that can be preloaded while the balance is attached to a window sash and window frame.  
           [0010]    It is another object of the invention that the window balance is preloaded by turning a gear.  
           [0011]    Other objects and advantages of the invention will become apparent to persons skilled in the art from the ensuing description.  
           [0012]    A window balance includes a torsion spring having a first end and a second end, a spiral rod having a first end and a second end, a threaded follower mounted on the spiral rod for being rotated by the spiral rod when the follower is moved along the spiral rod between the first end and the second end of the spiral rod. The threaded follower is attached to the first end of the torsion spring for rotating the first end of the torsion spring by rotation of the follower.  
           [0013]    The window balance also includes first means for attaching the second end of the torsion spring to a window sash for moving the follower along the spiral rod by moving the sash, second means for attaching the first end of the spiral rod to a window frame against rotation of the spiral rod. The second means for attaching incluses means for rotating the spiral rod for changing base force in the torsion spring.  
           [0014]    The window balance also includes a tension spring having a first end connected to the first means for attaching, and having a second end connected to the second means for attaching, and means for longitudinal engagement for prevention of differential rotational movement, connected to the first means for attaching and to the second means for attaching, for prevention of differential rotational movement between the first end of the tension spring and the second end of the tension spring when the first means for attachment is moved between a first distance and a second distance from the second means for attachment.  
           [0015]    A window balance includes a torsion spring having a first end and a second end, a spiral rod having a first end and a second end, a threaded follower mounted on the spiral rod for being rotated by the spiral rod when the follower is moved along the spiral rod between the first end and the second end of the spiral rod, the threaded follower being attached to the first end of the torsion spring for rotating the first end of the torsion spring by rotation of the follower, first means for attaching the second end of the torsion spring to a window sash for moving the follower along the spiral rod by moving the sash, a gear bearing comprising means for attaching the gear bearing to a window frame against rotation of the gear bearing, a first gear, mounted in the gear bearing, connected to the spiral rod for rotating the spiral rod, second means for receiving external rotational force, mounted on the first gear, keyed to the first gear for rotating the first gear, means for urging the second means from a first position on the first gear to a second position on the first gear, and means mounted on the bearing configured for contacting the second means for preventing rotation of the second means when the second means is in the second position.  
           [0016]    A window balance includes a window frame, a window sash movably mounted on the window frame, a torsion spring having a first end and a second end, a spiral rod having a first end and a second end, a threaded follower mounted on the spiral rod for being rotated by the spiral rod when the follower is moved along the spiral rod between the first end and the second end of the spiral rod, the threaded follower being attached to the first end of the torsion spring for rotating the first end of the torsion spring by rotation of the follower, the second end of the torsion spring being mounted on the window sash for moving the follower along the spiral rod by moving the sash, a bearing housing attached to the window frame, a first gear mounted in the housing, axially connected to the spiral rod for rotating the spiral rod, a second gear rotationally engaged with the first gear for rotating the first gear, a keyed hole in the second gear, an insert in the keyed hole, keyed to the hole so that insert rotates the second gear when the insert is rotated, means for urging the insert from a first position on the second gear to a second position on the second gear, and means on the housing contacting the insert for preventing rotation of the insert when the insert is in the second position. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0017]    In order that the invention will be more fully comprehended, it will now be described, by way of example, with reference to the accompanying drawings, in which:  
         [0018]    [0018]FIG. 1 is a schematic cross section view of a balance of the invention including a bracket for attaching the balance to a sash.  
         [0019]    [0019]FIG. 2 is a side view of the bracket of FIG. 1  
         [0020]    [0020]FIG. 3 is a side view of another bracket for attaching the balance to a window sash by way of a balance shoe.  
         [0021]    [0021]FIG. 4 is a perspective front view of a gearbox of the invention taken from above.  
         [0022]    [0022]FIG. 5 is a perspective front view of the gearbox of FIG. 4 taken from below.  
         [0023]    [0023]FIG. 6 is a perspective view of a first half of the split housing of the gearbox of FIG. 5 taken from below.  
         [0024]    [0024]FIG. 7 is a perspective view of the second half of the split housing of the gearbox of FIG. 5 taken from below, containing the geartrain, the first and second sides of the split housing being mirror images of each other.  
         [0025]    [0025]FIG. 8 is a perspective rotated view of one half of the gearbox of FIG. 5 taken from below.  
         [0026]    [0026]FIG. 9 is a perspective rotated view of one half of the gearbox of FIG. 5 taken from below.  
         [0027]    [0027]FIG. 10 is a perspective front view of a first gear of the gearbox of FIG. 7.  
         [0028]    [0028]FIG. 11 is a perspective rotated view of the first gear of FIG. 10.  
         [0029]    [0029]FIG. 12 is a perspective view of a second gear of the gearbox of FIG. 7.  
         [0030]    [0030]FIG. 13 is a perspective rotated view of the second gear of FIG. 12.  
         [0031]    [0031]FIG. 14 is a perspective view of an insert of the gearbox of FIG. 7, taken from above, including a spring that is installed in the second gear with the insert.  
         [0032]    [0032]FIG. 15 is a perspective view of the insert of FIG. 14, taken from below, without the spring.  
         [0033]    [0033]FIG. 16 is a perspective view of another balance of the invention. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0034]    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.  
         [0035]    Referring to FIGS.  1 - 5 , tension plus torsion balance  30  is attached to the upper part of stile or window frame  32  by screw  34  which passes through hole  36  in housing  92  of gearbox  40  at top  44  of the balance.  
         [0036]    Balance  30  is attached to sash  42  by screws  46  through bracket  48  which is attached by pin  52  through holes  54  in the bracket and holes  58  in lugs  60  at the bottom of balance  30 .  
         [0037]    Balance  30  may be attached to a sash by way of one of the many shoes commercially available for attaching a balance to a sash. For this, metal strip  66  instead of bracket  48  is attached to lugs  60  by pin  52  through hole  74  in the strip and holes  58  in lugs  60 . Studs  68 ,  70  are provided on the strip for engaging a shoe.  
         [0038]    Extension or tension spring  80  is fixedly attached at lower end  82  of the spring to block  86  which is fixedly attached to lugs  60 . The spring is fixedly attached at upper end  88  of the spring to the housing  92  of gearbox  40   
         [0039]    Tube  96  is fixedly attached at end  98  of the tube to housing  92  of gearbox  40 . The other end,  99 , of the tube is unattached. Tube  96  covers spring  80  insofar as spring  80  is not extended. When spring  80  is extended or stretched by sash drawing block  86  downward, a portion of the lower end of the stretched spring past the free lower end of the tube is not covered by the tube.  
         [0040]    Torsion spring  100  is fixedly attached at lower end  102  of the spring to block  86 , and is fixedly attached at top end  106  of the spring to internally threaded follower  104  which is rotated by the treads  109  of threaded spiral rod  108 .  
         [0041]    Tube  94  separates spring  80  from spring  100  to prevent one rubbing against the other.  
         [0042]    Spiral rod  108  is shown in FIG. 1.  
         [0043]    Upper end  112  of spiral rod  108  is fixedly attached by pins  122 ,  124  in holes  116 ,  118  of slotted shaft  120  of gearbox  40 . Spiral rod  108  extends from slot  110  in shaft  120 . Lower end  126  of spiral rod  108  is not restricted from rotating. In FIG. 1, lower end  126  is shown removably extending into recess  130  of block  86 , but when the block is drawn down, away from screw  34 , end  126  is left depending downward above and outside of recess  130 .  
         [0044]    As block  86  is moved downward and upward by a window sash, the block moves torsion spring  100  upwards and downward. Since the upper end of spring  100  is attached to follower  104 , spring  100  moves follower  104  upward and downward along threaded spiral rod  108 .  
         [0045]    The follower, rotated by the threads of rod  108  as the follower moves up and down the rod, rotates top end  106  of torsion spring  100 . Rotation of torsion spring  100  as the sash is lowered, stores twisting force in the torsion spring that is translated into lifting force upon the torsion spring by the follower, and upon lugs  60  by the torsion spring, as the twisting force urges the follower to wind its way up the thread of the spiral rod.  
         [0046]    In order to provide a minimum lifting force, herein called a “base force”, other than the lifting force stored in spring  100  by lowering a sash to wind the spring, a screw driver is inserted into tool hole  134  in keyed insert  140  and is turned. Insert  140  is set into keyed hole  144  in gear  150 , urged outward of the keyed hole by spring  152 , but prevented from exiting the keyed hole by wall  154  comprising wall portions  154   a,    154   b,  of the halves of gearbox  40  housing  92 .  
         [0047]    Hexagonal opening  160  of wall  154 , comprising wall portions  154   a,    154   b,  engages hexagonal head  162  of insert  140  preventing rotation of gear  150  unless the head and insert is pushed behind wall  154  by pushing inward on the screw driver.  
         [0048]    Gear  150  rotationally engages gear  170  which turns shaft  120 .  
         [0049]    Preferably when gear  150  is turned to add base force, block  86  is restrained from turning relative to housing  92  of gear box  40  by means other than that of the resistance to twist of tension spring  80 . Attaching the balance to a window frame and window sash provides a restraint that prevents turning of block  86 .  
         [0050]    Thus, base force can be added, increased, or reduced while the balance is attached to the window frame and sash. This is an advantage over balances that require disconnection from the sash or window frame in order to add or change the base force in a torsion spring and follower assembly.  
         [0051]    Gear  150  turns in bearing liner halves  164  and gear tooth clearance slot halves  166 .  
         [0052]    Gear  170  turns in bearing liner halves  174  and gear tooth clearance slot halves  176 .  
         [0053]    In FIG. 16, block  196  of tension plus torsion balance  198  is prevented by tube  204  from rotating on axis  206  relative to gearbox housing  210  by longitudinal engagements of finger, groove  216 ,  214  and groove, finger  218 ,  220 .  
         [0054]    Longitudinal grooves  214  receive longitudinal fingers  216 . Longitudinal grooves  218  receive longitudinal fingers  220 . Thus, when gearbox housing  210  is fixed to a window frame by a screw through hole  212 , block  196  cannot rotate on axis  206  relative to the frame or to gearbox housing  210 , even when lugs  226  are not connected to a sash against rotation and when block  196  is moved axially away from gearbox housing  210 , so long as at least one finger and groove  214 ,  216  and at least one finger and groove  218 ,  220  are engaged at each end of the balance.  
         [0055]    The longitudinal engagements are not limited to finger and groove, but can be finger and slot, pin and hole or other longitudinal arrangement that stays in longitudinal alignment when block  196  is moved away from gear housing  210 . Base force in balance  198  can be adjusted by winding the spiral rod (not shown) by pushing in and turning insert  230  even when the gearbox housing is attached to a window frame while lugs  226  are left free, not attached to a sash.  
         [0056]    The longitudinal engagement can be between one end only of the tube and either one of the gearbox and the block, the other end of the tube being fixedly attached to or extending from the other of the gearbox and the block.  
         [0057]    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.