Abstract:
A counterbalance system for a tilt-in window having novel components. The counterbalance system includes brake shoes, curl springs and spring anchor mounts. The brake shoe assembly of the counterbalance system has a unique, low cost locking mechanism that uses a looped wire. The brake shoe assembly may also be configured with external rib projections that reduce the friction of the brake shoe assemblies as they move through the tracks of the window. The spring anchor mount is formed with a recess in its body that enables the tilt latch of a window sash to pass the spring anchor mount within the track of the window frame. As a result, the spring anchor mounts can be placed within the window frame at points previously not available.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   In general, the present invention relates to counterbalance systems for windows that prevent open window sashes from closing under the force of their own weight. More particularly, the present invention system relates to counterbalance systems for tilt-in windows that use curl springs to create a counterbalancing force. 
   2. Description of the Prior Art 
   There are many types and styles of windows. One of the most common types of window is the double-hung window. A double-hung window is the most common window found in traditional home construction. A double-hung window consists of an upper window sash and a lower window sash. Either the upper window sash or the lower window sash can be selectively opened and closed by a person sliding the sash up and down within the window frame. 
   A popular variation of the double-hung window is the tilt-in double-hung window. Tilt-in double-hung windows have sashes that can be selectively moved up and down. Additionally, the sashes can be selectively tilted into the home so that the exterior of the sashes can be cleaned from within the home. 
   The sash of a double-hung window has a weight that depends upon the materials used to make that window sash and the size of the window sash. Since the sashes of a double-hung window are free to move up and down in the frame of a window, some counterbalancing system must be used to prevent the window sashes from always moving to the bottom of the window frame under the force of their own weight. 
   For many years counterbalance weights were hung next to the window frame in weight wells. The weights were attached to the window sash using a string or chain that passed over a pulley at the top of the window frame. The weights counterbalanced the weight of the window sashes. As such, when the sashes were moved in the window frame, they had a neutral weight and friction would hold them in place. 
   The use of weight wells, however, prevents insulation from being packed tightly around a window frame. Furthermore, the use of counterbalance weights on chains or strings cannot be adapted well to tilt-in double-hung windows. Accordingly, as tilt-in windows were being developed, alternative counterbalance systems were developed that were contained within the confines of the window frame and did not interfere with the tilt action of the tilt-in windows. 
   Modern tilt-in double-hung windows are primarily manufactured in one of two ways. There are vinyl frame windows and wooden frame windows. In the window manufacturing industry, different types of counterbalance systems are traditionally used for vinyl frame windows and for wooden frame windows. The present invention is mainly concerned with the structure of vinyl frame windows. As such, the prior art concerning vinyl frame windows is herein addressed. 
   Vinyl frame, tilt-in, double-hung windows are typically manufactured with tracks along the inside of the window frame. Brake shoe mechanisms, commonly known as “shoes” in the window industry, are placed in the tracks and ride up and down within the tracks. Each sash of the window has two tilt pins or tilt posts that extend into the shoes and cause the shoes to ride up and down in the tracks as the window sashes are opened or closed. 
   The shoes serve two purposes. First, the shoes contain a brake mechanism that is activated by the tilt post of the window sash when the window sash is tilted inwardly away from the window frame. The shoe therefore locks the tilt post in place and prevents the base of the sash from moving up or down in the window frame once the sash is tilted open. Second, the shoes either support or engage curl springs. Curl springs are constant force coil springs that supply a constant retraction force when unwound. 
   Single curl springs are used on windows with light sashes. Multiple curl springs are used on windows with heavy sashes. The curl springs provide the counterbalance force to the window sashes needed to maintain the sashes in place. The counterbalance force of the curl springs is transferred to the window sashes through the structure of the shoes and the tilt posts that extend from the window sash into the shoes. 
   The curl springs are utilized within the structure of a tilt-in window in two distinct operating systems. In the first operating system, the curl spring moves with the window sash as the window sash moves up and down in the window frame. In the second operating system, the curl spring is fixed and does not move with the window sash. 
   In the first operating system, where the curl spring moves, the end of the curl spring is anchored to the fixed part of the window frame. The remaining coils of the curl spring are supported by the shoe and move in unison with the shoe. As each shoe moves away from the anchor point, the curl spring unwinds. Conversely, as each brake shoe moves toward the anchor point, the curl spring rewinds. Such an operating system requires that the anchor mounts be set into the tracks of the windows so that the free ends of the curl springs can be anchored to the window frame. However, the presence of the anchor mount in the window track presents a problem to the free movement of the sashes. Often the movement of a window sash must be limited so that it does not contact the anchor mounts that are present. This often prevents a window sash from being able to open as fully as would otherwise be expected. 
   Another problem that is inherent to many window counterbalance systems is the complexity of the shoes that retain the springs and move with the springs in the tracks of the window frame. Of the various components that create a counterbalance system, one of the most expensive components is the shoe. The shoes must contain a brake mechanism strong enough to lock a window sash in place. In addition, the shoes must engage and retain at least one strong curl spring. Furthermore, the shoe must remain reliable for years of operation. Accordingly, prior art shoes are built with large, wear resistant components that tend to make the prior art shoes expensive and complex to manufacture. 
   A need therefore exists in the field of vinyl, tilt-in, double-hung windows, for a counterbalance system that has an improved spring anchor mounting assembly that does not limit the movement of window sashes. A need also exists in the field of vinyl, tilt-in double-hung windows for a counterbalance system that provides inexpensive shoe assemblies. As such, window assemblies can be made to be more reliable, less expensive and easier to manufacture. These needs are met by the present invention as described and claimed below. 
   SUMMARY OF THE INVENTION 
   The present invention is a counterbalance system for a tilt-in window. The counterbalance system includes brake shoes, curl springs and spring anchor mounts. The brake shoe assembly of the counterbalance system has a unique, low cost locking mechanism that uses a looped wire. The brake shoe assembly may also be configured with external rib projections that reduce the friction of the brake shoe assemblies as they move through the tracks of the window. 
   The spring anchor mount is formed with a recess in its body that enables the tilt latch of a window sash to pass the spring anchor mount within the track of the window frame. As a result, the spring anchor mounts can be placed within the window frame without concern of contact interference with the tilt latch. The result is a lower cost, more reliable counterbalance system for a window that provides a greater degree of movement in the window sashes so that the window sashes can be opened wider than previously possible. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     For a better understanding of the present invention, reference is made to the following description of exemplary embodiments thereof, considered in conjunction with the accompanying drawings, in which: 
       FIG. 1  is a partially fragmented view of a window assembly in accordance with the present invention; 
       FIG. 2  is an exploded perspective view of the components of the present invention counterbalance system; 
       FIG. 3  is a cross-sectional view of an exemplary embodiment of a shoe assembly component of the counterbalance system; 
       FIG. 4  is a cross-sectional view of an exemplary embodiment of the shoe assembly component of  FIG. 3 , shown engaging the pivot post of an untilted window sash; 
       FIG. 5  is a cross-sectional view of an exemplary embodiment of the shoe assembly component of  FIG. 3 , shown engaging the pivot post of a tilted window sash; 
       FIG. 6  is a perspective view of a first exemplary embodiment of a spring anchor mount in accordance with the present invention; 
       FIG. 7  is a side view of a second exemplary embodiment of a spring anchor mount in accordance with the present invention; 
       FIG. 8  is a front view of a third exemplary embodiment of a spring anchor mount containing a locking mechanism; and 
       FIG. 9  is a front view of a counterbalance system having a single moving curl spring. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   Referring to  FIG. 1 , there is shown an exemplary embodiment of a vinyl, tilt-in, double-hung window assembly  10 . The window assembly  10  has an upper sash  11  and a lower sash  12 . Each of the sashes  11 ,  12  has two side elements  17 . The upper sash  11  and the lower sash  12  are contained within a window frame  14 . The window frame  14  has two vertical sides  16  that extend along the side elements  17  of both sashes  11 ,  12 . Within each of the vertical sides  16  of the window frame  14  is formed a track  18 . 
   At the top of each sash  11 ,  12  are two tilt latches  19  that extend a predetermined distance into the tracks  18  on the side of each sash  11 ,  12 . The tilt latches  19  are used to disengage the top of a window sash  11 ,  12  from the track  18  so that the top of a window sash  11 ,  12  can be tilted inwardly for cleaning. 
   At the bottom of each of the sashes  11 ,  12  is a tilt pivot post  21  that also extends into the track  18 . When a sash  11 ,  12  is tilted inwardly, the sash  11 ,  12  tilts about its tilt pivot posts  21 . The tilt pivot posts  21  are received by shoe assemblies  20  that ride up and down within the tracks  18 . The shoe assemblies  20  support at least one curl spring  22 . The free end of each curl spring  22  is attached to the track  18  via a spring anchor mount  24 . 
   In the prior art, an anchor mount of a curl spring for a particular sash would often have to be mounted below the tilt latch for that sash. In that way, the tilt latch would not have to pass the anchor mount as the window sash moved up and down in the track. 
   In the shown embodiment, the spring anchor mount  24  is attached to the track  18  above the tilt latch  19 . As such, the tilt latch  19  passes the spring anchor mount  24  as the window sash  12  is moved up and down. However, as will later be described, the structure of the spring anchor mount  24  allows the tilt latch  19  to travel past the spring anchor mount  24  without interference. The window sash  12  is therefore capable of opening wider than many prior art window configurations. 
   Referring to  FIG. 2 , it can be seen that the present invention counterbalance system  25  is comprised of a plurality of interconnecting components. These components include a shoe assembly  20 , a spring anchor mount  24  and at least one curl spring  22 . The shoe assembly  20  contains a brake mechanism that locks the shoe assembly  20  in place in the window track whenever the window sash is tilted. The functionality of the brake mechanism will later be explained. One shoe assembly  20  is provided for each side of a window sash. 
   At least one curl spring  22  is also provided for each side of a window sash. The curl springs  22  provide the tension force that is used to counterbalance the weight of a window sash as it is moved in a window frame. Each curl spring  22  is a length of ribbon steel  23  that is wound in a circular coil. The curl spring  22  applies a generally constant retraction force when the free end  26  of the ribbon steel is pulled away from the coil. The number of curl springs  22  used depends upon the size and weight of the window sash that is to be counterbalanced. Small window sashes may require only a single curl spring  22 . Larger window sashes require multiple curl springs  22 . In most standard windows, between one and four curl springs  22  are used. 
   The free end  26  of each curl spring  22  contains a mounting feature, such as a mount hole  27  or a barb that enables the free end  26  of the curl spring  22  to be readily mounted to the spring anchor mount  24 . 
   Each spring anchor mount  24  has at least one side surface that contains a retaining structure  32  for receiving and engaging the free end  26  of the steel ribbon  23  of the curl spring  22 . In the shown embodiment, each curl spring  22  is terminated with a mount hole  27 . Accordingly, the side surface of the spring anchor  24  includes a retaining structure  32  in the form of a protrusion that is sized to pass into and engage the mount hole  27 . Such a configuration is only one of many ways to interconnect the curl spring  22  to the spring anchor mount  24 . It will be understood that if the free end  26  of the curl spring  22  were terminated with a screw hole, threaded bores would be present in the spring anchor mount that would enable the free end  26  of the curl spring  22  to be connected to the spring anchor mount  24  with a screw. 
   In the shown embodiment, each spring anchor mount  24  is capable of engaging and retaining the free end  26  of up to four curl springs  22 . Most vinyl window counterbalance systems use between one and four curl springs. As such, a single spring anchor mount  24  is capable of engaging the curl springs of the most common counterbalance configurations. 
   Each spring anchor mount  24  has an attachment structure that enables the spring anchor mount to be attached to the track in the window frame. In the shown embodiment, the spring anchor mount  24  defines mounting holes  34  that enable the spring anchor mount  24  to be directly mounted to the window frame with screws. As will be later described, alternate attachment structures can be used to lock the spring anchor mount  24  into a set position. The details of the configuration of the spring anchor mount  24  is later described when referencing  FIG. 6  and  FIG. 7 . 
   In  FIG. 2 , it can be seen that the shoe assembly  20  has a body that has a face surface  40  and a rear surface  42  disposed between two opposing side surfaces  44 . When the shoe assembly  20  is connected to a curl spring  22  within a window frame track, the curl spring  22  commonly applies a slight torque to the shoe assembly  20 . This causes the side surfaces  44  of the shoe assembly  20  to contact the track as the shoe assembly  20  moves within the confines of the track. To reduce the amount of friction caused by this contact, at least one rib protrusion  46  is optionally formed on the side surfaces  44 . The rib protrusions  46  contact the window frame track and reduce the amount of surface area on the shoe assembly  20  that is in contact with the track. By reducing the surface area in contact, the amount of friction is also reduced. 
   The rib protrusions  46  can be molded of wear resistant material and added to the side surfaces  44  of the shoe assembly  20 . However, in a preferred method of manufacturing, the rib protrusions  46  are molded as part of the shoe assembly  20 . 
   Referring to  FIG. 3 , a cross-section of the shoe assembly  20  is shown. From  FIG. 3 , it can be seen that on the side surfaces  44  of the shoe assembly  20  are two side openings  48 . The side openings  48  interconnect with an internal chamber  50 . A post access hole  53  ( FIG. 2 ) is formed in the face surface of the shoe assembly  20  that extends into the center of the internal chamber  50 . Disposed within the internal chamber  50  and side openings  48  is a single loop torsion spring  52 . The single loop torsion spring  52  is made of a spring wire that travels in one direction, is looped around and continues in that same general direction. The loop  54  in the center of the torsion spring  52  lays in the internal chamber  50  of the shoe assembly  20 , while the arms  56  of the torsion spring  52  extend into the side openings  48 . The loop  54  of the torsion spring  52  defines a central open area that is aligned with the post access hole  53  ( FIG. 2 ) in the face surface of the shoe assembly  20 . 
   The central open area defined by loop  54  of the torsion spring  52  is elongated, where the loop  54  is taller than it is wide. When the shoe assembly  20  is assembled into a window, the pivot arm of a window sash passes into the post access hole  53  ( FIG. 2 ) in the shoe assembly  20  and then passes into the central open area defined by the loop  54  of the torsion spring  52 . 
   It is well known in the art of tilt-in windows, that the pivot arms that extend from window sashes typically have non-round cross-sectional profiles. Most commonly, such pivot arms have a rectangular or otherwise oblong configuration. Referring to  FIG. 4 , it can be seen that when the pivot arm  21  of a window sash is disposed in the loop  54  of the torsion spring  52 , the presence of the pivot arm  21  deforms the loop  54  and expands the loop  54 . Due to the configuration of the torsion spring  52 , as the loop  54  is expanded, the arms  56  of the torsion spring  52  retract into the body of the shoe assembly  20 . Accordingly, the ends  64  of the torsion spring  52  do not extend out of the body of the shoe assembly  20 . 
   Since the ends  64  of the torsion spring  52  do not extend out beyond the side surfaces  44  of the shoe assembly  20 , the shoe assembly  20  is free to move up and down in the track defined by the vinyl window frame. The pivot arm  21  expands the torsion spring  52  and retracts the arms of the torsion spring  52  when the window sash is flush in the window frame. Thus, when the window sash is moved up and down in the window&#39;s track, the shoe assembly  20  provides little resistance to the movement. 
   However, when the window sash is tilted inwardly out of the plane of the window frame, the pivot arm  21  in the torsion spring  52  rotates with the window sash. Referring to  FIG. 5 , it can be seen that when the window sash is tilted, the pivot arm  21  turns and no longer expands the loop  54  in the center of the torsion spring  52 . With the pivot arm  21  no longer a barrier, the loop  54  contracts. As the loop  54  contracts, the arms  56  of the torsion spring  52  extend outwardly from the side surfaces  44  of the shoe assembly  20 . The ends  64  of the arms  56  extend past the rib protrusions  46  and directly engage the walls of the track in which the shoe assembly  20  moves. The ends  64  of the arms  56  bite into the vinyl and lock the shoe assembly  20  into a fixed position within the track. It will, therefore, be understood that the torsion spring  52  is a brake mechanism. When the sash of a window is in the plane of the window frame, the arms  56  of the torsion spring  52  are retracted and the shoe assembly  20  can travel freely up and down the window frame. However, as soon as the window sash is tilted, the arms  56  of the torsion spring  52  extend and the arms  56  engage the surrounding track of the window frame, thereby locking the shoe assembly  20  into a set position within the track. 
   From the description of the function of the brake mechanism created by the torsion spring  52 , it will be understood that the torsion spring  52  itself is a single, inexpensive component with no secondary moving parts. As such, the torsion spring  52  is a highly reliable brake mechanism that resists wear much better than prior art shoe assemblies that contain complex brake mechanisms with multiple moving parts. 
   Referring to  FIG. 6 , a first embodiment of the spring anchor mount  24  is shown. The spring anchor mount  24  is preferably molded or machined as a single piece. The spring anchor mount  24  has a head section  72  that is sized to just fit within the track of a window. A body section  74  extends below the head section  72 . The body section  74  is recessed and has a cross-sectional area smaller than that of the head section  72 . Accordingly, the side walls  76  of the body section  74  of the spring anchor mount  24  do not contact the side walls of the window track when the spring anchor mount  24  is placed in the window track. 
   A recess  78  is formed in the face surface of the spring anchor mount  24 . The recess  78  extends from the top to the bottom of the spring anchor mount  24  passing through both the head section  72  and the body section  74  of the spring anchor mount  24 . The recess thins the center of the spring anchor mount  24 . Preferably, the recess  78  in the head section  72  reduces the thickness of the head section  72  by at least thirty percent and may be as much as seventy percent. 
   At least one countersunk screw hole  34  is formed through the spring anchor mount  24  in the area of the recess  78 . Mounting screws  79  are provided to attach the spring anchor mount  24  to a surface of the window track through the screw holes  34 . Due to the countersunk screw holes  34  and shape of the mounting screws  79 , it will be understood that the screws lay flush in the recess  78  and do not protrude into the area of the recess  78 . 
   Referring back briefly to  FIG. 1  in conjunction with  FIG. 6 , it will be understood that the recess  78  formed in the spring anchor mount  24  allows the tilt latch  19  that protrudes from the top of the sash  12  to pass the spring anchor mount  24  without contacting the spring anchor mount  24 . On different model windows, the tilt latch  19  extends into the window track  18  by varying amounts. The recess  78  formed in the spring anchor mount  24  is larger than the protrusion of the tilt latch  19  by at least 1/32 nd  of an inch so as to prevent any inadvertent contact. 
   Referring to  FIG. 7 , an embodiment of a spring anchor mount  31  is shown having an alternate attachment means. The spring anchor mount  31  of  FIG. 7  has the same structure as that previously described in  FIG. 6 , except the embodiment of  FIG. 7  does not have mounting holes. Rather, a locking protrusion  33  extends from the rear surface of the spring anchor mount  31 . The locking protrusion passes into a hole preformed in the frame of the window, thereby setting the spring anchor mount  31  in a fixed position. 
   Referring now to  FIG. 8 , another alternate embodiment of the spring anchor mount  80  is shown. In this embodiment, the spring anchor mount  80  still has a recess  82  that enables a window sash tilt latch to pass the spring anchor mount  80  without contacting the spring anchor mount  80 . However, in the shown embodiment, the spring anchor mount  80  is not attached to the window track with mounting screws. Rather, the spring anchor mount  80  is provided with a looped wire locking system very similar to that already described with reference to the brake mechanism of  FIGS. 3 ,  4  and  5 . 
   In the spring anchor mount  80  is a looped wire  84 . The ends  86  of the looped wire  84  extend out of the sides of the spring anchor mount  80  unless the loop  85  in the center of the looped wire  84  is internally expanded. A key or screwdriver head is inserted into the loop  85  of the looped wire  84 . Once a key or screwdriver head is inserted into the loop  85 , the key or screwdriver head is turned. When the key or screwdriver head is turned, the loop  85  expands and the ends  86  of the looped wire  84  retract into the spring anchor mount  80 . 
   To install the spring anchor mount  80 , a screwdriver head or other key is placed in the loop  85  of the looped wire  84  and turned. This retracts the ends  86  of the looped wire  84 . Once the ends  86  of the looped wire  84  are retracted, the spring anchor mount  80  can be moved to any desired position in the window track. Once in a desired position, the key or screwdriver head is removed and the ends of the looped wire  84  extend and engage the sides of the window track, thereby locking the spring anchor mount  80  in place. 
   Referring to  FIG. 9 , a counterbalance system  25  is illustrated in accordance with the present invention. The counterbalance system  25  is being applied to a window assembly having a counterbalance operating system where the curl springs  22  used to create the counterbalance force move with the sash of the window. 
   From  FIG. 9 , it can be seen that the curl spring  22  is attached to the shoe assembly  20  so that the curl spring  22  moves with the shoe assembly  20  in the track  18  of the window. The free end  26  of the curl spring  22  is drawn away from the curl spring  22  and is attached to a spring anchor mount  24 . The spring anchor mount  24  is mounted in a fixed location to the window frame using one of the mounting systems previously described. The curl spring  22  and the shoe assembly  20  glide up and down in the track  18  with the movement of a window sash. The shoe assembly  20  locks in place when the window sash is tilted, as has previously been explained. 
   It will be understood that the embodiments of the present invention counterbalance system and its components that are described and illustrated herein are merely exemplary and a person skilled in the art can make many variations to the embodiments shown without departing from the scope of the present invention. All such variations, modifications and alternate embodiments are intended to be included within the scope of the present invention as defined by the appended claims.