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BACKGROUND OF THE INVENTION  
       [0001]     1. Field of the Invention  
         [0002]     The invention pertains to the field of window balances. More particularly, the invention pertains to a wiper for the curl springs of these balances.  
         [0003]     2. Description of Related Art  
         [0004]     Constant force curl springs have been used in window balance systems where they have the advantage of applying a constant lifting force to counterbalance the constant weight of a window sash. The constant force of these springs is derived from the curling tendency of an uncurled length of a spring steel strip that has been formed to curl up. When the strips are uncurled and extended, each increment of the extended strip is biased to recurl itself and thus exerts a constant force against spring extension.  
         [0005]     However, until fairly recently, curl springs were not popular in window counterbalance systems, because each of their known arrangements suffered from at least one competitive drawback. For example, sash mounted arrangements of curl springs did not allow the sash to tilt; jamb mounted arrangements took up window space that manufacturers were unwilling to commit to balance systems; and tilt sash arrangements were inefficient and sometimes short-lived or inadequate in performance. The result was that only a few of the many different proposed arrangements of curl spring balance systems were being marketed, and these had only a small market share.  
         [0006]     However, new discoveries in the realm of curl spring and shoe arrangement were patented in U.S. Pat. Nos. 5,353,548 and 5,463,793. The arrangements claimed in these patents accommodate a tilt sash and employ curl springs in a much more efficient manner. Curled up convolutions of the springs are carried by or contained within sash shoes, also referred to as curl spring mounts, that run in sash channels alongside a sash moving in sash runs. A connection between the shoes and the sash allows the sash to tilt, and the springs apply a constant counterbalance lifting force to the shoes, which transmit this lift to the sash. Free end regions of uncurled lengths of the springs are mounted within the shoe channels so that the springs curl up into the shoes as the shoes move upward in the shoe channels and uncurl from the shoes into the shoe channels as the shoes move downward in the shoe channels. Alternative designs involve the use of two shoes, one fixed to the window jamb channel at a desired location and a traveling shoe which contains one end of the curl spring and is affixed to the stile of the window sash so that as the sash is moved the traveling shoe uncoils the curl spring from the fixed shoe. The traveling shoe is also referred to as a locking shoe.  
         [0007]     One specific problem that arises when such window designs are used in new construction is that when the curl spring is extended as the sash is moved from its resting position along the window jambs, there is a great potential for dust and dirt to attach to the extended spring. Then when the sash is returned to its resting or closed position and the spring is re-coiled within the shoes, the dust and dirt will accumulate within the coiled spring, causing it to become clogged. This can either partially or completely inhibit the movement of the sash. This problem is particularly acute with new construction because the windows are usually installed early in the construction process, before insulation and drywall are installed. Since drywall installation requires repeated sanding, the fine particulate plaster dust freely drifts around the room attaching itself not only to horizontal surfaces, but vertical ones, as well, such as the exposed curl springs of open windows, leading to the problems discussed above.  
       SUMMARY OF THE INVENTION  
       [0008]     The invention is a spring wiper for curl springs used in window sash systems. The curl spring is contained in a coiled position within a carrier, mount, cassette, shoe or holder. The curl spring uncoils from its coiled position within the holder as the sash is moved either up or down to open the window. In a first embodiment of the invention, the spring wiper is deployed on top of and interlocks with features of the curl spring holder. In this first embodiment, the curl spring holder, or shoe, is pinned to the bottom of each of the two sash stiles by a sash pin while the open end of the spring is secured in the shoe channel at the end of the uppermost limit of travel of the bottom rail of the sash.  
         [0009]     In a second embodiment of the invention, a curl spring mount is permanently secured at the top of the shoe channel of the window frame jamb. In this second embodiment, the end of the curl spring is secured to a locking shoe which is pinned to a stile of the sash by a sash pin which allows it to travel up and down the shoe channel as the sash is raised and lowered. In this embodiment, the spring slides along the surface of the shoe channel as the sash is raised and lowered. The wiper blade is an integral part of the curl spring mount and wipes the side of the spring facing the window opening as the sash is returned to its closed window position and the curl spring returns to its coiled position inside the curl spring mount.  
         [0010]     The spring wiper has a wiper blade that is deployed on the curl spring holder or mount so that it presses against the side of the uncoiled portion of the curl spring that is exposed to airborne particulate contamination. The wiper blade has an edge that is preferably transverse to the curl spring, spanning its width, and wipes/scrapes debris clinging to and/or accumulated on the curl spring when it is extended prior to its being re-coiled within the curl spring mount or holder. In this way, it is able to keep such debris from entering the coiled portion of the curl spring and interfering with the continued fluid operation of the sash.  
         [0011]     Either the first or the second embodiment may include a curl spring mount or holder that can accommodate more than one curl spring, usually two and sometimes three. The additional spring(s) would travel in and out of the curl spring mount or holder through an opening on the opposite side from the opening for the first curl spring. A separate wiper blade wipes clean the additional spring(s) before their re-entry into the curl spring mount or holder. 
     
    
     BRIEF DESCRIPTION OF THE DRAWING  
       [0012]      FIG. 1  is a partially schematic side view of a window with sash shoe showing the balance system cooperating with a tilted sash.  
         [0013]      FIG. 2  is a side view of the curl spring holder of  FIG. 1 .  
         [0014]      FIG. 3  is a cross-sectional view of the curl spring holder of  FIG. 2 .  
         [0015]      FIG. 4  provides a perspective view of the spring wiper for curl spring holders of the first embodiment of the invention.  
         [0016]      FIG. 5  provides a schematic side view of the first embodiment of the spring wiper in functional position on a curl spring holder.  
         [0017]      FIG. 6  provides a perspective view of the second embodiment of the invention with the curl spring extended between a fixed curl spring mount and a locking shoe.  
         [0018]      FIG. 7  provides a perspective view of the second embodiment of  FIG. 6  with the curl spring re-coiled within the fixed curl spring mount.  
         [0019]      FIG. 8  provides a perspective view of the second embodiment showing a variation of the design of the spring wiper with the curl spring extended.  
         [0020]      FIG. 9  provides a perspective view of the variation of the second embodiment of  FIG. 8  with the curl spring re-coiled within the fixed curl spring mount. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0021]     U.S. Pat. Nos. 5,353,548 and 5,463,793 provide numerous details related to the construction, operation and advantages of the curl spring holder  50  of the first embodiment of this invention and are hereby incorporated by reference.  FIG. 1  schematically shows a generally preferred arrangement for employing curl springs  10  and curl spring holders  50  with a counterbalancing sash  20 . Free end regions  11  of springs  10  are fixed in positions within shoe channels  15 , as schematically indicated by fastener  12 . Curled up convolutions  13  of springs  10  are contained within curl spring holder  50 , which move up and down in shoe channels  15  as sash  20  moves up and down in vertical sash runs within the frame of the window (not shown). Curl spring holders  50  are interconnected with sash  20 , preferably by means of pivot bars or pins, which allow sash  20  to tilt, as shown in  FIG. 1 . Curl spring holders  50  preferably lock in shoe channels  15  when sash  20  tilts, but it is also possible to allow curl spring holders  50  to rise in channels  15  from the upward bias of springs  10  when tilting of sash  20  removes some of the sash weight from curl spring holders  50 .  
         [0022]     The curl spring counterbalance arrangement schematically shown in  FIG. 1  achieves the general advantages mentioned above. In this design, potential friction caused by sliding an uncurled length of a curl spring against a shoe channel surface as a sash moves is substantially eliminated. Spring  10  rests flat and motionless against shoe channel wall  15  as spring  10  recurls into coiled convolutions  13  when curl spring holders  50  and sash  20  are moved upward and uncurls from curl spring holders  50  into shoe channel  15  when curl spring holders  50  and sash  20  are moved downward.  
         [0023]     Containment of curled up spring convolutions  13  in curl spring holders  50  accommodates the balance springs to the vertical travel desired for sash  20 . Free end region  11  of spring  10  can be secured in shoe channel  15  above the uppermost limit of travel of curl spring holders  50  with sash  20 . This level can be above the upper rail of sash  20 , because a tilt latch, which is commonly arranged at the upper rail of a tilt sash (not shown), can move up and down over the mounting of free end region  11  without interference.  
         [0024]     As illustrated in  FIGS. 2 through 3 , curl spring holder  50  can advantageously be formed of two identical parts or halves  51  so that any one of the parts  51  can join with any other part  51  to form a complete body for curl spring holder  50 . Each body part  51  is formed to provide half of a containment region  53  for receiving the curled up convolutions  13  of spring  10 . Each body part  51  also provides half of an opening  52  for a pin or pivot bar receiver  60 . Opposite lower sides  54  of body parts  51  are parallel and separated by a suitable distance for a smooth sliding fit in shoe channel  15 , and upper sides  55  of body parts  51  are separated by a smaller distance to allow a length of spring  10  to pass from containment region  53  in between one of the curl spring mount side walls  55  and a wall of shoe channel  15 . Assembling curl spring holder  50  from a pair of identical body parts  51  also gives curl spring holder  50  identical front and rear faces so that the curl spring holder  50  can be installed with either face confronting sash  20 . Conventional moldable materials, such as plastics, resins, nylon and the like may be used to make the various components of the curl spring holder.  
         [0025]     A projection  57  and a recess  58  are formed at the top of each body part  51  so that the downward facing portion  59  of each projection  57  can be slid into recess  58  of a confronting body part as shown in  FIG. 3 . When body parts  51  are then pressed together, the downward facing portions of projections  59  interlocking with slots  58  and thus hold body parts  51  in the assembled relation of  FIGS. 2 and 5 . Before this is done, curled spring convolutions  13  are placed in containment region  53  so that spring  10  extends out of an opening  56 , and receiver  60  is positioned in opening  52  between the body parts. This makes the assembly of curl spring holder  50  simple and inexpensive because it is accomplished by positioning a spring  10  and a receiver  60  in one body part and then simply pressing another body part into a confronting position that is held securely by the interference fit between projections  59  and slots  58 .  
         [0026]     Receiver  60  has a preferably cylindrical body  61  with a through opening  62  that receives a pin or pivot bar connected to sash  20 . Receiver  60  thus participates in a connection between curl spring holder  50  and sash  20 , and many variations of such a connection are possible. A platform or other support can extend from curl spring holder  50  to sash  20 , for example. Window jambs normally include a slot between the sash run and the shoe channel  15  allowing a connector such as pin  63  to extend between curl spring holder  50  and sash  20 .  
         [0027]     Receiver  60  preferably includes a cam  65  formed as an annular sector extending part way around cylindrical body  61 . Cam  65  fits within a recess  45  in each of the body parts  51 , and inclined cam follower surfaces  46  connect recess  45  with a confronting face surface  47  of each body part  51 . When cam surface  65  is positioned in recess  45 , in the neutral or sash vertical position for receiver  60 , confronting surfaces  47  of body parts  51  are closed or engaged. When sash  20  tilts, receiver  60  is turned or pivoted within curl spring holder  50 , which makes cam  65  ride up one of the inclined surfaces  46  onto face surface  47 . This spreads body parts  51  apart by the thickness of cam  65 . It also allows cam  65  to pivot in either direction to accomplish the cammed separation of body parts  51 . This thickens or widens curl spring holder  50  by increasing the separation between its front and back surfaces so that curl spring mount  50  locks in shoe channel  15  when sash  20  tilts. The amount that the curl spring mount widens is determined by the thickness of cam  65 , which can be varied to meet different shoe locking requirements. The top of curl spring holder  50 , which is held together by projections  59  in recesses  58 , remains tightly assembled, and shoe body parts  51  flex to allow the cammed separation of their lower regions when the shoe locks. This provides not only a simple locking arrangement for a sash curl spring holder, but it also provides more locking force from the torque applied by sash tilting than is achieved with other locking mechanisms that operate by spreading apart portions of the mount. The spreading of curl spring holder  50  occurs in a direction parallel with sash  20 , which extends across the narrower of the generally rectangular dimensions of shoe channel  15 ; and this may account for the improved locking force provided by cam  65  disposed between face surfaces  47 .  
         [0028]     Curl spring holder  50  can also be provided with adjustable friction, although there is less need for friction adjustment in curl spring balance systems because of the normally constant force of the curl springs. If the spring lift is a little excessive, though, or if the upper sash has a tendency to drop from an uppermost position, the frictional fit of curl spring holder  50  in shoe channel  15  can be increased. This is preferably done by means of an opening  44  formed eccentrically into an upper region of body parts  51  so that openings  44  in a pair of assembled body parts do not register with each other. Then, a screw  43  can be threaded into an opening  44  in one of the body parts  51 , and its leading end will engage a confronting surface of the mating body part. Further turning of the screw will urge the upper regions of body parts  51  apart, to thicken curl spring holder  50  enough to increase its frictional resistance to movement in channel  15 .  
         [0029]     When exposed to excessive dust, such as during new construction, including extremely fine particulates resulting from, for example, the repeated sanding of drywall in proximity to the window, this dust accumulates on the uncoiled length of curl spring  10  when sash  20  is moved from its resting or closed position (which draws curl spring  10  out of curl spring holder  50  and extends it along shoe channel  15 ). In this position, an inward side  10 A of the spring  10 , the side facing the window opening, is particularly exposed to dust accumulation, while a wall facing side  10 B rests flat against shoe channel wall  15  and is largely protected from such accumulation. Thus, it is extremely important that the inward side  10 A be cleaned prior to or while moving the sash  20  upward, as upward movement otherwise results in the recoiling of spring  10  within curl spring holder  50 , trapping construction dust in the curled up spring convolutions  13  within the curl spring holder  50 . Although not shown in the drawings, at least one more curl spring may be employed. The other spring(s) would travel in and out of the other side of the curl spring holder  50   
         [0030]     In order to alleviate this problem, the first embodiment of the invention consists of a mounting apparatus  70  having a spring wiper  71  for curl spring holders  50  that is deployed on top of and engages interlocking features of curl spring holder  50 . The wiper blade  71  extends from a mounting apparatus (base  72 ) that can be affixed in spaced relationship adjacent spring  10 . In this embodiment, base  72  is mounted onto curl spring holder  50  via interlocking mating elements (projections  57  having heads  67 ) on the top of the curl spring holder  50 . Projections  57  and heads  67  snap onto or securely slide into interface elements (recesses  80 ) of the base  72 . Spring wiper  71  is inclined in relation to, and presses against, the inward surface  10 A of the curl spring  10  adjacent the curl spring holder  50 . Its edge  71 A is somewhat arcuate and transverse to the curl spring  10  and spans the width of the curl spring. Thus, as the curl spring holder  50  moves with the sash (and curl spring  10  recoils in its interior containment region  53 ), the edge  71 A of cleaning member  71  acts as a scraper, scraping dust and other detritus off of and away from the inward surface  10 A of curl spring  10  before it is recoiled into interior containment region  53 .  
         [0031]     A second embodiment of the present invention is illustrated in  FIGS. 6-9 . One variation is shown in  FIGS. 6 and 7 . It consists of a curl spring mount  150  that contains an internal containment region for accommodating at least one curled up spring, as illustrated in the curl spring holder  50  in  FIG. 3 . Instead of the curl spring mount  150  riding up and down a shoe channel in the window jamb, as described above with respect to the first embodiment, a locking shoe  160  is secured to the vertical stile of a sash (not shown) and travels in the shoe channel as the sash is moved up and down. The locking shoe  160  performs a function similar to that of curl spring mount  50  described in the first embodiment during the tilting operation of the sash. The curl spring mount  150  is secured at a fixed position within the shoe channel of the window jamb. One end of the curl spring  110  is securely affixed in a spring lock channel  180  of locking shoe  160  by a plurality of locking tabs  190 . At least one outwardly projecting wiper blade  171   a  is an integral part of the body of the curl spring mount  150 . The outwardly projecting wiper blade  171   a  is positioned to be in forceful contact with the exposed inward surface  110   a  of curl spring  110 . As the window is closed, the sash is returned to its closed position. The locking shoe  160  returns to meet the curl spring mount  150  and curl spring  110  returns to its coiled position within curl spring mount  150 . As the curl spring  110  retracts into the curl spring mount  150 , surface  110   a  is wiped of dust and other detritus by outwardly projecting wiper blade  171   a . Variations of this embodiment provide that at least one more spring may be incorporated within the curl spring mount  150 . The additional spring(s), at most two, would travel in and out of the curl spring mount  150  through an opening on the opposite side of the curl spring mount  150  from the opening for curl spring  110 . A separate integral wiper blade, also designated  171   a , wipes clean the additional spring(s) before re-entry into the curl spring mount  150 .  
         [0032]      FIGS. 8 and 9  show another variation of the second embodiment of the invention, the only difference being that the wiper blade  171   b  is projects inwardly. Either an outwardly projecting wiper blade  171   a  or an inwardly projecting wiper blade  171   b  is suitable for use with this second embodiment. The choice is simply the result of design optimization for each particular application. The wiper blade is made of a material that provides it with a degree of flexibility to exert a sufficient force on the inward surface  110   a  of the curl spring  110  to enable it to remove unwanted dust and detritus therefrom. Suitable materials are well known and may include various molded plastics or elastomeric materials.  
         [0033]     It should be readily apparent that the separate wiper  70  described within the curl spring balance system of the first embodiment may be used with the curl spring mount and locking shoe system,  150  and  160 , respectively, described within the second embodiment. Similarly, the integral wiper described in the second embodiment may be utilized with the curl spring holder  50  of the first embodiment. The common element is the wiper blade that is used to wipe the inward surface of the curl spring upon retraction into its curled position within the curl spring mount or holder within which it is housed.  
         [0034]     However, and notwithstanding the foregoing description of a preferred embodiment, it is clear that numerous variations can be made without exceeding the scope of the inventive concept. Accordingly, it is to be understood that the embodiments of the invention herein described are merely illustrative of the application of the principles of the invention. Reference herein to details of the illustrated embodiments is not intended to limit the scope of the claims, which themselves recite those features regarded as essential to the invention.

Summary:
A spring wiper for curl springs contained within curl spring mounts, holders or shoes operatively engaged with window sashes that are located in window shoe channels. The spring wiper is deployed on the curl spring holder or mount and contains a wiper blade that is transverse to the curl spring, spanning its width, in order to wipe or scrape debris clinging to and/or accumulated on the surface of the curl spring exposed to airborne particulate matter when the curl spring is extended prior to its being retracted into the curl spring mount or holder, thereby keeping such debris from entering the inside of the curl spring mount or holder and interfering with the continued fluid operation of the sash.