Abstract:
A block and tackle sash balance assembly for providing a counterbalancing force to a sash window pivotally and slideably mounted within a sash window frame is disclosed. The assembly is adapted to disable the counterbalancing force responsive to pivoting of the sash window.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application claims priority of U.S. Provisional patent application Ser. No. 60/347,640, filed Oct. 23, 2001. 

   FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT 
   Not Applicable. 
   TECHNICAL FIELD 
   The present invention relates to a block and tackle type sash balance assembly, and more particularly, to a braking mechanism therefore. 
   BACKGROUND OF THE INVENTION 
   A sash window arrangement disposed within a frame is well known. The frame is comprised of a pair of opposed vertical tracks or jam. The tracks are adapted to slidably guide a pair of sash windows within the frame. 
   Various types of balance systems are known and are used to counterbalance the weight of the sash window. In particular, block and tackle counter balance assemblies are known and have become popular due to their combination of relatively compact size and ease of installation. The block and tackle balance combines a system of pulleys and an extension spring mounted within a rigid balance channel for conversion of a high spring tension applied over a short working distance to a lower tension applied over a longer working distance. The extension spring is anchored at one end of the balance channel and the pulley system is anchored at the other end of the channel. 
   A traditional arrangement utilizing a block and tackle balance is disclosed in U.S. Pat. No. 5,530,991 to deNormand. In deNormand &#39;991, an end of the balance channel is is attached to the track via a hook or other intermediate structure. An end of a cord woven through the pulley system and extending from a second end of the channel is attached, via a hook or other intermediate structure, to a shoe. This shoe is in turn attached to the window sash and slides therewith, within the track. An inverted block and tackle counterbalance system is disclosed by U.S. Pat. No. 6,041,476 to deNormand. In this arrangement, the end of the cord extending from the channel is attached to the track via a hook or other intermediate structure. The balance channel is then attached to the sash shoe via a hook or other intermediate structure such that the balance channel slides within the track as the window slides within the frame. 
   If the sash is pivotable, typically the shoe includes a braking mechanism which expands within the channel, to prevent the sash from moving upwards when tilted. While such braking mechanisms are effective, they are relatively complex and expensive, and rely on friction for braking. This results in a need for tight part tolerances. 
   The present invention is provided to solve these and other problems. 
   SUMMARY OF THE INVENTION 
   It is an object of the invention to provide a braking sash balance assembly for a pivotable sash window disposed between a pair of shoe channels. 
   In accordance with one aspect of the invention, the pivotable sash window is pivotable between a first, generally vertical orientation and a second, generally non-vertical orientation. The braking sash balance assembly comprises a channel and means disposed within the channel for providing an upward bias on the sash window. The assembly further comprises a locking member movable with the upward biasing means. The locking member is pivotable between a first position in locking engagement with the channel and a second position disengaged from the channel. 
   In accordance with another aspect of the invention, the assembly comprises a channel and means disposed within the channel for providing an upward bias on the sash window. The assembly further comprises a locking member movable with the upward biasing means. The locking member is pivotable between a first position in locking engagement with the shoe channel and a second position disengaged from the shoe channel. 
   It is contemplated that the upward bias providing means comprises a block and tackle type balance assembly, although other assemblies could be used. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view of a double hung sash window assembly; 
       FIG. 1   a  is a cross-sectional view of a block and tackle balance channel in a sash window shoe channel; 
       FIG. 2  is a front perspective view of a conventional block and tackle sash balance; 
       FIG. 3  is a rear perspective view of a conventional block and tackle sash balance assembly; 
       FIG. 4  is a perspective view of one embodiment of a locking member of a block and tackle balance assembly in accordance with the invention; 
       FIG. 5  is a side view of the balance assembly of  FIG. 4 ; 
       FIG. 6  illustrates the sash balance assembly of  FIG. 4 , located within a sash window shoe channel, with the sash window in the vertically closed position; 
       FIG. 7  illustrates the sash balance assembly of  FIG. 4 , located within a sash window shoe channel, with the sash window in the vertically open position; 
       FIG. 8  illustrates the sash balance assembly of  FIG. 4 , located within a sash window shoe channel, with the sash window in the vertically open position; 
       FIG. 9  illustrates the sash balance assembly of  FIG. 4 , located within a sash window shoe channel, with the sash window in the vertically closed position; 
       FIG. 10  illustrates a second embodiment of the locking member of the present invention; 
       FIG. 11  illustrates a third embodiment of the locking member of the present invention, in its unlocked position; and 
       FIG. 12  illustrates the third embodiment of the locking member in its locked position. 
   

   DETAILED DESCRIPTION OF THE INVENTION 
   While this invention is susceptible of embodiment in many different forms, there is shown in the drawings and will herein be described in detail preferred embodiments of the invention with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the broad aspect of the invention to the embodiments illustrated. 
     FIG. 1  shows a double hung window assembly  1  having a pair of sash windows  3  slidably disposed in a master frame  5 . Each sash window  3  is comprised of a top sash rail  21 , a base sash rail  23  and a pair of vertical stiles  25  having outer stile walls  25   a . The master frame  5  has two pair of vertical tracks or shoe channels  4 . The sash windows  3  are pivotally mounted within the frame  5  between a vertical, or closed position (the upper sash window  3 ) and a non-vertical, or open position (the lower sash window  3 ). A block and tackle balance assembly  7  provides an upward force on the sash window  3 , to counter the weight of the sash window  3 . 
   Each vertical track or shoe channel  4 , as illustrated in  FIG. 1   a , is comprised of a rear wall  9 , a pair of lateral walls  15  and a front wall consisting of a pair of shoulders  17 . The shoulders  17  are separated by a slot  19  extending substantially the length of the track or shoe channel  4 . 
   A conventional sash balance assembly  7  is illustrated in  FIGS. 2 and 3 . The conventional block and tackle balance assembly  7  generally includes a balance channel  6 , an extension spring  12 , a pulley system comprised of a first pulley block  14  and a second pulley block  16 , and a cord  22 . The balance channel  6  has a base  8 , with an inner base surface  8   a  and an outer base surface  8   b , and a pair of side walls  10 . The balance channel  6  further has a first end  18  and a second end  20 . At the first end  18 , the balance channel  6  has a pair of openings  11 , one each located in a respective side wall  10 . 
   The extension spring  12  has a hook  13  formed in each end thereof. One end of the extension spring  12  is rigidly fixed to the balance channel  6  in the proximity of the first end  18  via a rivet or other suitable connecting means. The first pulley block  14  is rigidly fixed to the second end  20  of balance channel  6  via a rivet or other suitable connecting means. A second end of the extension spring  12 , via the hook  13  formed therein, is attached to the second pulley block  16 . The cord  22  is fixed to the second pulley block  16 , and reeved alternatingly through the first pulley block  14  and second pulley block  16 . A free end  24  of the cord  22  extends out of the balance channel  6  through its second end  20 . Attached to the free end  24  is a jam hook  26  adapted to be connected to track  4 . 
   Embodiments of the sash balance braking assembly according to the present invention are illustrated in  FIGS. 4–12 . 
   Specifically, a locking member  40  is disposed between the upper spring hook  13  and the second pulley block  16 , via upper and lower holes  40   a ,  40   b , respectively. As shown in  FIG. 5 , the upper and lower holes  40   a ,  40   b , are vertically offset, such that the spring force presents a pivotally outward bias. The locking member  40  can pivot between a vertical ‘unlocked’ position and a non-vertical ‘locked’ position. The locking member  40  includes a pair of teeth  42  on opposing sides thereof, and an engaging surface  44 . 
   The base  8  of the balance channel  6  includes a series of equally spaced notches  50  along its length. As noted above, each of the sash windows  3  is pivotally mounted in the master frame  5  between a vertical, or closed, orientation and a non-vertical orientation. The notches  50  are dimensioned to receive the teeth  42 . When the sash window  3  is in its closed orientation, the engaging surface  44  of the locking member  40  engages the respective outer stile wall  25   a , opposing the pivotally outward bias, and maintaining the locking member  40  in its unlocked position. However, when the sash window  3  is in its open orientation, the engaging surface  44  of the locking member  40  is released from the respective outer stile wall  25 ′, permitting the pivotally outward bias to move the locking member  40  to its locked position, wherein the teeth  42  engage the notches  50  at the particular location along the base  8 . 
   When the teeth  42  engage the notches  50 , the extension spring  12  is positively locked relative to the balance channel  6 , thus removing the upward force of the extension spring  12  on the sash window  10 . 
   One embodiment of the locking member  40  is illustrated in  FIG. 5 . According to this embodiment, the locking member  40  is a single piece construction of either plastic or metal. Another embodiment of the locking member  40  is illustrated in  FIG. 10 . 
   According to this embodiment, the locking member  40  is a two-piece construction, having a brake linkage  40   a  formed of stamped steel and a cap  40   b  of plastic. 
   In an alternative embodiment, instead of the notches  50 , the inner base surface  8  could be serrated to engage the teeth  42 . 
   A further embodiment of the locking member  40  is illustrated in  FIGS. 11 and 12 . According to this embodiment, the locking member  40  is pivotably mounted to a pivot pin  54  in the channel  6 . The locking member  40  includes a tooth  60 . The tooth  60  engages the rear wall  9  of the shoe channel  4  when the sash window  3  is in its open orientation, thus removing the upward force of the extension spring  12  on the sash window  10 . 
   While the specific embodiments have been illustrated and described, numerous modifications come to mind without significantly departing from the spirit of the invention and the scope of protection is only limited by the scope of the accompanying claims.