Abstract:
A balance assembly for a sliding sash window, where a spring-loaded pulley arrangement is interconnected between the window frame and the window, to counter the weight of the window, and permit ease of opening and closing the window. The spring-loaded pulley arrangement is located within a housing, which also facilitates attachment of the shoe. The shoe of this balance assembly being rotatable between a first and a second position to permit fitting the assembly into the side of the window frame, when the shoe is in the first position, and to permit final installation of the assembly when the shoe in the second position. The shoe is retained in the first and second positions by detents. This rotatable shoe feature permitting installation, of the Balance Assembly of this invention, into a window frame at later stages of the window assembly sequence.

Description:
FIELD OF THE INVENTION 
     This invention relates to a balance system for use in a pivotable, sliding window assembly of a sash window, and more particularly to a block and tackle balance assembly with a rotatable shoe. 
     BACKGROUND OF THE INVENTION 
     A sash window is comprised of one or more moveable panels or sashes, where each sash forms a frame that may hold multiple panes of glass, and both sashes are themselves mounted into a window frame. A “single hung” sash window ordinarily opens by having one sash member, typically the lower sash, sliding vertically relative to the window frame. An arrangement where both sash members can slide vertically is termed a “double hung sash window” or double hung window. For applications in buildings with tall openings, such as for church windows, triple and quadruple-hung windows have been utilized to accommodate the opening. 
     Each sash member, being comprised of multiple panes of glass housed in a wood frame of the sash, would be quite heavy for most homeowners to open or close with relative ease. Such sash members have traditionally been fitted with a means of counterbalancing the weight of the window panes and frame of the sash member, where such balancing means even permits small children to raise and lower the heavy sash member. Although advances in the materials used for the construction of sash frames, beyond the use of wood, may have lead to reductions in the final weight of the sash members, any reductions have been largely been offset by the use of the double paned glass arrangement, which was developed to increase thermal efficiency. 
     The means of counterbalancing the sliding sash windows, in its early and perhaps simplest form, was just a cord attached at one end to a counter weight, with the cord crossing a pulley and, at the opposite end, attaching directly to the window. The mass of the weight in that arrangement is necessarily calibrated to counter the weight of the sash member and the friction of the pulley. If the counterweight were sized excessively, the sash member would be difficult to close and would tend to not remain shut. Conversely, if the counterweight were undersized, the sash member would be difficult to open, and would tend to not remain open. 
     An early patent, U.S. Pat. No. 395,165 to Morgan, shows an arrangement in which the counterweight was replaced by a reel or drum to collect the cord, and a coiled counterbalancing spring within the drum. A common spring for this application was a negator spring, which is a thin flat metal band that is coiled similar to a tape measure. The Morgan approach eliminated the need for the weights, but necessitated housing a drum having a diameter of significantly size, as well as ordinarily permitting some exposure of the drum to provide access for the cord to run down to and attach to the window. These reels or drums are visible, even today, in the windows of many older homes and apartments. Some of these older balance arrangements also make use of a chain in place of the cord. 
     Counterbalancing of sash windows in the early to middle part of the twentieth century saw the use of helical coil springs in place of the negator spring and reel combination. An early example is shown by U.S. Pat. No. 2,329,463 to Froelich. The Froelich patent incorporates a helical spring within a tubular member which is rotatably mounted, where the tubular member has a spiral thread on its exterior surface that is designed to be engaged by a member secured to the window frame. As the upper sash window is lowered from its rest position, the tubular member is turned and applies more tension to the spring, so that energy stored in the spring can check the window from falling, and may also help in raising the sash member when desired. The arrangement could similarly be rotated to be preloaded upon installation, to counterbalance the weight of the lower sash member and assist in raising it at the appropriate time. Also, U.S. Pat. No. 3,064,306 to Beasley shows another basic spring arrangement, both of which were advantageous over the Morgan approach for, among other things, the reduction in the depth required to house the reel. 
     An early example of a balance system with helical coil springs and a block and tackle system for countering the weight of the sash member, is shown by U.S. Pat. No. 3,358,403 to Dinsmore. This basic arrangement is part of a class of similar patents, which have progressively become more streamlined and efficient, and have even been adapted to permit use with a pivotable window. 
     But a serious deficiency of these inventions—because of the limited envelope of the frame, and the size of the “shoe” on such balance assemblies that must necessarily nest within that envelope—is the limitation that the balance assemblies must be fitted into the frame at an early stage of the window assembly sequence by using an intricate installation procedure. This invention eliminates those restrictions by providing a window balance assembly which is transformable to facilitate installation into the frame with ease and at later stages. 
     SUMMARY OF THE INVENTION 
     The balance system of this invention is adapted to easily fit into the frame of a sliding sash window, and is specially configured so that it may be so installed during almost any phase of window assembly, but particularly at a later phase of assembly than is ordinarily possible. 
     The balance assembly of this invention includes a spring-loaded pulley arrangement that connects to the window frame and to the sash window, in order to counter the weight of the window, and to permit ease of opening and closing the sash window. The pulley arrangement can include of one or more pulleys, but in a preferred embodiment, is a block and tackle arrangement utilizing two upper pulleys in an upper rectangular frame and two lower pulleys in a lower diamond shaped frame, with a flexible interconnection means. The interconnection may be a cord, cable, chain or other flexible member. In the preferred embodiment, the interconnection means attaches to the diamond shaped frame, usually with a simple knot, then loops around the pulleys to exit past the rectangular frame and attach to a mounting clip. The interconnection means usually attaches to the mounting clip by running through an orifice in a mounting clip flange and terminating in a knot. 
     The housing may be in many different cross-sectional shapes, bit is preferably a U-shaped channel. The block and tackle pulley arrangement may be installed within the housing of the balance assembly using a number of different fastening systems, including but not limited to screws, nut and bolts, etc. but in a preferred embodiment, a pin is used to fix the upper rectangular frame to the housing. The lower diamond shaped frame of the block and tackle pulley arrangement is biased relative to the housing by attaching a helical spring member, preferably having hooked open ends, to a pin that spans the housing sidewalls, and to an orifice in the diamond shaped frame. The housing may also facilitate attachment of the rotatable shoe. 
     The shoe of this balance assembly is configured to accommodate a cam, which is utilized to provide the pivot feature of a pivotable window. In a preferred embodiment the cam motion may be inhibited, for a portion of its rotation. The motion may be inhibited, in a preferred embodiment, through use of a leaf spring, where cam features and the spring combine to act like a detent to initially restrict cam motion, and thus the pivoting motion of the window. The shoe may be attached to the housing using a hook means which enables the shoe to rotate between a first and a second position, which permits fitting the balance assembly into the side of the window frame when the shoe is in the first position, where subsequent shoe rotation permits final installation of the balance assembly when the shoe in the second position. The shoe may be retained in the first and second positions by detents in the shoe, where the detents act upon the hook means that attaches the shoe to the housing. 
     This rotation ability of the shoe permits installation of the Block and Tackle Balance Assembly with Rotatable Shoe into a window frame at any stage of the window assembly sequence, permitting the balance assembly to be easily installed at a more advantageous time in the assembly sequence. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a front view of the Block and Tackle Balance Assembly with Rotatable Shoe. 
         FIG. 1A  is a front view of the Housing Assembly. 
         FIG. 2  is a front view and side view of the Block and Tackle arrangement. 
         FIG. 3  is a perspective view of the top of the Shoe Assembly. 
         FIG. 4  is a perspective view of the bottom of the Shoe Assembly. 
         FIG. 5  is an exploded view of the components of the Shoe assembly, including the Shoe, Cam, and Leaf Spring. 
         FIG. 6  is a perspective view of the openings in the Shoe. 
         FIG. 7  is a perspective view of the Hook Means and the Lower end of the Housing, of the preferred embodiment. 
         FIG. 8  is a perspective view of the Hook Means fitted into the Lower End of the Housing before being permanently attached to the housing, in the preferred embodiment. 
         FIG. 9  is a perspective view showing the retaining tab of the U-shaped channel bent around the hook means, to permanently attach the hook to the channel, in the preferred embodiment. 
         FIG. 10  is a first alternate embodiment of the hook means and housing. 
         FIG. 11  is a second alternate embodiment of the hook means and housing. 
         FIG. 12  is a third alternate embodiment of the hook means and housing. 
         FIG. 13  is a fourth alternate embodiment of the hook means and housing. 
         FIG. 14  is a perspective view of the Housing Assembly attached to the Shoe Assembly. 
         FIG. 15  is a side view of the Block and Tackle Balance Assembly with Rotatable Shoe, shown in the 90 degree rotated position, ready for installation in a window frame. 
         FIG. 16  is a perspective view of the Block and Tackle Balance Assembly with Rotatable Shoe shown in a 90 degree rotated position, after being set into a window frame. 
         FIG. 17  is a perspective view of the assembly shown in the 90 degree rotated position after installation in a window frame, and with the assembly twisted 90 degrees for final shoe orientation relative to the window frame. 
         FIG. 18  is a perspective view of the assembly shown in the zero degree position after installation in a window frame, with part of the frame cut away to permit viewing the assembly. 
         FIG. 19  is a perspective view of the assembly shown in the zero degree position after installation in a window frame, with part of the frame cut away to permit viewing the assembly, which has the toothed leaf spring exposed, which may contact the window frame. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     The Block and Tackle Balance Assembly with Rotatable Shoe  10  is shown in  FIG. 1 . The block and tackle balance assembly with rotatable shoe  10  is comprised, in a preferred embodiment, of Housing Assembly  130 , and Shoe Assembly  60 . 
     The housing assembly  130  is comprised of housing  131 , Hook Means  160 , a pulley arrangement  20 , Helical Member  50 , and Pins  15  and  16  (see  FIGS. 1 ,  4 , and  8 ). The pulley arrangement  20  (see  FIG. 2 ) could include of a pulley, but in the preferred embodiment is a block and tackle. The block and tackle pulley arrangement  20  of the preferred embodiment includes an interconnection means  21 . The interconnection means  21  may be, but is not limited to, a cord, string, a cable, a chain, etc. 
     The block and tackle pulley arrangement  20  may also include frame  24  with a cavity  29  in which the frame  24  is capable of pivotally mounting a first upper pulley  25  and a second upper pulley  26 . Frame  24  may be in many different shapes, but in a preferred embodiment, it is a rectangular frame. Pivotal mounting to frame  24  is achieved through use of pin  27 , which spans the frame  24 , to trap pulleys  25  and  26  within cavity  29  of frame  24 . Frame  24  will preferably include an orifice  28  to aid in mounting the frame  24  into housing  131 , which be discussed later. The block and tackle pulley arrangement  20  may further include a second frame  30 , which, similar to the rectangular frame  24 , has a cavity  35  in which first lower pulley  31  and second lower pulley  32  are pivotally mounted through use of pin  33 . The second frame  30  may also be in many different shapes, but in the preferred embodiment, frame  30  is diamond shaped. The diamond shaped frame  30  also has an orifice  34  which will be utilized during installation of the block and tackle pulley arrangement  20 , as described later. With the upper pulleys  25  and  26  pivotally mounted in rectangular frame  24 , and the lower pulleys  31  and  32  pivotally mounted in the diamond-shaped frame  30 , the first end of interconnection means  21  may be attached to the diamond shaped frame  30 , preferably using knot  23 . The interconnection means  21  then runs up into the cavity of the rectangular shaped frame and around pulley  25 , down to pulley  31 , around pulley  31  and then up to pulley  26 , around pulley  26  and then down to pulley  32 , around pulley  32  then up through the cavity  29  of rectangular frame  24  and out the top of frame  24 , where the second end of interconnection means  21  attaches to mounting clip  40 , in a preferred embodiment, using knot  22 . 
     Mounting clip  40  may be utilized in many different shapes, but is preferably just a clip with two flanges—first flange  41  and second flange  42 —that are generally at some angle to each other, which preferably is roughly a 90 degree angle. The first flange  41  has an orifice  43  through which interconnection means  21  runs, and beyond which knot  22  on interconnection means  21  is created. The second flange  42  may have an orifice  44  for use in attaching the mounting clip to a window frame, or alternatively, it may be attached to the window. 
     The housing may have an Upper End  132 , and a Lower End  133  ( FIG. 1A ). The U-shaped Housing  132  may have a base  134  that is generally flat with a top surface  135  and a bottom surface  136  and a pair of sidewalls—first sidewall  137  and second sidewall  138 —extending from the top surface  135  ( FIGS. 1A and 7 ). The sidewalls  137  and  138 , are generally parallel to each other throughout the upper end  132  of housing  131 , but angle and converge towards each other in the housing lower end  133 . In both sidewall  137  and sidewall  138  there is preferably one or more orifices  148 . These orifices in each sidewall may generally be in-line with each other, to be able to receive pins  15  and  16 . The pins pass through one orifice of sidewall  139  and extends across the open area between each of the sidewalls to the orifice on the opposite sidewall  140 . The pins  15  and  16  may have a head on one end to prevent the pin from passing through the orifice completely. The opposite end of the pin may be provided with a rivet type head to facilitate installation in U-shaped housing  131 . 
     Pin  15  may be utilized, as shown in  FIG. 1 , to mount the block and tackle pulley arrangement  20  in the housing  131 . With the block and tackle pulley arrangement  20  set into the U-shaped housing  131 , pin  15  may be inserted into the in-line orifices  148  of housing  131  to attach the rectangular frame  24  of block and tackle pulley arrangement  20  using orifice  28  of frame  24  to the housing  131 . In the preferred embodiment, a helical member  50  with a plurality of turns  53  creates a spring having a first end  51  and a second end  52 . The ends  51  and  52  may be configured many different ways, but preferably form an open hook. End  51  of helical member  50  may be hooked onto pin  16 . Due to the location of pin  16  and the specific length of interconnection means  21  of the block and tackle pulley arrangement  20 , a minimal force will need to be applied to end  52  of helical member  50  in order for it to reach and then hook through orifice  34  of diamond shaped frame  30  of the block and tackle pulley arrangement  20 . This will pre-load the block and tackle pulley arrangement  20  so that mounting clip  20  is maintained flush to the top of rectangular frame  24 . For a different window configuration, the length of interconnection means  21  may alternatively be increased so no preload is necessary, such that the mounting clip may hang from the end of frame  24  ( FIG. 2 ). But, the length of interconnection means  21  is often set so a small pre-load maintains the mounting clip  20  flush with frame  24 . 
     In the preferred embodiment, the lower end  133  of housing  131  ( FIGS. 1 and 7 ), where the sidewalls  137  and  138  converge, may also have a step  139  in first sidewall  137 , a step  140  in second sidewall  138 , and a step  141  in base  134 . The sidewall steps  139  and  140  may include, in a preferred embodiment, notches  146  and  147 , respectively. The notches  146  and  147  may be V-shaped, U-shaped, octagonal-shaped, or some other appropriate shape, but in the preferred embodiment, notches  146  and  147  are rectangular. In the preferred embodiment, the converging sidewalls in lower end  133  of housing  131 , as well as the sidewall step  138  and step  141  in base  134 , enable formation of first curved wall  142 , which is at the junction of sidewall step  139  and base step  141 . Second curved wall  143  is likewise formed at the junction of sidewall step  140  and base step  141 . The first and second curved walls  142  and  143 , in a preferred embodiment, contain extensions  144  and  145 , respectively. 
     In a preferred embodiment, Hook Means  160  may be comprised of a buckle portion  162 , where the buckle portion is formed by the cross-arm  163 , and first and second buckle arms,  164  and  165 . The buckle arms  164  and  165  may each have corresponding bends  166  and  167 , which lead to corresponding first and second buckle legs  166  and  167 . The first and second buckle legs  166  and  167  may terminate in double bends  170  and  171 , respectively, which connect to first offset leg  172  and second offset leg  173 . At the end of offset legs  172  and  173  may be curved portions that make up the first end hook  174  and second end hook  175 , of hook means  160 . 
     In the preferred embodiment, hook means  160  may nest into the housing lower end  133  as seen in  FIG. 8 . The hook means  160  may nest by having the buckle cross-arm  163  of the hook means  160  fitting within notches  146  and  147  of housing  131 , so that buckle arms  164  and  165  are outside of sidewall steps  139  and  140 . Also, the hook means may be rotated, while buckle cross-arm  163  rests in notches  146  and  147 , such that the buckle first leg  168  nests between sidewall step  139  and extension  144 , and buckle second leg  169  nests between sidewall step  140  and extension  145 . With the hook means  160  nested within lower end  133  of housing  131 , the extensions  144  and  145  may be deformed, as seen in  FIG. 9 , to fix the hook means  160  to the housing. 
     There are many possible alternate embodiments for the hook means and corresponding attachment features of the housing. In a first alternate embodiment, Housing Assembly  190 , shown in  FIG. 10 , may have hook means  192  that closely resembles hook means  160  of the preferred embodiment, but without double bends  170  and  171 , and without offset legs  172  and  173 . As with the preferred embodiment, a cross-arm of the hook means would nest within notches in the housing. However, the housing  191 , instead of having extensions  144  and  145  to be deformed around the hook means  192 , may have raised beaded portions  194  and  195 . The beads  194  and  195  would wrap partially around the hook means  192 , and provide a convenient point for application of a single weld to secure the hook means  192  to the housing  191 . 
     In a second alternate embodiment, Housing Assembly  200 , shown in  FIG. 11 , may have hook means  202  that closely resembles hook means  160  of the preferred embodiment, except that the buckle first leg  168  and buckle second leg  169  may be closer together so as to be trapped on the inside of the housing  201  side walls. A portion of the sidewalls of housing  201  are dimpled to create dimple  204  and  205  to fix part of the hook means to housing  201 . The other end of the hook means, instead of having the straight cross-arm of the preferred embodiment, may have several helical turns  203 , about pin  206 , where pin  206  extends between the housing sidewalls. 
     In a third alternate embodiment, Housing Assembly  210 , shown in  FIG. 12 , may have hook means  212  in the form of a simple J-hook shape. Two hooks  212  are set into recesses  214  and  215 , which are created by deforming the outside of the sidewalls of the housing  211 . Each of the hooks  212  may then be welded, in at least one location and preferably two or more locations, to permanently fix the hooks  212  to housing  211 . 
     In a fourth alternate embodiment, Housing Assembly  220 , shown in  FIG. 13 , may have hook means  222  in the form of an S-shaped hook. The two S-shaped hooks  222  may be set into recesses  224  and  225  in housing  221 , where the recesses may be created by deforming the outside of the sidewalls of the housing  221 . The housing  221  additionally may have an elongated orifices,  226  and  227 , in the sidewalls to accommodate insertion of one end of the S-shaped hook, which, along with the recesses, assists in fixing the S-shaped hooks  222  to the housing  221 . Each of the hooks  222  may then be welded at a location to permanently fix them to housing  211 . 
     With the preferred embodiment, and similarly with any of the four alternate embodiments, the first and second end hooks  174  and  175  may be designed to provide for attachment and retention of the shoe assembly  60 , which is shown in  FIGS. 3 and 4 . Shoe assembly  60  may, in a preferred embodiment, be comprised of shoe  61 , leaf spring  90 , and cam  110 . 
     Shoe  61  may, of course, take many different geometric shapes, but is shown in a preferred embodiment ( FIG. 5 ) as a rectangular block-shaped member having a generally flat top  62  and bottom  63 , as well as a generally flat front  64  and back  65 . First and second ends  66  and  67  may also be flat, but preferably have some curvature to assist in installing the Block and Tackle Balance Assembly with Rotatable Shoe  10  of this invention in a window frame  180 . 
     An orifice  70  may be located in shoe  61 , with the orifice being generally centered upon and extending up from the bottom  63  of the shoe. Orifice  70  preferably does not reach top  62 , and orifice  68 , being smaller than but in-line with orifice  70 , may run from top  62  of shoe  61  into orifice  70 , to create shoulder  80 . 
     On top  62  of shoe  61  ( FIG. 5 ), between orifice  68  and first shoe end  66 , may be a set of openings,  71 ,  73 , and  72 . Openings  71 ,  72  and  73  may follow many different simple geometric forms, and could be also have a more complex shape including simple and complex curvature. However, in a preferred embodiment, openings  71 ,  72 , and  73  are generally rectangular openings. Opening  73  in top  62  may generally be parallel to first shoe end  66 , and may reach a depth approximately midway between top  62  and bottom  63 . Opening  73  may, but does not reach front  64  or back  65  of shoe  61  in the preferred embodiment. Opening  71  may generally be parallel to and comparable to rectangular opening  73 , except that opening  71  extends to front  64 , and opening  71  may also interrupted by small protrusions that form detent  77  and detent  82  (see  FIGS. 5 and 6 ). Opening  72 , in the preferred embodiment, may be generally perpendicular to openings  71  and  73  and connects opening  71  with opening  73 . Opening  72  may generally be rectangular, and may also narrow, or dog-leg, or have curvature, or even have protrusions forming a detent, any of which may occur near the midpoint between top  62  and bottom  63 , to be capable of rotatably mounting the first and second end-hooks of hook means  160  (see  FIG. 6 ). 
     Openings  74 ,  75 , and  76  may be comparable to openings  71 ,  72 , and  73 , and in the preferred embodiment, are mirror image openings that are located on top  62 , but on the opposite side of orifice  68 . They may similarly include detents  78  and  83  in opening  74 . 
     Shoe  61  may have one other opening,  69 , which is on top  62  and may generally be parallel to openings  71 ,  73 ,  74 , and  76 . Opening  69  may be of any suitable shape including trapezoidal, but in the preferred embodiment it is roughly rectangular in shape. Opening  69  may connect orifices  68  and  70  with front  64 , but opening  69 , in the preferred embodiment, does not extend all the way to bottom  63 , and instead stops approximately midway between top  62  and bottom  63 . 
     Bottom  63  of shoe  61  may have two other features—opening  79  and orifice  81 —to accommodate leaf spring  90 , however, they are more aptly described in a later paragraph, following the description of the leaf spring  90 . 
     Cam  110  may have a top  112  and a bottom  113 , and may feature a cylindrical shape  111  that may begin at bottom  113 , but generally stops short of top  112 , in the preferred embodiment. A second cylindrical shape  114 , having a diameter less than that of cylinder  111  but a common axis, may run from the top  112  to where cylinder  111  stops, forming shoulder  121 . Cam  110  may have an opening  119  in portions of top  112 , cylinder  114  and cylinder  111 , but opening  119 , in the preferred embodiment, does not penetrate both sides of cylinders  114  and  111  (see  FIG. 5 ). Opening  119  may also be any suitable simple or complex geometric shape including trapezoidal, but in the preferred embodiment it is generally rectangular. Extending from a portion of cylinder  114  may be a flange or lip  115  that is generally located opposite opening  119 . Lip  115  may run from top  112  but stops short of shoulder  121 , in the preferred embodiment, such that the distance between lip  115  and shoulder  121  is approximately the same as the distance, on shoe  61 , between top  62  and shoulder  80 . This arrangement permits installation of cam  110  into shoe  61  by inserting top  112  of cam  110  into orifice  70  on bottom  63  of shoe  61 , with the lip  115  of cam  110  oriented to be inline with opening  69  of shoe  61 . Cam  110  may be inserted until shoulder  121  of the cam  110  reaches shoulder  80  of shoe  61 , at which point cam  110  may be rotated within orifice  70  and orifice  68  of shoe  61 . Cam  110  may have generally flat portions  117  and  118  on cylinder  111 . Flat portions  117  and  118  may run from flange  116  on bottom  113  to approximately midway between top  112  and bottom  113 . Flat portions  116  and  117  are designed to interact with leaf spring  90  as discussed in the following paragraph. Also, cam  110  may have a flange  116  on bottom  113  to assist in retaining leaf spring  90  within shoe  62 . This cam configuration with flange  116  would necessitate installing the cam  110  into shoe  61  after installing the leaf spring  90 , which is also described below. 
     Leaf spring  90  may take many different shape, but, in a preferred embodiment ( FIG. 5 ), is Ω-shaped, having an outer surface  91 , inner surface  92 , a top  94 , a bottom  93 , a first end  95 , and a second end  96 . The ends  95  and  96  may have teeth  97 . The leaf spring  90  may have a curved portion  98 , which may connect, through bends  99  and  100 , to first angled leg  101 , and second angled leg  102 , where angled leg  101  and curved portion  98  may be at an acute angle, and angled leg  102  and curved portion  98  may similarly form an acute angle. Bends  103  and  104  may connect angled legs  101  and  102  with angled base leg  105  and angled base leg  106 , respectively. Angled leg  101  and base leg  105  may additionally form an acute angle. Also, angled leg  102  and base leg  106  may similarly form an acute angle. The lengths of the angled legs  101  and  102 , and base legs  105  and  106 , as well as the respective acute angles formed, in the preferred embodiment, may be arranged so as to create a distance between bends  103  and  104  that is slightly less than the distance between flat portions  117  and  118  on cam  110 , providing for proper loading and interaction between leaf spring  90  and cam  110 . 
     As previously mentioned, bottom  63  of shoe  61  may have two other features to accommodate leaf spring  90 —opening  79  and orifice  81 —which are now appropriately described (see  FIGS. 4 and 5 ). Orifice  81  may generally be provided in bottom  63  in approximately the same shape of flange  116  of cam  110 . The depth of orifice  81  may be approximately equal to the thickness of flange  116  of cam  110 . 
     The opening  79  on bottom  63  of shoe  61  may be irregularly shaped, however, in the preferred embodiment it generally follows the Ω-shape of leaf spring  90 , and is to a depth approximately equivalent to the width of leaf spring  90 , as shown by the distance between top  94  and bottom  93  of leaf spring  90 . The opening  79  may extend to reach first and second ends  66  and  67  of shoe  61 , as well as reaching back  65  of shoe  61  ( FIG. 5 ). The opening  79  may also extend into orifice  70  of shoe  61  (see  FIG. 6 ). With the leaf spring  90  inserted into opening  79  of shoe  61 , the cam  110  may be installed into shoe  61 . The insertion will, in the preferred embodiment, require elastically deforming angled legs  101  and  102  of leaf spring  90  so that the opening between bends  103  and  104  of leaf spring  90  is large enough to accommodate admitting cylinder  111  of cam  110 . Installation will be complete when flange  116  of cam  110  is flush with bottom  63  of shoe  61 . 
     The normal at-rest cam position, in the preferred embodiment, occurs when bends  103  and  104  of leaf spring  90  rest on flat portions  117  and  118  of cam  110 . This at-rest position corresponds to the sliding sash window, which is capable of also pivoting open by using cam  110  to accomplish such pivoting, occupying the un-pivoted position. 
     This cam/spring arrangement of the preferred embodiment creates a preload between leaf spring  90  and cam  110  such that the leaf spring  90  behaves like a detent tending to initially inhibit rotation of the cam  110  within shoe  61 , while the leaf spring bends  103  and  104  are positioned on flat portions  117  and  118 , which is while the window is in the un-pivoted position. Once a sufficiently high force—a person seeking to pivot the window open—causes rotation of the cam  110  to widen the distance between bends  103  and  104  of leaf spring  90 , and the bends  103  and  104  contact cylinder  111  of cam  110 , cam (and window) rotation continues with application of a minimal force. This widening of the distance between bends  103  and  104  of leaf spring  90  may correspondingly cause the toothed ends  95  and  96  of leaf spring  90  to protrude beyond ends  66  and  67  of shoe  61 . The toothed ends  95  and  96 , when so protruding after the balance assembly has been installed in a window, may be used to prevent movement of the balance assembly relative to the window frame. 
     Assembling the Block and Tackle Balance Assembly with Rotatable Shoe  10  will be completed, in the preferred embodiment, once the shoe assembly  60  ( FIG. 3 ) is attached to housing assembly  130  ( FIG. 9 ). Attachment of housing assembly  130  to shoe assembly  60  may be accomplished by inserting the first and second hook ends  174  and  175  of hook means  160  ( FIG. 7 ) into openings  72  and  75  ( FIG. 5 ) until passing the angled surfaces to be urged, through a narrow area, into the rectangular openings  72 A and  75 A ( FIG. 6 ,  FIG. 14 , and  FIG. 15 ), which then pivotally retrain the hook means. The housing assembly  130  may be retained, by detents  77  and  78  of shoe  61 , in the 90 degree rotated position, as shown in  FIG. 15 , which facilitates installation into the C-shaped window frame  190 , as shown in  FIGS. 16 and 17 . 
     This rotation ability of the shoe permits installation, of the Block and Tackle Balance Assembly with Rotatable Shoe  10 , into a window frame at any stage of the window assembly sequence. The balance assembly thus may be installed at a more advantageous time in the assembly sequence. 
     Once inserted into the window frame  190  ( FIG. 16 ), the Block and Tackle Balance Assembly with Rotatable Shoe  10  may be twisted 90 degrees ( FIG. 17 ). A force can then be applied to the housing assembly  130  to overcome the detents  77  and  78  in shoe  61 , and the housing assembly  130  can be rotated to the zero degree position for final installation into the window frame, as shown in  FIG. 18 . Detents  82  and  83  ( FIG. 6 ) provide a positive tactile signal for when the assembly has reached the zero degree position, as well as provide a means for retaining the housing and shoe at the zero-degree position. It should be noted that throughout the installation of the Block and Tackle Balance Assembly with Rotatable Shoe  10 , bottom  63  of shoe  61  always maintains contact with the window frame. 
     Other modifications, substitutions, omissions and changes may be made in the design, size, materials used or proportions, operating conditions, assembly sequence, or arrangement or positioning of elements and members of the preferred embodiment without departing from the spirit of this invention as described in the following claims.