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RELATED APPLICATIONS 
   This is a continuation in part of application Ser. No. 10/978,943 filed Nov. 1, 2004, now allowed, which is a continuation in part of application Ser. No. 10/116,915 filed Apr. 8, 2002, now U.S. Pat. No. 6,823,626, which is a continuation in part of application Ser. No. 09/657,243 filed Sep. 7, 2000, abandoned as of the filing of this application. 

   FIELD OF THE INVENTION 
   The present invention relates to a window assembly with a sash which is both slidable and tiltable relative to the frame supporting the sash. In a different aspect of the invention, a tiltable sash when open automatically changes angle according to an ambient condition. 
   BACKGROUND OF THE INVENTION 
   Many of today&#39;s modern windows have sashes which are both slidable and tiltable relative to their supporting frames. The tilt feature adds the benefit that the sash can be cleaned when tilted to an open position. However, this same tilt feature can also be detrimental because current windows that have slidable and tiltable sashes do not include any type of a sash tilt control. Without this control the sash, if not properly handled by the person at the window, can easily fall completely out of the frame creating a very hazardous situation. 
   In a typical window having sliding and tilting sashes the frame jambs of the window usually have undercut openings known in the industry as balance pockets or channels. These channels contain balancing devices i.e., balance springs or the like which help to hold the sashes at different positions to which they are slid relative to the frame. Any sash tilt control that can be added to current window designs must not interfere with these balance devices. Furthermore, any such sash tilt control must not adversely affect the tilt opening or tilt closing of the sash. 
   The window industry is very competitive and as such any changes to known window assembly construction are not readily accepted both from a cost and a market appeal standpoint. Therefore, any modifications made to existing windows having slidable and tiltable sashes must be at low cost and should be compatible with current window assembly design. 
   SUMMARY OF THE INVENTION 
   The present invention provides a window assembly having a frame, a sash and a low cost sash tilt control which prevents the sash from tilting out of the frame and which is extremely compatible with existing window design. 
   More particularly, the window assembly of the present invention comprises a frame and a sash in which the frame is elongated relative to the sash and the sash is slidable to different vertical settings within the frame. The frame has side jambs with interior channels opening at the sash. Each of these channels is provided with a balancing device which slides with and balances weight of the sash at the different vertical settings of the sash in the frame. 
   The sash is further tiltable between a tilted closed and different tilted open positions relative to the frame. 
   The assembly includes a sash tilt control bar. This bar has a first end attached to the sash and a second end which is slidably held within one of the channels of the frame. The frame, the sash and the bar all vertically align with one another when the sash is in the tilted closed position where the bar is sandwiched between the frame and the sash. 
   When the sash is tilted open the second end of the bar slides vertically of the channel in which it is held. The vertical sliding of the second end of the bar does not interfere with the balance device in that channel. The vertical travel at the second end of the bar causes the bar to tip away from its vertical position towards a more horizontal position. However, the bar should not reach a fully horizontal position i.e., a position perpendicular to the frame where the bar might otherwise block the tilt closing of the sash. In order to avoid this problem, the bar limits the tilt opening of the sash to positions which do not allow the second end of the bar to travel sufficiently far as to allow the bar to move to a position perpendicular to the frame. This in turn stops the vertical travel of the second end of the bar before the bar tips to a position perpendicular to the frame as the sash is tilted open. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The above as well as other advantages and features of the present invention will be described in greater detail according to the preferred embodiments of the present invention in which; 
       FIG. 1  is a perspective view looking down on a window assembly having first and second sashes, the first sash being in a closed position, the second sash being tilted open and both sashes being provided with sash tilt controls according to a preferred embodiment of the present invention; 
       FIG. 2  is a sectional view of the window assembly of  FIG. 1  showing both sashes tilted open and the first sash being slid downwardly from its closed position of  FIG. 1 ; 
       FIG. 3  is a view similar to  FIG. 2  with the sashes and sash tilt controls removed from the window assembly; 
       FIG. 4  is a front view of a further window assembly made in accordance with a preferred embodiment of the present invention; 
       FIG. 5  is a sectional view along the lines  5 - 5  of  FIG. 4 ; 
       FIG. 6  is a view similar to  FIG. 5  showing the upper and lower sashes in tilted open positions; 
       FIG. 7  is a front view of either one of the sashes from the window assembly of  FIG. 4  when removed from the supporting frame; 
       FIG. 8  is an end view of the sash of  FIG. 7  without the tilt limit bar in position; 
       FIG. 9  is the same view as  FIG. 8  but showing the tilt limit bar attached to the sash; 
       FIG. 10  is an end view of the window assembly of  FIG. 4  with the two sashes tilted open relative to the frame; 
       FIG. 11  is a top view of a tilt limit bar according to a preferred embodiment of the present invention; 
       FIG. 12  is a side view of the tilt limit bar of  FIG. 11 ; 
       FIG. 13  is a perspective view showing the engagement of the tilt limit bar with the balance channel of the frame for either one of the sashes from the window assembly of  FIG. 4  with the sash tilted open as shown in  FIG. 6 ; 
       FIGS. 14 through 17  are perspective views of sashes and sash tilt controls according to further preferred embodiments of the present invention; 
       FIG. 18  is an enlarged view of the outside edge of the sash stile of  FIG. 17  showing in phantom the insertion of the end of the sash tilt control bar into the stile opening to receive the bar end; 
       FIGS. 19 and 20  are perspective views of sashes with sash tilt control arms according to further preferred embodiments of the invention; 
       FIG. 21  is a front view of a window assembly having a frame supporting a pair of sashes including tilt controls for each of the sashes according to a preferred embodiment of the present invention; 
       FIG. 22  is a perspective view of the window assembly of  FIG. 21  showing the lower sash tilted open with a preferred embodiment of the present invention mounted on the stile and fitted to the frame jamb; 
       FIG. 23  is a sectional view along lines  3 - 3  of  FIG. 1  showing the sashes closed and in their normal operating position; 
       FIG. 24  is a sectional view along lines  3 - 3  of  FIG. 21  and similar to the view of  FIG. 23  except the sashes are shown tilted open at an angle for ventilation; 
       FIG. 25  is a view similar to that of  FIG. 24  with the exception that the sashes are shown tilted to the position they would take after the spring arms have been affected by atmospheric changes and become more resistant to bending; 
       FIG. 26  shows a short section of bimetallic material with one side composed of a material having properties different than those of the material comprising the opposite side; 
       FIG. 27  is a preferred embodiment of the present invention showing the attachment of the spring arm to the window sash; 
       FIG. 28  is a view showing the attachment of the spring arm according to a further preferred embodiment of the present invention; 
       FIG. 29  is a view showing the attachment of the spring arm according to yet another preferred embodiment of the invention; 
       FIG. 30  is a sectional view along lines  4 - 4  of  FIG. 21  with the lower sash opened showing the hook engagement of one embodiment along the wall of the window jamb; 
       FIG. 31  shows the same embodiment as that in  FIG. 30  with the hook positioned for its release and removal from the balance channel of the frame. 
       FIG. 32  is another preferred embodiment of the present invention showing a spring arm constructed from two dissimilar materials; 
       FIG. 33  is the assembly shown in  FIG. 31  with the spring arm fully bent; 
       FIG. 34  shows the assembly shown in  FIG. 33  but an atmospheric change has caused the spring arm to change shape and move the hook end closer to the sash stile; and 
       FIG. 35  shows an alternate spring arm assembly; 
       FIG. 36  is a perspective view of an alternate window sash and a small diameter control arm with a jamb-slide connection; 
       FIG. 37  is a partial top view of the bent end of the wire control bar that engages the jamb-slide; 
       FIG. 38  is a cross section through a window looking downwardly showing the relationship of the sash and frame; 
       FIG. 39  is a view similar to  FIG. 38  showing insertion of control bars either side of the sash; 
       FIG. 40  is a view similar to  FIG. 39  with one sash tilted inwardly; 
       FIG. 41  shows the end of the wire control bar retained in the jamb-slide; 
       FIG. 42  shows the end of the control bar releasing from a jab-slide; and 
       FIGS. 43 ,  44 ,  45  and  46  are perspective view of alternate embodiments of the wire control bar configured for effective engagement with the window sash. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1  shows a window assembly generally indicated at  1 . This window assembly mounts in an opening of a building wall. 
   Window assembly  1  is built around a standard window construction and additionally includes novel features of the present invention added to that construction. The assembly  1  can be made from plastic, wood, aluminum or other suitable materials. 
   The assembly includes a frame  2  which supports sashes  9  and  11 . These sashes are both slidable and tiltable relative to the frame. The frame is elongated relative to the sashes to accommodate slide opening and closing of the sashes. 
   The frame itself is formed of a pair of side jambs  3 , header  5  and a sill  7 . As seen in  FIGS. 2 and 3  side jambs  3  include first and second channels  17  and  19 . These channels have an undercut configuration with a relatively narrow mouth which faces at the sash within the frame. The channels widen behind their mouth walls to receive balancing devices generally indicated at  22  and  32 . 
   Balancing device  22  comprises a fixed position cylinder  23 . Extending from cylinder  23  is a rod  25  which slides relative to the cylinder. The cylinder contains means, e.g. a spring or the like, which provides resistance to the sliding of the rod. A sash mount  27  is provided on the lower end of rod  25 . Sash mount  27  includes a pivot connector  29  to which the lower end of the sash  9  secures as to be described later in more detail. 
   Balancing device  32  has a similar construction to device  22  and includes a cylinder  33  fixed in channel  19 , a rod  35  slidable relative to the cylinder and a sash mount  37  at the lower end of the rod. Sash mount  37  includes a pivot connector  39  which secures to the lower end of sash  11 . 
   In comparing  FIGS. 1 and 2  it will be seen that sash  9  is at different height settings in the frame. Balance device  22  is used to offset weight of the sash to hold these different settings. Sash  11  is also slidable to different height settings for a slide opening and closing of the window. Balance device  32  is used to help support sash  11  at these different height settings. 
   Each of the sashes  9  and  11  is also tiltable relative to the frame for a tilt opening and closing of the window. The sashes tilt open to different tilted settings and in accordance with the present invention tilt control bars  13  and  15  are provided to help hold the sashes in their different tilted positions. These tilt control bars pivotally secure at one of their ends to the respective sash and slidably engage at the other of their ends within the respective balance channel of the frame as also to be described later in more detail. The bars do not in any way interfere with the balance devices in the channels. 
   The description above shows very generally the window assembly construction including the sash tilt control feature of the window assembly.  FIGS. 4 through 6  show, in greater detail, another window assembly which once again incorporates this same sash tilt control. For drawing clarity purposes, the balancing devices are not shown in these particular figures. They are, however, included in the window assembly of  FIGS. 4 through 6  and they do operate in the same manner as that already described. 
     FIG. 4  shows an overall window assembly generally indicated at  101 . This assembly comprises a frame  103  which mounts within a building opening and which supports upper and lower sashes  105  and  109  respectively. 
   Referring now to  FIG. 5 , frame  103  comprises a header  113 , a sill  115  and opposite side jambs  114 . Each of these jambs includes a front channel  119  and a rear channel  120 . These two channels which contain balancing devices that are not shown extend essentially the complete height of the frame. 
   Sash  105  comprises a header  121 , a sill  125  and side jambs or stiles  123 . The header, sill and jambs of sash  115  hold a glass pane  107 . 
   The sash  109  is formed by a header  127 , a sill  131  and opposite side jambs  129 . The header, sill and jambs of sash  109  contain a glass pane  111 . 
   The side jambs  123  of the upper sash and more particularly the pivot pins and the spring locks of the jambs are slidably received within frame channel  120  while the pivot pins and spring locks of the side jambs  129  of the lower sash are slidably received within frame channel  119 . In order to prevent sliding of the two sashes relative to one another, i.e. for locking the window closed, the window is provided with a lock mechanism  112  having cooperating locking parts on the sill of the upper sash and the header of the lower sash. 
   The two sashes are not only slidable but additionally they are tiltable relative to the frame. As better shown in  FIG. 7  of the drawings, each of the sashes, as represented by sash  105 , has a lower end pin  135  and an upper end spring lock  137 . The pins connect to the pivot connectors of the sash mounts of the balance devices as earlier described with respect to  FIGS. 1 through 3 . The pins then ride within the frame channel as do the two spring locks when the locks are in the position shown in  FIG. 7 . However, the two spring locks are retractable to allow the upper end of the sash to release from the frame for tilt opening of the sash.  FIG. 6  of the drawings shows the two sashes in their tilted open positions. 
   Again, the key to the present invention lies in the provision of a tilt control bar unique to the present invention. 
   An example of a preferred embodiment tilt control bar generally indicated at  141  is best seen in  FIGS. 11 and 12  of the drawings. The bar is used with sash  105 . A similar bar  110  is used with sash  109 . 
   Bar  141  includes an elongated bar portion  143  terminated at one end with a short right angle leg portion  145  and a small hole  147  through the main body of the bar near the short leg. The other end of the bar is provided with a hook-like member  149  which extends to the opposite side of the main body of the bar from leg portion  145 . 
   Returning to  FIG. 8 , it will be seen that the outside surface of the sash jamb  123  includes a pair of vertically spaced holes  151  and  153 . Hole  153  is larger than hole  151 . 
   Tilt limit bar is mounted to sash jamb  123  by means of a screw  155  which fits through opening  147  in the bar and threads into sash opening  151 . Leg  145  of the bar locates within sash opening  153 . The sash opening is oversized relative to the leg allowing the leg some play within the sash opening. However the amount of play is limited to provide a bar movement controller as described later in more detail. 
   As earlier mentioned the window frame includes channels  119  and  120 . These channels not only contain the sash balancing devices but in addition are used to trap one end of the tilt limit bars on each of the sashes. 
   More particularly, referring to  FIG. 13 , it will be seen that the hooked end  149  of bar  141  wraps around and locks onto the mouth wall  120  of the undercut balance channel  119 . This in no way prevents sliding action of the sash within the frame nor does it interfere with the operation of the balance device. The hooked end of the bar slides vertically of the channel at the same time as, and always stays above, the sash mount of the balance device. 
   As also earlier mentioned the tilt bar leg portion  145  has some play within the sash jamb opening  153 . The mounting of the tilt bar by means of screw  155  in combination with the leg play noted immediately above provides a tilt bar movement controller. This controller limits the amount of pivotal movement of the bar at the sash. The limiting of this pivotal movement in turn controls the amount of vertical slide of the other end of the bar in the frame channel. This is important because the bar should never reach a position perpendicular to the frame where it could easily block the tilt closing of the sash. 
   More particularly, when the sash is tilted closed the tilt control bar aligns with and is sandwiched between the sash and the frame as shown in dotted lines in  FIG. 5 . When the sash is tilted open the control bar begins to tip from its  FIG. 5  vertical position towards a more horizontal position. During the tipping of the bar two things happen. Firstly, there is a pivoting movement at the connection of the one end of the bar to the sash and secondly the other end of the bar starts to slide vertically i.e., upwardly within the frame channel. However, the bar movement controller, which in this case is leg portion  45  of the bar  53 , controls the amount of pivot at the one end of the bar which sets the degree to which the bar is allowed to tip. As soon as the pivoting movement at the sash end of the bar is stopped by the controller, the other end of the bar can no longer ride upwardly in the channel. This happens before the bar can reach the fully horizontal i.e., frame perpendicular position. 
   In the preferred embodiment as shown the pivot movement between the bar and the sash is controlled to allow the bar to swing or tip through a maximum angle of about 15.degree. This angle is indicated at A in  FIG. 6 . At this angle of the bar the sash reaches its maximum tilted open position of about 45.degree relative to the frame. This is a position from which the sash can easily be pushed closed. 
   Another feature of the present invention is that the tilt bar, although normally in its frame engaged position can easily be manually released from the frame. This is done by pushing the sash, when tilted open, towards the closed position and holding the bar from sliding downwardly along the frame channel. By doing this the hooked end of the bar is pushed off of the mouth wall of the balance channel. The bar can then be pushed or flexed inwardly to move the hooked end of the bar out of the channel. When the bar is moved to this disengaged position, the sash can be tilted open as far as desired for cleaning or maintenance purposes. 
   Although the drawings and description above show the tilt limit bar being used in a double hung window, it could equally as well be used in a single hung window. Furthermore, the degree to which the sash is allowed to tilt relative to the frame could easily be modified from the 45.degree angle described above. The sash should however be limited to a tilt angle of something less than 90.degree when under the control of the bar. 
   The embodiments described above show only a few of the ways in which to prevent the tilt control bar from reaching a position perpendicular to the frame. Other embodiments of the invention fulfilling the same function are shown in  FIGS. 14 through 20  of the drawings. Note that in each of these drawings the sash and the tilt control arm are shown away from the frame but it will be readily understood from each of the figures how they interact with the frame. 
     FIG. 14  shows a sash  160 . A tilt control bar  162  is pivotally mounted at its one end by pivot mount  163  to the sash. The other end of the bar has a hooked end for engaging the balance channel of the frame in the same manner as that found in the earlier embodiments. 
   In this particular embodiment, the bar movement controller which limits the amount of pivot of the bar relative to the sash is in the form of a pin  167  supported by the sash. The edge of the bar will engage the pin when the sash has reached the degree to which it is allowed to tilt in its fully tilted open position. When the sash reaches this position the tilt control bar is well away from reaching a frame perpendicular position. 
   In the embodiment shown in  FIG. 14 , the sash is provided with a plurality of insert holes  165  to selectively receive the pin  167 . When the pin is inserted into the uppermost of the holes  165  the sash will be allowed to tilt farther open than it would be if the pin is positioned in one of the lower holes. Therefore, in this embodiment the maximum tilt angle of the sash is adjustable by virtue of the positioning of pin  167 . 
     FIG. 15  shows a sash  170  with a tilt limit bar pivotally mounted at  172  to the sash. Also provided in this embodiment is a flexible or bendable bar movement controller in the form of a chain  174  having one end secured to the bar and the other end secured to the sash. 
   As will be appreciated from  FIG. 15  the sash will reach its maximum tilted open position when the chain is extended to its maximum length. The chain then stops the pivotal movement between the control bar and the sash. This occurs well before the bar is able to reach a position perpendicular to the frame. 
     FIG. 16  shows a sash generally indicated at  176 . A tilt control bar  177  is used to determine the maximum tilted open position for the sash. 
   In this particular embodiment, bar  177  is provided with a right angular extension  179 . This extension, as shown, has a semi-circular configuration with a rounded side  179  and a flat side  181 . 
   Sash  176  is provided with an opening for receiving the extension  179 . This opening is defined by a rounded wall part  183  and a flat wall part  185 . The rounded wall part circumscribes more than 180 degrees of a circle e.g., something in the neighborhood of about 240 degrees of a circle. This allows a limited pivot of the extension  179  within the opening. The amount of pivot is dictated by the flat edge surface  181  of the extension abutting the flat wall  185  of the opening of the sash. This occurs when the sash has been tilted to its maximum tilted open position of for example, 15 degrees relative to the frame. 
     FIGS. 17 and 18  show another embodiment of the invention. In this embodiment, a tilt control arm  192  fits with a sash  190 . As best shown in  FIG. 18  this sash includes a curved slot  194  and the control arm includes a head  196  having a pair of pivot pins  198  and  199  located within the slot  196 . 
   The provision of the two spaced apart pivot pins prevents the head of the arm from rotating relative to the sash. 
   The sash will tilt open to the point where the pivot pin  199  runs into the upper blind end of the slot  194 . This then blocks any further tilt opening of the sash. 
   It is to be understood that in each of the embodiments shown in  FIGS. 14 through 18  the hooked end of the control bars shown in these figures will once again rise in the frame channel. Furthermore this occurs without interfering with the balance device located in the channel in the same manner as disclosed with respect to  FIGS. 4 through 11  of the drawings. Also like the  FIGS. 4  through  11  embodiment, the amount of pivot at the sash end of the bar is controlled to limit the amount of vertical travel of the hook end of the bar thereby preventing the bar from tipping to a frame perpendicular position. 
     FIGS. 19 and 20  show still further embodiments of the invention. In each of these embodiments, to be described in more detail below, a sash is fitted with a tilt control bar where the bar once again has a hooked end to slide vertically within a balance channel of a frame. However, unlike the earlier described embodiments the control bar does not pivotally mount to the sash but rather it is the nature of the construction of the bar itself which provides the bar movement control. 
   More specifically,  FIG. 19  shows a sash  201  removed from a frame which slidably and pivotally holds the sash. Provided to one side of the sash is a tilt control bar generally indicated at  203 . This tilt control bar is made from a bendable spring steel material. 
   Bar  203  is provided with a hooked end  205  which hooks onto and slides along the channel mouth wall of the frame which receives sash  201 . 
   The control bar is formed with two loops  207  and  209  directly within the body of the control bar. Fastening devices such as screws or the like are then fitted through the loops into the sash to secure the control bar to the side of the sash. 
   In this embodiment, as the sash is tilted open, the hooked end of the bar once again slides upwardly along the mouth wall of the channel without interfering with the balance device in the channel. However, the bar does not pivot relative to the sash because of the spaced apart mounting locations of the bar to the sash. Instead the bar bends between the loop  209  and the hooked end  205  of the bar. The amount of bend in the bar is dependent on the strength of the bar material. In all instances using the bar  203  the bar material would be sufficiently strong to prevent the sash from tilting to a frame perpendicular position. 
     FIG. 20  shows another embodiment using a bendable tilt control bar  13  which fits with a sash  211 . In this embodiment, the control bar has a right angle extension  217  at one end of the bar and a hook  215  at the other end of the bar. The extension  217  secures within a sash opening  219 . The hook  215  slidably mounts to the mouth wall of the channel of the frame which receives sash  211 . 
   Additionally provided is a bar to sash fastening device  223 . The sash includes openings  225 ,  227  and  229  to selectively receive a screw or the like to attach fastening device  223  to the sash. 
   The provision of the extension  217  secured within the sash and the mounting of the fastening device  223  spaced from extension  217  prevent the bar from rotating relative to the sash. As the sash is tilted open the hooked end  215  of the bar once again slides vertically upwardly along the balance channel without interfering with the balance device in the channel. At the same time the bar bends between fastening device  223  and the hooked end  215  of the bar. The resiliency and stiffness of the bar dictate the degree to which the sash can be tilted open. In all instances, the sash will not tilt to a position in which the sliding end of the bar travels sufficiently far to place the bar in a frame perpendicular position. 
   When the fastening device  223  is secured at sash opening  225  the sash will tilt farther open than it will when the fastening device is secured at sash opening  227 . The least amount of tilt is provided when the fastening device is secured at sash opening  229 . The reason for this is that the lower the fastening device is located along the body of the bar, the less the bar will bend. By lowering the fastening device there is a decrease in the length of bar material between the fastening device and the hooked end of the bar. This stiffens the bar in the region where the bar bends with the tilt opening of the sash. 
     FIGS. 21 and 22  show a window assembly generally indicated at  1 . This window assembly is formed by a frame comprising side jambs  303 , a header  305  and sill  307 . Contained within that frame is a pair of sashes  313  and  315 . Both of the sashes are closed relative to the frame. Lock  317  cooperating between the top of the lower sash and the bottom of the upper sash holds them in their closed positions. 
   As will be described later in detail both of the sashes can be opened in a sliding mode upon release of lock  317  and a tilting mode upon the release of locks  316 ,  317  and  318 . 
     FIG. 22  shows locks  316 ,  317 , and  318  released and lower Sash  315 , being tilted inward of the frame. The first end of spring arm  320  is mounted to the sash stile  319  at  321  and  365 . The second end of spring arm  320  is engaged with frame jamb  303  as will be described later in greater detail. 
     FIG. 23  shows  FIG. 21  through section  3 - 3  whereby sashes  313  and  315  are slidably attached to and slide along a pair of channels  309  and  311  located in the window frame jamb. The other jamb has the identical construction. 
   Both of these channels are referred to in the industry as balance channels. Balance channel  309  is located to the interior side of the window i.e., the side of the window facing the interior of a building in which the window is used while balance channel  311  is located to the outer side of the window. 
     FIG. 23  also shows slide members  375  and  376  mounted within channels  309  and  311 . The sashes are pivotally connected to the slide members with pins  326  and  327  respectively located at the lower edges of each of the sashes. Latches  316  and  328  keep the sashes vertical relative to the frame. This mounting is identical to both sides of the window. 
   More specifically, rigid slide member  375  is trapped within balance channel  309  while rigid slide member  376  is trapped within balance channel  311 . The lower end of sash  315  is pivotally mounted at  326  to slide member  375  while the lower end of sash  313  is pivotally mounted at  327  to slide member  376 . As will be appreciated from  FIG. 23 , when lock  317  is released both sashes and their corresponding slide members are slidable relative to the frame in their respective channels providing for the slide opening of the window. 
     FIGS. 24 and 25  show sashes  313  and  315  also being openable in a tilting manner relative to the frame. Here it will be seen that when latches  316 ,  317  and  328  along with latches  318  and  329  which are hidden from view are released sashes  313  and  315  are no longer locked in relation to the frame and the upper end of the sashes are free to rotate outwardly and downwardly away from the frame. The two sashes can be tilted open one at a time or simultaneously with one another. 
   Each sash is also provided with a tilt control. In  FIGS. 23 ,  24  and  25  the tilt controls are in the form of spring arms  320  and  340  mounted rigidly to the sash stiles at their first end at locations  321  and  365  on sash  315  and at  371  and  379  on sash  313 . Hook  352  is mounted to the second end of spring arm  320  and hook  372  is mounted to the second end of spring arm  340 . Each of these hooks is inserted into corresponding channels  309  and  311  in the frame jamb. Such a combination may be provided to only one side or to both sides of each of the sashes. 
   More specifically, referring to the embodiment in  FIGS. 23 ,  24 , and  25  spring arms  320  and  340  are used to control tilting movement of sashes  315  and  313  respectively to prevent a free falling of the sashes from their fully closed to their fully tilted open position. 
   Referring to lower interior sash  315 , control arm  320  has a first end secured at  321  and  365  to the stile of sash  315  and a second end in the form of a circular hook  352  slidably trapped within channel  309  of the frame jamb. In comparing  FIGS. 23 , and  24  it will be seen that as sash  315  is tilted farther open i.e., moved to increased tilt angles, hook  352  of spring arm  320  slides upwardly along channel  309  of the jamb causing spring arm  320  to bend outwardly and upwardly relative to points  321  and  365 . The bending moment and tension within spring arm  320  increases until the second end of the spring arm bends to a point where spring arm attachment points  321  and  365  are applying a pulling force to hook  352  that is nearly perpendicular relative to the frame at which time the sash reaches its maximum tilt angle of something less than 90 degrees relative to the frame. 
   As can be seen from  FIGS. 23 ,  24 , and  25  two separate forces counteract one another during the tilt opening of the sash. Firstly, the downward loading of the sash on the spring arm increases the farther the sash is tilted open. This is due very simply to the outward levering of the weight of the sash as the sash moves from a more vertical to a more horizontal position i.e., as the upper end of the sash moves downwardly and outwardly away from the frame. 
   At the same time as the sash applies increasing force on the tilt control arm the bending of spring arm  320  becomes more pronounced which in turn provides increased resistance to the tilt opening of the sash the farther the sash tilts open. This resistance is not sufficient to prevent the tilt opening of the sash, but it is sufficient to prevent a free falling of the sash. 
   As will also be apparent from  FIGS. 23 ,  24  and  25  the tilt control i.e., spring arms  320  and  340  or hooks  352  and  372  do not block sliding of the sash within the frame. 
     FIG. 25  shows sashes  313  and  315  tilted to intermediate positions between those seen in  FIGS. 23 and 24 . The sashes can be set to this position under normal operator control but can also be moved to this position by an unattended means if spring arms  320  and  340  were to be constructed from bimetallic materials and formed to provide movement as shown in the preferred embodiment in  FIG. 35  to cause the spring arms to move in a forward and backward direction perpendicular to the window frame. The warping of the spring arms causes the sashes to tilt closer to the window frame or to tilt to an angle further away from the window frame depending on atmospheric conditions surrounding the spring arms. 
     FIG. 26  shows a section of a spring arm manufactured from two different materials  332  and  333  that have been bonded together at  334 . Each of the two materials exhibit different behaviors when subjected to specific atmospheric conditions. When bonded materials  332  and  333  are shaped to form a spring arm and subjected to atmospheric changes affecting one of the materials the spring arm will be caused to warp to varying and predictable positions. 
   For example, bimetallic warping behavior will be observed in the spring arm shown in  FIG. 26  if materials  332  and  333  have different expansion and contraction rates over a specified temperature range. 
   It can be appreciated how the shape of spring arm  320  and position of hook  352  shown in  FIG. 35  would be altered if coil  380  were composed of the aforementioned bimetallic materials where the exterior side of the material composing the coil decreased its length in colder temperatures while the interior side remained essentially the same length. 
   Referring back to  FIG. 25 , sashes  313  and  315  are shown rotated toward the closed position from the more rotated open position of  FIG. 24  due to local atmospheric conditions causing bimetallic spring arms  320  to alter their shape forcing hook  352  to move toward the sash stile. This movement causes the sash to rotate toward a more closed position. 
     FIG. 27  shows a spring arm assembly generally indicated at  350  formed from a single piece of spring material. 
   More specifically, the spring arm assembly shown in  FIG. 27  comprises a generally straight arm with a hook  329  and a leg portion  331  that mates with port  321  in the sash stile. Located between hook  329  and leg  331  is a loop  330  formed to accept screw  323 . Screw  323 , loop  330  and hole  365  aligning to allow the spring arm assembly to be secured to the sash stile. 
     FIG. 28  shows a similar spring arm with the following exceptions: Hook  341  has been shaped to make inserting and removing the hook from the window jamb balance pockets more difficult. The action required in inserting and removing this configuration will be described in greater detail further on in the description. 
   Unlike the earlier embodiment the spring arm does not make use of a loop in the spring arm material rather it uses a separate clip  335  that secures a portion of the spring bar to the sash stile with a screw  339 . Clip  335  can be moved and secured at locations closer to as shown at  337  or further away as shown at  336  from leg  331  providing more or less initial spring stiffness and more or less angles of tilt allowable to the sash. 
   Like the earlier embodiment the spring arm shown in  FIG. 28  includes leg  331  at the first end that fits into port  321  located on sash stile  319 . 
     FIG. 29  shows a further embodiment of the invention where leg  331  does not fit directly into an opening in sash stile  319  but rather fits into opening  353  located in a separate fitting  355 . Opening  353  is further elongated to allow leg  331  free movement of several degrees. This free movement allows spring arm  320  to pivot around screw  358  far enough so the sash is able to free fall a short distance before encountering spring resistance. Screw  358  is mounted through hole  357  in the spring arm and secures into fitting  355 . Fitting  355  attaches to opening  356  in sash stile  319 . 
   As will be seen in  FIG. 29  hook  352  is the same hook shown in  FIGS. 23 ,  24  and  25 . This hook is more difficult to remove from the window balance channel than the hook indicated in  FIG. 27 . 
     FIG. 30  shows another view of the embodiment in  FIGS. 23 ,  24 ,  25  and  29  looking through section  4 - 4  of  FIG. 21 . The inner sash has been tilted in for ventilation and is in position for removal of hooks  352  and  362  from side jambs  303 . 
     FIG. 31  shows how spring arm  320  must be positioned and bent by the operator to enable release of hooks  352  and  362  from side jamb  303 . In this position hooks  352  and  362  can be easily slid out of their respective balance pockets and the sash can be tilted fully open or removed for maintenance. By reversing the above action hooks  352  and  362  can be reinserted into their respective side jambs. 
     FIG. 32  shows an embodiment where two spring arms  361  and  362  are used in conjunction. Both spring arms are unattached at their centers and joined at their ends  363  and  366 . Spring arm  361  is constructed from a different material than spring arm  362 . In this case spring arm  361  is constructed from a material having an expansion and contraction rate that is greater than that of spring arm  362  over the 0.degree. F. to 100.degree. F. temperature range.  FIG. 32  shows the configuration of spring arms  361  and  362  in the closed and normal operating position at a temperature of 70.degree. F. Hook  352  is slidably held in balance channel  309  (not shown for clarity) and pivot bar  326  is held in slide member  375  which is also slidably held in frame balance channel  309 . Both hook  352  and pivot bar  326  are lined up with stile  319  and the sash  315  is in its vertical and normal operating position. Referring back to  FIG. 30 , sash  313  is seen in its closed position resting against frame steps  387  and  388 . In this configuration it can be appreciated when extreme cold temperatures exist at the exterior face of the window and bimetallic spring arm material is used the resulting bimetallic reaction will force hooks  372  and  382  inwardly against the interior walls of their corresponding balance channels causing sash  313  to press more firmly against steps  387  and  388  further improving the window&#39;s efficiency in cold weather. 
     FIG. 33  shows the configuration of spring arms  361  and  362  at a temperature of 700F. as shown in  FIG. 32  after the sash has been tilted open to the greatest extent allowed by the bending of spring arms  361  and  362  for ventilation. Hook  352  and pivot bar  326  remain lined up vertically but stile  319  is now rotated away from vertical by about 30 degrees. 
     FIG. 34  shows the configuration of spring arms  361  and  362  as shown in  FIG. 33  after the temperature has dropped to 40 degrees. Because spring arm  361  is made from a material having a greater expansion and contraction rate than spring arm  362  it has contracted sufficiently along its length to cause spring arm  362  to straighten. Hook  352  and pivot bar  326  continue to be lined up vertically but the straightening of spring arm  362  has caused sash  315  to rotate to a 20 degree angle. 
     FIG. 35  is yet an alternate embodiment of a spring arm assembly  350 . The assembly includes a retaining guide  352  releasably captured in channel  309  or  311 . Alternately, retaining guide  352  may be of such size and shape to be permanently captured within channel  309  or  311  and the spring arm releasable from retaining guide hole  359 . In this embodiment spring arm  320  includes an integral wound coil  380  to be received and preferably retained within port  365  of sash stile  319 . The coil wire includes a retaining segment  383  integral with the transition arm  385  terminating in the inward directed leg portion  331  received in port  321 . A clip  381  and screw  323  secure transition arm  385  to the sash stile  319 . 
   Coil  380  can be composed of bimetallic or other suitable spring material having a high rate of thermal movement. When exposed to temperature variations expansion or contraction of the material wound within the coil amplifies movement of spring arm  320  producing an opening or closing force on the sash. 
   The spring arm assemblies are made of suitable gauge material to avoid any interference in the operation of the sash. 
   As can be seen from the different wire spring arm assemblies, the wire is preferably a continuous wire configured with bent or adapted ends for retention in a sash or channel and often include an offset intermediate the length of the wire for retention in the sash. This intermediate offset portion can also be designed to act as a securement section. The wound coil intermediate portion can also act as an amplifier increasing the response of the wire to changes in atmospheric conditions. 
     FIG. 36  is a perspective view of a preferred embodiment of the invention where the bar  405  is composed of a small diameter spring steel wire having a first end of the bar  401  for insertion into hole  402  formed in the sash stile  411 . The bar  405  is rotated downwardly until loop  403  snap-fits into slot  404  holding the bar against and parallel with the sash stile  411 . The second end  407  of the bar  405  is fed through hole  409  located in jamb-slide  408 . Though not shown in this view, sash  406  and jamb-slide  408  are mounted within and are able to slide along a channel in the frame jamb of the window. 
     FIG. 37  shows a detail of the second end  407  of the bar  405  shown in  FIG. 36 . The second end  407  includes a pivot shaft  423  bent  909  to the elongate axis of control bar  405  with an additional end segment  424  bent approximately  459  to the pivot shaft  423  of the wire. The angle of end segment  424  can be adjusted to increase or decrease the force required to disengage the wire from hole  409  in jamb-slide  408 . The attachment and disengagement of the spring wire from the jamb-slide  408  is described in detail in  FIGS. 38 ,  39 ,  40 ,  41  and  42 . 
     FIG. 38  shows the relationship of the sash  406 , frame  481  and jamb slide  408 . In this view, looking at a cross section of the window from above, the lower sash has been rotated slightly inward in preparation for the installation of the bars onto the sash stile  411  and insertion into the jamb-slide  408 . 
   In  FIG. 39 , the control bars  405  have been attached to the sash  406  at  425  and the center portions of the bars have been bent inwardly until end segment  424  aligns with the hole  409  located in the corresponding jamb-slide  408 . 
     FIG. 40  shows the control bars  405  after insertion into the jamb-slide holes  409  and bending pressure on the center portion of the bars has been released. The bars have sprung back into their original configuration and bending near the attachment points close to the sash when the sash is tilted open as shown in earlier  FIG. 22 . 
   Additionally shown in  FIG. 40 , the sash  406  has been left in its tilted in position and is prevented from free falling by the attachment and spring action of the bar  405 . The wire control bar bends intermediate the attachment points at the sash  406  and the jamb-slide, causing the jamb slide to move vertically along the balance track  483  without interfering with window sash balance  412 . Tension on the spring arm limits the vertical movement of the jamb-slide and stops the jam-slide before the arm  405  moves to a position perpendicular to the frame  481 . An identical arm and spring combination is used to control sash  416 . A releasable latch  413  allows tilting open of the sash. 
     FIG. 41  shows the second end  407  of the spring wire control bar  405  inserted into the jamb-slide  408  and rotated to the tilted in position (no torsion on bar). The angled segment  424  prevents the wire control bar  405  from pulling out of hole  409  in jamb-slide  408  and disengaging from the jamb-slide  408  during normal sliding and tilting operations of the sash. Jamb-slide  408  is composed of a semi-rigid material such as glass-filled nylon or spring steel making it capable of deforming without breaking and accommodating sliding in the window frame. 
   As shown in  FIG. 42 , excessive outward and/or downward pressure on the sash  406  has increased stress on the tilted in sash causing the wire to move out of hole  409 . The angled segment  424  has distorted the material surrounding the hole in jamb-slide  408 . The excessive pressure has also caused the jamb-slide  408  to rotate a few degrees within the balance  483  channel causing the jamb-slide shoulder  485  to deflect. Additional pressure applied to the sash causes the angled end segment  424  of the control bar  405  to distort the jamb-slide material further until angled segment  424  is able to pull free of hole  409  in jamb-slide  408  releasing the window sash and allowing it to pivot inwardly fully. This disengagement under excessive stress prevents damage to the jamb-slide, wire or window frame, should excessive weight be applied accidentally or intentionally. The formed angle of angle segment  424  determines the force required to pull the bar  405  free of hole  409  in combination with the jab-slide. The closer to parallel segment  424  is formed to the elongate axis of bar  405  the greater the force required to release it from jamb-slide  408 . Conversely the more flexible the material of jamb-slide  408 , the less force required to disengage the bar  405  from hole  409 . (NOTE: Tests with glass filled nylon jamb-slides and 0.080 diameter spring stainless steel wires show a release force of about 100 lbs. per side). 
     FIG. 43  shows a preferred embodiment where the first end of a formed spring wire bar  405   a  is inserted into a tooled hole  418  located at the upper corner of sash  406  used to retain slide-in tilt latches  419  of the type found in many modern window designs. This embodiment also shows how a jamb-slide  408  can be rotatably riveted to a loop  487  formed in the second end of spring wire control bar  405   a.  The jamb-slide in this embodiment would be non-releasable from the balance pocket in the window jamb except at cutouts located at the head and sill of the window in which it is installed. These cutouts are normally provided for replacement of the window balance shoe devices. If the window in which the tilt device is installed contains these cutouts, this is a viable way of inexpensively installing the control bar assembly after the window has been installed, or at a later date. Control bar  405   a  includes a loop insertion segment  489  that is received and held in the sash stile  411 . 
     FIG. 44  shows another preferred embodiment of a modified control  405   b  having a first end  491  attached to plate  417  formed to fit underneath surface mounted hardware  416  used with many other modern window designs. This embodiment also shows a flattened portion  493  of the control bar  405   b  located between the upper sash attachment point and the jamb-slide attachment point at the second end of the control bar  405   b . This flattened portion  493  of control bar  405   b  more easily fits the through the narrow gap between the sash and the frame of the window. It is important to note that this flattening of the wire will work equally well in all the preferred embodiments described herein. 
     FIG. 44  also shows an additional embodiment whereby a rotatably mounted component  495  cooperates with the modified jamb-slide  408   a  enabling the jamb-slide  408   a  be removed. As can be seen in  FIG. 44  the rotatably mounted component  495  is attached by rivet  420  that is used to attach control bar  405   b  to jamb-slide  408   a.  Jamb-slide  408   a  is also fitted with notches  421  and cam latches  422  that releasably hold rotatably mounted component  495  in position perpendicular to the direction of movement of jamb-slide  408   a.    
     FIG. 45  shows a further variation where control bar  405   c  includes an end segment  496  that is fed through hole  498  that has been formed to closely match the width of the end segment  496 . This reduces movement of the control bar  405   c  at the first end and makes the attachment of the bar to the sash more rigid. It is understood this widened section may also be accomplished by welding, brazing or otherwise attaching the first end of the bar to a plate which fits snugly into hole  498  of the sash. 
     FIG. 46  shows a further modified control bar  405   d  where the first end  502  of the control bar is pivotally attached to the sash stile and the second end  504  of the control bar is held rigid at jamb-slide  408   d.    
   It is also possible to have both ends of the control bar non pivotally secured to the sash and the jamb-slide. This may produce an “S” bend in the control bar during tilting opening of the sash. 
   The control bar and jamb-slide arrangement shown in  FIGS. 36 to 45  can be installed as a retrofit arrangement for many recently installed windows. 
   Although various preferred embodiments of the present invention have been described in detail, it will be appreciated by those skilled in the art that variations may be made without departing from the spirit of the invention or the scope of the appended claims.

Summary:
The window assembly structure includes a control bar for limiting the extent of inward tilting of the sash commonly used for safe window cleaning. The control bar is forced to bend or distort during tilting of the sash producing a bias force that limits the amount of tilting. In a preferred structure the control bar is of a spring steel wire structure with various bent segments for effective and cost efficient securement of the control bar to the sash and frame.