FIELD OF THE INVENTION  
       [0001]     The present invention relates to two bar stays for supporting a sash or a vent between a closed position and an open position.  
       BACKGROUND OF THE INVENTION  
       [0002]     Commercially available two bar stays generally comprise a vent arm, a link and a track, wherein the link is immovably fastened to said track at a pivot point and the vent arm is mounted on a slider that may move along the track. The link is joined to the vent arm at a point along its length. The tracks of these stays have one side wall which possesses a region flanged to form a U section that is adapted to receive a slider, said slider possessing a lip in order to restrain it within the U section. A disadvantage of these stays is that as the slider is only restrained upon one side there is scope for substantial free play of the two bars from the frame, causing significant instability when the stay is used to support a vent.  
         [0003]     A further disadvantage of these stays is that they are either right or left handed rather than being universally fittable. The fixing of the link to the track may also be disadvantageous with regard to ease of assembly, particularly when fitting the vent within a fixed frame. Additionally, when the two bar stay is fully open, the vent lies substantially at one side of the fixed frame and therefore the outer surface of the vent, e.g. a window, cannot be easily accessed to allow cleaning. This disadvantage becomes particularly important in situations where access to the exterior of the vent is difficult or impossible, for example in a high rise building.  
       SUMMARY OF THE INVENTION  
       [0004]     In view of the foregoing, the present invention provides a two bar stay comprising a slider within a track, wherein the track comprises a base and two side walls substantially perpendicular to the base and wherein at least one of the side walls is flanged to provide a partially closed channel. Preferably, both side walls are flanged. More preferably the flanges face each other. The two bar stay can support a sash or vent between a closed position, in which it lies within a fixed frame, and an open position, in which it extends substantially perpendicular to the fixed frame. The two bar stays of the present invention have advantages with regard to ease of manufacture, ease of assembly, ease of use, stability and strength, amongst other benefits.  
         [0005]     The slider preferably includes a friction adjusting device to control the movement of the slider along the support track. In this way, the speed at which the vent arm moves along the support track can be controlled.  
         [0006]     The two bar stay preferably includes a second slider, which may support an end of a link. A releasable restricting means may act between the second slider and the track to allow the second slider to be locked into at least one position on the track to form a fixed pivot. Preferably, the releasable restricting means is attached to the second slider and moves along the track therewith. More preferably the releasable restricting means is formed integrally with the second slider. The releasable restricting means may be operated by a push button or by a twisting, screwdriver operated mechanism.  
         [0007]     The track may be shaped to receive a releasable restricting means. The releasable restricting means may include ears that engage the track, limiting the motion of the second slider. If the track includes a bottom, two side walls and a pair of inwardly facing flanges, the inwardly facing flanges are preferably shaped to receive the ears of the releasable restricting means. The releasable restricting means may also, or alternatively, comprise a spring clip that may engage with cut out regions of the side walls that are adapted to receive it. At least one of the sliders may be shaped to avoid obstacles in the base of the track. This has the advantage of avoiding a clash between the slider and screw heads holding the track in place in a fixed frame.  
         [0008]     Preferably at least one slider possesses a lip shaped to grip the flanged area. This lip restricts any rotational motion of the slider within the track and provides the advantage of preventing friction and wear between the link and the track when the vent arm is under load. At least one slider may comprise a nylon thermoplastic.  
         [0009]     Preferably, at least one of the track and bars (i.e. the link or vent arm) comprises austenitic stainless steel. Additionally, at least one of the sliders may also comprise austenitic stainless steel. The track may be adapted for mounting to a larger structure and at least one of the bars, e.g. the vent arm, is preferably adapted for supporting a sash.  
         [0010]     The two bar stay is preferably substantially universally fittable.  
         [0011]     A method of assembling a two bar stay may comprise the steps of: locating a first slider in a track; moving the first slider until a second slider can be located in the track; and moving the second slider until the releasable restricting mechanism locates within an area of the track shaped to receive it. Preferably the track has at least one cut out region on its uppermost surface for receiving the sliders and thereby facilitating assembly.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]     Specific embodiments of the present invention are now described by way of example with reference to the accompanying drawings in which:  
         [0013]      FIG. 1  is a plan view of a first embodiment.  
         [0014]      FIG. 2  is a perspective from above of a first embodiment.  
         [0015]      FIG. 3  is an enlarged fragmentary perspective view in the direction of arrow A in  FIG. 2 .  
         [0016]      FIG. 4  is a plan view of a first embodiment in an alternative configuration.  
         [0017]      FIG. 5  is a perspective from above of a first embodiment in an alternative configuration.  
         [0018]      FIGS. 6, 7 , and  8  are planned views of a first embodiment during assembly.  
         [0019]      FIG. 9  is a fragmentary perspective view from below of a friction slider of the first embodiment.  
         [0020]      FIG. 10  is a fragmentary perspective view from below of a pivot slider of the first embodiment.  
         [0021]      FIG. 11  is a perspective from above of a second embodiment.  
         [0022]      FIG. 12  is a perspective from above of a second embodiment in an alternative configuration.  
         [0023]      FIG. 13  is a perspective view of the pivot slider of the second embodiment.  
         [0024]      FIG. 14  is a view on arrow B in  FIG. 13 .  
         [0025]      FIG. 15  is a perspective view of the friction slider of the second embodiment.  
         [0026]      FIG. 16  is a further perspective view of the friction slider of the second embodiment; and  
         [0027]      FIG. 17  is a view on arrow C in  FIG. 16 . 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0028]     With reference to  FIGS. 1-10 , a first embodiment of a two bar stay  1  of the present invention comprises a support track  3 , a vent arm  5 , a link  7 , a first slider  9  and a second slider  11 . The vent arm  5  is pivotally attached to the slider  9  by a rivet  13 . The link  7  is attached to the slider  11  by a rivet  15  at one end and its other end is pivotally attached by a rivet  17  to a midpoint of the vent arm  5 . The first and second sliders  9 ,  11  are positioned within the support track  3 .  
         [0029]     The support track  3  comprises a base  19  and two side walls  21  which possess a pair of flanges  23  that face each other to form a C section. The first and second sliders  9 ,  11  are shaped to be received in the support track  3  and to be held therein by means of the flanges  23 . The sides of the first and second sliders  9 ,  11  are lipped to give a U shape that grips the flanges  23 , preventing the vertical displacement (i.e., free play) seen in sliders of the prior art and constraining the sliders to moving in one dimension along the track. Additionally, the tops of the first and second sliders  9 ,  11  are positioned such that they prevent friction and wear between the link  7  and the flanges  23 .  
         [0030]     The first slider  9  (see  FIG. 9 ) possesses a friction cam  25  that can be operated by screw  27  using a standard screwdriver (not shown) to flex the sides of the first slider  9  outwards thus increasing their friction with the side walls  21  of the support track  3 . The second slider  11  (see  FIG. 10 ) possesses a releasable restricting means in the form of a spring clip  29  that engages with cut out regions  31  in the side walls  21 . The spring clip  29  can be retracted from the cut out regions  31  by operation of a release button  35 . When the spring clip  29  is received in the cut out regions  31 , the second slider  11  is held in position in the support track  3  and acts as a pivot. The first slider  9  is, however, still free to move along the support track  3 , thereby moving the vent arm  5  between its open and closed positions.  
         [0031]     In the closed position, the vent arm  5  lies above the link  7 , which in turn lies above the support track  3  and the three components lie substantially in parallel. On opening the vent, the first slider  9  moves towards the second slider  11  and the vent arm  5  moves outwardly until it is substantially perpendicular to the support track  3  and the vent (not shown) is in its fully open position.  
         [0032]     When the two bar stay  1  is fully open (as shown in  FIGS. 1 and 2 ), the vent mounted on the vent arm  5  allows egress as it is supported at one side of the fixed frame (not shown) to which the support track  3  is attached and therefore does not hinder entry or exit through the frame. In order to allow the outside surface of the vent, such as a window, to be cleaned, the release button  35  can be depressed to disengage the spring clip  29  from the cut out regions  31  in the side walls  21 . The vent arm  5 , the link  7  and the first and second sliders  9 ,  11  can then be moved, along with the vent itself, relative to the support track  3  until the spring clip  29  locates in a second set of cut out regions  33  (shown in  FIG. 3 ). The vent arm  5  is now positioned somewhere near to the middle of the support track  3  (as shown in  FIGS. 4 and 5 ) and access is readily available to both sides of the vent.  
         [0033]     Once the cleaning of the vent has been achieved, the release button  35  can be depressed again to disengage the spring clip  29  from the second cut out regions  33  and the whole assembly can be slid back along the support track  3  to its original position. When the spring clip  29  has relocated in the cut out regions  31 , the vent can be returned to standard operation.  
         [0034]     The two bar stay  1  is advantageous with regard to ease of assembly (shown in FIGS.  6  to  8 ). The first slider  9  can be placed in the support track  3  at the cut out regions  37  in the flanges  23 . The first slider  9  is then slid along the support track  3  to allow the second slider  11  to be aligned with the cut out regions  37  and then placed in the support track  3 . The chamfered edges of the spring clip  29  enable the second slider  11  to locate in the support track  3  without the release button  35  needing to be depressed. The assembly is then moved along the track until the spring clip  29  self locates in the cut out regions  31  in the side walls  21 .  
         [0035]     In a second embodiment of the present invention, shown in  FIGS. 11-17 , the two bar stay  2  comprises a support track  4 , vent arm  6 , a link  8 , an alternative first slider  10  and an alternative second slider  12  (shown in  FIG. 11 ). The first slider  10  includes a spring clip  39  (shown in  FIG. 15 ) that forces the flexible legs  41  against the side walls  22  of the support track  4  ( FIG. 15 ). The screw  43  allows an adjustable amount of force to be placed on the spring clip  39  thus providing adjustable friction ( FIG. 16 ).  
         [0036]     The second slider  12  is formed integrally with a releasable restricting means  45  that comprises a neck region  47  and two ears  49  extending perpendicular thereto ( FIG. 13 ). The neck  47  extends from a region of the second slider  12  and is coplanar with it.  
         [0037]     The ears  49  of the restricting means  45  can engage with cut out regions  51  in the flanges  28 , thereby holding the second slider  12  in position and causing it to act as a pivot. The first slider  10  is, however, still free to move along the support track  4 , thereby moving the vent arm  6  between its open and closed positions. In a similar fashion to the first embodiment, there is also a mechanism to allow the outer surface of the vent to become accessible for cleaning. When the two bar stay  2  is fully open, with the vent arm  6  substantially perpendicular to the support track  4 , the restricting means  45  can be depressed into the support track  4 . The ears  49  then disengage from the cut out regions  51  and the second slider  12  is free to move along the support track  4  with the ears  49  of the restricting means  45  continuously biased against the undersides of the flanges  24 . The vent arm  6 , the link  8  and the first and second sliders  10 , 12  can then be moved, along with the vent itself, relative to the support track  4  until the ears  49  locate in a second set of cut out regions  53  ( FIGS. 11 and 12 ). Access is thereby facilitated to both sides of the vent.  
         [0038]     The first and second sliders  10 ,  12  comprise a composite stainless steel insert covered by a durable nylon thermoplastic moulding. They are channelled at  55  and  57  respectively so that they can pass freely over the fixing screws (not shown) holding the support track  4  in place ( FIGS. 14 and 17 ).  
         [0039]     The embodiments described above are advantageous in terms of being substantially universally fittable, providing access to the exterior surface of a vent for washing and providing stable support for a vent by both sides of the sliders being held in place by the track.  
         [0040]     It will of course be understood that the present invention has been described purely by way of example and that modifications of detail can be made within the scope of the invention that is defined by the following claims.
The present invention describes two bar stays that include a slider within a track, wherein the track comprises a base and two side walls substantially perpendicular to the base and wherein at least one of the side walls is flanged to provide a partially closed channel. The two bar stays have advantages with regard to ease of manufacture, ease of assembly, ease of use, stability and strength.