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Claim 1

A WINDOW INCLUDING A STATIONARY SUPPORT FRAME OF GENERALLY RECTANGULAR SHAPE AND HAVING VERTICAL GUIDE GROOVES IN OPPOSITE SIDES THEREOF, AT LEAST ONE WINDOW UNIT MOUNTED FOR VERTICAL MOVEMENT IN SAID GUIDE GROOVES AND PIVOTAL ABOUT AN AXIS NORMAL TO SAID VERTICAL MOVEMENT INTO A POSITION EXTENDING OUT OF SAID SUPPORT FRAME, SAID WINDOW UNIT INCLUDING A WINDOW FRAME HAVING OPPOSITE VERTICAL SIDE MEMBERS AND A CROSS MEMBER CONNECTED THEREBETWEEN, A GUIDE MEMBER OPERATIVELY MOUNTED IN EACH WINDOW FRAME VERTICAL SIDE MEMBER AND NORMALLY EXTENDING LATERALLY THEREFROM INTO A GUIDE GROOVE FOR GUIDING SAID WINDOW UNIT IN VERTICAL MOVEMENT IN SAID SUPPORT FRAME, RETRACTING MEANS OPERATIVELY ARRANGED FOR VERTICAL MOVEMENT WITHIN SAID WINDOW FRAME VERTICAL SIDE MEMBERS ADJACENT EACH SAID GUIDE MEMBER, COOPERATING CAM MEANS ON EACH SAID RETRACTING MEANS AND ON AN ASSOCIATED ADJACENT GUIDE MEMBER OPERATIVELY ARRANGED SO AS TO CAM SAID GUIDE MEMBER THROUGH RETRACTING LATERAL MOVEMENT WITHIN SAID WINDOW FRAME VERTICAL SIDE MEMBER IN RESPONSE TO VERTICAL MOVEMENT OF SAID RETRACTING MEANS, AXLE MEANS MOUNTED IN SAID WINDOW CROSS MEMBER AND EXTENDING FROM OPPOSITE SIDES THEREOF INTO SAID WINDOW SUPPORT FRAME FOR DEFINING AN AXIS NORMAL TO SAID VERTICAL MOVEMENT OF SAID WINDOW UNIT AND ABOUT WHICH AXIS SAID WINDOW UNIT IS SELECTIVELY PIVOTAL AFTER RETRACTION OF SAID GUIDE MEMBERS, AND MEANS DISPOSED IN SAID GUIDE GROOVES MOUNTING SAID AXLE MEANS AND EFFECTIVE TO FRICTIONALLY ENGAGE SAID SUPPORT FRAME UPON PIVOTAL MOVEMENT OF A WINDOW UNIT TO MAINTAIN THE PIVOTED POSITION OF SAID WINDOW UNIT.