Metal window construction

Claim 1

IN IN WINDOW CONSTRUCTION, A WINDOW FRAME HAVING A PAIR OF VERTICAL TRACKWAYS PROVIDED THEREIN, AN UPPER AND LOWER SASH SLIDABLY DISPOSED IN SAID TRACKWAYS FOR VERTICAL SLIDING MOVEMENT PAST EACH OTHER, EACH OF SAID SASHES HAVING AN ENLARGED INSERT FORMING THE MAJOR PORTION OF THE SASH AND A PERIPHERAL FRAME FOR THE INSERT, SAID INSERT INCLUDING AN ENLARGED PANEL OF TRANSPARENT MATERIAL PROVIDED WITH A PERIPHERAL FRAME MEMBER, MEANS HINGEDLY AND RELEASABLY SECURING THE PERIPHERAL FRAME MEMBER OF THE TRANSPARENT PANEL TO ONE EDGE OF THE PERIPHERAL FRAME OF THE SASH, LOCK MEANS ON THE UPPER PORTION OF THE INSERT FRAME MEMBER FOR SECURING THE EDGE OF THE PERIPHERAL FRAME MEMBER OF THE PANEL TO THE EDGE OF THE FRAME OF THE SASH THEREBY RETAINING THE INSERT IN CLOSED RELATION TO THE SASH FRAME AND PERMITTING OPENING AND REMOVAL THEREOF FROM THE INTERIOR OF THE WINDOW, SAID WINDOW FRAME, SASH FRAME AND INSERT FRAME ALL BEING CONSTRUCTED OF METAL, AND LOCK MEANS INTERCONNECTING THE OVERLAPPING EDGES OF THE SASH FRAMES FOR RETAINING THEM IN CLOSED POSITION IN RELATION TO THE WINDOW FRAME, EACH OF SAID TRACKWAYS INCLUDING A VERTICAL CYLINDRICAL BORE RIGID WITH THE WINDOW FRAME WITH THE OUTER SURFACE OF THE BORE BEING PROVIDED WITH A SLOT COMMUNICATING THE SURFACE OF THE TRACKWAY WHICH FACES INWARDLY WITH THE BORE, EACH SLIDABLE SASH HAVING A LONGITUDINAL CYLINDRICAL PROJECTION THEREON SLIDABLE IN THE BORE, SAID PROJECTION BEING HOLLOW AND INCLUDING MEANS FOR EXPANDING THE PROJECTION FOR VARYING THE FRICTIONAL RESISTANCE TO SLIDING MOVEMENT OF THE PROJECTIONS WITHIN THE TRACKWAYS FOR RETAINING THE SASHES IN ADJUSTED POSITION.