Abstract:
A combined window shelf and sill component is formed by extrusion of plastics material and has a top wall and a bottom wall connected by webs to form ducts therethrough and providing a window shelf end, a sill end and an intermediate portion for siting a window frame thereon.

Description:
TECHNICAL FIELD OF THE INVENTION 
     Background of the Invention 
     This invention cocerns improvements in and relating to installation of windows. 
     Generally a window frame is mounted on top of a window sill, so that part of the sill extends outwardly from the window frame. At the rear of the frame i.e. inside a building, a shelf is butted up again the sill and/or the frame. Often when installing replacement u-PVC window frames, for example, the original window shelf is left in position and only a u-PVC window sill is fitted. The junction of the shelf with the sill and/or the frame needs to be masked for the sake of appearance. Even if the window shelf is also replaced, the problem of making a neat junction between the shelf and the frame still exists possibly because of irregularities in the window opening. 
     One proposal for dealing with this problem was made in GB 2287273A, which describes a window frame system comprising a window shelf abutting a window sill member, a window frame mounted on a part of the window sill member and a beading strip for masking the junction of the window shelf with the window fame and/or sill, wherein the beading strip comprises a cover piece and a channel section depending from the cover piece located on an upstand of the window frame system, whereby the beading strip is locatable in position after assembly of the window frame shelf and sill. 
     Even this arrangement is not entirely satisfactory because of the possible unevenness of a window opening causing the beading not to seal properly along its entire length. Furthermore, there is no possibility of adjusting the lateral position of the frame relative to the window sill. 
     An object of this invention is to provide a solution to the above-mentioned problems of window installation. 
     According to this invention it is proposed that a combined window shelf and sill be provided i.e. as a one-piece construction. Preferably the combined window shelf and sill is formed by extrusion of plastics material, especially u-PVC. 
     The preferred combined window shelf and sill of the invention has a top wall and a bottom wall connected by webs to form ducts therethrough. At its window shelf end the combined component is preferably shaped to provide a rounded top edge profile and preferably has a return on its underside. 
     At its window sill end, the combined component preferably has a downwardly sloping top wall leading to an overhang extending below the bottom wall of the component whereby water falling on the sill can drop off the overhang rather than travel back along the underside of the component and into the supporting brickwork. 
     Between the shelf and sill parts, the combined component has a part on which a window frame can be mounted. That part preferably has means for lateral adjustment in the positioning of the frame relative to the shelf/sill. By lateral adjustment is meant adjustment normal to the plane of the window. Preferably the combined component has a series of locations for a locating element that also locates in a part of the window frame. The window frame can have a channel or slot on its underside and the combined component can have a sense of parallel slots in its top sure, whereby a peg, strip or the like can locate in the frame and one of the slots of the combined component according to the desired position of the window frame relative to shelf/sill component. 
    
    
     BRIEF DESCRIPTION OF THE DRAWING 
     This invention will now be further described, by way of example only, with reference to the accompanying drawing, which is a section through a window shelf and sill arrangement according to the invention. 
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to the accompanying drawings, a double layer brick wall  10  has a combined window sill and shelf  12  mounted thereon and a window frame  14  mounted on the window sill/shelf. 
     The window sill and shelf  12  is made as a hollow plastics extrusion, typically of u-PVC. The window sill and shelf  12  has a top wall  16 , bottom wall  18  and end walls  20  and  22  enclosing a plurality of ducts  50 ,  52 ,  54 ,  56 ,  58 ,  60 ,  62 ,  64 ,  66 ,  68 ,  70  and  72  formed by webs  24 ,  26 ,  28 ,  30 ,  32 ,  34 ,  36 ,  38 ,  40 ,  42 ,  44 , and  46  connecting the top and bottom walls. The bottom wall  18  is straight apart from two channels  76  in its underside. The top wall  16  has a first part  78  forming a window shelf for the interior of a building which is parallel to the bottom wall over most of its width. At one end the top wall first part  18  is curved at  80  to meet end wall  20  which extends below the bottom wall as does the web  24 . The extension of the web  24  has on its outer face a dusted flange  82  returning parallel to the bottom wall. This provides a neat and pleasing appearance to the window shelf. 
     At its opposite end the top wall  16  first part  78  has an upwardly inclined portion  84  leading to a second part  86  of the sill/shelf on which the window frame  14  is mounted. That part  86  of the sill/shelf has a first section  88  that has a series of parallel slots  90  in its top surface and a second flat section  92 . The tops of the ridges forming the slots  90  are level with the top of the flat section  92 . The slots  90  receive in one or other of them a peg or strip  94 . The peg or strip  94  also locates in a channel  96  in the underside of the window frame  14 . By locating the peg or strip  94  in a different slot  90 , adjustments can be made to the position of the window frame  14  relative to the window sill/shelf  12 . 
     The top wall  16  has a third section  96  forming the window sill. The top wall  16  slopes downwardly over this section and curves downwardly, at a free edge of the window sill, to form the end or front wall  22 . The front wall  22  continues below the level of the bottom wall and is bridged to a downwards flange  98  of the bottom wall to form an overhang. That is so water landing on the sill will travel down the top wall  16  and down the front wall  22  where water drops will form and fall of the sill rather than travel back under the sill, which is to avoid water penetration between the sill and the wall. 
     Thus, the invention provides a one-piece window sill and shelf that is easy to fit and provides for variations in position of a window frame as well as simplifying installation of u-PVC windows without tile need for adjustments to be made to accommodate an existing window shelf.