Patent Publication Number: US-6701670-B2

Title: Pulley for double hung windows

Description:
TECHNICAL FIELD 
     The invention pertains to double hung windows and also to a pulley system for counterbalancing, in a double hung window, one sash with the other sash. 
     BACKGROUND ART 
     A window sash consists of a window pane which is surrounded by a frame. A double hung window consists of an arrangement of two sashes, each of which may travel vertically in one of two pair of adjacent parallel grooves formed in the vertical stiles which abut or form a portion of the window&#39;s jamb. Various mechanisms are known whereby springs or counterweights are used to offset the effort required to raise a sash or correspondingly, to prevent the sash from falling under its own weight. Known methods of accomplishing this are considered complicated or expensive and many known methods are not suitable for retrofitting to existing windows. 
     According to one aspect of the invention there is provided a pulley apparatus for a double hung window comprising: 
     a base which supports a pair of pulleys each having an axle; 
     the base having a pair of ears which extend away from the pullies; 
     the base having a pair of cord openings each cord opening in registry with an outer extremity of a pulley so that the axles are between the openings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a front elevation of a double hung window, 
     FIG. 2 is a cross-sectional view through lines A—A of FIG. 1, 
     FIG. 3 is a cross-section of a sash and window head according to one embodiment of the present invention, 
     FIG. 4 is a top plan view of a pulley according to one embodiment of the invention, 
     FIG. 5 is a cross-sectional view of the pulley depicted in FIG. 4, taken through lines A—A of FIG. 4, and 
     FIG. 6 is an end elevation of the pulley depicted in FIG.  5 . 
    
    
     MODES FOR CARRYING OUT THE INVENTION 
     FIG. 1 illustrates a double hung window  10 . The window comprises upper and lower sashes  11 ,  12 . The window frame includes vertical jambs  13 . Each jamb  13  includes or is joined to a stile  14 . Each stile  14  includes a pair of adjacent and parallel vertical tracks. 
     As shown in FIG. 2, the window further comprises a head  20  and a sill  21 . The full length vertical grooves in the stile  14  are defined by the central parting bead  22  and the pair of stop beads  23 . These tracks guide the sashes in their vertical movement. 
     As further shown in FIG. 2, the pair of sashes  11 ,  12  are counterbalanced against one another. The vertical side edge of each sash  11 ,  12  is provided with a recess or groove  24 . The groove  24  is sized to receive a sash cord  25  which is affixed by screws  26  or otherwise into the groove  24  and against the sash. A length of sash cord (equal to about half the length of the sash) is affixed in each groove  24 . 
     In order that one sash counterbalances the other, a pulley device  27  is recessed into the window head  20  above each of the stiles  14 . Each of the two sash cords  25  passes over a pulley device  27 . 
     As shown in FIG. 3, the pulley device  27  is located within a recess  30  formed within the window head  20 . The outer or lower flat surface  31  of the pulley device  27  is generally flush with the lower surface  32  of the window head  20 . The pulley device  27  comprises a base  32  which supports a pair of parallel side plates  33 . As shown in FIG. 4, two pairs of opposing slots  35 ,  36  are formed into the interior facing surfaces of each side plate  33 . Each of the pairs of slots  35 ,  36  receives a “U” shaped yoke  40 , the yoke  40  supporting an axle  41  about which a pulley  42  rotates. 
     As shown in FIGS. 4 to  6 , the base  32  includes ears  43  which extend away from the pullies and the underside of each ear  43  includes a through hole  44  which is preferably countersunk to permit the pulley device  27  to be mounted flush using a pan headed screw or the like with the lower surface  32  of the window head  20 . The base  32  also incorporates a pair of openings  53  which allow the cord to pass around the pair of pulleys  42 . The opening are in registry with an outer extremity  60  of a pulley, so that the axles  41  of both pullies are located between the openings  53 . 
     One or both of the pulleys  42  may be made vertically adjustable by providing a vertical through opening  50  in the base  32  below the yoke  40 . The threaded vertical opening  50  receives a threaded member, bolt or screw  51  which may be used to raise (or lower) the effective height of the yoke, axle and pulley above the base  32 . IN the alternative, both pullies may be mounted in a common yoke for simultaneous adjustment. In this way, any slack in the sash cord  25  caused by stretching or ageing can be adjusted out. 
     It will be observed that this arrangement allows the pulleys to be mounted directly above the stile grooves and sash cord slots. The arrangement provides a suitable means of constructing new windows as well as a convenient means of retro-fitting existing double hung windows having broken or damaged counterweights or springs. 
     The present invention thereby provides a pulley device, a kit of parts and a method for retrofitting a window, hardware and a method for assembling a new window, and windows when fitted according to the teachings of the invention. 
     It will be appreciated that the above described system is a compact and efficient way of counterbalancing a sash in a window. It will be appreciated that the invention is preferably deployed in a timber window but that the invention may be extended into any window incorporating similar constructions methods, irrespective of the material in which it is constructed. 
     While the present invention has been described with reference to particular details of construction it should be understood as having been provided by way of example and not as limitations to the scope or spirit of the invention.