Known four bar hinges have, in general, tended to occupy the cheaper end of the market and, as a result, have tended to be very basic in design. Indeed, a typical four bar hinge for a window simply comprises two elongate brackets attached to each other by means of two links or struts which are pivoted at each end. One of the brackets is for attachment to a fixed frame of a vent and the other of the brackets is for attachment to a sash of the vent. In use, the sash can be moved from a position closing the opening of the vent to a position in which the vent is open.

It is also well known to use a rivet to connect two components of a window hinge together. Since these components, in use, move relative to each other, with one component rotating about the pivot axis, it is also common practice to include a plastics washer between the two components. However, as a result of usage of the window hinge, the plastics washer begins to wear and the connection between the two component parts of the hinge can become loose. Furthermore, any friction between the component parts and the washer, which may be used to assist in positioning one of the components relative to the other, will begin to reduce as the washer is worn away.

In the light of the foregoing, the present applicant has developed a new range of four bar hinges or stays which are a marked improvement over the prior art four bar hinges, and yet are still relatively cheap and easy to manufacture.

With the foregoing in mind, the present invention provides a new and inventive four bar hinge which is a distinct improvement over known four bar hinges.

The proposed four bar hinges have a number of novel features, as discussed below. Where applicable these novel features may also be incorporated into other forms of hinge,

such as six bar hinges or friction hinges.

In each four bar hinge according to the present invention there is provided a frame bracket (or support track) for attachment to a fixed frame of a vent, a vent arm for attachment to a sash or window of the vent, a first link pivotally attached to the frame bracket and to the vent arm and a third link pivotally attached to the frame bracket and to the vent arm at points spaced from the pivot points of the first link.

Although the frame bracket may be a C-section support track of known shape, it may alternatively be formed from a simple flat strip of metal. Further, it may be preferable that the frame bracket includes a raised portion, possibly formed by means of kinks in the flat strip, for each pivot point on the frame bracket. As a result, the hinge may be fitted into the grooves of many different vent frame profiles.

In the prior art, it is usually the case that a vent arm of a four bar hinge does not become aligned over the frame bracket when the hinge is in its closed position. However, the present applicant has overcome this problem, while still allowing the vent arm to open in a satisfactory fashion, by off-setting the two pivot points of the frame bracket and/or off-setting the two pivot points on the vent arm. As a result, when the hinge is closed, the vent arm is positioned over and aligned with the frame bracket of the hinge. This is a marked improvement over known four bar hinges.

Further, the idea of off-setting pivot points of links on a support track and/or a vent arm may be useful in many different types of hinge, other than four bar hinges.

In a preferred embodiment, the pivot points of the first link are positioned towards the edges of the vent arm and frame bracket respectively which are furthest from each other, whereas the pivot points of the third link are preferably positioned towards th edges of the vent arm and frame bracket respectively which are closest to each other.

Further, the pivot points of the first and/or third links may be offset from the longitudinal axis of the

respective link to ensure that the link completely overlays the frame bracket when the four bar hinge is closed. In this way, the links will not protrude outside the edges of the frame bracket, thereby avoiding any chance of clashing with adjacent parts of the vent.

As will be appreciated, the frame bracket and the vent arm each include holes or apertures through which fastening devices, such as screws, may be applied to secure the frame bracket and the vent arm to the fixed frame and the sash respectively of the vent, in use.

The vent arm may include an end point which is asymmetric. In one embodiment, the end point is produced by simply chopping off a corner from the end of the vent arm such that an inclined edge is produced defining an apex adjacent the edge of the vent arm nearest the frame bracket.

This apex may engage an end cap on the frame bracket to assist in aligning the vent arm over the frame bracket when the hinge is closed. With this in mind, the distance from the apex to the pivot point of the first link on the vent arm is preferably longer than is normally the case in four bar hinges, thereby enabling better engagement between the end point and the end cap to be achieved during closing of the hinge.

In one embodiment, the end cap is simply formed by deforming the end of the frame bracket. Such an end cap is very cheap to manufacture, since no additional component is required.

Preferably the end cap defines a surface inclined to the axis of the frame bracket. Further, it may be preferable for the angle of inclination of the end cap surface to be slightly different to that of the complementary surface on the end point of the vent arm. As a result, better pull-in of the end point of the vent arm by the end cap during closing of the hinge can be achieved.

Preferably a portion of the frame bracket, which is deformed to define the end cap, is removed to accommodate the apex of the vent arm end point when the hinge is fully closed.

Alternative forms of end cap and/or end point, which may be applicable to other types of hinge, may be used, as appropriate. For example, a separately formed end cap, such as disclosed in GB-A-2133074, may b attached to the frame bracket during manufacture or during installation of the hinge. If the end cap is attached to the frame bracket during manufacture, a rivet may be applied through both the frame bracket and a tongue of the end cap. Further, the end cap may include a top cover or lid which prevents the end point of the vent arm from rising up and out of the end cap, when the hinge is closed.

The end cap and/or the end point may be manufactured from plastics material, thereby giving a little flexibility during entry of the end point into the end cap. As a result, improved closing of the hinge is achieved.

If a separately formed end cap is used, it may include two bearing surfaces inclined at different angles to the axis of the frame bracket. If this is the case, the inclined surface first engaged by the end point of the vent arm during closing of the hinge may be at a relatively large angle, whereas the second inclined surface of the end cap may conform to the inclined edge of the end point of the vent arm.

In another form of end cap, the cap may include a recess into which the end point of the vent arm may fall during closing of the hinge after having passed an initial abutment of the end cap. A subsequent abutment of the end cap will preferably force the end point of the vent arm into its final desired closed position as the vent arm reaches its closed position over the frame bracket. By providing the recess in the end cap, more efficient closing of the stay can be achieved with a reduction in the friction between the end point and the end cap.

Additionally, the inclined edge of the end point may be curved, preferably in a concave fashion, to improve the engagement of the end point with the end cap during closing the hinge.

Another improved feature provided by a hinge according

to the present invention is the inclusion of a stop or stops to define the maximum opening of the hinge. In one embodiment, a stop acts between the vent arm and the first link to define the maximum opening of the hinge. If necessary, or if simply preferable, a second stop may act between the vent arm and the third link of the hinge. In either event, the stop may be formed by means of a crack formed in an edge of the vent arm with the portion of the vent arm defined by the crack being bent out of the plane of the vent arm to act as the stop. Other forms of stop may, of course, alternatively be used as appropriate.

By including one or more stops to define the maximum opening of the hinge, particularly at an edge of the vent arm, angle additional strength is given to the hinge.

The hinge may be further strengthened by including a novel shape of shoulder around the pivot point of the first link to the vent arm. More particularly, the vent arm may include an S or Z shaped shoulder adjacent to the pivot point. With this in mind, it is known to have a straight shoulder running across the width of the vent arm to enable the end point of the vent arm to be offset from the plane of the remainder of the vent arm, but a non-straight shoulder is a feature of the present invention which is not known in the prior art. More particularly, the shoulder may include two portions extending from opposite edges of the vent arm with a central portion or rib which runs substantially parallel to the longitudinal axis of the vent arm and joins the two other shoulder portions. This central shoulder or rib preferably runs along the vent arm from one side of the pivot point between the first link and the vent arm to the other side of the pivot point.

A support of guide block may be included on the first link and/or on the third link to assist the motion of the vent arm over the first link and/or the third link during closing of the hinge. Such a guide or support block may be attached to the first link or the third link by means of a rivet or simply a push fit connection. Any other means for connecting the block to the link may, of course,

alternatively be used.

Although the guide block may only come into play when the hinge is partly closed, in another embodiment a portion of the guide block may act as a washer or lubricating surface between the vent arm and the link. If this is the case, the block will preferably have a shape which conforms substantially to the shoulder of the vent arm adjacent the pivot between the vent arm and the first link.

If preferable, a support block may also be mounted on the frame bracket to assist the vent arm as it closes over the frame bracket. Such a support block may be held in position by means of the pivot between the frame bracket and the first link, for example, or an additional rivet may be used, if necessary.

As will be appreciated, a hinge according to the present invention includes four pivot points. Each of these pivot points includes a pivot, such as a rivet, for joining two components together. To assist in smooth movement between the two components as the hinge is opened or closed, at least one washer is preferably included about the pivot between the components. This washer may include an integral spigot on one or both sides of the washer which can carry the components. Alternatively, a second simple washer may be included under the head of the rivet between the rivet head and the adjacent component. As a result, smoother opening and closing of the hinge can be effected.

Additionally, by including one or more washers, a degree of controlled friction can be introduced in the hinge to enable the hinge to be held in a particular position intermediate the fully open and the fully closed positions of the hinge. Such a hinge equates to the known friction stays, wherein a slider is included in a support track of the stay for defining the position of the stay.

In a preferred embodiment, a pivot of a four bar hinge according to the present invention includes two washers which are essentially identical. One of the washers is, however, deformed by means of the head of the rivet defining the pivot.

According to a second aspect of the present invention, there is provided a friction pivot which is a significant improvement over the known prior art. In particular, a friction pivot according to the present invention continues to apply friction between the component parts mounted on the pivot even after significant usage of the hinge.

More particulary, the present invention provides a friction pivot of a hinge, comprising a friction pad between a link of the hinge and a support, a pivot member acting between the link and the support to urge the link into contact with the friction pad and biasing means which, following rotation of the link about the pivot member and resulting wear of the friction pad, continue to tias the link into contact with the friction pad. As a result, friction continues to exist which acts against rotation of the link relative to the support, even after significant usage of the hinge.

In a preferred embodiment, a plastics washer acts between the pivot member and the link. This plastics washer may act between a head of the pivot member, which is preferably a rivet, and/or between the shaft of the pivot member and the link. If this latter option is the case, the plastics washer will have a cylindrical portion which surrounds a portion of the pivot member.

Preferably the support is resilient and acts as the biasing means. Other biasing means may, however, be used, if desired. For example, some form of resilient spring device may be incorporated in the pivot member which results in the link being continually biased into contact with the friction pad.

Preferably the support is a C-section channel. If so, the friction pad preferably bears against inwardly extending flanges of the channel. Other forms of support may, however, be used, although it is envisaged that the support will need to include a region where a portion of the friction pad is spaced from the support, so that biasing means can act to urge the link into contact with the friction pad.

In a preferred embodiment, the friction pad includes means for positioning the pad on the support. Such positioning means may comprise location lugs or a pair of walls which extend substantially perpendicularly to the friction pad. If this is the case, the friction pad can be manufactured by extrusion.

In any event, the friction pad is preferably manufactured from plastics material. A particularly preferred plastics material is acetal resin.

The support is preferably manufactured from metal, more preferably steel.

Although the present invention is applicable to any form of friction pivot, it is particularly applicable to friction pivots of window hinges. More particularly, the pivot can be used in a friction stay of the four bar type which has fixed pivot points on a support track.

When a heavy vent is side-hung, the hinges which support the vent at its top and bottom can "give" slightly, such that the vent drops. As a result, the lower end of the vent can catch on the lower part of the fixed frame whilst the upper part of the vent leans outwardly from the fixed frame.

This problem, which is shown in Figures lla and lib of the accompanying drawings, is well known in the prior art and makes a window look in bad repair.

One way of overcoming the unsightly "leaning out" of a side-hung vent as discussed above is by shortening a first link of the hinge. However, by following this route, an unwanted geometric locking of the hinge can occur due to a resulting incorrect opening and/or closing the hinge.

With the foregoing in mind, a further aspect of the present invention aims to overcome problems associated with the leaning out of a vent from a fixed frame. Furthermore, smoother opening and closing of the hinges supporting the vent can result.

According to the present invention, there is provided a hinge comprising a plurality of links for attaching a vent to a fixed frame such that the vent, in use, can move from a position closing an opening in the fixed frame to an open

position, the hinge further comprising an end point mounted on one of the links and an end cap for receiving the end point when the hinge is closed, wherein the end cap defines a channel along which the end point travels during closing of the hinge.

By providing a channel, either formed in the end cap or between the end cap and another formation, controlled opening and/or closing of the hinge can occur, even when the hinge supports a heavy side-hung vent.

Preferably the end point comprises a guide rail which travels along the channel during closing of the hinge. By including a guide rail, continual engagement between the end point and the end cap can occur, even if a vent supported by the hinge drops slightly relative to its ideal position.

The rail preferably has a substantially constant cross- section along its length.

In an alternative embodiment, the end point may include another form of locating device, such as a pin or stub, in preference to the rail. If this is the case, the end cap could define an arrowhead, with the channel V-shaped, such that the hinge is not handed.

The channel preferably narrows in the closing direction of the hinge. As a result, misalignment of the end point with the end cap during closing of the hinge is less likely to occur.

The channel is preferably defined by an end block and a guide block spaced from the end block. The spacing of the guide block from the end block is preferably in the longitudinal axis direction of the hinge.

The end block and the guide block are preferably joined by a support tongue. The support tongue may be received in a support track of the hinge. If this is the case, the support track preferably has a C-shaped cross-section.

The end block may define two active surfaces against which the end point bears during opening or closing of the hinge. By including two active surfaces at different angles, better puli-in of the end point can occur during closing of the hinge.

Preferably the end point includes a rubbing block which overlays a portion of the end cap when the hinge is closed.

The rubbing block may be recessed to accommodate the guide block.

If the end point includes a rubbing block, the rubbing block preferably extends between two links of the hinge. As a result, the rubbing block may also act as a form of washer between the two links.

Preferably the end cap is a plastics moulding.

Furthermore, the end point may also be a plastics moulding.

In theory, however, the end point could simply form an integral part of a metal vent arm, for example.

Although the present invention is particularly applicable to four bar hinges, six bar hinges may also take advantage of the invention.

Specific embodiments of the present invention are now described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a plan view of a stay according to the present invention in an open position; Figure 2 is a plan of the stay of Figure 1 in a fully closed position; Figure 3 is a side view of the stay in Figure 2; Figure 4 is a plan view of a second type of end cap for a stay according to the present invention; Figure 5 is a plan view of a third embodiment of end cap for a stay according to the present invention; Figure 6 is a partial view of a second embodiment of stay according to the present invention showing the vent arm, first link and third link only; Figure 6A is a side view of the stops shown in Figure 6; Figure 6B is a side view of the shoulder of the vent arm shown in Figure 6; Figure 7 is a partial plan view of another embodiment of stay according to the present invention showing only the vent arm, first link and frame bracket; Figure 7A is a plan view of an alternative guide block

of the type shown in Figure 7; Figure 8 is a sectional side view of a pivot included in a stay according to the present invention; Figure 9 is a plan view of a four bar stay incorporating two friction pivots according to the present invention; Figure 10 is a cross-sectional view on the line AA shown in Figure 9 of a friction pivot according to the present invention; Figure lla is a front view of a side-hung vent which is "falling out" from a fixed frame; Figure llb is a side view of Figure lla; Figure 12 is a plan view of a hinge according to the present invention in an open position; Figure 13a is a side view of the end cap shown in Figure 12; Figure 13b is a side view of the end point shown in Figure 12; and Figure 14 is a perspective view of the end cap end of the hinge shown in Figure 12.

With reference to Figures 1-3 of the accompanying drawings, a four bar stay 1 acording to the present invention comprises a frame bracket 3 for attachment to a fixed frame (not shown), a vent arm 5 for attachment to a sash (not shown), a first link 7 pivotally attached to both the frame bracket 3 and the vent arm 5 and a third link 9 similarly pivotally attached to both the frame bracket 3 and the vent arm 5. The pivot axes are defined by rivets 11 of the type shown in Figure 8. In each case, a first annular plastics washer 13 separates the two components held together by the rivet 11 and a second plastics washer 15 is deformed by the head 17 of the rivet 11 during assembly of the stay 1. The washers could be identical before assembly, both being made of acetyl resin or any other appropriate material. As shown in Figure 8, however, the washer between the components of the stay 1 has a larger diameter and a greater thickness than the washer 15 under the head 17 of the rivet 11.

By including the two washers 13,15 about each rivet 11, a smoother action is provided for the stay 1 during opening and closing the stay 1. Furthermore, a degree of controlled friction is provided to the stay 1, which can be used to control the position of the vent arm 5 relative to the frame bracket 3 in an open position of the stay 1.

As seen in Figures 1 and 3 of the drawings, each pivot on the frame bracket 3 is formed at a portion 19 of the frame bracket 3 which is raised relative to the main plane of the frame bracket 3. This helps to avoid clashing of the links 7,9 with the frame bracket 3 during closing of the stay 1. Such raised portions 19 are readily formed in the frame bracket 3 because the frame bracket 3 is simply a strip of metal that can be readily deformed into the desired shape. Furthermore, an end cap 21 can be formed at the end of the frame bracket 3 simply by bending the tip of the frame bracket 3 through 90°. The resulting surface 23 of the end cap 21 is inclined to the longitudinal axis of the frame bracket 3 to assist in pulling in the vent arm 5 during closing of the stay 1.

The vent arm 5 includes an end point 25 which is simply formed by cutting off a corner of the end of the vent arm 5 to define an apex 27. It is this apex 27 which engages the inclined surface 23 of the end cap 21 and is guided into the fully closed position of the stay 1 as shown in Figure 2 of the drawings. To accommodate the apex 27 of the end point 25 of the vent arm 5, a corner of the frame bracket 3, including a portion of the end cap 21, is removed, as clearly seen in Figure 1 of the drawings.

If a plastics end cap is required for the frame bracket 3, an end cap such as shown in Figure 4 or Figure 5 could be used. In either event, it will be necessary to attach the end cap to the frame bracket 3, possibly by means of a rivet 29 engaging through a tongue 31 of the end cap 33 and the frame bracket 3, as shown in Figure 4 of the drawings.

Alternatively, the end cap could simply be fixed to the frame bracket 3 with a snap-on fit, by means of a detent (or stake) formed in the frame bracket engaging the tongue or

by means of a screw applied through both the tongue 31 of the end cap 33 and the frame bracket 3 during installation of the stay 1.

As can be seen in Figure 4 of the drawings, the end cap 33 includes two bearing surfaces 35,37 instead of the one surface 23 as in the end cap 21 shown in Figure 1 of the drawings. Although the first bearing surface 35 is at a similar angle (to the longitudinal axis of the frame bracket 3) as in the first embodiment, the second bearing surface 37 is at an angle which corresponds to the angle defined by the end point 25 of the vent arm 5 when the stay 1 is in its closed position. By including the bearing surfaces 35,37, more efficient pull-in of the vent arm is achieved during closing of the stay 1.

With regard to the third embodiment of end cap 39 as shown in Figure 5 of the drawings, this includes a first abutment 41, a second abutment 43 and a recess 45 therebetween. During closing of the stay 1, the apex 27 of the end point 25 of the vent arm 5 is initially guided by the first abutment 41 prior to the apex 27 being free to enter the recess 45. Subsequently, the apex 27 is guided by the second abutment 43 into its final position as shown in Figure 5 with the vent arm 5 overlaying the frame bracket 3.

By allowing the apex 27 to enter the recess 45, a smoother closing action of the stay 1 is achieved. This closing action may be further improved by forming the end point 25 of the vent arm 5 with a concave surface 47, as shown in Figure 5 in the drawings.

In many prior art four bar stays, the length of the part of the vent arm 5 between the rivet 11 joining the first link 7 to the vent arm 5 and the end point 25 of the vent arm 5 is very short. This distance is shown in Figure 1 as X. In a stay 1 according to the present invention, distance X is significantly longer than in the prior art stays, and this has the effect of enabling a smooth entry of the end point 25 into the end cap 21 to occur during closing of the stay 1.

As can be seen clearly in Figures 1 and 2 of the

drawings, the two pivot axes 49,51 on the frame bracket 3 are offset to opposite sides from the longitudinal axis of the frame bracket 3. In particular, the pivot axis 49 of the first link 7 is offset in a direction away from the vent arm 5, whereas the pivot axis 51 is offset from the longitudinal axis of the frame bracket 3 towards the vent arm 5.

Similarly, the pivot axes 53,55 of the vent arm 5 are offset from the longitudinal axis of vent arm 5, with the pivot axis 53 of the first link being offset away from the frame bracket 3 and the pivot axis 55 of the third link being offset towards the frame bracket 3. As a result, closing of the stay 1 occurs in a smooth fashion and results in the longitudinal axis of the vent arm 5 being parallel to and aligned with the longitudinal axis of the frame bracket 3.

This is shown in Figure 2 of the drawings. As mentioned above, this is a marked improvement over the known prior art four bar stays, wherein the vent arm 5 is often inclined to the axis of the frame bracket 3 when in its closed position.

Such misalignment can result in difficulties in installation of a sash on a vent arm, because it is difficult to know at what angle exactly the vent arm 5 should be attached to the sash.

As can be seen in Figure 2 of the drawings, if the pivot axes 49,51 on the frame bracket 3 pass through the longitudinal axes of the first link 7 and third link 9, the first link 7 and third link 9 can. lie partly outside the periphery of the frame bracket 3 when the stay 1 is closed.

To avoid this, the present applicant has suggested that the pivot axes 49,51 of the first link 7 and third link 9 on the frame bracket 3 be offset from the longitudinal axes of the first link 7 and third link 9. This is shown in Figure 7 for the first link 7. As a result, when the stay 1 is in its fully closed position, the first link 7 and third link 9 will lie fully within the periphery of the frame bracket 3. A very narrow and compact stay 1 is thereby produced, which can readily be accommodated within any normal channel of a PVC extruded vent frame. Further, less preparation, such as routing, will be required if the stay is to be

applied to a timber or aluminium vent frame.

Turning now to Figure 6 of the drawings, the vent arm 5 may include a pair of stops 57 formed by cutting slits or "cracks" in an edge 58 of the vent arm 5 and deforming the resulting free metal of the vent-arm 5. A side view of one of the stops 57 is shown in Figure 6A of the drawings.

During use, the stay 1 is opened fully and the stops 57 bear against the first link 7 and third link 9 respectively to prevent further opening of the stay 1. This arrangement ensures that the design geometry of the stay is not exceeded and provides the stay 1 with significant strength, thereby resulting in a safer stay.

Further strength can be provided to the say 1 by means of an S or Z shaped shoulder 59 formed around the pivot 53 between the first link 7 and the vent arm 5. In a normal prior art stay, a simple shoulder perpendicular to the longitudinal axis of the vent arm 5 is provided to step the end point 25 of the vent arm from the remainder of the vent arm 5. However, if a rib 61 is included as shown in Figure 6, which extends substantially parallel to the longitudinal axis of the vent arm 5, additional rigidity is provided to the vent arm 5, thereby strengthening the area around the pivot 53. This is particularly important when the stay 1 is to be used for side hung windows, which result in additional stresses being applied to the pivot 53 between the first link 7 and the vent arm 5. A side view of the rib 61 can be seen in Figure 6B of the drawings.

If a heavy sash is applied to a stay 1 according to the present invention, the vent arm 5 may clash slightly with the first link 7 and/or the third link 9 during closing of the stay 1. Accordingly, with reference to Figure 7 of the drawings, the applicant has suggested the inclusion of a plastics support or guide block 63 mounted on the first link and/or the third link 9 adjacent the vent arm 5. The or each guide block 63 will be riveted or otherwise fixed to the link 7,9 and will include a ramp portion 65 which is engaged by the vent arm 5 during closing of the stay 1. As a result of this engagement, the vent arm 5 will be raised

slightly by the ramp 65, thereby ensuring that the vent arm 5 does not clash with remainder of the link 7,9 as the stay 1 closes.

Another form of guide block 63 is shown in Figure 7A of the drawings, wherein an extension 67 of the guide block 63 is designed to fit between the vent arm 5 and the first link 7. Further, an edge of the extension 67 is chamfered to conform to the shape of the shoulder 59 of the vent arm 5.

By including the extension 67, movement of the vent arm 5 up the ramp 65 during closing of the stay 1 will occur more smoothly.

Finally, an additional plastics block 69 may be included on the frame bracket 3 to facilitate closing of the stay 1.

This block 69 will be held in position by means of the rivet 11 between the frame bracket 3 and the first link 7, together (optionally) with a second rivet 71 joining the block 69 directly to the frame bracket 3. The plastics block will assist in preventing the first link 7 from clashing with the frame bracket 3 during closing of the stay 1.

Turning now to Figures 9 and 10 of the drawings, a four bar stay 101 comprises a support bar 103, a vent arm 105, a first link 107 and a third link 109. The first link 107 is pivotally attached by rivets 111,113 to the support bar 103 and the vent arm 105, and the third link 109 is similarly pivotally attached by rivets 115,117.

As shown in Figure 9, the four bar stay 101 (or hinge) is in an open position with the vent arm 105 spaced from and inclined to the support bar 103. Following closing of the hinge 101, the vent arm 105 is substantially aligned with and overlays the support bar 103 to close a window (not shown) mounted on the vent arm 105. Due to friction between the first link 107 and/or third link 109 and the support bar 103 and/or vent arm 105, the vent arm 105 can be held fairly firmly in an open position. In the prior art cases, however, this friction reduces following use of the hinge 101 and can result in the hinge 101 becoming loose, such that the vent arm 105 cannot be held firmly in an open

position. The present invention overcomes this problem by virtue of friction pivots 119 between the support bar 103 and the first and third links 107,109, as shown more clearly in Figure 10 of the drawings.

With reference to Figure 10 of the drawings, the friction pivots 119 incorporate a stainless steel pivot member or rivet 111,115 which acts between a link 107,109 and a base 121 of the support bar 103. Further, the support bar 103 has a substantially C-shaped cross-section with a pair of inwardly extending flanges 123 which support a friction pad 125. The friction pad 125 is held in position on the support bar 103 by means of lugs or walls 127 which extend substantially parallel to the axis of the support bar 103 and substantially perpendicular to the friction pad 125, and engage in the opening between the flanges 123 of the support bar 103.

The rivet 111,115 passes through apertures in the link 107,109 and the friction pad 125, with the head 129 of the rivet retaining a plastics washer 131 between the head 129 and the link 107,109. By including the washer 131, wear between the head 129 of the rivet 111,115 and the link 107,109 is reduced.

During manufacturing of the friction pivot 119, pressure is applied to the rivet 111,115 such that the base 121 and/or the flanges 123 and/or the side walls of the support bar 103 are caused to deform resiliently. In the case of the base 121, this deformation is towards the link 107,109.

Due to the resilience of the support bar 103, the head 129 of the rivet 111,115 is continuously urged, during use of the hinge, towards the base 121, thereby continually biasing the link 107,109 into contact with the friction pad 125.

Thus, following use of the hinge 101, which results in wear of the friction pad 125, a significant degree of friction between the l-ink 107,109 and the friction pad 125 will remain. This is a significant improvement over the prior art pivot mounts, because the hinge 101 will not become loose as has been found to be the case with some prior art arrangements.

With reference to Figures 12-14 of the accompanying drawings, a hinge 201 according to the present invention comprises a C-section support track 203, a first link 205, a second link 207 and a vent arm 209. The first link 205 and the second link 207 are each pivotally attached to the support track 203 and the vent arm 209, such that the vent arm 209 can be moved from a closed position overlying the support track 203 to an open position inclined to the support track 203 (as shown in Figure 12). Such a configuration is known as a four bar hinge, and is well known in the art.

An end cap 211 comprising an end block 213, a guide block 215 and a support tongue 217 is inserted in the end of the support track 203. An oval aperture 219 in the support tongue 217 can be aligned with an aperture (not shown) in the support track 203, such that the end cap 211 is fixed to the support track 203 when the support track 203 is screwed or otherwise fastened to a fixed frame (not shown) of a window.

The end block 213 and guide block 215 both extend above the support track 203, as seen in Figure 13a. Further, the end block 213 and guide block 215 define a channel 221, which tapers in the closing direction of the hinge 201 shown by arrow A. Further, the end block 213 defines two surfaces 223,225 at different angles which assist in pulling in an end point 227 of the hinge 201 during closing of the hinge 201.

The end point 227 is a plastics moulding held on the end of the vent arm 209 by means of an integral rubbing block 229 which is gripped between the first link 205 and the vent arm 209, and is held in position by a rivet 231. The rubbing block 229 acts as a washer between the first link 205 and the vent arm 209 during relative motion of the two components.

As can be seen in the Figures, the rubbing block 229 includes a recess 233 which accommodates the guide block 215 when the hinge 201 is closed. Further, a rail 235 is formed at the end of the end point 227 for being received in and

moving along the channel 221 during opening and closing of the hinge 201. The rail 235 has a substantially constant cross-section along its length and is integrally attached to the rubbing block 229 such that an extension 237 of the rail 235 abuts the end of the vent arm 209, as shown-clearly in Figure 12.

During use of the hinge 201, a vent of a window is mounted on the vent arm 209 and the support track 203 is attached to a fixed frame. As the hinge 201 is closed, the rail 235 of the end point 227 enters the channel 221 and is guided by the first surface 223 of the end block 213 and/or the guide block 215 along the channel 221. Due to the geometry of the hinge 201, it is preferable for the vent arm 209 to be pulled-in and this is achieved by means of the guide rail 235 being redirected against the second surface 225 of the end block 213. As a result, improved weatherproofed closing of the window is achieved.

Conversely, during opening of the hinge 201, the rail 235, and hence the end point 227 and the vent arm 209, is guided by the end cap 211. As a result, the motion of both the bottom and the top of the vent can be controlled to provide smooth and even opening of the top and bottom hinges of a side-hung window. Accordingly, "falling out" of the vent is reduced, if not avoided, thereby producing a window which is more acceptable to customers and users.

As mentioned above, the end point 227 is a one piece plastics moulding. Further, the end cap is also preferably a one piece plastics moulding, thereby allowing the improvement provided by the present invention to be achieved in an extremely cheap and simple manner. Furthermore, the invention of this patent application is applicable to many different types of hinge.

As will be appreciated, many of the features described herein can be used independently or in combination with other features in a four bar stay according to the present invention. Further, it will be understood that the present invention has been described purely by way of example, and that modifications of details can be made within the scope of the invention.