NZ238318A

NZ238318A - Friction stay with offset pivot joint to frame when fully closed

Info

Publication number: NZ238318A
Application number: NZ23831891A
Authority: NZ
Inventors: Ronald Percival Davis
Original assignee: Ronald Percival Davis
Priority date: 1991-05-29
Filing date: 1991-05-29
Publication date: 1994-05-26

Description

<div class="application article clearfix" id="description"> * «• f i v, h j 2 4 0 2 S .3 2 V KAY 1992/ Patents Form No. 5 Number 238318 240289 PATENTS ACT 1953 Dated May 29, 1991 October 18, 1991 COMPLETE SPECIFICATION A WINDOW STAY I, RONALD PERCIVAL DAVIS, a New Zealand citizen, of 77 Breaker Bay Road, Seatoun, Wellington, New Zealand do hereby declare the invention for which we pray that a Patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: - 1 - 238318/ 24028 My present invention comprises a friction stay for a window. A variety of forms of friction stays for windows are known. The four bar window stay the subject of New Zealand patent No. 144922/146130/146886/ for example, has for over two decades proved particularly successful in its basic and subsequently refined forms, in many countries of the world. The success of this four bar friction stay has derived from its simplicity of construction, because the stay does not have the externally exposed sliding pivot and track arrangement of pantograph type stays. Such externally exposed moving parts are prone with time to clogging with dirt causing sticking of the mechanism, increased wear and tear and so forth. Also, the geometry and operation of the four bar stay in use lifts the window sash out of the window aperture, enabling the provision of a peripheral sealing flange about the entire sash while still facilitating access for cleaning. With conventional four bar friction stays, even when the window sash is closed, the stay itself is still a few degrees open. It is believed necessary that even when the window sash is closed, the friction stay not be fully closed to ensure correct operation of the stay when the window is again opened. With the four bar geometry, designers have ensured that the stay is slightly open even when the window is closed because of the danger that otherwise the stay might not operate correctly and that the head of the window could begin to move 238318/ iA»»aV outwardly before the bottom of the window sash, which would result in jamming of the stay. wood have become popular, particularly in the replacement window market. The uFVC material is produced by extrusion and is then cut and the window sash(es) and frame(s) are constructed. A common standard uPVC extrusion profile has a cavity comprising a narrow groove to accommodate the stay between the sash and frame to suit pantograph type stays, and which will not accommodate a conventional four bar stay. Although the four bar friction stay is superior, it has not been possible to employ a four bar stay. allowed to close fully, for various reasons this has inhibited the use of some form of integral head locking mechanism with the four bar stay. Some form of head locking mechanism is desirable because of another disadvantage of the four bar stay, which is that the head can be forced open from outside the window frame, by levering between the peripheral sealing flange at the head of the window and the window frame with a crowbar for example. A separate locking device can be added between the window sash and frame on the inside of the window to counter this danger, but this is not as desirable as use of an integral mechanism. For as long as the four bar friction stay has been produced, Windows produced from uFVC instead of aluminium or Also, because the four bar friction stay has not been these problems have remained. 238 518/ NOW AMENDED ^ ^ ^ ^ ^ - 4 - My present invention provides an improved or at least alternative form of friction window stay which possesses advantages over the conventional/ four bar /stay as will be described. In broad terms the^ invention/comprises a friction window stay for mounting a Window sash/in a window frame, the stay comprising: a frame mounting number for s^curement of the stay to the frame of a window; a sash mounting member fy6r securement to the sash of a window; a long axpa having a rfivot joint between the frame end of the long arm/ and the frauae mounting member and a pivot joint t / between the/ sash end of the long arm and the sash mounting i ' member; and a short atm having a pivot joint between the sash end of the short arm/and the sash mounting member which joint is spaced from the Aong arm - sash mounting member pivot joint and "tan offset pivou joint between the frame end of the short arm and ^ \ / tjiw frame mounting member, said offset joint being spaced from / tpe long Arm - frame mounting member pivot joint and v/ L sufficiently offset from a line passing through the centres of the/othe^r pivot joints when the stay is fully closed that the —/ AS AMENDED2 38 3 1 g/ 240289 My present invention provides an improved or at least alternative form of friction window stay which possesses advantages over the conventional four bar stay as will be described. window stay for mounting a window sash in a window frame, the stay comprising: a frame mounting member for securement of the stay to the frame of a window; a sash mounting member for securement to the sash of a window; a long arm having a pivot joint between the frame end of the long arm and the frame mounting member and a pivot joint between the sash end of the long arm and the sash mounting member; and of the short arm and the sash mounting member which joint is spaced from the long arm - sash mounting member pivot joint and an offset pivot joint between the frame end of the short arm and an offset land of the frame mounting member offset from the main body of the frame mounting member, said offset joint being spaced from the long arm - frame mounting member pivot joint and sufficiently offset on said offset land from a line passing through the other pivot joints when the stay is fullv closed In broad terms the invention comprises a friction a short arm having a pivot joint between the sash end that the 2.5831 fife 4028 - 5 - long arm, sash mounting member and frame mounting member are aligned and the short arm extends at an angle relative to the said line from the pivot joint of the short arm - sash mounting member to said offset pivot joint, with at least some of said pivot joints being friction pivot joints. Preferably the stay of the invention incorporates integral means to lock the head of the window against forced opening, comprising an engagement means on the short arm end of the sash mounting member which engages co-operable engaging means on the frame mounting member as the stay is closed, with the distance between the short arm-sash mounting member pivot joint and said engagement means on the end of the sash mounting member being less than two thirds, and most preferably less than one half, of the length of short arm between pivot joint centres. In a most preferred form as will be described, the engagement means comprises a protrusion from the end of the sash mounting member and the co-operable engaging means comprises a recess into which the protrusion engages a# the stay reaches its fully closed position. Preferably the length of the short arm between pivot joint centres is between one half and three quarters of the length of the long arm between pivot joint centres. In terms of dimensions, in typical sizes of stays in common use, the offset pivot joint is preferably offset from -1 DEC 1993 , rV • nv< 238 318/ - • - said line passing substantially through the other pivot joints by between 10 and 40 mm and most preferably between 15 and 30 mm, measured between said line and the centre of the offset pivot joint. The angle between the short arm and the sash mounting member when the stay is closed is preferably between 13 and 20 degrees and most preferably about 15 degrees. Most preferably the frame mounting member of the stay of the invention is formed of a plastics material and the pivot joints between the frame mounting member and each of the arms of the stay may then be of a preferred fonr wherein at each joint an annular shoulder of the plastics material of the body of the frame mounting member projects from the frame mounting member, and there is an aperture in the arm whereby the arm is located for pivotal movement about the shoulder. A fixing means for fixing the joint and applying friction creating pressure extends through the joint and is fixed within the shoulder and/or within an aperture in a frame mounting member below the shoulder, with plastics material extending from the shoulder between the arm and fixing means to prevent direct contact therebetween. This form of friction pivot joint will be described further but other forms of friction pa.vot joints could be used, such as the joint described in my cognate New Zealand patent specification 212599/213772 which is incorporated herein by reference for description of this friction pivot joint. Both of these pivot joints have a hollow centre which allows screws for fixing the stay to a window frame (or sash) to be screwed - 7 - through the pivot joint, so that loads are taken directly at the ends of the stay arms. The stay of my invention is suitable for use in both awning and casement applications. With the stay of the invention when the window is closed the stay is also fully closed i.e. the sash and frame mounting members and long arm are fully aligned. This allows the stay to be used with common standard uPVC window profiles. Also, in initial opening the head of the window has a slight downward and then an outward movement (the stile of the sash moves sideways then outward in the case of a casement window). This enables the stay to employ an integral head locking mechanism, if desired. The sash mounting points of the stay may be properly spaced apart giving good sash stability when the sash is open and the stay possesses a high degree of inherent strength. Forming the frame mounting member or frame plate of a plasties material with the preferred construction described, enables the number of components used to produce a pair of stays to be halved. A preferred form of the friction stay of the invention is illustrated, by way of example, in the accompanying drawings, wherein: Fig. 1 is a view of a preferred form window stay of the invention from one side in its fully extended or open position, Fig. 2 is a view of the stay of Fig. 1 in its closed _ position, -iODECW?!' 23 8 3 1 8 "8 " X-40X& Fig. 3 is an end view of the preferred form stay in the direction of arrow A in Fig. 1, Fig. 4 is a cross-sectional view of a friction pivot joint of the invention between a frame plate and an arm, also showing a mounting screw as would be used in practice for mounting the stay to a window frame, Fig. 5 is a view from above of the preferred form joint (with no mounting screw shown), Fig. 6 is a cross-sectional view through the end of the frame plate of Fig. 4 without the arm, fixing means, and mounting screw of Fig. 4, Fig. 7 is a view from above of the end of the frame plate shown in Fig. 6, in the direction of arrow D in Fig. 6, Fig. 8 is a cross-sectional view through a preferred form button fixing means, Fig. 9 is a view from above of the preferred form button fixing means in the direction of arrow E in Fig. 8, Fig. 10A is a cross-sectional view of a form of joint related to that of Figs. 4 to 7 for optional use between an'arm.., • > < f * *7 and a metal sash plate when the sash plate is not also fornted y T. O S' 23 3 3 18/24 0 2 8 - 9 - of plastics, Figs 10B and IOC showing steps in assembly of the joint, and Figs 11A, 11B and 11C are views f^om above for each of Figs 10A, B and C. Referring to Figs 1 to 3 the preferred form stay illustrated in the drawings comprises a short arm 1 and a long arm 2. The arms are preferably formed from stainless steel or could alternatively be formed of aluminium, for example. The frame ends of the short and long arms 1 and 2 are pivotally connected to a frame mounting member comprising a frame plate 3 for securing to the frame of a window, by way of suitable friction pivot joints 4 and 5 as will be further described, at points spaced from each other. In the preferred form stay shown in the drawings the frame plate 3 is formed by injection moulding from a plastics material such as acetyl or other self lubricating and wear resistant synthetic material, but theJEre«ne ,.*V E"'-: /" plate 3 could alternatively be formed of metal such as stainless c V* steel or aluminium. - ^ I^f_„ -t DEC 1993 \ The sash ends of the shoirt arm 1 and long arm ?.are pivotally connected to a sash mounting member comprising a sash plate 6 for securing to the sash of the window, by way of similar pivot joints 7 and 8 which are preferably also friction pivot joints, at points spaced from each ether. Where the frame plate 3 is formed from a plastics material, the sash plate 6 is preferably also formed of a plastics material, but again the 23 8 3 1dfe4 0 2 8 9 - 10 - sash plate could alternatively be formed of metal such as stainless steel or aluminium. II formed from metal the frame and sash plate could be powder coated for example. A land or extra section of material 9 is provided on the framo plate 3 as shown in Figs 1 and 2. This land 9 extends behind so as to be offset from the main body of the frame plate 3 as shown. The pivot joint 4 of the frame end of the short arm 1 to the frame plate 3 is provided on this land, so that this pivot joint is also offset. The short arm-frame plate pivot joint 4 is offset away from a line passing through the other pivot joints of the stay when the stay is closed as shown in Fig. 2, being the long arm-frame mounting member pivot joint 5, the long arm-sash mounting member pivot joint 8 and the short arm-sash mounting member pivot joint 7, and the long arm 2, frame plate 3 and sash plate 6 are aligned. The short arm 1 extends at an angle from the short arm-sash plate pivot joint 7 to the offset pivot joint 4 as shown, preferably of about 15 degrees or more in a typical size of stay. In a typical size of stay the offset joint 4 may be offset between 15 mm and 30 mm from this line. This offsetting of the short arm-frame plate pivot joint 4 enables the stay to be fully closed so that the long arm 2, frame plate 3 and sash plate 6 are aligned when the stay is in its closed position, in comparison to conventional four bar Btays where, even when the window sash and stay are in their closed positions, the geometry of the stay is not fully closed i.e. the long arm and sash mounting member are not aligned as shoto^ln 1 ^ c • v' -Vi' - I DEC 1993 ^ 238318/ •" ■ UMW Fig. 2 (with the stay of the invention) but are still a few degrees away from this position. Another advantage of the stay of the invention is that when the stay is within about 10 degrees of its closed position, the window sash will tend naturally to spring shut. This is in contrast to the conventional four bar stay geometry, wherein when the window is closed but not latched shut, the stay and sash tend to spring to a slightly open natur&l position of rest. Each of the frame and sash plates 3 and 6 may be provided with suitable mounting holes whereby the stay may be mounted to a window frame and sash in use. When the pivot joints employed are of the preferred form type described herein the frame and sash plates 3 and 6 can additionally or alternatively be secured to the frame and sash by screws or like fasteners passing through the pivot joints themselves (as in Fig. 4). This is advantageous, particularly in casement window applications, as the frame plate is secured to the frame at the same point that loads are applied so that deformation of the frame plate is minimised. In use the stay can be moved from its fully extended or open position shown in Fig. 1 wherein the sash plate 6 and a sash mounted thereto (sash not shown) extend at an angle to the window aperture, to or towards its closed position (or vice versa) by pulling (or pushing) on handles suitably mounted to the window sash. The stay of Fig. 1 is shown in its closed position in Fig. 2, and the movement of the sash plate/short £3 3 3 1 8/24 0 2 i NOW AMENDED - 12 - arm, sash plate/long arm pivot joints is as indicated by arrows Y and Z in Fig. 1. During the last part of the closing movement of the stay the good 'pull in' is provided. / / When the frame plate of the stay is formed as^a'single component from plastics material for/example by /injection / / moulding it may have a raised rib yS along its fear edge to assist in strengthening the frame ,£late. Abou^/the short arm frame-plate joint the body of the frame plat^ may be enlarged below the joint/arm 6 as at jfl to provide' a bearing surface which will tend to support the shprt arm from below, particularly in casement applications wfiere the bearing surface 11 may be enlarged further than sliown if desired. In the preferred form injection moulded ip^ay shown, the land 9 for the / / offset bearing is provided on tKe main body of the frame plate, but in other fc^ifms of the stay such as stays of the invention having a metaif frame plate/ the frame plate could be as wide as ic/9 is the lancr 9 throughout the whole of the length of the frame plate. liie frame plajbe (and sash plate) could be pressed from / / metal^or example. / / / / As stated, the stay of the invention closes up fully so that the long arm and mounting plates of the stay are aligned when the stay is clo&ed as compared to a conventional four bar stay. The stay comprises a minimum of externally moving parts such as sliding tracks or the like. In addition the sash mounting points of the arms of the stay are properly spaced part so that the stay stably mounts a window sash. The - 1 DEC 1993 mo /ap o & AS AMENDE - 12 - arm, sash plate/long arm pivot joints is as indicated by arrows Y and Z in Fig. 1. During the last part of the closing movement of the stay the good 'pull in' is provided. component from plastics material for example by injection moulding it may have a raised rib 10 along its rear edge to assist in strengthening the frame plate. About the short arm frame-plate joint the body of the frame plate may be enlarged below the joint/arm 6 as at 11 to provide a bearing surface which will tend to support the short arm from below, particularly in casement applications where the bearing surface 11 may be enlarged further than shown if desired. so that the long arm and mounting plates of the stay are aligned when the stay is closed as compared to a conventional four bar stay. The stay comprises a minimum of externally moving parts such as sliding tracks or the like. In addition the sash mounting points of the arms of the stay are properly spaced apart so that the stay stably mounts a window sash. The When the frame plate of the stay is formed as a single As stated, the stay of the invention closes up fully 23 b»3 18/24 0 2 89 - 13 - stay provides a 'lifting out' of the window sash type operation so that the sealing strip extending about the window aperture is not tended to be dislodged/ and enabling full cleaning access. The stay provides increased 'pull in' during final closing. Also, the stay has a slight downward and then outward initial opening movement, which in turn enables the stay to incorporate an integral head locking mechanism. The preferred form of stay shown in Figs 1 to 3 incorporates a preferred form of head locking mechanism as will now be described. The top end of the sash plate 6 is formed with an engagement means in the form of a protrusion 12 (see Fig. 1). A recess 13 is formed in an integral enlarged head 14 of the frame plate 3. The protrusion 12 and recess 13 each have an adjacent downwardly sloping land 12a and 13a on the side opposite the offset bearing 4 as shown. The arrangement is such that when the window stay is closed/ the sash plate 6 will move such that the protrusion 12 engages into the recess 13 as shown in Fig. 2. When the stay is fully closed and the protrusion 12 is fully engaged into the recess 13, the head of the window is locked and cannot be opened by force or prising open between the top of the window sash and the window frame. The locking mechanism can again only be opened by proper opening of the window by pushing on the bottom of the sash from within. In the form shown in the drawings the protrusion 12 is formed in the plastics material of the sash plate, and the c recess 13 in the top of the frame plate, but other forms of %. -1DEC199J£ 23.8 3 10 24 02 89 14 interlocking engagement means on the sash plate and co-operable engaging means on the frame plate are possible. For example, the respective positions of the protrusion and recess could be reversed. The distance between the short arm-sash plate pivot joint 7 and the protrusion 12 on the end of the sash plate is less than two thirds, and very preferably less than one half, of the length of the short arm, between centres of the pivot joints 4 and 7, to ensure proper operation of the head locking mechanism. It is preferred but not essential that offset four bar stays of the invention incorporate a head locking mechanism. Figs 4 to 7, which is very preferably employed for the pivot joints between the arms 1 and 2 and the frame plate 3 of the window stay, and also optionally for friction joints between the arms and the sash plate 6 of the window stay if the sash plate is also formed of a plastics material. The frame (or sash) plate is indicated at 3. An arm is indicated at 1. An annular shoulder 14 surrounds and projects from the periphery of an aperture 15 through the frame plate 3 as shown. Figs 6 and 7 show the shoulder integrally formed on the mounting plate before forming of the joint. An annular base to the joint is preferably moulded as shown so that the end of the button fixing means 16 will not be exposed. The arm 1 has an aperture whereby the arm 1 is located about the shoulder 14. An annular fixing means or button 16 extends through the joint and is fixed within the int^itot of A preferred form of friction pivot joint is shown in v 1 DEC 1993 £ 23 8 3 1 8/ 15 the annular shoulder 14 and/or the aperture below, to fix the joint and apply friction creating pressure thereto so that a friction pivot joint is provided. In the preferred form the button 16 is screw threaded into the interior of the shoulder 14 and aperture below. Preferably a thread is not formed in the interior wall of the shoulder 14 so that the button 16 will tap its own thread and bite into the plastics material. It is possible that the button could be fixed by other than screw threading, by barbs on the button biting into the plastic of the interior wall of the shoulder or aperture below for example. part 14a (see Fig. 6) of the shoulder 14 is bent over to become interposed between the underside of the top of the button and the arm 1 as shown in Fig. 4, so that there is no metal to metal contact. Preferably the top part 14a of the shoulder has a lesser wall thickness than the main body 14b of the shoulder as shown in Fig. 6, which shows the shoulder before placement of the arm. Figs 8 and 9 and comprises a flange like top portion 16a and a cylindrical body portion 16b and which is screw threaded as shown. The button 16 is shown in Figs 10a and 11a. The button preferably has a hollow interior so that a fixing screw for the stay may be screwed through the joint as shown in Fig„v 4. Then the button may have a hex interior to enao As the button 16 is inserted and screwed home the top The preferred form button fixing means 16 is shown in - 16 - 23 8 3 1 8/ 24Q2%^ the button during forming of the joint with a hex key, and friction adjustment after installation. friction pivot joint described be used in the stay of the invention when the frame and/or sash plates are formed of plastic, as such joints can be formed with less components than conventional friction pivot joints. The stay can be produced more economically. Another advantage of the preferred form pivot joints is that because they include a central aperture the joints in the frame and sash mounting plates can be 'screwed through' with mounting screws, as well as the mounting holes. The stay is then secured to the frame and sash of the window at the same point that loads are applied by the stay arms, particularly in casement applications, so that distortion of the frame and sash mounting plates is minimised. related to that of Figs 4 to 7 that may optionally be used between an arm and a metal sash plate when the sash plate is not also formed of a plastics material. The joint comprises a shoulder or upstand 17 formed from the metal material of the sash plate 6. The interior of the shoulder is threaded for receiving a similar threaded button 16. An annular bushing 18 is placed about the shoulder to prevent direct contact between the shoulder, the arm, and the button. Fig. IOC shows the shoulder on the sash plate before the placement ...jQf^..other It is very preferred that the preferred form of Fig. 10A shows in cross-section a form of joint components, and Fig. 10B the shoulder with - 17 - 238 3 18/ 24©2.&V> before the button 16 is inserted home. The bushing has a base part 18a and an upstand part 18B which, similar to the Fig. 4 joint, is bent over by the button 16 when it is screwed home. Fig. 11A shows the finished joint from above without the screw for fixing the stay in place to the window sash, and Figs 11C and 11B are plan views from above corresponding to Figs IOC and 10B. The foregoing describes my invention including a preferred form of friction pivot joint, and various alterations and alternatives. Other alterations and modifications as will be apparent to those skilled in the art are intended to be incorporated within the scope hereof as defined in the following claims. o o vO v£> C~»' -M; fn ,i r-ii J </div>

Claims

<div class="application article clearfix printTableText" id="claims"> £3 83 18/24 02 NOW AMENDED - 18 - WHAT I CLAIM IS: / 1. A friction window stay for mounting a window sash in a window frame, the stay consisting of: / / a frame mounting member for securement of the ftay to the frame of a window; a sash mounting member for f&curement of/the stay to the sash of a window; a long arm having a pivot joint between a frame end of the long arm and the frame mounting member/and a pivot joint between a sash end of the long/arm and the >eash mounting member; and a short .arm having aypivot joint between a sash end of the short arm ana the sash mounting member which joint is spaced from the long' arm - sash/mounting member pivot joint and an offset pivo£ joint between a frame end of the short arm and the frame mounting member/ said offset joint being spaced from the long arm - frame mounting member pivot joint and sufficiently t from a st^ight line passing through the centres of the er pivot joihts when the stay is fully closed that the long , sash mounting member and frame mounting member are aligned and the sh^rt arm extends at an angle relative to the said line from the' pivot joint of the short arm - sash mounting member to - 1 DEC 1993 AS AMENDED is 238318/ 240289 WHAT I CLAIM IS: 1. A friction window stay for mounting a window sash in a window frame, the stay consisting of: a frame mounting member for securement of the stay to the frame of a window; a sash mounting member for securement of the stay to the sash of a window; a long arm having a pivot joint between a frame end of the long arm and the frame mounting member and a pivot joint between a sash end of the long arm and the sash mounting member; and the short arm and the sash mounting member which joint is spaced from the long arm - sash mounting member pivot joint and an offset pivot joint between a frame end of the short arm and an offset land of the frame mounting member offset from the main body of the frame mounting member, said offset joint being spaced from the long arm - frame mounting member pivot joint and sufficiently offset on said offset land from a straight line passing through the other pivot joints when the stay is fully closed that the long arm, sash mounting member and frame mounting member are aligned and the short arm extends at an angle relative to the said line from the pivot joint of the short arm - sash mounting member to a short arm having a pivot joint between a sash end of £38 "3 18/240 2 89 - 19 - said offset pivot joint, with at least some of said pivot joints being friction pivot joints. 2. A window stay as claimed in claim 1, comprising an engagement means on a short arm end of the sash mounting member which interlocks with a co-operable engaging means on the frame mounting member when the stay is fully closed, with the distance between the short arm - sash mounting member pivot joint and said engagement means on the end of the sash mounting member being less than two thirds of the length of the short arm between pivot joint centres to lock the head of a window mounted by the stay against forced opening. 3. A window stay as claimed in claim 2, wherein the engagement means on the end of the sash mounting member comprises a protrusion from said end of the sash mounting member and the co-cperable engaging means on the end of the frame mounting member comprises a recess to receive said protrusion, the protrusion being arranged to engage into the recess as the stay reaches its fully closed position. 4. A window stay as claimed in claim 3, wherein the protrusion on the end of the sash mounting member has a land on the side of the protrusion away from the offset pivot joint which land slopes back away from the end of the sash mounting member, and the recess in the frame mounting member has a complementary land which slopes back away from the end of the frame mounting me^ex$T>v y - J DEC 1993^' *i> J:;238318 240 2 89;20;5. A window stay as claimed in any one of claims 2 to 4f wherein the distance between the short arm - sash mounting member pivot joint and said engagement means on the end of the sash mounting member is not more than one half of the length of the short arm.;6. A window stay as claimed in any one of claims 1 to 5, wherein the length of the short arm between pivot joint centres is between one half and three quarters of the length of the long arm between pivot joint centres.;7. A window stay as claimed in any one of claims 1 to 6, wherein said angle between the short arm and the said line when the stay is closed is between 13 and 20 degrees.;8. A window stay as claimed in any one of claims 1 to 6, wherein said angle between the short arm and the said line when the stay is closed is substantially 15 degrees.;9. A window stay as claimed in any one of claims 1 to 8, wherein the offset pivot joint is offset from said line passing substantially through the centres of the other pivot joints by between 10 and 40 mm, measured between said line and the centre of the offset pivot joint.;10. A window stay as claimed in any one of claims 1 to 8r wherein the offset pivot joint is offset from said liife* by . - f DEC 1993 233318/ -21" between 15 and 30 mm, measured between said line and the centre of the offset pivot joint. 11. A window stay as claimed in any one of claims 1 to 10, wherein the frame mounting member is formed of a plastics material and the pivot joints between the frame mounting member and each of the arms of the stay have a hollow centre to allow screws for fixing the stay to a window frame to be screwed through the pivot joints. 12. A window stay as claimed in any one of claims 1 to 11, wherein the frame mounting member is formed o£ a plastics material and the pivot joints between the frame mounting member and each of the arms of the stay comprise: an annular shoulder of the plastics material of the body of the frame mounting member projecting from the frame mounting member; an aperture in the arm whereby tva arm is located for pivotal movement about the shoulder; and a fixing means for fixing the joint and applying friction creating pressure thereto extending through the joint and fixed within the shoulder and/or within an aperture in the frame mounting member below the shoulder, with plastics material ) 238 318/ -22 ■ extending from the shoulder between the arm and part of the fixing means to prevent direct contact therebetween. 13. A window stay as claimed in claim 12, wherein the annular shoulder prior to locating of the arm about the shoulder and insertion of the fixing means comprises a first annular part projecting from the frame mounting member and a second annular part above the first part said second part being of reduced wall thickness, said second part having been bent over to lie between the fixing means and the arm to prevent direct contact therebetween during insertion of the fixing means. 14. A window stay as claimed in either one of claims 12 and 13, wherein the fixing means is fixed within the shoulder by self-tapping screwing into the plastics material within the annular shoulder and/or an aperture in the frame mounting member below the shoulder. 15. A window stay as claimed in any one of claims 12 to 14, wherein the sash mounting member is also formed of a plastics material and the pivot joints between the sash mounting member and the arms of the stay each comprises a pivot joint of the construction defined in any one of claims 12 to 14 for the frame mounting member - arms pivot joints. 16v, A window stay substantially as herein described with .. } reference to Figs 1 to 3 of the accompanying drawings. 238318/ - 23 - 17. A window stay substantially as herein described with reference to Figs 1 to 9 of the accompanying drawings. WEST-WALKER McCABE p«> ATTORNEYS FOR THE APPLICANT </div>