GB2105780A - Improvements in friction stays for windows - Google Patents

Abstract

The invention relates to friction stays for windows of the kind having rivetted friction pivots 8 and two arms 5,6 of different length. To provide additional support and control of such stay for supporting a sash, a third intermediate arm 7 is provided. The third arm 7 is pivotally connected to the mounting plates 1 and 3 respectively for securing to a window frame and sash. The second and third arms 6,7 move substantially parallel, and in the fully opened position of the sash, the third arm provides support approaching the centre of gravity of the sash. Furthermore, the third arm is a restraint and can avoid the provision of separate stops or limits. <IMAGE>

Description

SPECIFICATION Improvements in friction stays for windows This invention concerns improvements in friction stays suitable for windows. In particular, this invention concerns friction stays which are of the kind herein specified as comprising two arms that are connected to respective mounting plates by friction pivot joints which permit restrained pivotal movement of the arms, the mounting plates of the stay being adapted and arranged respectively for mounting on a sash and for securing to the associated frame so that the sash is supported for frictionally restrained movement on and relative to the frame.

Such stays of the kind specified are conventionally used in pairs, one each side of the sash and associated frame. The sash may be hung on the stays for top, bottom or side opening. The frictional restraint to maintain the sash in an adjusted position is provided in the pivot joints by suitable design and manufacture of the pivot joints. Generally, in a stay of the defined kind the pivot joint includes a rivet which extends through the stay parts with the rivet being clinched in a mannerto generate forces which, after clinching, provide the frictional restraint.

The common construction of friction stays of the kind defined is to provide one short arm and one long arm with the lengths of the arms and the pivot centres being selected to control the movement of the sash. However, as will be appreciated, such friction stays are desirably to be used with a wide range of window sizes, types and styles. To a large extent, acceptance of friction stays in the design of architectural window systems requires the stays to take heavy loads, both static and dynamic, and to be safe and reliable in service. In these systems, the windows are usually hung with the stays at the side and the sash is referred to as a projecting top hung sash.

The common construction of friction stays as aforementioned has certain important disadvantages for some architectural window systems. For example, the stays rely on four rivets for all static and dynamic loads, including side and top loads, such as under wind pressure or top impact on the sash. Additionally, although it is possible to build in limit stops against which the stay arms may abut to avoid over-loading certain of the pivot joints, these limit stops introduce further problems being usually concealed in the window rebate, and the limit stops do not strengthen the load carrying capacity of the stay.

It is an object of the present invention to provide a friction stay of the kind specified having an improved construction to overcome the disadvantages and problems as aforementioned.

Accordingly, this invention consists in a friction stay of the kind specified characterised that a third arm is connected to the respective mounting plates by friction pivot joints, the third arm being pivotally connected to the respective mounting plates intermediate the pivot joints for the first and second arms, and the length and positions of the pivot centres of the third arm being arranged in relation to the first and second arms to control and limit the opening extent of the stay when installed in a window.

By the provision of a third arm, located by it's respective pivot joints intermediate the first and second arms, the load carrying capacity of the stay is increased, particularly under impact loads as may be applied to the top of the sash frame when in the partially or fully open top projecting position. The provision of the third arm increases the overall strength of the pivot joints and in the event of failure of one arm or joint provides a fail-safe link connection.

Furthermore, the provision of the third arm avoids the prior essential need to provide an independent limit for one of the stay arms.

Preferably, the third arm is arranged to extend and to pivot substantially parallel to the second arm and to be shorter than the second arm.

Other advantages arise from the provision of the third arm which may be used in the design of a friction stay in accordance with this invention.

One advantage is that the frictional restraint for holding the sash in the desired open position is dependent on the aggregate restraint value of six pivot joints, not four as previously. This advantage may be used to increase the frictional restraint for heavier or more highly loaded sashes, and/or to accommodate a range of manufacturing tolerances or performance. Thus the manufacturer or user can apply the stays of this invention to a wide range of applications or window systems.

Another advantage is that in service, the third arm may be arranged to provide a braking action on progressive opening of the sash so that the extreme limit of opening movement is only reached by increasing effort of the user. This reduces maximum strain on the joints and the fixings of the mounting plates which in the prior constructions using a limit stop could lead to severe distortion or failure of the stay parts of fixings.

Yet another advantage is that where it is desired to provide a force acting to pull in the top of the sash against the frame by ensuring a residual force in the longer lower arm, this function may be retained by suitable selection of the lengths of the arms and position of pivot centres whilst still more uniformly distributing the sash loads by three arms and their respective pivot connections.

An exemplary embodiment of this invention will now be described with reference to the accompanying drawings wherein: Figure 1 is a side elevation depicting a friction stay in three operative positions; Figure 2 is an exploded detail view of a friction rivet joint in the stay shown in Figure 1.

The stay comprises a mounting plate 1 adapted by holes 2 along the length thereof for fixing to the side of a rebate in a fixed window frame (not shown).

The stay further comprises another mounting plate 3 also adapted by holes 4 along the length thereof for fixing to the side of a sash (not shown).

As will be understood, in a window, two such stays are used to support the movable sash, one on each side, and the stays act as hinges.

The two mounting plates 1,3 are connected together by first, second and third stay arms 5,6 and 7 respectively. Each stay arm is connected at each respective end by a friction rivet joint 8 for restrained pivotal movement.

The friction rivet joints 8 may be of any suitable kind and arranged in any manner to suit assembly and manufacture. A suitable friction rivet joint is shown in Figure 2 and comprises a rivet 9 having a frusto-conical head 10 seated in a complementary recess 11 adjacent the end of an arm 5. The shank of the rivet 9 extends through a clearance hold in the arm concentric with the recess 11. The rivet extends through a hole 13 in the plate 1 which is pierced and plunged to leave a recess on the underside of the plate. Disposed on the rivet shank between the arm 5 and the plate lisa plastics support plate 14 having a central hole in which a washer 15 is received. The support plate and washer provide a spacer separating the arm 5 and the plate 1 to prevent metal-tometal contact on relative movement.The washer 15 may be of metal or plastics or metal coated with plastics.

The tail of the rivet is clinched to the underside of the plate 1 with a spiked washer 16 disposed adjacent to the plate 1 so that on pressure clinching the rivet, the rivet material is deformed into the interstices between the spikes and the spikes are pressed onto the plate 1. Following clinching, the clinched tail of the rivet is located and fixed against rotation relative to the plate 1. In known manner, the tail is clinched under pressure to leave a desired residual frictional force within the joint.

The rivet may be plastics coated, or a cone-like washer may lie under the head of the rivet and be seated in the recess.

This form of rivetted joint has advantages in providing a large bearing area between the head of the rivet and the arm for transmitting and supporting high loads in surface.

In use of the friction stay, the stay is opened from the fully folded position as shown in ghost broken lines in Figure 1 with the direction of effort being shown by the large arrow E. The successive stages of the position of the sash mounting plate 3 on opening movement are shown with the direction of movement of the sash being shown by the arrows D.

For closing movement the directions are reversed.

The first stay arm 5 controls the projection of the top of the sash from the window frame in the hinging movement to fully open, and in closing movement when the arms fold up into the window rebate to lie in between the overlying mounting plates. In particular, the length of the first arm 5 and the position of the pivot centres is selected to ensure that the top of the sash advances to and from the closed position without interference with the surrounding fixed window frame, for instance a top weatherboard (not shown). The first stay arm 5 has a movement greater than 90".

The second stay arm 6 is the longest arm and controls the direction of movement of the bottom of the sash. The pivotal movement of the second stay arm is less than 90". By arranging for the effective length of the arm 6 (that is the distance between the pivot centres at each end) to be greater than simply required to achieve folding movement in the closed position, the second arm may be stressed in the approach to the closed position to provide a force acting on the sash to pull-in the top of the sash.

The stay according to this invention includes the third arm 7 which has a pivot centre on the mounting plate 1 centrally intermediate those centres of the first and second arms. The loads arising through the three arms 5, 6 and 7 are therefore uniformly spread along the length of the mounting plate 1. The pivot centre on the mounting plate 2 is spaced from the pivot centre of the second arm 6 by a slightly less distance than the distance between the opposed pivot centres of the other ends of the arms 6 and 7 on the mounting plate 1.Accordingly, by this arrangement the arms 6 and 7 will move substantially parallel but due to the differences between the respective pivot centres, and the constraining effect of the short arm 5, the third arm serves as a restricting strut which limits opening movement of the mounting plate 2 without it being essential to provide any separate limit stop, for instance a lug or face on the mounting plate 1 engageable by the short arm 5.

Furthermore, by the selection of the effective lengths of the second and third arms and the distances between their associated and respective pivot centres, the amount of stress applied to the second arm may be selected for the desired pull-in feature.

As will now be understood, the third arm provides significant additional load carrying support for the sash load applied from the mounting plate, and ensures that loads are uniformly distributed, particu larly intermediate the pivot centres of the extreme ends of the mounting plates to which the first and second arms are connected. By this means it is also important to note that the third arm provides load carrying support approaching the expected centre o gravity of the sash when in the fully open position.

The friction stay according to this invention may have mounting plates in one or more parts if desirec and the shape, including cross-section, may be varied to suit the particular window system. The arms may also be of any suitable shape or configure tion.

Preferably, the friction stay is made of metal, such as aluminium or steel, and it may include a corrosio resistant finish or coating as desired.

Although the friction rivet joints are generally described as all being of the same kind or arrangement, this is not essential and if desired, or as selected for ease of manufacture or assembly, different types of friction rivet pivot joints could be used for different parts of the friction stay in accordance with this invention.

Claims (8)

1. In a friction stay of the kind specified character rised that a third arm is connected to the respective mounting plates by friction pivot joints, the third ar being pivotally connected to the respective mounting plates intermediate the pivot joints for the first and second arms, and the length and positions of the pivot centres of the third arm being arranged in relation to the first and second arms to control and limit the opening extent of the stay when installed in a window.

2. Afriction stay according to claim 1 wherein the third arm is arranged to extend and to pivot substantially parallel to the second arm and to be shorter than the second arm.

3. A friction stay according to claim 2 wherein the third arm is pivotally connected to the mounting plate by a rivetted friction joint having it's pivot centre substantially centrally disposed intermediate the pivot centres of the first and second arms on the said mounting plate.

4. A friction stay according to any one of the preceding claims wherein each pivot joint is a rivetted friction joint.

5. Afriction stay according to claim 4wherein each friction joint comprises a rivet having a frustoconical head received in a complementary recess for relative rotation.

6. Afriction stay according to claim 5 wherein the tail of the rivet is clinched to the underside of the mounting plate with a spiked washer being interposed between the underside of the tail prior to clinching to locate and restrain the rivet against rotation relative to the mounting plate after clinching.

7. Afriction stay according to any one of the preceding claims wherein the mounting plates are extrusions of aluminium alloy.

8. A friction stay substantially as hereinbefore described with reference to the accompanying drawings.