GB2092221A - Pivot joints for window stays - Google Patents

Abstract

The invention concerns friction joints for foldable window stays including a mounting plate 5 and an arm 4 which are pivotally connected by a rivetted joint. The joint includes a rivet 1 having a head 7 received in a counterbored low friction bushing 2 which is non-rotatably seated in a recess 9 in the arm 4. The rivet shank 6 extends through aligned holes 10, 12 in the arm 4 and plate 5 between which a spacer 3 is interposed. The tail of the rivet is clinched on the underside of the plate 5 to locate the rivet against rotation relative to the plate 5 and by such clinching, frictional restraint is achieved in the joint. High loads on pivotal movement of the joint in use of a window stay are transmitted between the co-operating bearing surfaces of the bushing 2 and the rivet head and shank. An exemplary embodiment of a stay is also described. <IMAGE>

Description

SPECIFICATION Pivot joints for window stays This invention concerns pivot joints for stays designed and arranged to mount a sash (as hereinafter defined) on a frame for adjustable movement relative to the frame, in particular but not exclusively, stays for windows.

The term "sash" as used herein means a closure member adjustable relative to a frame and arranged to close an aperture in the frame. Thus the term "sash" may include a glazed light for top, bottom or side opening, a non-glazed or partly glazed member such as a fan-light, door or casement.

It is already known to provide stays comprising one or more arms or links and/or mounting plates or bracket that are connected together by one or more pivot joints which permit free pivotal movement. With such stays, additional means has to be provided to restrain free swinging movement of the sash, for instance a locating stay arm or locking means acting between the sash and the frame. Furthermore, in some stays, frictional resistance to restrain free movement is provided by means of friction plates or sliding shoes forming parts of the stay construction. In these stays, the pivot joints are simple pivotal connections, and the conventional type used is a rivet or pin extending through bores or piercings in the two arms or links, or mounting plates to which the arms or links are connected for attachment to either the sash or the frame.

It is also known to provide stays comprising two or more arms or links with a pivot joint of a construction such that the frictional restraint to hold the sash, for instance in an open position, is generated within at least one of the pivot joints of the stay. In old forms of stay of this kind, one or more of the pivots comprised a threaded element which, if desired could be tightened or ioosened manually in use to control the ease of movement of the sash and possibly to secure the sash in an open position.

It is also known to use a rivet which provides a pivotal connection between the arms, links or mounting plates with the river being maintained in tension to generate friction in the joint.

The pivot joints in stays of the kind aforementioned are subject to severe loads and stresses in use, such as arise from the weight of the sash, possibly with double glazing or heavyweight glass, wind loads, twist and warpage due to thermal changes and gradients. Additionally, in most applications the joints are subject to weathering, dirt and other contamination which can lead to wear and corrosion. In practice, problems and failures arising from the foregoing are increased having regard to the limitations on materials suitable for attaining the desired strength, and the need to select materials which are compatible with the stay arms or links, the mounting plates (if any) and the materials of the sash and frame.

Additionally, such stays are designed to fold up and to be contained within the rebate between the sash and the frame when the sash is closed. This means that use may be intermittent, possibly without use for long period. Usually, there is no service or maintenance, and the actual condition of the stay is not readily ascertained until failure, for instance, by breakage of a rivet or pin, and/or undue wear at a pivot joint leading to twisting or bending of one or more of the arms or links.

Objects of this invention include providing an improved pivot joint for a stay which has integral frictional restraint within the joint, which is compact and provides substantial strength, which is wear resistant, and which is designed to prevent the ingress of detritus in the joint.

It is a further object of this invention to provide a pivot joint for a stay which is simple to manufacture to consistent performance requirements.

Another object of this invention is to provide an improved stay incorporating such pivot joint or joints.

Other objectives and advantages of this invention will be described later herein.

According to this invention, in a stay having two relatively movable elements, there is a pivot joint connecting the two elements together for restrained frictional movement, the pivot joint comprising a rivet extending through aligned bores or piercings in each element, a bushing located in a recess in the first element and through which the shank of the rivet extends, the bushing including a counterbore seating the head of the rivet with the head being in bearing engagement with the faces of the bushing counterbore for relative rotation, the bushing further providing an inner bearing surface for engagement with the rivet shank, spacer means disposed between said first and the second elements and through which the shank of the rivet extends, and the rivet extending through the piercing in said second element and located against rotation relative to said second element, the tail of the rivet being clinched to maintain the rivet shank in tension to a degree sufficient to provide frictional resistance in the joint for controlled pivotal movement of said first and second elements.

By this invention a special form of pivot joint is provided in which the rivet is clinched and maintained in-tension to generate the frictional restraint induced by the compression forces applied through the rivet head and tail which act through the abutting surfaces whilst adequate bearing surfaces for pivotal movement and axial and radial loads are provided in the joint.

Preferably, the head of the rivet is flat and circular having a thickness substantially the same depth as the counterbore in the bushing.

The bearing surfaces are the substantial faces of the side and base of the counterbore in the bushing which are engaged by the relatively rotatable underside and side wall of the rivet head, and the inner bearing surface of the bushing engaging the relatively rotatable shank of the rivet.

In prior constructions, the shank of the rivet or the pin and the head thereof has not been engaged by a bushing providing such bearing surfaces which are designed for both axial and radial loads under static and dynamic conditions as arise in service.

Accordingly, the loads and forces to which the pivot joint is subjected in use are transmitted through substantial bearing areas so that high Roads and stresses greater than the known tensile and shear strength of the rivet can be avoided by suitable selection of the surface areas with respect to loads/stresses arising in service. In particular, the radial or bending loads applied to the rivet shank are transmitted through the inner bearing surface of the bushing as well as through the head of the rivet which is in bearing engagement within the counterbore in the bushing.

As the bushing is located in the recess in the first element of the stay, the bushing is confined and the resultant loads are evenly distributed to the first element subject to any absorption by the bushing itself on local deformation or distortion.

The engagement of the underside and the edge of the rivet head and the shank with the bushing also provides proper co-axial bearing support for the rotation of the rivet relative to the bushing without the rivet abutting against the edge of the bore or piercing through said first element. As the rivet is supported for rotation in the bushing counterbore, it is found that the head of the rivet is unlikely to shear despite the axial tensile forces acting thereon to maintain the frictional restraint.

The bushing is seated in the recess in the first element, and it is located therein to prevent relative rotation. The external configuration of the bushing may be square or splined for such location, or it could be keyed into the recess.

However, in the simplest configuration the bushing is of circular section and is restrained against relative movement in the recess of circular shape by a tight interference fit.

The fitting of the bushing into the recess, and the reception of the head of the rivet in the recess in the bushing ensures that dirt, dust or detritus cannot penetrate into the pivot joint under the head of the rivet. Conveniently, to ensure a compact joint, the head of the rivet is flush with the bushing and said first element.

Preferably, the bushing is made of a low friction material which is self-lubricating, such as an acetal resin. The rivet is of aluminium or stainless steel, and the stay arms or links or mounting plates constituting the first or second elements can be of any suitable material, although aluminium or steel is usually desirable for strength. Thus metal to metal contact between the rivet and the first element can be avoided, and, if required, metals which are non-compatible can be employed for the rivet and the first element because they are separated by the bushing. This means that there is little likelihood of the rivet seizing and shearing in service.

Preferably, the first element and the second element are separated by spacer means which is of a low friction material and in the form of a washer. The spacer means provides opposed thrust bearing surfaces against which adjacent surfaces of the first and second elements bear, and. such spacer also prevent detritus entering the pivot joint.

Additionally, the spacer means may provide an additional inner bearing surface for engagement by the shank of the rivet.

The rivet tail may be clinched by any suitable method having regard to the type and material of rivet employed. In order to apply the tension to the rivet shank, compression rivetting is preferred with the bushing being subject to the predetermined rivetting pressure that is transmitted thereto through the rivet head. Thus, the frictional restraint required for the particular stay design and loads likely to be supported thereby can be selected utilising the dynamic and static frictional characteristics of the rivet head and the bushing and the areas of the abutting and load transmitting faces.

The rivet is located against rotation relative to the second element and this can be achieved by providing a piercing in the second element of noncircular shape, for instance a square, into which the tail of the rivet is clinched to secure the rivet in situ against rotation. Alternatively, self-locking means could be disposed under the clinched tail of the rivet, for instance a spurred washer can be used.

Preferably, the underside of the head of the rivet is planar and provides a substantial annular area in engagement with the base of the counterbore in the bushing.

The pivot joint according to this invention can be applied to various types of stays. This invention is deemed to include stays comprising one or more pivot joints as aforementioned.

An exemplary embodiment of a pivot joint according to this invention and a window slay incorporating the invented pivot joint will now be described with reference to the accompanying drawings wherein.

FIGURE 1 is an exploded perspective view of a pivot joint for connecting two element of a stay; and FIGURE 2 is a sectional view of the assembled pivot joint; and FIGURE 3 is a front view of a window stay including such pivot joints.

With reference to Figures 1 and 2 the pivot joint depicted in the drawings comprises a rivet 1, a bushing 2, a spacer washer 3 and a first element 4 connected to a second element 5 for relative movement.

The first element 4 is an arm pivotally connected to the second element 5 which is a mounting plate, and only an end portion of the first and second elements 4, 5 respectively is shown.

The rivet 1 has a cylindrical shank 6 and a squat cylindrical head 7, and it may be made of aluminium, stainless steel or other suitable material. The rivet 1 is located in the bushing 2 which has a counterbore 8 in which the head 7 of the rivet is seated with the shank 6 of the rivet extending through the through bore of the bushing. The bushing 2 is located in a complementary recess 9 adjacent the end of the first element 4 and is a tight interference fit in the recess so that the bushing cannot rotate in the recess.

The end of the first element has a bore 1 0 concentric with the circular recess 9 and the bore 10 is of a diameter greater than the diameter of the shank 6 of the rivet which extends through the bore 10.

The second element 5 is of inverted channelshape and provides lipped flanges 11 extending along each longitudinal edge. The end of the second element 5 has an opening or piercing 12 aligned with the bore 10 and through which the shank 6 of the rivet is also arranged to extend. The piercing 12 is of square shape but can be of other non-circular configuration.

The annular spacer 3 is mounted on the shank 6 of the rivet and is intermediate the adjacent faces of the first and second element 4, 5.

The tail 13 of the rivet is clinched on the underside of the second element 5, the clinched tail is disposed within the channel-shaped recess underside of the element 5. On clinching deformation of the tail of the rivet, the rivet is keyed and located relative to the second element so that the rivet cannot rotate with respect to the second element. Such location is ensured by the use of the non-circular form of the piercing 12 into which some of the material of the tail of the rivet is forced on the clinching operation.

The bushing 2 and the spacer 3 are made of a low friction material such as an acetal resin which has known self-lubricating properties and which is resistant to corrosion. The bushing and/or the washer or other spacer can be a moulding of suitable plastics or machined from extruded section. The first and second elements may be of any suitable material, particularly metal, and aluminum or steel, (especially stainless steel) are preferred. Extruded metal sections can be employed.

On clinching of the rivet, the head of the rivet is pressed into engagement within the counterbore in the bushing, and as the bushing is confined by the recess in the first element no radially outward spread of the bushing can occur. Additionally, as the throughbore of the bushing engages with the rivet shank, radially inward deformation is obviated so that the axial load applied during clinching is sustained to obtain the desired frictional restraint.

As will now be appreciated, the rivet is arranged to rotate relative to the first element and provides the pivot axis. The shank of the rivet is supported by the inner bearing surface of the bushing provided by the throughbore of the bushing. If desired the spacer may also have a central bore which provides an additional bearing surface for engaging the shank. The shank of the rivet is prevented from contacting the edges of the respective bores or piercings 10, 1 2 by the support and centralisation of the rivet through the bushing and the bearing surface(s) engaging therewith.

The rivet is additionally supported andWlocated for rotation relative to the first element through the engagement of the head 7 of the rivet in the counterbore 8 in the bushing 2 which provides bearing surfaces complementary to the head of the rivet.

The axial tensile load applied to the joint is maintained through the shank of the rivet and is transmitted primarily through the engagement of the underside of the rivet head with the base of the counterbore in the bushing.

With reference to Figure 3, a window stay comprises a mounting place 14 for fixing to a frame by suitable fasteners (not shown) extending through holes 1 5 in the plate. There is a second mounting plate 1 6 for fixing to one side of a sash (not shown) by suitable fasteners (not shown) extending through holes 1 7 in the plate. Extending between the mounting plates 14, 1 5 there are two arms 18, 1 9 of which the upper one is shorter.

Each end of each arm is connected to the respective mounting plate by a pivot joint generally referenced 20.

Each pivot 20 is of the construction as just described in detail with reference to Figures 1 and 2. In such previous description the first element 4 corresponds to the arms 18, 19 and the second element 5 corresponds to the mounting plates 14, 1 5. The pivot joints 20 connect the mounting plates and arms for relative pivotal movement. The stay is shown in the 'open' position, and on pivotal movement to close the stay so that the plates 14, 1 5 overlie each other, the arms 18, 1 9 fold upwardly and lie in between the overlying mounting plates.

In known manner, to support a sash for hinged or pivotal movement on a frame two such stays would be provided, one on each of two opposed sides of the sash and frame. Each folded stay is received within the rebate of the frame on closure of the sash. The frictional restraint in each pivot joint is arranged to support the sash in the range of open positions.

The radial loads of the pivot joints arising in use, especially during pivotting movement are transmitted through the respective bearing faces which are concentric to the revelant axis. In each joint, the bearing faces are the side walls of the rivet head engaging the side of the bushing counterbore and the inner bearing surface of the throughbore of the bushing, as well as the possible additional provision of the bearing -surface of the spacer.

The pretensile axial load applied to the rivet to ensure the frictional restraint can be calculated in accordance with the equivalent loads that can be determined for a particular design of stay and application.

In the joints, the head of the rivet is in close proximity with the bushing so that dirt and detritus cannot penetrate the pivot to cause wear and other undesirable effects. The rivet shank is engaged by the inner bearing surface of the bushing which further protects the shank, and the thickness or shape of the spacer can be modified as desired.

It is envisaged that the spacer could be located against movement relative to the stay elements.

Such location could be provided by providing an abutment engageable by the spacer, or having an irregular shaped spacer seated in a recess, or engaging abutments, such as small lugs.

The clinched tail of the rivet can stand proud of the stay element in some constructions of stay without interfering with folding movement.

However, it will be appreciated that the stay element can be bent, kinked, cranked or joggled to provide clearance for folding and pivotal movement. Furthermore, the element could be formed with a recess such as a depression, counterbore or countersunk aligned with the piercing so that the clinched tail is sunk therein.

As will also be appreciated, rivets and moulded or formed plastics can be made to tight tolerances by mass manufacturing techniques. The use of the bushing and optional spacer as an additional bearing permits accurate fitting of the bearing for the rivet to form the pivot joint. The byres or piercings in the stay elements do not have to be exact fit or tolerance as all that is required is the clearance for the shank of the rivet to pass therethrough. Thus, in the manufacture of stays using the invented pivot joint, certain tight limits and precision operation such as have been required previously can be avoided to reduce manufacturing costs.

Accordingly, the pivot joint according to this invention is simple but provides adequate bearing surfaces for pivotal movement and for axial and radial loads in service whilst also protecting the shank of the rivet from undue wear and possible corrosion.

The pivot of this invention can be applied to a wide variety of stays besides that previously described. In other forms of stays, there are intermediate links or arms pivotally connected together, and one or more of the pivots can be constructed in accordance with this invention. It will therefore be understood that the terms "first element" and "second element" are not restricted to meaning an arm or mounting plate but are intended to cover an arm, a link, a mounting plate, a bracket or cross-member in any combination.

Claims (10)

1 In a stay having two relatively movable elements, there is a pivot joint connecting the two elements together for restrained frictional movement, the pivot joint comprising a rivet extending through aligned bores or piercings in each element, a bushing located in a recess in the first element and through which the shank of the rivet extends, the bushing including a counter bore seating the head of the rivet with the head being in bearing engagement with the faces of the bushing counterbore for relative rotation, the bushing further providing an inner bearing surface for engagement with the rivet shank, spacer means disposed between said first and the second elements and through which the shank of the rivet extends, and the rivet extending through the piercing in said second element and located against rotation relative to said second element, the tail of the rivet being clinched to maintain the rivet shank in tension to a degree sufficient to provide frictional resistance in the joint for controlled pivotal movement of said first and second elements.

2. A stay according to claim 1 wherein the head of the rivet is flat and circular having a thickness substantially the same depth as the counterbore in the bushing.

3. A stay according to claim 1 or claim 2 wherein the bushing is seated in the recess in the first element, and it is located therein to prevent relative rotation.

4. A stay according to claim 3 wherein the bushing is of circular section and is restrained against relative movement in the recess of circular shape by a tight interference fit.

5. A stay according to any one of the preceding claims wherein the bushing is made of a low friction material which is self-lubricating, such as an acetal resin.

6. A stay according to any one of the preceding claims wherein the rivet is of aluminium or stainless steel.

7. A stay according to any one of the preceding claims wherein the first element and the second element are separated by spacer means which is of a low friction material and in the form of a washer.

8. A stay according to any one of the preceding claims wherein the said stay elements comprise - an arm and a mounting plate and the stay includes a second arm and a second mounting plate, the two arms being of different length and one end of each arm being connected to a respective one of the mounting plates by a respective pivot joint.

9. A stay according to claim 8 wherein the tail of the rivet of each pivot joint is located against rotation by clinching the tail into a non-circular recess formed in the associated mounting plate.

10. A pivot joint for a window stay substantiallV as hereinbefore described with reference to Figures 1 and 2 of the accompanying drawings.

1 A window stay according to claim 10 and substantially as hereinbefore described with reference to Figure 3 of the accompanying drawings.