EP0948697A1

EP0948697A1 - Frame structures

Info

Publication number: EP0948697A1
Application number: EP97911362A
Authority: EP
Inventors: Graham Baker; John Edgar Credland; Michael Hampe; John Kenneth Taylor
Original assignee: Voestalpine Metsec PLC
Current assignee: Voestalpine Metsec PLC
Priority date: 1996-11-09
Filing date: 1997-11-07
Publication date: 1999-10-13
Anticipated expiration: 2017-11-07
Also published as: DE69707015T2; EP0948697B1; WO1998021435A1; AU4877397A; DE69707015D1; ATE206182T1

Abstract

An elongate structural element for a window, door, or like structure, comprising a hollow, elongate UPVC or similar plastics structural member (11), and an elongate metal reinforcing member (12) housed within the structural member, said reinforcing member having at least one protrusion so shaped as to engage the structural member to take up clearance, at least in one plane, between the reinforcing member and the interior of the structural member and so to retain the reinforcing member in position longitudinally within the structural member, said protrusion being arranged to provide substantially the same resistance to movement of the reinforcing member relative to the structural member in either longitudinal direction.

Description

FRAME STRUCTURES

This invention relates to a metal reinforced, plastics, structural element for a window, door, or like frame.

Window and door frames are now commonly an assembly of UPVC or other plastics structural elements in the form of hollow, rectangular cross- section, elongate box section, plastics structural members reinforced internally by mild steel reinforcing members in the form of correspondingly elongate mild steel sections which may be of correspondingly rectangular box cross-section, or other cross sectional shapes including L-sections, C-sections and closed sections having one or more curved sides.

It is necessary to provide a clearance between the outer surface of a reinforcing member and the inner surface of the corresponding structural member in order to permit the reinforcing member easily to be introduced into the structural member. However, in order to prevent longitudinal movement of the reinforcing member within the structural member during handling of the reinforced elements, for example when positioning two or more structural elements prior to joining them to produce a 90° or other corner, it is customary to secure the reinforcing member in position longitudinally within the structural member by means of a plurality of self tapping screws introduced through the wall of the structural member to engage the reinforcing member. The use of screws is both expensive, and labour intensive, and it has been proposed to avoid the use of screws by providing the reinforcing member with a plurality of longitudinally spaced, integral, barbs which take up the clearance between the reinforcing member and the structural member thus holding the reinforcing member in position. Unfortunately it is found that such barbs can damage the interior of the structural member by scoring its surface, and that such barbs, while permitting the reinforcing member to be moved into the structural member in one direction prevent return movement of the structural member and thus hinder the accurate positioning of the reinforcing member within the structural member.

It is an object of the present invention to provide a metal reinforced structural element for a window, door, or like frame wherein the aforementioned disadvantages are obviated or minimised.

In accordance with the present invention there is provided an elongate structural element for a window, door, or like structure, comprising a hollow, elongate UPVC or similar plastics structural member, and, an elongate metal reinforcing member housed within the structural member, said reinforcing member having at least one protrusion so shaped as to engage the structural member to take up clearance, at least in one plane, between the reinforcing member and the interior of the structural member and so to retain the reinforcing member in position longitudinally within the structural member with substantially the same resistance to movement relative to the structural member in either longitudinal direction.

Preferably the reinforcing member has at least one protrusion on each of two adjacent faces so as to take up clearances between the reinforcing member and the structural member in two mutually perpendicular planes. Desirably said reinforcing member has first and second generally parallel planar sides and a third generally planar side transverse to said first and second sides, each of said first, second and third sides having at least one respective protrusion.

Preferably the or each side of said reinforcing member has a plurality of protrusions spaced apart along its length.

Desirably the or each protrusion is integral with the reinforcing member.

Conveniently said protrusions are each in the form of a bowed strip of material connected at both ends to the remainder of the member, and defined between parallel slits in the material of the member.

Preferably said strips, and the parallel slits defining the strips, extend longitudinally of the reinforcing member.

Desirably said protrusions are arranged to be resiliently movable towards and away from the centre-line of the member.

Alternatively the protrusions are substantially rigid.

Preferably said protrusions present substantially smooth surfaces to said structural member.

Alternatively said protrusions present edges to said structural member which edges bite into the structural member. Alternatively each said protrusion is formed separately from and secured to the reinforcing member.

Conveniently the or each protrusion is a plastics component.

Preferably the or each plastics protrusion is retained in place on the reinforcing member by the resilience of a region of the protrusion.

Desirably the or each protrusion is engaged as a snap-fit with the reinforcing member.

Preferably the or each plastics protrusion includes a resilient tongue which bears against the structural member.

Preferably the reinforcing member is formed from mild steel strip by a cold rolling technique.

The invention further resides in a metal reinforcing member for use in a UPVC or other plastics structural member.

One example of the invention is illustrated in the accompanying drawings wherein:-

Figure 1 is a transverse cross-sectional view of a UPVC structural element of a window frame,

Figure 2 is a diagrammatic perspective view of the mild steel reinforcing member illustrated in section in Figure 1 , Figures 3A and 3B are scrap sections of part of the structural element of Figure 1 , illustrating the operation of the protrusion,

Figures 4, 5 and 6 illustrate alternative sections for use as reinforcing members,

Figures 7, 8 and 9 illustrate a first alternative protrusion form,

Figures 10,1 1 and 12 illustrate a second alternative protrusion form,

Figure 1 3 illustrates in cross-section a range of further protrusion forms,

Figure 14 illustrates in plan view still further protrusion forms,

Figure 15 is a diagrammatic perspective view of a mild steel reinforcing member having a still further protrusion form,

Figures 16 and 1 7 are scrap sectional views of the reinforcing member of Figure 15 in conjunction with a corresponding plastics structural member,

Figure 18 is a side view of a modification of the reinforcing member of Figure 15,

Figure 19 is a scrap plan view of the Figure 18 arrangement,

Figure 20 is a scrap sectional view of a further alternative protrusion arrangement, Figure 21 is a scrap sectional view of a yet further alternative protrusion arrangement,

Figure 22 is a sectional view similar to Figure 21 illustrating how the reinforcing member is located within a plastics box section structural member,

Figures 23, 24, 25, and 26 illustrate modifications of the arrangement of Figure 22,

Figure 27 is a sectional view illustrating the shaping of the reinforcing member in Figure 26,

Figure 28 is a view similar to Figure 27 of an alternative,

Figures 29 and 30 are sectional views illustrating modifications to the arrangement shown in Figure 26,

Figure 31 illustrates a further alternative arrangement,

Figures 32 and 33 illustrate a modification of the arrangement of Figure 29,

Figure 34 illustrates a modification of the arrangement of Figure 33,

Figures 35 and 35 illustrate a further alternative arrangement,

Figure 37 illustrates a further variant of the Figure 29 arrangement, Figure 38 illustrates a still further alternative,

Figure 39 illustrates a modification of Figure 24,

Figure 40 is a sectional view of a further alternative,

Figure 41 is a plan view of Figure 40,

Figure 42 is a view similar to Figure 40 illustrating the arrangement in use, and,

Figures 43 to 45 are views similar to Figures 40 to 42 respectively of a modification.

Referring to the drawings, the structural element shown in Figure 1 includes a structural member 1 1 in the form of an elongate, tubular, UPVC extrusion of square cross-section reinforced internally by a metal, conveniently mild steel, aluminium or aluminium alloy, reinforcing member 12. The structural element is intended to be connected to a plurality of other structural elements of similar form each cut to an appropriate length and end mitre, to form a door, window or like frame, either the fixed frame with which the door or window moving member cooperates or a frame part of the moving member itself.

Figure 1 illustrates a reinforcing member 12 which is formed from mild steel strip by a cold rolling operation, to define an elongate member of square cross-section, having a longitudinally extending gap in one face of the square cross-section where the two opposite edges of the strip from which the member 12 is formed do not butt against one another. It will be recognised that if desired a closed section could be produced by ensuring that the cold rolling operation butts the opposite marginal edges of the strip against one another.

It can be seen that the reinforcing member 12 is of smaller dimensions than the interior of the structural member 1 1 , and in order to take up the clearance between the reinforcing member 12 and the interior of the structural member 1 1 , in both mutually perpendicular planes transverse to the length of the members, the reinforcing member 12 is formed with a plurality of longitudinally extending equi-distantly spaced protrusions 13. Thus protrusions are formed in at least two and preferably three adjacent sides of the reinforcing member 12, and as is apparent from Figure 2 the protrusions in one side are arranged to be longitudinally intermediate the protrusions in the adjacent side, this arrangement being desirable but not essential. Figure 1 illustrates protrusions 13 formed in the base side of the member 12 opposite the side in which the strip edges are present, and in the two opposite parallel sides, so as to be present in three of the four sides of the member 12. The protrusions in the opposite sides of the member are aligned transverse to the length of the member.

Each protrusion 13 is formed during the cold rolling of the member 12 and each is defined by cutting the strip material forming the member 12 along two parallel longitudinal lines and then stretching the material to bow outwardly. Thus each protrusion is in effect formed by a "crack and lance" operation producing a strip between the parallel "crack" lines which is then "lanced" to bow it outwardly between its captive ends during the cold-rolling operation. The curvature of the protrusions 13 is such that in their rest position they project above the surface of their respective wall of the member 12 by an amount greater than the clearance between the outer surface of the reinforcing member 12 and the inner surface of the structural member 1 1. Thus as the member 12 is introduced into the member 1 1 the protrusions bear against the inner surface of the member 1 1 to take up the clearance between the members 1 1 , 12.

The protrusions 13 may deform or indent the material of the member 1 1 and/or may flex against their inherent resilience towards the centre line of the member 12 as illustrated in Figures 3A and 3B. It will be recognised that where protrusions are provided only on two adjacent faces of the member 12 then the protrusions 13 bear against the inner surface of the member 1 1 and thus urge the opposite faces of the member 12 into facial contact with the interior of the member 1 1.

The coaction of protrusions 13 with the inner surface of the member 1 1 generates sufficient friction to hold the member 12 longitudinally in position within the member 1 1 during normal handling of the structural member 1 1.

The resistance to longitudinal movement of the member 12 in the member 1 1 is substantially the same in both longitudinal directions such that should re-positioning of the reinforcing member 12 become necessary then the reinforcing member can be moved longitudinally in either direction relative to the member 1 1 by overcoming the friction generated by the protrusions 13. It will noted that the protrusions 13 do not bite into the inner surface of the member 1 1 since their curvature is such that they make surface rather than edge contact with the member 1 1 in relation to longitudinal movement. As the primary objective of the protrusions 13 is to produce a fit resisting longitudinal movement of the member 12 within the member 1 1 , it is to be understood that if desired only one wall of the member 12 need be provided with protrusions 13. However in preferred embodiments, protrusions 13 will be provided in three adjacent walls of the member 12 as illustrated in Figure 1.

In a modification, during manufacture of the member 12 one longitudinal end of each protrusion 13 is severed from the remainder of the member 12 to convert each protrusion into an elongate curved tongue and so enhance its flexibility in a direction towards and away from the centre line of the member 12.

It should be recognised that the invention is not limited to reinforcing members of rectangular box-like cross-section and can be applied with a wide variety of sectional shapes of open or closed form. Figure 4 shows a simple L-section with which the invention could be employed, protrusions being provided on one or both limbs of the section. Figure 5 shows a lipped L-section and Figure 6 shows a complex closed section having opposite curved walls, the provision of protrusions being restricted to the plane walls. Other sections capable of utilizing the invention include simple and lipped rectangular channel sections.

A wide variety of protrusion shapes is possible including simple domed or flat topped projections of circular section, and complex projections such as raised lettering or other indicia for example designating the origin, manufacturer and/or specification of the member. Figures 7, 8 and 9 illustrate a further possible form of protrusion designed to have a flexibility between that of the Figure 1 form and the tongue mentioned above. Figure 7 shows the rest condition and Figure 8 shows the deflection of the protrusion 13 as the member 12 is inserted into the member 1 1. Figure 9 illustrates that material may be cut away on either side of the protrusion to provide a clearance to give unimpeded flexure in use. The protrusion of Figures 7, 8 and 9 is a strip sinuous along its length but in the alternative shown in Figures 10, 1 1 and 12 the protrusion is a domed formation 14 intermediate the ends of a downwardly bowed strip. The strips are integral with the member 12 at their ends and their length is chosen in conjunction with the gauge of the metal to give the resilience necessary to provide the required grip.

The bowed strips or tongues 13 could, if desired, extend transverse to rather than parallel to, the length of the member 12 thus defining edges which would resist more strongly longitudinal movement of the member 12.

Figure 13 shows, in views A - H, a selection of protrusion longitudinal cross-sections, all of which are suitable for longitudinal adjustment in the member 1 1 in either direction. The forms shown in Figure 13 could be produced as resilient strips between two generally parallel cut lines in the material (as in Figures 9 and 12) or could be in the form of projections integral with the parent material around their whole periphery.

Figure 14 shows, in plan views A-F, a further selection of protrusion shapes some of which could embody a cross-section shown in Figure 13, it being understood that neither Figure 13 nor Figure 14 is an exhaustive list of shapes. In addition it is to be recognised that the or each side of a reinforcing member may have a single elongate protrusion defined, for example, by bowing the wall outwardly except adjacent the ends of the member, the ends thus providing a guide or lead to facilitate insertion of the member 12 into the member 1 1. The bowing could be provided by deformation of the walls or by inclination of opposite walls outwardly rather than parallel to one another.

In a modification the member 12 embraces an internal rib of the member

1 1 and thus the protrusions are inwardly directed.

In a further modification the protrusions are broken or otherwise open at their outermost points to provide one or more edges which bite into the material of the member 1 1 to enhance the engagement of the member

12 in the member 1 1.

Reference is made herein to the member 12 being cold rolled, but it is to be understood that it could be a hot rolled member. Moreover welded profiles such a seam welded box section could be used if desired.

Referring now to Figures 15 to 19 of the drawings, the mild steel reinforcing member 12 is intended to be used in exactly the same manner as described above and the same variants thereof are possible. It can be seen that the protrusion 13 is in the form of an outwardly inclined tongue integral with the material of the member 12 at its root. Adjacent its free end the tongue is turned downwardly so that the outermost surface of the tongue is a curved surface 13a which does not bite into the material of the member 1 1 in use. Closely adjacent the root 13b of the tongue 13 the material of the member 12 is cut (or cracked) to define a second, oppositely extending tongue 23. The tongue 23 extends from the root 13b of the tongue 13, and thus in effect the tongues 13 and 23 share a common root region at which they are both integral with the material of the member 12. The tongue 23 is inclined downwardly, and thus lies within the hollow interior of the member 12.

The tongue 23 serves no function in retaining the member 12 within an extrusion 1 1 unless the extrusion 1 1 has an internal rib around which the reinforcing member 12 engages. However, the formation of the tongue 23 simultaneously with the formation of the tongue 13 determines the nature of the root 13b and thus the flexure characteristics of the tongue 13 relative to the remainder of the member 12. Naturally, the length of the root region of the tongue 13, in the direction of the length of the tongue 13 will, up to a calculable maximum length, affect the flexing characteristics of the tongue 13 since some of the flexure of the tongue 13 occurs within the root region 13h where it is integral with the remainder of the member 12, some flexure occurring of course along the length of the tongue 13. It is believed that this characteristic is further modified by the presence of the tongue 23, since the formation of the tongue 23 may alter the characteristics of the root region 13h, by virtue of the work done on this region when the tongue 23 is created, and also in that the presence of the tongue 23 may render the region 13b more rigid.

It follows therefore that the flexure characteristic of the tongue 13 can be adjusted to suit particular applications by adjusting the longitudinal spacing between the tongues 13 and 23 thereby adjusting the length of the root region 13b- It is possible also that the flexure characteristics of the tongue 13 can be 'fine-tuned' by adjusting the amount through which the tongue 23 is deflected during its production. However, insufficient experimentation has been conducted in relation to this aspect to be certain.

It will be recognised that the presence of the tongue 23 may not be essential in that a significant degree of control over the flexure characteristics of the tongue 13 can be achieved by varying the length of the root region 13b. Figures 18 and 19 illustrate a modification in which such control is achieved without a tongue 23, the length of the root region 13b within which some of the flexure of the tongue 13 occurs, being controlled by the positioning of an aperture 24 relative to the end of the parallel cuts which define the sides of the tongue 13.

A rectangular aperture 24 is illustrated in Figure 19, and its positioning in relation to the tongue 13 determines the amount of material in the root region 13b. It will be understood that a circular aperture could be used in place of the rectangular aperture 24 as could apertures of other shapes, or a rectangular aperture of width less than the width of the tongue 13, and actually extending into the material of the tongue so that the root region 13b is in effect two separate regions at opposites respectively of the tongue (as illustrated in broken lines in Figure 19). A further possibility is that the width of the tongue 13 could be reduced adjacent its root by extending inwardly from one or both sides the cut or crack which forms the tongue, so as to produce a neck of narrower width joining the tongue to the remainder of the member 12. The objective of the invention is to take up tolerances between the member 12 and the interior of the member 1 1 without damaging the interior of the member 1 1. Thus the or each protrusion could if desired be provided as, or could carry, a synthetic resin button or cover element which provides the surface which engages the interior of the extrusion.

Figures 20 and 21 show two further alternatives in which a synthetic resin element 31 takes the place of the integral protrusion from the member 1 1. In Figure 20 the element is a rounded button having a snap-fit retainer 32 locking the element in an aperture in the member 12. The button may be resiliently deformable if desired, to take up tolerances in use.

The Figure 21 arrangement uses a synthetic resin device again secured as a snap-fit in an aperture in the member 12 but incorporating a flexible resilient tongue 33. Other forms of protrusion, moulded or otherwise formed from suitable synthetic resin material can be used, as can alternative securing arrangements such as hot staking or rivetting in which a region of the element is melted to form a securing to the member 12.

Figures 22 to 45 show further variants of the use of a synthetic resin element in place of the integral protrusion from the reinforcing member 12 disclosed in Figures 1 to 19 above. In Figure 22 the flexible resilient tongue 33 shown in Figure 21 is shown attached to the mild steel, cold- rolled, section constituting the reinforcing member 12, by means of a pair of integral resilient barbed prongs 34 which pass through a circular, or other appropriately shaped aperture in a wall of the member 12, the barbs engaging the undersurface of the wall of the member 12 to lock the tongue 33 in place on the exterior of the member 12. In use, when the member 12 is introduced into an extruded plastics structural member 1 1 the flexing tongue 33 takes up clearance between the interior of the member 1 1 and the exterior of the member 12, and as noted above there may be a plurality of tongues 33 spaced along the length of the member 12, and positioned on one, two, or three walls of the rectangular section member 12.

Figure 23 illustrates a modification in which the outwardly inclined tongue 33 is replaced either by a pair of downwardly inclined tongues 35 which bear at their free ends against the outer surface of the member 12, or alternatively by a resilient domed member having the prongs 34 extending downwardly from its mid-point and its periphery engaging the outer surface of the member 12. It will be recognised that flexure of the arms 35, or the wall of the dome, reduces the height of the protrusion above the outer surface of the member 12, and causes it to bear against the inner surface of the member 1 1 in use, thereby taking up the clearance within a predetermined range of clearances.

Figure 24 illustrates that the arms, or the dome, may have a double curvature so as to engage the outer surface of the member 12 both at the mid-point, where the prongs 34 protrude, and the free end (or periphery in the case of a dome). In this instance flexure to take up clearances does not move the prongs 34 relative to the member 12, the arms or the dome flexing relative to the member 12.

In Figure 25 the arms or dome of Figures 23 and 24 are replaced by a planar component 36 having the prongs 34 projecting integrally downwardly therefrom and a plurality of posts or fins 37 projecting upwardly therefrom. The intention is that as the member 12 is introduced into the member 1 1 then the posts or fins 37 will be crushed towards the member 12, or alternatively will be deflected, flexing along their length, resiliently to take up the clearance between the member 12 and the member 1 1. It will be recognised that where the planar element 36 carries fins, then the fins will normally be disposed with their planes at right angles to the length of the members 11, 12. However, if desired other orientations of the fins relative to the members 1 1 , 12 could be utilised, and, for example the plane of the fins 37 could be parallel to the lengths of the members 1 1 and 12.

Figure 26 illustrates an alternative means for securing the protrusion to the member 12. For convenience Figure 26 illustrates a flexible tongue 33 as the chosen protrusion form, although it is to be understood that any of the other protrusion forms could be utilised if desired. The fixing of the protrusion to the member 12 is achieved by displacing a region 12a of the wall of the member 12 downwardly out of the plane of the remainder of the member 12 to leave a cut edge 12b with an aperture below it. The root of the protrusion is moulded with a U-shaped section 38 one limb of which lies in contact with the outer surface of the member 12 and has the protrusion extending therefrom, and the other limb of which passes through the aperture in the member 12 and engages the inner surface of the member 12. The based wall of the U- section 38 engages the cut edge 12b of the member 12. The frictional grip of the U-shaped section 38 on the member 12 resists withdrawal of the section 38 from the member 12.

Figure 27 illustrates that the region 12a and the cut edge 12b are provided by forming the wall of the member 12 with a transverse slit and stretching the material downwardly at one side of the slit to produce the region 12a. Figure 28 illustrates an alternative in which the region 12a and the cut edge 12b are defined by a U-shaped cut in the material of the member 12, the tongue within the U-shape being deformed downwardly to produce the region 12a.

Figure 29 illustrates that the U-shape section 38 of the moulded plastics protrusion may have a shoulder 39 which engages the free end of the region 12a to lock the section 38 in place. The shoulder 39 is formed with an inclined wall which facilitates a deflection of the material of the sections 38 and/or the free end of the region 12a of the member 12 during fitting of the protrusion as such that as the shoulder 39 clears the free end of the region 12a a snap-fit engagement of the section 38 on the member 12 is achieved.

Figure 30 illustrates a minor modification of the arrangement illustrated in Figure 29 in that the shoulder 39 is defined by the end surface of the section 38 the length of the portion 12a being shortened so that there is a gap between the free end of the region 12a and the cut edge 12b equal to the thickness of the base wall of the U-section 38 of the protrusion.

Figure 31 illustrates a moulded protrusion 41 secured to the member 12 in the same manner as illustrated in Figure 30, but in the form of a bowed tongue, rather than an upwardly inclined tongue. It can be seen in Figure 31 that the free end of the tongue 41 bears against the outer surface of the member 12, such that the curved, raised portion intermediate the ends of the tongue 41 is engaged by the inner surface of the member 1 1 in use. Figures 32 and 33 illustrate a modification of the arrangement shown in Figure 29 which modification can also be applied to the arrangements of Figures 26, 30 and 31. In each of those cases it can be seen that the U- shaped section 38 of the protrusion is shaped to fit a particular gauge (thickness) of the metal defining the member 12. The modification in Figures 32 and 33 permits a single moulding to be used with a range of material gauges, and thus obviates the necessity to provide separate protrusion mouldings for different gauges of material. The dimension "h" illustrated in Figure 32 is chosen to be approximately 0.5 mm bigger than the maximum thickness of material to be used for the member 12. However, the natural rest position of the lower limb of the U-shaped section 38 is such that the section 38 must be flexed to introduce even the thinness gauge of material between the limbs of the section 38. Thus the whole range of material thicknesses can be gripped. The protrusion of Figures 32 and 33 is shown to incorporate the shoulder 39 as in the arrangement described above with reference to Figure 29. However, it is to be understood that a similar arrangement without a shoulder 39, and equivalent to Figure 26 above could be provided, as could an arrangement of the kind illustrated in Figures 30 and 31 where an end surface of the section 38 defines the shoulder.

It will be recognised that the fixing arrangement using a "universal" U- shaped section 38 as illustrated in Figures 32 and 33 can be utilized with a wide variety of protrusion forms, not simply those making use of a tongue 33.

Figure 34 shows an alternative "universal" arrangement in which the upper limb of the U-section 38 defines the region of the protrusion which engages the inner surface of the member 1 1 in use. Thus at the base end of the U-section the clearance between the upper and lower limbs exceeds the sum of the maximum clearance anticipated between the members 1 1 and 12 and the maximum gauge of material of the member 12. The outer surface of the upper limb of the section 38 will thus engage the interior of the member 1 1 , and as appropriate the base region of the section 38 will be flexed laterally thus reducing the height of the protrusion to match the clearance between the member 12 and the inner surface of the member 1 1.

Figures 35 and 36 illustrate a further alternative arrangement in which the protrusion is in the form of a curved strip 43 having an integral stepped foot portion 44 at each end. The member 12 is formed with a region 12a displaced downwardly between a pair of parallel cuts in the material 12. The spacing "W" of the cuts is less than the spacing "L" between the steps of the feet 44 of the protrusion 43 in its rest configuration. Thus in order to assemble the protrusion 43 to the member 12, the protrusion is flexed about its midpoint to increase its curvature and decrease its overall length thus permitting the two feet 44 to be introduced beneath the plane of the member 12 through the cuts defining the region 12a. The steps of the feet 44 abut the cut edges of the member 12 while the lower faces of the feet 44 seat on the portion 12a- The inherent resilience of the protrusion 43 attempting to restore it to its length "L" resists disengagement of the protrusion 43 from the member 12, and the resilience of the material from which the protrusion 43 is moulded, is such that the bridge like upstanding portion of the protrusion 43 can be flexed downwardly to accommodate tolerances in the clearance between the members 1 1 and 12. It will be recognised that the protrusion 43 of Figures 35 and 36 can be arranged transverse to the length of the member 12, or aligned with the length of the member 12, and can, if desired, be utilized with a member 12 in which the portion 12a is simply depressed downwardly between a pair of parallel cuts, or forms a downwardly depressed tongue by being defined by a U-shaped cut as illustrated in Figure 28.

Turning now the arrangement illustrated in Figure 37 it can be seen that it is a variant of the arrangement illustrated in Figure 29, differing therefrom in the provision of a second, oppositely directed, flexible tongue 33a. A similar additional tongue can be applied to the arrangements of Figure 26, Figure 30 and Figure 31 if desired, in order to increase the area of contact between the protrusion and the member 1 1 in use.

Figure 38 illustrates the use of a much thicker section of material for the protrusion, with the objective of applying a greater resilient loading to the member 1 1 to increase the grip thereon. Thus the protrusion in Figure 38 has a curved tongue 45 similar to the tongue 33 or 33a, but of substantial thickness and therefore greater rigidity. The anchorage of the protrusion in Figure 38 to the member 12 differs in that the protrusion includes an integral foot portion 46 which is inserted through the aperture defined between the major portion of the member 12 and the region 12a, the foot portion 46 having a first shoulder 47 engaging the cut edge 12b of the member 12 to limit insertion of the foot portion, and a second shoulder 48 which snaps into engagement behind the free edge of the portion 12a of the member 12 to resist withdrawal of the foot portion 46. The foot portion 46 seats on the under surface of the member 12 and the top surface of the region 12a to accept loads imposed on the tongue 45 when it is flexed by engagement with the inner surface of the member 1 1 in use.

It will be recognised that the form of anchorage illustrated in Figure 38 can be used with other forms of protrusion, not necessarily those making use of curved tongues such as the tongue 45.

Figure 39 is in effect a modification of the arrangement illustrated in Figure 24 in which the downturned end regions of the arms 35 are omitted, and the arms 35 are thickened to increase their rigidity. As illustrated the protrusion can be housed in a recessed region 12a of the member 12, the depth of the recess accommodating the extra thickness of the arms 35 so that the height of the arms 35 above the outer surface of the member 12 is not changed by comparison with the arrangement of Figure 24. Alternatively however the profile of the arms 35 could be lowered such that the protrusion could be arranged, as illustrated in Figure 24, on a planar region of the member 12.

It will be recognised that the synthetic resin material from which the protrusion is moulded, or otherwise formed, is not of crucial importance, provided it exhibits the necessary resilience. However, a convenient material is an injection mouldable Acetal copolymer which may, if desired, be reinforced with glass fibres. The various protrusion forms can be secured to the member 12 by other arrangements, for example hot staking or riveting.

As described above one or more walls of the metal reinforcing member 12 may be cut, in the form of a U-shape, to define a flexible integral tongue 13, and the end region of the tongue 13 may carry a synthetic resin button or cover element which provides the surface which engages the interior of the plastics member 1 1. Such an arrangement is illustrated in Figures 40 to 42 where it can be seen that the wall of the cold rolled section 12 is cut or cracked in a rectangular U-shape to define a tongue 13 integral with the remainder of the wall of the member 12 at a root end. The tongue 13 can thus be flexed out of the plane of the remainder of the wall 12 and, as illustrated in Figures 40 to 42, the tongue carries a synthetic resin button 51 which has a domed head engageable with the interior of the plastics extruded member 1 1. The height of the head of the button 51 above the plane of the member 12 is greater than the clearance between the member 12 and the member 1 1 and thus the tongue 13 is flexed downwardly against its own inherent resilience by engagement of the button 51 with the interior of the member 1 1. The button thus bears against the interior of the member 1 1 frictionally to resist movement of the member 12 within the member 1 1.

The button 51 can be a simple press-fit in an aperture punched in the tongue 13, or alternatively can be a snap-fit in any convenient manner.

Figures 43, 44 and 45 illustrate a modification of the arrangement shown in Figures 40, 41 and 42, where the material of the member 12 is too thick for the tongue 13 to be readily flexible. Accordingly, at its root 13b the tongue is scored or otherwise weakened along a line transverse to the length of the tongue 13 so as to permit the tongue 13 to flex downwardly as the member 12 is introduced into the member 1 1. It will be understood that the notch 13£ which weakens the root 13b of the tongue 13 can be provided in a number of different ways. Conveniently however it will be formed simultaneously with the cut or crack which defines the tongue within the wall of the member 12.

Claims

1 . An elongate structural element for a window, door, or like structure, comprising a hollow, elongate UPVC or similar plastics structural member (1 1 ), and, an elongate metal reinforcing member (12) housed within the structural member, said reinforcing member having at least one protrusion so shaped as to engage the structural member to take up clearance, at least in one plane, between the reinforcing member and the interior of the structural member and so to retain the reinforcing member in position longitudinally within the structural member, the element being characterised in that said protrusion is arranged to provide substantially the same resistance to movement of the reinforcing member relative to the structural member in either longitudinal direction.

2. An elongate structural element as claimed in Claim 1 characterised in that the reinforcing member has at least one protrusion on each of two adjacent faces so as to take up clearances between the reinforcing member and the structural member in two mutually perpendicular planes.

3. An elongate structural element as claimed in Claim 1 characterised in that said reinforcing member has first and second ^• generally parallel planar sides and a third generally planar side transverse to said first and second sides, each of said first, second and third sides having at least one respective protrusion.

4. An elongate structural element as claimed in any one of Claims 1 to 3, characterised in that the or each side of said reinforcing member has a plurality of protrusions spaced apart along its length.

5. An elongate structural element as claimed in any one of Claims 1 to 4, characterised in that the or each protrusion is integral with the reinforcing member.

6. An elongate structural element as claimed in Claim 5, characterised in that said protrusions are each in the form of a bowed strip of material connected at both ends to the remainder of the member, and defined between parallel slits in the material of the member.

7. An elongate structural element as claimed in Claim 6, characterised in that said strips, and the parallel slits defining the strips, extend longitudinally of the reinforcing member.

8. An elongate structural element as claimed in any one of the preceding Claims, characterised in that said protrusions are arranged to be resiliently movable towards and away from the centre-line of the member.

9. An elongate structural element as claimed in any one of Claims 1 to 7, characterised in that the protrusions are substantially rigid.

10. An elongate structural element as claimed in any one of the preceding Claims, characterised in that said protrusions present substantially smooth surfaces to said structural member.

1 1. An elongate structural element as claimed in any one of Claims 1 to 9, characterised in that said protrusions present edges to said structural member which edges bite into the structural member.

12. An elongate structural element as claimed in any one of Claims 1 to 4, characterised in that each said protrusion is formed separately from and secured to the reinforcing member.

13. An elongate structural element as claimed in Claim 12, characterised in that the or each protrusion is a plastics component.

14. An elongate structural element as claimed in Claim 12 or Claim 13, characterised in that the or each protrusion is retained in place on the reinforcing member by the resilience of a region of the protrusion.

15. An elongate structural element as claimed in Claim 12 or Claim 13, characterised in that the or each protrusion is engaged as a snap-fit with the reinforcing member.

16. An elongate structural element as claimed in any one of Claims 12 to 15, characterised in that the or each protrusion includes a resilient tongue which bears against the structural member.

1 7. An elongate structural element as claimed in any one of the preceding Claims, characterised in that the reinforcing member is formed from mild steel strip by a cold rolling technique.

18. A metal reinforcing member for use in a UPVC or other plastics structural element as claimed in any one of the preceding Claims..