Technical Field.

This invention is concerned with joint forming, and, more particularly, with the forming of joints for corners of frames such as, for example, window or door frames, and frames including such joints. Background Art.

In the forming of joints it is known to connect two frame members together to provide a corner in which (a) each of the frame members has an end face inclined to the lengthwise direction of the respective frame member and is provided with cavities extending into each frame member through said inclined end face at localities such that, when the frame members are assembled to form a joint with said inclined end faces abutting, corresponding cavities in the frame members communicate, (b) each communicating pair of cavities has assembled therein a reinforcing member extending frd one cavity of the pair into the other, and (c) settable plastics material is injected into each communicating pair of cavities so as to provide, on setting of the plastics material, a bridging member extending from a cavity in one frame member into a corresponding cavity in the adjacent frame member so as to secure those frame members together-.

It is an object of the invention to provide an improved joint of the type referred to which will be particularly strong and resistant against opening even during prolonged use. Disclosure of invention.

According to the invention a method of forming a joint for connecting two frame members to provide a corner as set out in the last preceding paragraph is characterized in that said cavities comprise a pair of slot-like cavities extending into each frame member through its inclined end face and provided with ridged walls, ridges of which extend at an angle to the length-

wise dimension of each slot-like cavity lying at least substantially parallel to a plane containing the two assembled frame members, and the slot-like cavities being spaced apart . widthwise of the frame members, and an additional cavity extending through the end faces of each frame member in a direction extending lengthwise of the frame member at a locality lying between the pair of slot-like cavities.

Preferably, in carrying out a method as set out in the last preceding paragraph^ the slot-like cavities are formed by drilling a series of at least substantially parallel bores through the inclined end faces of the frame members, the bores being arranged to overlap and provide said ridged formation in the walls of the slot- like cavities. The ridged walls of the cavities and the apertures in the rein orcing member placed therein provide means with which the plastics material keys on setting. Preferably the bores providing a slot-like cavity are arranged to extend into the associated frame member in a direction inclined to a normal to its end face at an angle in the range of from about 10 to about 30 . The ridges provided by the overlapping bores do not then extend parallel to the lengthwise direction of the frame member, thus resisting further the withdrawal of the reinforced plastics material from the cavity in which it is formed.

In carrying out a method as set out in the last preceding paragraph but one preferably each reinforcing member for assembly in the slot-like cavities is formed from expanded metal sheet material, and each reinforcing member for assembly.in the additional cavities is in the form of a rod provided with surface indentations, thus providing a key for the plastics material.

Furthermore in carrying out a method as set out in the last preceding paragraph but two the plastics material is preferably injected into each cavity at a

joint through a bore communicating with the cavities, said bore extending through an inside face of one of the frame members. While any suitable plastics material which is capable of being rendered fluent for injection into the cavities of the joint and then sets to provide, with the reinforcing members, strong corner joint bridging members may be used, a particularly suitable material comprises nylon.

One field of application of the invention is in the formation of joints for frames for windows or the like made from cored extruded plastics profiles, for example, as disclosed in the specification of my co-pending International Patent -application No.FCT/GB80/00133. The profiles disclosed in said specification were provided with cores of shape-retaining material such, for example, as good quality plywood or a cement bound material, for example a cement bound chipboard.

In carrying out a method as set out in the last preceding paragraph but four and forming the cavities in the end portions of the adjacent frame members by drilling through the inclined end faces of the frame members as set out in the last preceding paragraph but three it can be assured that the cavities do not break through outer surfaces of the frame members and are_thus completely hidden in the completed joint. Furthermore, joints made in accordance with the invention are likely to be particularly strong and resistant against opening in view of the ^' fact that any tendancy for separation of the frame members in a direction parallel to their lengthwise dimension is resisted by the action of the ridged formation of the slot-like cavities locking with the plastics material therein, while any tendancy for separation of the frame members in directions parallel to the ridges in the walls of the slot-like cavities is resisted by the action of the reinforcing rods and plastics material in the additional cavities formed υ

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by the bores extending parallel to the lengthwise dimension of the frame members.

There will now be given, with reference to the accompanying drawings, a more detailed description of a method of forming joints illustrative of the invention. It is to be clearly understood, however, that such description is given by way of exemplification of the invention and not by way of limitation thereof. Brief description of the drawings. In the accompanying drawingss-

Figure 1 is a detail view, partly in section and partly broken away, showin two- rame members connected together by means of a joint illustrative of the invention; Figure 2 is a section Of the line II - II in Figure 1 showing the location of cavities in one of the frame members, the frame member being of a more complex shape than that shown in Figure 1j

Figure 3 is a plan view of a re-inforcing member used in making the joint shown in Figure 1;

Figure 4 is a side view, and Figure 5 is an end view, of an additional reinforcing member used in making the joint shown in Figure 1. Best mode of carrying out the invention. In following the illustrative method of forming a joint for connecting two frame members 201, 203 (Figure 1) to provide a corner, each frame member is provided with an end face 205 (like that shown at the left hand end ^" portion of the member 201 as seen in Figure 1) which is inclined, preferably at an angle of at least substantially 45 , to- the lengthwise direction of the respective frame member. When a corner is made the end face of one frame member abuts against the corresponding end face of the other frame member to provide a mitre joint, the faces abutting along the dotted line 206 indicated in Figure 1. In following

the illustrative method a pair of slot-like cavities 207 is caused to extend into each frame member 201, 203 through the inclined end faces 205 thereof which, when the joint is made,will abut. As shown in Figure 2,the cavities 207 are spaced apart widthwise of the frame member. As will be observed from the drawings the slot¬ like cavities are formed with their lengthwise dimension lying at least substantially parallel to a plane containing the frame members 201, 203 when they are assembled. The cavities 207 are so located in the frame members that each cavity in one frame member communicates with a corresponding cavity in the other frame member when they are brought together with their end faces 205 in abutting relationship. Each of the two frame members forming the joint is also provided with an additional cavity 220 in the form of a bore extending through its end face 205 in a direction lengthwise of the frame member and located, between the cavities 207, in such locations that, when the frame members are assembled, the cavities 220 communicate the one with the other.

During assembly of the frame members there is introduced into each pair of communicating cavities 207 a plate¬ like reinforcing member 211 having a plurality of apertures 212 extending therethrough, the reinforcing member preferably being formed from expanded metal sheet material. The outline shape of each reinforcing member 211 is such that, when it is introduced into a pair of communicating cavities, it is substantially co-extensive therewith (see Figure 1). Also, during assembly of the frame members, there is introduced into the cavities 220 an L-shaped reinforcing member 222 of somewhat less cross-sectional area than the cavities 220. Each member 222 conveniently comprises a piece of steel rod provided with surface indentations 223 (Figures 4 and 5) to provide good keying with plastics material injected into the cavities 220 as will now be described.

The abutting frame members 201 and 203 are then firmly clamped together while a settable plastics material 213 is injected into the communicating cavities 207 at least substantially to fill those cavities and enter the 5. apertures 212 in the reinforcing members 211 therein, and at the same time, the settable plastics material is injected into the cavities 220 to fill the space remaining between the reinforcing member 222 and the cavity walls. The plastics material is injected into 10 the various cavities simultaneously through a cross "bore 214 extending through one of the frame members from an inside face 215 thereof. On setting, the plastics material 213 (wit -the reinforcing members 211 and 222 embedded therein) provides bridging members

15 -which extend from the cavities in one frame member to the corresponding cavities in the adjacent frame member so as to. secure the frame members together.

The cavities 207 are conveniently formed by drilling a series of at least substantially parallel

20. bores through each end face 205 of the frame members 201, 203, the axes of the bores forming the cavity through the left hand end face 205 of the frame member 201 seen in Figure 1 being indicated by the series of parallel dot-dash lines 209. The bores are arranged

25 to overlap (see Figure 2) to provide a ridged formation in the side walls of the cavities 207, some of the resulting ridges being indicated at 210 in Figure 2. The ridges provide good keying with the plastics material on setting thereof in the cavities 207. The bores 0 forming each cavity 207 in an end portion of a frame member are drilled to a controlled depth so that they do not break through an outside surface of the frame member. While the bores 209 may be drilled perpendicular to the inclined end face 205 of the frame member if 5 desired, a cavity of greater depth (for a given size of frame member) can be obtained by drilling the bores in

in a direction inclined at an angle θ (Figure 1) to a normal to that end face (the direction of the inclination being towards, the lengthwise axis of the- frame member), the angle θ preferably being in the range of from about 5.10° to about 30 to said normal. By drilling the bores at an angle as just referred to, rather than parallel to the lengthwise direction of the frame member, the result is achieved that the ridges 210 in the cavity walls extend somewhat obliquely with respect to the length of the 0 frame member to increase the resistance to lengthwise withdrawal of the plastics material from the cavity. Although the invention is not to be taken as limited to the formation of joints between frame members of any-particular shape or constructed of any particular 5 material, one area in which it is likely to find use is in the construction of frames for windows or the like from cored"extruded plastic profiles. The frame member shown in cross section in Figure 2 of the accompanying drawings is formed from a profile having a core 1 around 0 which is extruded a plastic cladding 3 together with a glass (or other panel) retaining member 9 and other shaped portions such as any necessary flanges 15, 17 and rib 11 for use in making a frame for a window or the like as described in the specification of my co-pending 5 International Patent Application No.PCT/GB80/001337

The core 1 may comprise any suitable material having the desired strength and shape retaining properties such, for example as a good quality multi-ply wood, or a cement- bound material, for example a cement-bound chipboard as 0 now available for use in the building industry, a sheet of the chipboard being cut into lengths of the desired width, the strips being joined end to end to form a core of indefinite length for feeding to appropriate plastics- extruding machinery to form the profile with its desired 5 shape all substantially as disclosed in said specification. In making such frames it is considered to be particularly

suitable to employ joints in accordance with the present invention since such joints are likely to be particularly resistant to opening or coming apart in use, in view of the fact that any tendancy for separation to occur parallel to the lengthwise dimension of a frame member (i.e. by movement parallel to a limb of the reinforcing member 222) is resisted by the action of the reinforcing members 211 and associated plastics material in the ridged bores (inclined to said lengthwise dimension) providing the cavities 207 and vice versa.

While any plastics material capable of being rendere fluent for injection into the various cavities and settable to produce bridging members of the required strength and durability may be used in carrying out a method in accordance with the invention, Nylon may be quoted as an example of a suitable plastics material. Furthermore, in assembling the frame members to form a joint the abutting faces 205 may be coated with adhesive further to strengthen and seal the joint.