GB2026125A

GB2026125A - Joint forming

Info

Publication number: GB2026125A
Application number: GB7924197A
Authority: GB
Original assignee: Individual
Current assignee: Individual
Priority date: 1978-07-11
Filing date: 1979-07-11
Publication date: 1980-01-30

Abstract

Slots 74 are formed in confronting end surfaces (72) of abutting frame members 62 so that the slot of one surface is in communication with the slot of the second surface, when assembled, to form a cavity into which molten plastics material is injected. If preferred, an L-shaped bridging insert 56 may be embedded in the plastics material in the cavity. The plastics is injected through bores 76. <IMAGE>

Description

SPECIFICATION Joint forming The invention is concerned with improvements in or relating to forming of joints, particularly joints between abutting ends of elongate members.

An example of a situation in which the present invention will find application is in the joining of frame members or the like in a mitre joint in a manner producing a joint having a high degree of strength. In the example to be described the frame membes are window frame members, but there is no limitation in this respect.

The invention provides a method of joining the abutting end portions of elongate members comprising the steps of procuring two members having confronting end surfaces, forming a plurality of slots comprising at least one slot in each of said surfaces so that, when said surfaces abut, one slot of a first of the two surfaces is in communication with one slot of a second of the surfaces to form a cavity, slots of said plurality thereof affording communication between the cavity and a side surface of each member, and injecting mouldable plastics material into said plurality of slots to form a bridge between the members.

Advantageously, a bridging insert may be received into said cavity so as to occupy a portion thereof, said insert being received partly in the slot of the first surface and partly in the corresponding slot of the second surface. However, where the mouldable plastics material is of sufficient strength, an insert is not required.

Conveniently, one or both of the confronting end surfaces of the elongate members may be provided with a pre-coating of adhesive. It may also be found advantageous when using an insertfor it to be provided with keying surfaces to enhance the interengagement between the insert and the injected plastics material. These keying surfaces may include ridges, apertures or the like.

Conveniently, the joint to be formed will be a mitre joint and a suitable form of insert may have an L-shaped cross-section. An insert may be preformed from any suitable material of sufficient strength for the purpose intended, for example, aluminium, steel or synthetic resin or plastics material.

There will now be described two examples of the invention. It will be understood that the description, which is intended to be read with reference to the accompanying drawings, is given by way of example only and not by way of limitation.

In the drawings: Figure 7 is a plan view of first example of a mitre joint in a window frame; Figures 2 and 2a are plan and side view respectively of an insert; Figure 3 is a sectional view on line III of Figure 1; Figure 4 is a side view of the joint of Figure 1; Figure 5 is a perspective view of a second form of insert for use with the method of the invention; Figure 6 is a plan view of a mitre joint incorporating the insert of Figure 5; Figure 7 is a perspective view of an elongate member comprising the mitre joint of Figure 6, with a cross-section taken on line VII-VII of Figure 6.

Figure 8 is a side view of the mitre joint of Figure 7 and 8; and Figure 9 is a diagrammatic view of two elongate members during assembly of the joint.

Figure 1 shows a mitre joint between two elongate members 30 of multi-ply wood intended for use in a window frame. The member is provided with a plastics material cladding 32, having flanges 34,36.

A cavity is formed which is composed of two slots 38, each formed in one of the confronting surfaces of the mitre joint which surfaces are bonded at 40 by adhesive.

The slots 38 are conveniently formed in the same operation as the mitre is cut, a series of four drills boring holes 42 in a first step and three intervening holes 44 in a second step, the spacing and diameter of the holes being chosen to provide the required slots, the walls of which have ridged surfaces, suitable for keying purposes as hereinafter explained. The mitring steps then follow and the bond 30 is made in a suitable jig means (not shown).

An insert 46 is then placed in the cavity formed by the confronting slots. This L-shaped insert is of flat sheet material which is, in the present example, aluminium. Two apertures 48 are formed in each arm of the L-shaped configuration. The clamped joint is then ready for presentation to an injection jointing machine which in the example accepts four frame members 38 clamped in an assembled manner and forms joints at all four corners simultaneously by injecting molten polyamide into each cavity. Polyamide then fills the region of the cavity not occupied by the insert 46, keying with the ridged wall surfaces of the slots 38 and the apertures 48 of the insert. The clamps may then be released as the polyamide sets.

The second example of an insert is shown at 52 in Figure 5, and is generally L-shaped in cross-section, being comprised of two portions 56 meeting at right angles to one another. Extreme marginal portions of each insert portions 56 carry an external ridge 58.

Apertures 60 are provided in the insert portion 56.

Figure 6 shows a mitre joint between two elongate members 62. These members 62 are of multi-ply wood in the present example and are intended for use in window frames. The wood comprises a core coated by an extrusion technique with plastics material 64 which besides cladding the wood is provided with flanges 66, 68 required for abutment with corresponding flanges of other confronting window frame portions.

A slot 70 is formed in an oblique end surface 72 of each member 62 so that when the two surfaces are bonded together by adhesive the slots confront each other to form an L-shaped cavity 74 having the same lengthwise dimensions as those of the insert but being generally wider than the width of the insert.

Bores 76 provide communication between the cavity 74 and external surfaces of the members 62.

Plastics material, in the present example polyamide, is injected into the cavity 74 and the bores 76 under pressure so that on solidification, the bridging insert 52 is securely embedded in the polyamide in the cavity 74 and a tough web of polyamide has been formed with protuberances, received in the bores 76, which key into the wood of the elongate members 62 to enhance the security of the mitre joint.

The steps in the assembly of the joint are as follows in the present example. Firstly elongate members (shown diagrammatically as members 62') are mitre-cut and placed in the clamp of a jig device (not shown). An oscillating chisel is then used to form the slots 70, one in each surface 72 conveniently along one ply of the multiply wood, and a boring tool forms three bores 76 in the longest side surface of each of the members 62' to communicate with the slots 70.

Adhesive is then applied to the re-entrant surfaces of the insert portions 46, one of which is placed in one of the slots 70. The two surfaces 72 are then coated with impact adhesive and the clamps bought together to bond the surfaces.

This traps the insert in the cavity 74 formed by the slots 70. The ridges 58 are received in the extreme ends of the chamber and act both as a keying device and also as an end surface against which the plastics material will now flow.

The clamped joint is now ready for presentation to an injection jointing machine, which in the present example accepts four elongate frame members clamped in an assembled manner and forms joints at all four corners simultaneously by injecting molten polyamide into one bore 76 of each joint (advantageously a bore adjacent the external corner). Polyamidethen fills the region of the cavity 74 not occupied by the insert 52, forces the adhesive coated surface of the insert against the cavity wall and travels outwardly along the remaining bores 76 which are closed by a clamping surface of the jig device.

The clamps are released as the polyamide sets and the frame is securely assembled.

In another example of the invention shown in Figure 10, the insert may be dispensed with and a mouldable plastics material 80 injected to fill the cavity in its entirety. In all other respects, the joint will resemble that shown in Figure 4. The material used will be chosen for its strength which will be at least equivalent to that of aluminium.

Various modifications may be made within the scope of this invention as defined in the following

Claims

claims. CLAIMS

1. A method of joining abutting end portions of elongate members comprising the steps of procuring two members having confronting end surfaces, forming a plurality of slots comprising at least one slot in each of said surfaces so that when said surfaces abut, one slot of a first of two surfaces is in communication with one slot of a second of the surfaces to form a cavity, slots of said plurality thereof affording communication between the cavity and a side surface of each member, and injecting mouldable plastics material into said plurality of slots to form a bridge between the members.

2. A method as claimed in claim 1, wherein a bridging insert is received into said cavity so as to occupy a portion thereof, said insert being received partly in the slot of the first surface and partly in the corresponding slot of the second surface.

3. A method as claimed in either one of claim 1 and 2, wherein one or both of the confronting end surfaces of the elongate members may be provided with a pre-coating of adhesive.

4. A method as claimed in claim 2 and in claim 3 so far as it is appendant to claim 2, wherein the insert is provided with keying surfaces to enhance the interengagement between the insert and the injected plastics material.

5. A method as claimed in claim 4, wherein the keying surfaces comprise ridges or apertures.

6. A method as claimed in claim 4 wherein the insert is L-shaped and the joint is a mitre-joint.

7. A method as claimed in claim 1, wherein there are four elongate members to be assembled as a rectangular frame comprising four mitre joints, said four members being placed in a jig device during formation of the slots in the end surfaces, including the steps of clamping said four members in the jig device prior to injection of the molten plastics material.

8. A method of joining abutting end portions of elongate members substantially as hereinbefore described with reference to and as shown in Figures 1 to 4; (b) Figures 5to9; (c) Figure 10, of the accompanying drawings.