ARCHITRAVE JOINT METHOD

Abstract: Architrave frames having mitred joints, in which a seemingly perfect mitre joint can be formed by overlapping a heavily undercut end (8) of a first architrave moulding (1) over a complementary end (14) of a second moulding (1) whose axis is about 90<o> to the axis od said first moulding.

Description: THIS INVENTION relates to a frame and is more specificall concerned with the formation of an approximately right " angle corner in a frame made by an apparently mitred joint between two straight members forming adjacent sides of the frame. Such a frame may provide the architrave for a window or a door when it is set against a wall surface surrounding an opening which is to be framed. Ideally the junction line between two adjacent corner members connected by a mitred joint is in the form of a straig line bisecting the angle of the corner. Any inaccuracy in a mitred corner is immediately apparent on close inspection the junction line is replaced by a wedge-shaped filling and superficial 'decoration on the members does not match up. For these reasons it is customary to prepare a mitred joint carefully. Normally a jig is used which provides a flat firm base for the members ' being cut, and a guide slot for ensuring a saw, used to cut the ends of the members, is at the correct 45 angle. If the ends of the members are correctly cut, when the members are perpendicular to one another and lie against coplanar surfaces, a clean and precise mitred joint will be produced. Unfortunately, it is not uncommon to find the boundary surfaces of a wall surrounding a window or door opening to be framed are not coplanar and the corners of the opening are often not a right angle. In both of these situations the mitred joint has to be "fudged" even though the members may have been prepared accurately. Errors then occur and the clean appearance of a well-mitred joint is often lost. An object of this invention is the provision of members " between which an apparently mitred joint of clean appearance can be made in the situations referred to in the preceding paragraph. In accordance with the present invention an apparently mitred joint is provided between the overlapping end-portions ^ of respective straight members having gradually tapering cross-sections such members having one end-portion terminating in a substantially 45° edge behind which an apparently mitred joint provided between overlapping dissimilar end-portions of 5 respective straight members the first of which has one end- portion terminating in a substantially 45 edge behind which the member is undercut to provide a cavity for receiving the end-portion of the second member, the dimensions of the cavity and the end-portion of the second member it accommodates being 10 - such that the second member can angularly displace in the plane of the joint a limited extent with respect to the first member while its end face remains hidden in the cavity. The invention also includes a straight member for forming one side of a joint as described ' in the preceding paragraph, 15 the member having dissimilar end-portions one of which terminat in a substantially 45 edge provided on a lip behind which the end-portion of the member is undercut to provide a cavity for receiving the issimilar end-portion of a similar member which is to provide an adjacent side of the joint. 20 The advantage of the invention is that a visually attracti apparently mitred joint can be provided in situations where the supporting wall surfaces for the members are not entirely coplanar or where the angles at the corners of an area to be framed are not exactly 90 . * ■• - Preferably the cavity is of obtuse triangular shape when viewed from the underside of the first member, the substantially 45 end-edge of the member forming the hypotenuse of the triangle and the shorter side of the triangle extending approx¬ imately one-third of the distance from the shorter parallel 30 side of the member to the longer parallel side. The shorter side of the triangle may subtend an angle of slightly less than 90 with the shorter parallel side of the member to ensure there is sufficient space in the cavity for the corner portion of the second member, when tilted,- to be accommodated in it. OMPI Advantageously the end-edge of the member which is not undercut makes an angle of about 50° with the shorter parallel side of the member, although this angle can be varied between about 46° and 60°. Ideally the angle chosen should be such as to allow the members to be set at angles of between 40 and 50° with respect to one another without spoiling the line of the mitre. Advantageously the profile of the.surface of the cavity which is to lie over the surface of the end-portion of the adjacent member of the joint, provides a lip of tapering thickness and which has a contour to allow -the edge of the overlying member to fit snugly over the surface profile of the end portion of the underlying member in the different possible positions of the members. Conveniently the thickness of the lip progressively increases from its tip at the 45 end- edge of the member towards the other two sides of the triangle of the cavity. The members may be made of wood or from a metal, such as aluminium, preferably fabricated by extrusion. The invention will now be described in more detail, by way of examples, with reference to the accompanying drawings , in which:- FIGURE 1 shows, in end elevation, a straight wooden member forming one side of a rectangular architrave to be provided with mitred joints at its corners; FIGURE 2 is a perspective view of the underside of one end- portion of the member; F IGURE 3 is a perspective underview of the opposite end- portion of the member; FIGURE 4 shows a perspective underview of a corner of a mitred joint formed from the end-portions of ^-~~ two members, as shown in figures 2 and 3, fitted ^ FIGURE 5 is a perspective plan view of the joint shown in Figure 4; FIGURE 6 shows the effect on the joint of the members making an angle of more than 90 with one 5 ' another; FIGURE 7 is a view corresponding to figure 6 but shows the shape of the joint formed when the angle between the members is less than -90°. FIGURE 8 is an exploded view of the mitred joint of 10 figure 5 , the overlapping and underlapping portions of the members at the joint being identified by shading; FIGURE 9 is a vertical section through a lower portion if a window surround having an extruded aluminium L5 _ architrave mitred at the corners using the invention; FIGURE 10 shows, in perspective, the reverse side of a mitred corner joint forming part of the window surround of Figure 9 ; X1 FIGURE 11 is the front side of the mitred joint of Figure FIGURE 12 is a cross-section through an aluminium extended member forming one side of the mitred joint; and FIGURE 13 and 14 are respectively perspective views of opposite ends of the member of Figure 12. 3:- Figure 1 shows a wooden member 1 for providing one side of a square architrave to frame a window aperture (not shown) . The member has a top surface 2 comprising two obtusely inclined surfaces 3 and .4. The underside of the member is rebated along its length at 6. The member 1 is formed in its underside 0:- with a cavity 8 The cavity 8 lies beneath a triangular lip 9 of thin wedge-shaped cross-section whose upper surface is continuous with the top surface 2 of the member 1. The end-edge of the lip 9 extends in a straight line at 45° to the parallel sides of the member 1, as is clearly apparent from figure 5. When viewed in under plan, the cavity 8 is of narrow triangular shap with the end-edge of the lip 9 forming the hypothenuse of the triangle and the vertex of the triangle at the extremity of the member having an angle of 8 °, but it should increase with increases in the overall thickness of the member being mitred. In practice any angle of between 30 and 90 may be chosen. The remaining two sides of the triangular cavity 8 are defined by end-faces 12 and 13 which extend perpendicularly to the undersurface of the member 1 and make an obtuse angle with one another. The end face 13 makes an angle of slightly less than 90 with the inside edge of the architrave. The opposite end portion of the member 1 is formed with a triangularly cut end-portion as shown in figure 3. This provides a flat end-face 14 making an angle at the tip of the member of between 46 and 60 , preferably 49 , when viewed in plan. Thus when the four members 1 of the architrave frame are fitted together, the end-face 14 of each member is accommodated within the cavity 8 of the adjacent member, as is shown in figure 4. The shape of the cavity 8 is such that the end-face 14 of each member is located behind the 45 end-edge of the overlapping lip 9 as shown in figure 5. This occurs despite the angle of the mitre corner ranging from a few degrees less than 90 to a few degrees more than 90°. As long as the angle is in this range the end faces 14 of the members remain hidden behind the lips 9 and the 45° edge of the lip is the only joint line visible from the front of the corner. A mitred joint of clean appearance thus results without "fudging" the ends of the members 1. Figure 8 shows the extent to which the ends of the members can overlap one another in a typical mitred joint made in accordance with the invention. As is apparent from figures 6 and 7, a failure of the members 1 at a corner to be truly perpendicular to one anothe is to cause one or other of the members 1 to extend beyond, at its end, the outermost end of the adjacent member. The protrusion which results is quite small and occurs at the out surface of the architrave from which it can be easily planed or cut off. The protrusions are indicated in figures 6 and 7 by the numerals 20 and 21 respectively. The above described method of forming a mitred joint is not only effective to hide -an imperfection in the corner angle of the supporting wall surface but will also hide a failure of the supporting surfaces to be coplanar with one another. The members may be made of wood, plastics or any other desired material. Likewise the shape of the cavity 8 is not critical, its only requirement being that it should accommoda limited movement of one member with respect to the other memb while keeping the end-portion of the underlying member hidden beneath the lip of the overlying member. Figure 9 shows a window aperture framed by a surround made from straight aluminium members mitred together at their corners in accordance with the invention. The wall around th aperture has inner cladding 102 and outer cladding 101 attach to a timber beam 103. A second beam 104 forms the reveal of the window and supports an extruded aluminium holder 105 providing a channel 106 into which a marginal edge of a windo pane (not shown) is fitted. The holder 105 has an intermedia web 107 secured to the beam 104. A set of spaced spring stri 108 are nailed at 109 through the cladding to the beam 103 an provide -a line of spaced clips 110 at their outer ends. At i outer end the support 105 has an outwardly turned strip 112. The window is provided with a rectangular aluminium architrave formed by four side members one of which is shown at 114. These are each provided at its inner end with a rect channel formation 115 and at its outer end with an edge strip terminating in a U-shaped channel groove 117 containing a neoprene strip of circular cross-section and.which is snapped into place behind the clips 110. Figures 12 to 14 show the member 114 in more detail. It has one corner cut at . 50° to the longitudinal axis of the member, as shown in figure 14. The channel 117 is cut back slightly from the corner edge, as shown at 113 in figure 14. The other end-edge is cut at an angle of 45 to the longitudina axis as shown at 118 in figure 13. The marginal portion of the member 114 has a progressively diminishing thickness as the edg 118 is approached. This is achieved by bevelling an elongated triangular-shaped cavity 120 of curved cross-section into the rear surface of the member. The cavity is shown in figure 13 between the line 119 and the edge 118. The depth of the triang cavity 120 progressively diminishes towards its vertex 121 whil at its other' end it terminates in an abrupt triangular heel 122. The curved cross-section of the cavity 12 achieved by bevellin ensures that in the vicinity of the • edge 118 the. wall thickness of the member is ' very thin indeed. The mitred joint is formed by lapping the corner of the member terminating in the 45 edge 118 over the dissimilar corne of the other member as shown in Figure 11. The overlap is "hidden" by slightly tilting the member having the edge 118 about its longitudinal axis so that the thin edge 118 bears on the outer surface of the outer member which is accommodated in the cavity 120 so that a noticeable step in the surface profi of the members is avoided. The cutting back of the channel 117 allows the longitudinal axes of the members to be inclined at a range of angles including 45 with respect to one another. This is effected without a "crack" opening along the 45° "mitre" line and while the inside corner of the architrave still appears as a sharp right-angle. This is achieved by the inside channell edge of the underlapping member 11.4 sliding along the heel 122 of the cut back channel formation 115 of the other member 114 as shown in Figure 10, so enabling the inside edges to intersect at a sharp angle in a range of angles including 90 . If the window corner angle is less than ' 90 , the members are tilted more about the longitudinal axes out of the plane of the architrave than is the case if the window corner angle is equal to or more than 90°. This tilting is not noticeable, however. Also, the external corner tip of the member not having the cavity 120, will project slightly beyond the corner tip of the other member which is accommodated in the space lef by cutting back the channel 117. This slightly projecting tip can be cut back with a hack saw and the slight gap left betwee the edge strip 116 of respective members 114 suitably filled. By using the architrave made from extruded aluminium side members, an apparently conventionally mitred joint can be form quickly and easily in situations where the corner angles to be followed are not truly 90°.

Claims: THE CLAIMS DEFINING THIS INVENTION ARE AS FOLLOWS: - 1. An apparently mitred joint provided between overlappi dissimilar end-portions of respective straight members hav gradually tapering cross-sections and the first of such me having one end-portion terminating in a substantially 45 behind which the member is undercut to provide a cavity fo receiving the end-portion of the second member, the dimensi of the cavity and the end-portion of the second member it accommodates being such that the second member can angularl displace in the plane of the joint a limited extent with re to the first member while its end face remains hidden in th cavity. 2. A joint as claimed in claim 1, in which the members ha similar end-portions at one pair of ends and the other end- portions are also similar to one another but dissimilar fro the first-mentioned end^-portions. 3. A joint as claimed in claim 1 or claim 2, in which the opposed surfaces of the opposed end-portions in the cavity form an obtuse triangle in the plane of the joint. 4. A joint as claimed in any one of the preceding claims, in which the end-portion of the second member lying within the cavity terminates in a straight edge making an angle of bbeettwweeeenn 4466°° aamnd 60° with the longer parallel side of the second member. 5. A joint as claimed in any one of the preceding claims, in which the cavity is of triangular shape when viewed in the plane of the joint and is formed behind a lip on the fi member, the cross-section of the lip progressively diminish from its root to the substantially 45° edge. 6. A joint as claimed in any one of the preceding claims, in which one side of the cavity is formed by a cut in the f member which extends inwardly from one end of its shorter parallel side to approximately one-third of the distance towards the other parallel side, the cut making an angle of slightly less than 90° with said shorter parallel side. 7. A joint as claimed in claim 1, in which the members are made of extruded aluminium and the cavity has a bevelled concav cross-section increasing in depth from the outside face of the joint to the inside face of the joint and the metal thickness of the overlapping member along the 45 line of the mitre is uniformly thin. 8. A joint as claimed in claim 7, in which the overlapping member is provided adjacent to the inside face of the joint with a heel surface defining one end of the cavity and which provides a slide abutment against which the overlapped member can- slide during formation of the joint. 9. A straight member for forming.one side of an apparently mitre -joint as claimed in claim 1 or claim 7, the member having dissimilar end-portions one of which terminates in a substantially 45 edge provided on a lip or edge behind which the end-portion of the member is undercut to provide a cavity ' for receiving the dissimilar end-portion of a similar member which is to provide an adjacent side of the joint. 10. A straight member as claimed in claim 9, which is of trapezoidal shape and has its opposite end-portions diverging outwardly towards its longer parallel side at different angles one of which is provided by the tip of the lip or edge and the other of which makes an angle of substantially 50° with the longer side of the member, the thickness of the member pro¬ gressively increasing from its shorter parallel side to its longer parallel side. 11. A joint as claimed in claim 1, arranged substantially as described with reference to one of the embodiments shown in the accompanying drawings. OMPI 2 . A straight member as claimed in claim 9 , having its end-portions formed substantially as described with reference to figures 1 to 3 or to figures 12 to 14 of the accompanying drawings .

Inventors: WATSON BRUCE SAMUEL, WATSON, BRUCE, SAMUEL
Applicants: WATSON BRUCE SAMUEL, WATSON, BRUCE, SAMUEL
Application year: 1984
Main classification: F16B12
IPC codes: E06B3