GB2529717A

GB2529717A - Improvements relating to window frame construction and method of assembly

Info

Publication number: GB2529717A
Application number: GB1415417.3A
Authority: GB
Inventors: Ian Widger
Original assignee: EVEREST Ltd
Current assignee: EVEREST Ltd
Priority date: 2014-09-01
Filing date: 2014-09-01
Publication date: 2016-03-02
Also published as: GB201415417D0

Abstract

A window frame is formed of three elements, wherein the first 10 and third 14 components have at least one slanted edge (24, 32), while the second part 12 has two angled faces. The faces of the first and third pieces abut either side of the edges of the second element about a node, and may be secured together by hot plate welding. The first and third elements may be aligned perpendicularly to the second element when joined together, and the sloped cuts of all elements may be 45 degrees with respect to their lengths. The first element may also have a second oblique face 26 which can adjoin the slanted face of the third element, such that the first and third elements are longitudinally aligned when connected to the second element. Also disclosed is a method for forming the window frame elements, and for assembling the window frame.

Description

IMPROVEMENTS RELATING TO WINDOW

FRAME CONSTRUCTION AND METHOD OF ASSEMBLY

The present invention relates to a window frame, the method of welding a window frame, and more particularly but not exclusively to a plastic window frame with at least one transom and or mullion and a method of welding said plastic to form said window frame.

Frames for doors and or windows, and methods of welding plastic to form said frames are well known in the art and PVCu is a commonly used frame material. It is of primary importance when manufacturing such frames to consider both the security and safety of the frame during normal operation.

A known method of PVCu frame assembly is hot plate welding. Components to be welded are loaded into holding fixtures and the surfaces to be welded are made clean, flat and free from distortion. The welding cycle is then initiated by positioning a hot plate between the two surfaces to be welded.

The welding then takes place in two phases. The first phase comprises pushing the components against the hot plate such that, under the axial load, melting of the surface in contact with the hot plate occurs. When melting occurs, a small continuous bead of molten material forms around the perimeter of the abutting surfaces of the component. This is commonly referred to as sprue. Once the entire joint surface of the component has melted the axial load is reduced. The reduction can be achieved, for example, by reducing the pneumatic pressure in the system, or by using melt depth stops. Melt depth stops are commonly positioned on the welding machine, between the hot plate. The machine slides to give a predetermined melt depth.

Upon reduction of the axial load, the second phase of the welding cycle begins wherein the hotplate is removed from between the two surfaces of the components to be welded and the components are brought together and allowed to cool under axial load for the joining phase. Melt depth stops can be used to control the amount of material displacement during the joining phase and when the joining phase is complete, the welded components are removed from the holding fixtures Hot plate welding may be used to assemble PVCu windows and doors that may include a transom and or a mullion. One method of assembly is to cut a V shaped notch into a first window frame element. A second window frame element is then cut in a complementary arrowhead fashion such that, when brought into abutment with the V shaped notch and hot plate welded thereto, the first and second window frame elements are perpendicular. Such a method of assembly is illustrated in Figure 1 (a), (b) and (c) and can be used to join a T section profile transom or mullion with an outer frame or sash element.

Another method of assembly is known as reverse butt welding. In this method a T or L profile frame element is cut in half lengthways, reversed through 180 degrees and then hot plate welded back together again. A V shaped notch, as described above, is then made at the weld intersection and a complementary arrowheaded frame element is welded into abutment with said notch to be secured perpendicular thereto. This method is illustrated in Figure 2 (a), (b), (c) and (d). The V shaped notch may also be made before cutting and welding the T or L profile frame element.

The arrowhead method may also be used to join four frame profiles into a crucifix or cross shape. An arrowhead is formed at the end of four frame elements. The arrowheads are sloped at 45 degrees such that when the four pieces are brought into abutment the adjacent frame elements are positioned at 90 degrees with respect to each other. This method is illustrated in Figure 3 (a) and (b).

The integrity and robustness of any of the abovementioned frame assemblies is thus heavily reliant on the quality of each hot plate weld. In addition to robustness, however, the customer demands an aesthetically pleasing window. As such any joins between frame elements must be subtle and inconspicuous.

An example of a hot plate welding apparatus that enables an improvement in the appearance of the join between two frame elements, whilst also providing an improvement in the strength and robustness of said join interface, is the Graf Synergy seamless welding system described in International Patent application W0201 3/132406.

In W02013/1 32406 a method and associated device is disclosed for welding together window frame and door frame elements such that said elements are fixed end to end and at 90 degrees to each other. The method includes the step of, prior to abutment, pressing the faces of the frame elements against a serrated hot plate face. Complementary serrations are then formed in the element faces and interlock when said faces are brought into abutment. The surface area of the abutting serrated faces is thus greater than compared to the surface area of abutting flat faces. This enables a more robust join than compared to prior art systems. Furthermore, the surface profile of each abutting face is such that excess sprue or beading generated when heated faces are brought it abutment under pressure (as per the method of hot plate welding) is forced inwardly, into the frame elements and thus hidden from view, rather than being forced outwardly to collect in an unsightly manner on the outer periphery of the abutted frame elements.

One significant disadvantage with the Graf Synergy welding method and apparatus described in WO2013/132406, however, is that, in the current configuration, it is not possible to use the Graf system to perform the aforementioned prior art methods of assembling a window frame with a transom, mullion or crucifix arrangement.

The Graf application discloses only a method and apparatus suitable for fastening outer frame elements to form, for example, a window frame or a sash comprising four perpendicular sides with no transoms or mullions.

Furthermore, the serrated topography of the opposing faces of frame elements brought into abutment means that said opposing faces must remain parallel with each other when they are brought together. If the opposing faces are brought together at an oblique angle then the heated serrations would collapse against the complementary serration on the face of the opposing frame element, rather than each serration interlocking with said complementary element. A weld with collapsed abutting serrations would not benefit from the increased contact surface area described above and so would not be as strong as a correctly abutted weld.

It is against this background that the present invention has been made.

The object of the present invention is to provide a window frame comprising at least three frame elements abutting about a node, wherein the abutting faces of said frame elements are shaped such that the Graf Synergy seamless weld system described in International Patent application W0201 3/1 32406 may be reconfigured to hot plate weld said abutting frame elements together. As such, the aesthetic and joint strength benefits achieved by using the Graf Synergy seamless welding system for hot plate welding two frame elements together may be achieved when hot plate welding at least three frame elements together about a node, as is the scenario when constructing a window frame comprising a transom and or a mullion. In order to clearly define the present invention it is to be understood that a node referred to herein is a common point about which the frame elements of the present invention abut.

It will be understood by the skilled person that the term window frame may refer to a window frame which holds an openable or fixed sash window, or the term window frame may refer to the frame elements which hold a sash window, or fixed pane glazed directly into a window frame.

From one aspect, the invention resides in a window frame comprising; a first element comprising at least one oblique face, a second element comprising first and second oblique faces, and a third element comprising at least one oblique face, wherein the at least one oblique face of the first element abuts the first oblique face of the second element about a node, and the at least one oblique face of the third element abuts the second oblique face of the second element about the node.

A window frame in accordance with the present invention has the advantage that, as described above, the Graf Synergy seamless welding apparatus of W02013/1 32406, with modifications, may be reconfigured to assemble such a window frame. Furthermore, the total surface area of each frame element face in abutment is greater than compared to the above described prior art frames, thus the weld area of each face is greater and thus the strength of each weld is improved. The increase in weld area is also achieved whilst reducing the number of machined faces used when joining three elements when compared to the prior art from a minimum of six (see the prior art assembly of Figure 2) to a minimum of five. The reduction in the number of machined faces simplifies the manufacturing process for some joint configurations and thus an associated time and cost saving may be realised.

The node may be a point on the tip of a frame element, wherein the tip is formed by the meeting of adjacent faces of said frame element.

Preferably, the first element comprises a second oblique face which abuts the at least one oblique face of the third element about the node.

Preferably, the abutting faces of the frame elements are secured together by welding, for example hot plate welding.

The inclination of the first oblique face of the first element advantageously corresponds with the inclination of the first oblique face of the second element such that in abutment the first and second elements are substantially perpendicular.

Further advantageously, the inclination of the second oblique face of the first element corresponds with the inclination of an oblique face of the third element such that in abutment the first and third elements are substantially aligned longitudinally.

Similarly, the inclination of the second oblique face of the second element may correspond with the inclination of an oblique face of the third element such that in abutment the second and third elements are substantially perpendicular. The aforementioned alignments are achieved, preferably, by inclining each oblique face at substantially 45 degrees with respect to the longitudinal length of their respective element. Such an angle of each oblique face enables a hot plate welding machine to be used wherein the angle of the hot plate with respect to a datum does not have to be altered in order to hot plate weld the various elements of a window frame and transom and or mullion assembly. One of a number of examples of a suitable hot plate welding apparatus that may be used is the Graf Synergy seamless welding system as described above.

The first, second, and third elements may be any combination of T, L, or Z section profile frame elements, transoms and or mullions.

From another aspect, the invention resides in a method of assembling a window frame comprising the steps of; forming at least one oblique face on a first element, forming first and second adjoining oblique faces on a second element, forming at least one oblique face on a third element, abutting the at least one oblique face of the first element to the first oblique face of the second element about a node and securing said elements together, and abutting the at least one oblique face of the third element to the second oblique face of the second element about the node and securing each abutting face together.

The aforementioned method provides the advantage that each oblique face abuts an oblique face. The technical effect of such is that the total surface area in abutment is increased when compared to the prior art, thus increasing the weld area of each face and increasing the strength of each weld.

Furthermore, the aforementioned method enables the use of the reconfigured Graf Synergy system described above, thus enabling the associated aesthetic benefits and joint strength benefits to be realised.

Preferably, the method includes the step of forming a second oblique face on the first element and abutting said second oblique face to the at least one oblique face of the third element about the node.

Preferably, the means of securing is welding, for example hot plate welding.

Advantageously, each oblique face of the first element is heated with a hot plate arranged at a constant angle, each oblique face of the second element is heated with said hot plate arranged at said constant angle and each oblique face of the third element is heated with said hot plate arranged at said constant angle. This enables a user to perform the aforementioned method without the need to adjust the hot plate angle and or datum of a hot plate welding machine, thus simplifying the manufacturing process.

Further advantageously the inclination of the second oblique face of the first element corresponds with the inclination of an oblique face of the third element such that in abutment the first and third elements are substantially aligned longitudinally. The inclination of the second oblique face of the second element preferably corresponds with the inclination of an oblique face of the third element such that in abutment the second and third elements are substantially perpendicular.

Further preferably, each oblique face is inclined at substantially 45 degrees with respect to the longitudinal length of their respective element. Such an arrangement maximises the total contact surface of each element whilst enabling the second element to be secured perpendicular to the first and the third element to be secured in longitudinal alignment with the first element and perpendicular to the second element.

Advantageously, the step of forming first and second oblique faces in an element comprises machining the first oblique face in the element, rotating the element through 180 degrees about the longitudinal axis of said element, and machining the second oblique face in the element. Alternatively, the first oblique face may be machined and then the angle of the machining head or blade altered before the second oblique face is machined.

Reference has already been made to Figures 1 to 3 of the accompanying drawings, in which: Figure 1(a) is a schematic side view of a known first frame element with V shaped notch; Figure 1(b) is a schematic side view of a known first frame element with a V shaped notch being brought into abutment with a known second frame element; Figure 1(c) is a schematic side view of a known frame element with a V shaped notch abutted with a known second frame element; Figure 2(a) is a schematic side view of known frame elements being brought into abutment; Figure 2(b) is a schematic side view of the frame elements of Figure 2(a) in abutment; Figure 2(c) is a schematic side view of the abutted frame elements of Figure 2(b) being brought into abutment with a further known frame element; Figure 2(d) is a schematic side view of the frame elements of Figure 2(c) in abutment; Figure 3(a) is a schematic side view of four known frame elements being brought into abutment with each other; and Figure 3(b) is a schematic side view of the four known frame elements of Figure 3(a) in abutment with each other to form a crucifix.

In order that the invention may be more readily understood, reference will now be made] by way of example, to Figure 4 and Figure 5, in which: Figure 4(a) is a schematic side view of first and second frame elements according to a first embodiment of the present invention being brought into abutment; Figure 4(b) is a schematic side view of abutted first and second frame elements according to a first embodiment of the present invention; Figure 4(c) is a schematic side view of a third frame element according to a first embodiment of the present invention being brought into abutment with the abutted first and second frame elements of Figure 4(b); Figure 4(d) is a schematic side view of the frame elements of Figure 4(c) abutted to form an outer frame portion with central mullion; Figure 5(a) is a schematic side view of first and second frame elements according to a further embodiment of the present invention being brought into abutment; Figure 5(b) is a schematic side view of third and fourth frame elements according to a further embodiment of the present invention being brought into abutment; Figure 5(c) is a schematic side view of the elements Figures 5(a) and 5(b) being brought into abutment; and Figure 5(d) is a schematic side view of the elements Figures 5(a) and 5(b) in abutment.

Terms such as "upper", "lower", "top", "bottom" and derivatives thereof shall be related to the side view of the invention as shown in Figure 4(d), i.e. as if the apparatus were assembled and in position in a substantially upright wall.

It is to be understood, however, that the invention may assume various other orientations, except where expressly specified to the contrary.

A first embodiment of the invention will now be described with reference to Figures 4(a), (b), (c) and (d). A frame assembly 15 is shown comprising three frame elements 10, 12, 14 which form a horizontal outer frame portion 16 with a central mullion 18.

The first frame element 10 is an elongate piece of PVCu material which has an arrowhead arrangement 22 at one end comprising a first oblique face 24 extending from the upper side of the first frame element 10 and a second oblique face 26 extending from the lower side of the first frame element 10 to meet the first oblique face 24 at the apex, or tip, of the arrowhead 22. The term oblique face referred to herein is defined as a face angled obliquely relative to the longitudinal length of the respective element on which the face is formed.

The second frame element 12 comprises a first oblique face 28 and a second oblique face 30 and is similarly shaped to the first frame element 10 but is rotated through 90 degrees such that the first oblique face 28 of the second frame element 12 abuts the first oblique face 24 of the first frame element 10 and is hot plate welded thereto so as to secure the first and second frame elements 10, 12 perpendicular to each other.

As with the first and second frame elements 10, 12, the third frame element 14 is also an elongate piece of PVCu material. However, instead of having an arrowhead arrangement at the end which abuts the first and second frame elements 10, 12 the third frame element 14 comprises one oblique face 32 which is inclined at 45 degrees to the horizontal and extends from the lower side of the third frame element 14 to the upper side of the third frame element 14. The oblique face 32 of the third frame element 14 and the second oblique faces of the first and second frame elements 10, 12 are complementary shaped such that when they abut, the first and third frame elements 10, 14 are substantially aligned longitudinally and the second and third frame elements 12, 14 are substantially perpendicular. As mentioned previously, the second frame element 12 forms the central mullion 18.

In the preferred embodiment, each oblique face 24, 26, 28, 30, 32 is inclined at 45 degrees with respect to the horizontal such that, in abutment, the perpendicular and longitudinal alignments as described above are achieved.

Also, in a preferred embodiment, the first and third frame elements 10, 14 have an L section profile and the second frame element 12 has a T section profile. Alternatively, the second frame element 12 may have a 7 section profile.

The sequence of Figures 4(a) to 4(d) show the method of assembling the window frame described above.

The method of assembling a T profile transom or mullion with an outer L or T profile frame element comprises the following steps: a) Machine a first face 28 angled at 45 degrees to the horizontal across the T section profile of the second frame element 12. In the orientation shown in Figure 4 the second frame element 12 will form the mullion. It will be apparent to the skilled person that if the elements of Figure 4 were rotated 90 degrees then the second frame element would form a transom.

b) Turn the second frame element 12 through 180 degrees, i.e. on to its back, and machine a second face 30 at 45 degrees to the horizontal to produce an arrowhead 23 which has sides of equal length positioned equally about the longitudinal centre line of the cut second frame element 12.

c) Cut an L or T profile frame element at 45 degrees to form two pieces; the first frame element 10 having a first face 24 and the third frame element 14 having a first face 32.

d) Move the third frame element 14 to a safe position.

e) Turn the first frame element 10 through 180 degrees, i.e. on to its back and machine a second face 26 at 45 degrees to the horizontal to produce an arrowhead 22 which has sides of equal length positioned equally about the centre line of the cut first frame element 10.

f) Position the first frame element 10 perpendicular to the second frame element 12 within a Graf Synergy seamless welding machine such that opposing faces 24, 28 abut, and weld at the intersection. This step may be achieved using the current Graf Welding system disclosed in g) Take the combined welded first and second frame elements 10, 12 and orientate them perpendicular to the third frame element 14.

h) Abut the first face 32 of the third frame element 14 with the second face 26 of the first frame element 10 and the second face 30 of the second frame element 12.

i) Weld the third frame element 14 to the abovementioned abutted faces 26, 30. This step may be achieved using a reconfigured Graf Welding system of W0201 3/132406.

In an alternative embodiment, the first frame and third frame elements 10, 14 have an L section profile and the second frame element 12 has a 7 section profile.

The assembly method of such profiled frame elements comprises the following steps: a) Machine a first face 28 angled at 45 degrees to the horizontal across the 7 section profile of the second frame element 12. The second frame element 12 will form the transom or mullion.

c) Take an L section profile frame element, reverse it through 180 degrees (i.e. turn it on its back) and machine a first face 32 angled at 45 degrees to the horizontal at one end. This is the third frame element 14.

d) Take another L section profile frame element and machine a first face 24 angled at 45 degrees to the horizontal. Reverse the frame element through 180 degrees (i.e. turn it on its back) and machine a second face 26 angled at 45 degrees to the horizontal to form an arrow head 22 at one end. This is the first frame element 10.

e) Align the first frame element 10 perpendicular to the second frame element 12 by abutting the respective faces 24 and 28 of respective arrow heads 22 and 23 and secure the abutted frame elements by welding at the intersection.

f) Abut the first face 32 of the third frame element 14 against the second face 26 of the first frame element and against the second face 30 of the second frame element such that the third frame element 14 is perpendicular to the second frame element 12 and secure each abutted frame element by welding. This step may be achieved using a reconfigured Graf Welding system of W0201 3/132406.

In a further alternative embodiment! the first frame and second frame elements 10, 12 have a Z section profile and the third frame element 14 has a T section profile.

The assembly method of such profiled frame elements comprises the following steps: a) Machine a first face 24 angled at 45 degrees to the horizontal across the Z section profile of the first frame element 10.

b) Turn the first frame element 10 through 180 degrees, i.e. on to its back, and machine a second face 26 at 45 degrees to the horizontal to produce an arrowhead 22 which has sides of equal length positioned equally about the longitudinal centre line of the cut first frame element 10.

c) Machine a first face 32 angled at 45 degrees to the horizontal in a 7 section profile frame element. This is the third frame element 14.

d) Take a T section profile frame element and machine a first face 28 angled at 45 degrees to the horizontal. Reverse the frame element through 180 degrees (i.e. turn it on its back) and machine a second face 30 angled at 45 degrees to the horizontal to form an arrow head 23 at one end. This is the second frame element 12 and will form the transom or mullion.

Referring finally to Figure 5, in a further embodiment, a crucifix arrangement is formed by performing the following steps: a) Machine an arrowhead into the end of four frame elements. Each face of the arrowhead having equal length and being inclined at 45 degrees to the horizontal.

b) Abut a first face of the first element with a first face of the second element and hot plate weld said faces together such that the first element is secured perpendicular to the second element as shown in Figure 5(a) and (c).

c) Clean weld debris such as sprue from the outer facing, non welded second faces of the first and second frame elements.

d) Abut a first face of the third element with a first face of the fourth element and hot plate weld said faces together such that the third element is secured perpendicular to the fourth element as shown in Figure 5(b) and (c).

e) Clean weld debris such as sprue from the outer facing, non welded second faces of the third and fourth frame elements.

f) Abut the outer oblique faces of the welded first and second elements with the outer oblique faces of the welded third and fourth elements such that a crucifix arrangement is formed with the first element perpendicular to the second element, the second element perpendicular to the third element, the third element perpendicular to the fourth element, and the fourth element perpendicular to the first element.

Alternatively, a method comprising fewer pre-cuts is as follows; step a) comprises machining a first oblique face of the first element, a first oblique face of the second element, a first oblique face of the third element and a first oblique face of the fourth element, then performing step b) above. Step c) then comprises machining a second oblique face in the first and second elements so as to form the arrowhead shape described above, then performing step d) above. Step e) then comprises machining a second oblique face in the third and fourth elements so as to form the arrowhead shape described above. Step f) is then performed as described above. This method of reducing the number of pre-cuts removes the need for the cleaning steps c) and e) described above.

Preferably, the abutting first and second element faces remain parallel with each other when they are brought together and the abutting third and fourth element faces remain parallel with each other when they are brought together.

Further advantageously, the outer oblique face of the welded first and second elements remain parallel with the outer oblique faces of the third and fourth elements when they are brought together.

It will be appreciated that the step of turning a frame element through 180 degrees, i.e. on to its back, to machine a second face at 45 degrees could be replaced with altering the angle of the machining means, rather than re-positioning the frame element.

The present invention is not limited to the specific embodiments described above. Alternative arrangements will be apparent to a reader skilled in the art, for example any combination of Z, T, or L profile frame element may be used.

The essential aspect of the frame and associated frame assembly method is that each abutting face is oblique relative to the longitudinal length of its respective element and, preferably, each abutting face is inclined at 45 degrees with respect to the longitudinal length of its respective element.

Claims

CLAIMS1. A window frame, comprising; a first element comprising at least one oblique face, a second element comprising first and second oblique faces, and a third element comprising at least one oblique face, wherein the at least one oblique face of the first element abuts the first oblique face of the second element about a node, and the at least one oblique face of the third element abuts the second oblique face of the second element about the node.
2. A window frame according to claim 1, wherein the node is a point on the tip of a frame element, the tip formed by the meeting of adjacent faces of said frame element.
3. A window frame according to claim 1 or claim 2, wherein the first element comprises a second oblique face which abuts the at least one oblique face of the third element about the node.
4. A window frame according to any of the preceding claims, wherein the abutting faces of the frame elements are secured together by hot plate welding.
5. A window frame according to any of the preceding claims, wherein the inclination of the first oblique face of the first element corresponds with the inclination of the first oblique face of the second element such that in abutment the first and second elements are substantially perpendicular.
6. A window frame according to any of the preceding claims, wherein the inclination of the second oblique face of the first element corresponds with the inclination of an oblique face of the third element such that in abutment the first and third elements are substantially aligned longitudinally.
7. A window frame according to any of the preceding claims, wherein the inclination of the second oblique face of the second element corresponds with the inclination of an oblique face of the third element such that in abutment the second and third elements are substantially perpendicular.
8. A window frame according to any of the preceding claims, wherein each oblique face is inclined at substantially 45 degrees with respect to the longitudinal length of their respective element.
9. A window frame according to any of the preceding claims, wherein the first element comprises a T section profile.
10. A window frame according to any of the preceding claims, wherein the second element comprises a T section profile.
11. A window frame according to any of the preceding claims, wherein the third element comprises a I section profile.
12. A window frame according to any of the preceding claims, wherein the first element comprises an L section profile.
13. A window frame according to any of the preceding claims, wherein the second element comprises an L section profile.
14. A window frame according to any of the preceding claims, wherein the third element comprises an L section profile.
15. A window frame according to any of the preceding claims, wherein the first element comprises a Z section profile.
16. A window frame according to any of the preceding claims, wherein the second element comprises a Z section profile.
17. A window frame according to any of the preceding claims, wherein the third element comprises a 7 section profile.
18. A method of assembling a window frame, comprising the steps of; forming at least one oblique face on a first element, forming first and second adjoining oblique faces on a second element, forming at least one oblique face on a third element, abutting the at least one oblique face of the first element to the first oblique face of the second element about a node, and securing said elements together, and abutting the at least one oblique face of the third element to the second oblique face of the second element about the node, and securing each abutting face together.
19. A method according to claim 18, wherein the node is a point on the tip of a frame element, the tip formed by the meeting of adjacent faces of said frame element.
20. A method according to claim 18 or claim 19, including the step of forming a second oblique face on the first element and abutting said second oblique face to the at least one oblique face of the third element about the node.
21. A method according to any of the preceding claims, wherein the means of securing is hot plate welding.
22. A method according to claim 21, wherein each oblique face of the first element is heated with a hot plate arranged at a constant angle, each oblique face of the second element is heated with said hot plate arranged at said constant angle and each oblique face of the third element is heated with said hot plate arranged at said constant angle.
23. A method according to any of the preceding claims, wherein the inclination of the first oblique face of the first element corresponds with the inclination of the first oblique face of the second element such that in abutment the first and second elements are substantially perpendicular.
24. A method according to any of the preceding claims, wherein the inclination of the second oblique face of the first element corresponds with the inclination of an oblique face of the third element such that in abutment the first and third elements are substantially aligned longitudinally.
25. A method according to any of the preceding claims, wherein the inclination of the second oblique face of the second element corresponds with the inclination of an oblique face of the third element such that in abutment the second and third elements are substantially perpendicular.
26. A method according to any of the preceding claims, wherein each oblique face is inclined at substantially 45 degrees with respect to the longitudinal length of their respective element.
27. A method according to any of the preceding claims, wherein the step of forming first and second oblique faces in the first element comprises; machining the first oblique face in the first element, rotating the first element through 180 degrees about the longitudinal axis of said first element, machining the second oblique face in the first element.
28. A method according to any of the preceding claims, wherein the step of forming first and second oblique faces in the second element comprises; machining the first oblique face in the second element, rotating the second element through 180 degrees about the longitudinal axis of said second element, and machining the second oblique face in the second element.
29. A method according to any of the preceding claims, wherein the first element is a T section profile transom.
30. A method according to any of the preceding claims, wherein the second element is a T section profile transom.
31. A method according to any of the preceding claims, wherein the third element is a T section profile transom.
32. A method according to any of the preceding claims, wherein the first element is an L section profile transom.
33. A method according to any of the preceding claims, wherein the second element is an L section profile transom.
34. A method according to any of the preceding claims, wherein the third element is an L section profile transom.
35. A method according to any of the preceding claims, wherein the first element is a Z section profile transom.
36. A method according to any of the preceding claims, wherein the second element is a Z section profile transom.
37. A method according to any of the preceding claims, wherein the third element is a Z section profile transom.
38. A window frame according to any of the preceding claims substantially as herein described with reference to the drawings.
39. A method of assembling a window frame substantially as herein described with reference to the drawings.