Field of the invention The invention relates to a corner joint according to the preamble of claim 1.

In a preferred embodiment the invention relates particularly to a joint for an insulated metal frame of a window.

Background to the invention

Corner joints of the aforementioned type are known for example in the field of window frames having a framework of extruded aluminium profiles each of which are joined at the frame corners by means of intermediate plastic connection members. Such a frame is shown in e.g. DE-A-3 310 230 which discloses a corner joint according to the preamble of claim 1.

One of the problems which must be overcome when designing frames for use with e.g. glass or other relatively rigid plate materials is the sealing of the window and frame against ingress of water. In an effort to overcome this, sealing compound or complicated seals of various types have been employed at the corner joints to fill the gaps which occur as a result of the manufacturing tolerances of the various members. This is particularly the case with frame members which have been mitre-cut (e.g. at 45°) where small deviations may cause large gaps.

However, even when sealing is achieved, water entering the frame, via running down the glass panel, past the seal and into the frame profile must be drained in some way. The

present method of accomplishing this is to arrange one or more openings in various faces of the frame profiles to allow the water to drain out (see e.g. US-A-2 787 034 or US-A-3 503 169) . This operation is not only time-consuming and expensive, but water in the frame between the corner and the drainage openings cannot easily exit. With aluminium window frames, problems of levelling when fitting may also result in a water build-up at one frame end which will exaggerate this problem.

A solution to this problem has been suggested in the field of sliding window assemblies (see e.g. US-A-3 845 599) whereby a drainage valve is provided in a frame member close to the corner thereof and a plastic valve is fitted in communication with this. The purpose of this valve is to prevent atmospheric conditions affecting the area on the inner side of the window, by means of a water-filled valve. No mention is made of sealing the frame corner or of how the valve body is sealed. The problem thus remains that special sealing measures will be required at the joint of the two frame members and around the valve body to stop water ingress, all the more due to the fact that each of the frame members must be recessed to accommodate the valve.

The corner assembly of US-A-3 845 599 is also not applicable to insulated frame constructions (for which the present invention is suitable) . Moreover, valves are all prone to valve sticking after a certain amount of time.

Joining together single plastic profiles of subframes for window mounting, as distinct from metallic frames, is known from US-A-4 136 496. Such a device also comprises drainage means which may drain condensation water and thus has nothing in common with insulated metal frames.

In prior art corner connections, especially in the field of windows, it is also common that the frame members to be joined will have different cross-sectional profiles which makes their production, fitting and assembly more expensive.

The prior art document DE-A-3 310 230 mentioned earlier discloses, in one embodiment, a separated glass arrangement in which each pane lies on a separate inner and outer frame member respectively. However, even though an insulating bridge is used to join the inner and outer frame members, the type of corner joint which is to be used with these frame members is not one which is at all suitable for an insulated window frame, but merely for a frame which has two panes of glass separated from one another by a gap. This unsuitability is present since two gaps are necessarily present in the central, internally facing portion of the corner piece, between the upper surface of the base of the connecting piece and two projecting plates, for allowing condensation water to drain away from the inside frame member. Thus since the water may flow out, cool air and water may flow into the inner frame member and also into the space between the glass panels. The frame is thus not an insulated frame at all, insulated frames having no access to drainage of condensation water due to the fact that an insulated frame should not produce condensation water since the inner frame is at the same temperature as the room itself.

Moreover the corner joint of this frame of the prior art reference has no requirement for a water-tight contact with the corner piece since water must be drained from between the panels as well as allowing condensation water to be drained. Thus the gaps present make it impossible to have a water-tight contact between all the end surfaces of the channel sections and the connection piece. Even the method

of attachment, being a form-fit between the arms of the corner piece into the frame sections, is totally unsuitable for use in a water-tight connection since any minor stresses on the frame (e.g. due to mounting or transport for example) would result in the box-sections separating from the corner piece. Thus any water-tight joint can only be achieved by e.g. complicated sealing means or the like.

It is therefore an object of the present invention to achieve a corner joint for an insulated metal frame which is capable of solving some or all of the above problems without resulting in unnecessary complication or expense.

Summary of the invention

In accordance with the invention the corner joint has the features defined in claim 1, preferred features being defined in the dependent claims.

Description of the drawings

The invention will now be described in more detail with reference to the accompanying drawings, in which:

Fig. 1 shows a perspective view of an insulated window frame assembly with one corner joint highlighted,

Fig. 2 shows a corner joint according to Fig.l, in more detail,

Fig. 3 shows the corner joint of Fig. 2 with the cover panels of each frame member moved upwardly,

Fig. 4 shows an exploded view of the connecting portions of the joint of Figs. 2 and 3,

Fig. 5 shows a cross-sectional view of the horizontal frame member of Fig. 2,

Fig. 6 shows a cross-sectional view corresponding to that of Fig. 5 adapted for use with an openable window

Detailed description of preferred embodiments Fig. 1 shows an insulated window frame 1 having four frame members 6-9 and four corners joints 2-5, one or more of which are made in accordance with the present invention. At each corner joint each of the four individual frame members 6-9 (e.g. of the type which are cut to length from extruded aluminium profiles) are joined at 90° to another frame member.

The frame members have the same cross-sectional profile and the end faces of each of the insulated frame members are cut at 90° to their longitudinal axis to leave a planar face. This aspect of the corner joint of the present invention thus presents a significant advantage with respect to many prior art frames which are generally itre- cut or recessed at the corners when the same profiles are used, which requires a precise individual cutting operation for each frame member in order to achieve a good fitting relationship. With the present corner joints one or more extruded profiles are merely cut square to length.

Although a window frame is depicted in Fig. 1, it will be clear to the skilled man that the corner joints of this invention may be applicable to other insulated frame constructions such as door frames, or other panel- supporting frames.

The corner joint 2 at the bottom left corner of Fig. 1 will now be described in more detail with respect to Fig. 2. The

two frame members generally denoted 6 and 7 are divided into inner parts 6a, 7a and outer parts 6b, 7b respectively and joined by means of suitable insulating plastic material bridges 12, 13, e.g of nylon polyamide, so as to form an inner and outer frame insulated from one another. Each of the inner and outer parts comprise box profile cross- sections as known per se.

Each of the channel faces 14, 15 would have a sealing strip (see e.g. part 39 in Fig.5) of rubber material or the like, applied thereto for sealing the window pane (see Fig. 5) completely from the inside. In a similar way, each of the channel faces 16 and 17 of the cover panels 10 and 11 would also be provided with a sealing strip for sealing the window pane from the outside (see e.g. part 40 in Fig. 5) .

Each frame member 6 and 7 is covered with a respective cover panel 10, 11 which can be added after fitting the window frame.

Fig. 3 shows the corner joint of Fig. 2 with the cover panels 10, 11 moved sideways to allow the ends of the frame members 6, 7 and the plastic connecting piece 18 to be visible. Fig. 3 also depicts drips of water W which for example have entered the upwardly facing channel 20, due to ingress past the outer seal (e.g. due to exposure of the outer seal to harsh atmospheric conditions) and which are being drained out of the corner joint via the outwardly sloping part 19 of the water drainage means. The portion 21 serves both as a glass pane support surface and as part of the drainage means. The lower part 19 of the drainage means may be horizontal or sloping, although clearly the design of the connecting piece 18 such that some or all of its upper surfaces are sloping towards the outlet is preferable.

Fig. 4 shows an exploded view of the corner joint. As will be apparent on comparison of Figs. 3 and 4, the end face areas of members 6 and 7 will abut with corresponding abutment surfaces (or abutment areas) on the plastic connection piece 18 in a water-tight manner. Reference numeral 22 thus indicates a planar face, which corresponds to the plane of abutment surfaces which will be in sealing contact with the end faces of the frame member 6. Similarly, the planar surface generally denoted as 36 corresponds to the plane of abutment surfaces which will lie in sealing contact with the corresponding surfaces of the end face of frame member 7. Additionally, the vertical surfaces which will not have their own sealing strip (for sealing the pane itself) will also lie in water-tight contact with corresponding vertical surfaces on the connection piece 18. Accordingly it will be apparent that the dimensions of the plastic corner piece 18 must be large enough to provide abutment surfaces giving a water-sealing contact with at least all the box-channel profiles of the corresponding frame members.

The connection piece 18 is provided with integral projecting portions 23-26, for example moulded in one piece therewith, which act as guide portions enabling the vertical and horizontal frame members to be fitted together correctly. The guide members should thus substantially correspond to the respective inner dimension of the box channel sections.

The corner joint is preferably held together by the use of screws 27-30 which hold the frames together and pass through the connection piece 18, as shown by the dashed lines (see e.g. screw 30 and holes 31-33) and are fixed into the frame members at locations 34, 35 and 37, 38.

Whilst the term "drainage" is used to describe the function of the plastic connection piece in the space between the frame members, the connection piece also serves to provide ventilation. When applied to a top corner joint, it is of course its function to act as a ventilation means for the frame. Thus where the term drainage is used in the description and claims, this term is applicable to both drainage and ventilation.

Figs. 5 and 6 show cross-sections of frame member 6 for a fixed and opening window respectively. Fig. 5 corresponds to the joint shown in Figs. 1 to 4 with a glass pane 41 and seals 39, 40 added appropriately. Reference 46 denotes a plastic block which is added below the pane 41 in a manner known per se. The cooperating projections 42, 43 and 44, 45 provide a means for snap-fitting the cover panel 11 to the frame.

Fig. 6 shows a fixed lower frame consisting of profiles 52 and 53 joined by insulators 54 and having a simple cover panel 51, together with an openable upper window frame which corresponds in most details to Fig. 5 and thus has references denoted with e.g. 11' instead of 11. The openable part may however be exactly as shown in Fig. 5 with profiles 6b and 6a remaining unaltered. The upper frame is openable towards the left in the figure and, when closed, seals against a seal 55.

In such a window, a separate plastic connection piece is required for the corner joints of each of the fixed and the moving frames. As will be appreciated, the parts 56 and 57 of the lower profile are fastening points for self-tapping screws such as 29 and 30 in Fig. 4. In all other important respects, the plastic connection pieces and formed in accordance with the previous fixed window type.

Whilst certain embodiments of the invention have been described above, the invention is not limited thereto but can be varied within the scope of the appended claims. For example, whilst the invention has particularly great advantages in the field of metal frames for windows, the form of the frame member profiles may be varied for any suitable purpose.