GB2353816A

GB2353816A - Method of and apparatus for welding door or window frame with fitted seals held in compression during the welding process

Info

Publication number: GB2353816A
Application number: GB9920845A
Authority: GB
Inventors: Steven Andrew Robins
Original assignee: PERMACELL FINESSE Ltd
Current assignee: PERMACELL FINESSE Ltd
Priority date: 1999-09-03
Filing date: 1999-09-03
Publication date: 2001-03-07
Also published as: GB9920845D0

Abstract

Door or window frames are formed from extruded plastics members 13 carrying coextruded sealing strips 18 extending along the member length. The first and second frame members maybe clamped on a support surface 22 by clamping means 32, the ends are heated and then urged together to form a weld. In order to prevent the weld interfering with the operation of the sealing strips 18, the sealing strips 18 are held compressed against the associated frame member during the welding operation. Optional movable dies 23,24 prevent migration of the sealing strip material around the weld. The frame member 13 is preferably T-shaped in cross section.

Description

1 2353816 DOOR/WINDOW FRAMES The invention relates to the manufacture of

door and window frames. The term "frame" includes both the fixed outer frame of a door or window and the inner movable (usually hinged) inner leaf frame.

Door or window frames are manufactured from plastics frame members whose ends are interconnected to form the frame. The frame members carry respective sealing strips which extend to the joined ends of the frame members and are joined together with the frame members. This is done by heating the ends of two frame members and the associated ends of the sealing strips and then urging the ends together to form a welded joint between the two frame members and between the sealing strips.

It is a problem with such manufacture that the urging together of the heated ends of the frame members and the sealing strips forms an upstanding bead extending around the join. In general, this is removed by milling or cutting at least flush with the surfaces of the members. There is, however, a problem in the region of the join of the sealing strips. In this region, it has been found that known joining methods can form a bead that extends outwardly of the uncompressed height of the sealing strip. Thus, when the bead is cut back, there remains a residual bead that still has the height of the uncompressed sealing strip.

2 The purpose of the sealing strip is to allow the frame to seal against a co-operating member (which, when the frame is a fixed outer frame, is a movable leaf frame and, when the frame is a movable leaf frame, is a fixed outer frame). In this case, the co operating part will seat against the residual bead and thus not compress the sealing strip, so reducing the effectiveness of the seal or rendering the seal ineffective.

In addition, it has been found that the heated material of the sealing strip, which is usually a dark, often black, elastomeric material, can creep into the heated joined material of the frame members, which can often be a white plastic, so making the join unsightly.

According to a first aspect of the invention, there is provided a method of forming a door or window frame comprising preparing first and second plastics frame members having respective first and second ends, the first frame member carrying a first sealing strip extending to the first end of the first frame member and the second frame member carrying a second scaling strip extending to the first end of the second frame member, heating the first ends of the first and second frame members and the associated ends of the sealing strips and urging the first ends together to form a welded joint between the first and second frame members and between the sealing strips, the sealing strips being held compressed against the associated frame members during the formation of the welded joint.

3 It has been found that such compression produces a weld which can be cut back to the compressed height of the sealing strip, so allowing the sealing strip to perform its sealing function.

According to a second aspect of the invention, there is provided an apparatus for forming a door or window frame comprising clamping means for clamping first and second frame members on respective supports with respective first ends of the first and second frame members adjacent, means for compressing first and second sealing strips carried by the first and second members respectively and means for heating the 10 first ends of the first and second members and for urging the first ends together to form a welded joint between the first and second frame members and between the compressed sealing strips. According to a third aspect of the invention, there is provided a die for forming a door 15 or window frame by the method of the first aspect of the invention and in which first and second frame members are clamped during the formation of the weld, the clamping compressing the sealing strips against associated dies and in which the dies form at least one additional gap therebetween which confines a portion of the weld formed therebetween, the first and second members having respective planar surfaces 20 facing in a direction generally opposite to associated base surfaces, each die having a die part that at least partially overlies the associated opposite surface, the parts forming an additional gap therebetween and the die parts being movable relatively to 4 the remainder of the associated dies as the first and second frame members are compressed so that the die parts remain in contact with the associated opposed surfaces during formation of the weld, the die having an end surface for co-operating with an end surface of a second die to form said gap for confining a weld fortned between the first and second frame members and the associated sealing strips supported by the dies, the die including a portion for compressing the sealing strip of the associated frame member and a die part movable relative to the remainder of the die to accommodate compression of the associated frame member.

The following is a more detailed description of an embodiment of the invention, by way of example, reference being made to the accompanying drawings in which:

Figure 1 is a cross-section of an extruded plastics window frame member carrying two sealing strips, Figure 2 is a similar view to Figure 1 but showing the frame member mounted in a frame forming apparatus and engaging with two dies prior to compression, Figure 3 is a plan view from above of the frame member of Figure 2 together with the second frame member and corresponding dies, the frame members being shown prior to being welded together, Figure 4 is a similar view to Figure 2 but showing the frame members compressed ready for welding the part compressing the members being omitted for clarity.

Figure 5 is a plan view from above of the frame members after welding showing the compression member removed but the dies in position, and Figure 6 is a section along the line X-Y of Figure 5.

Referring first to Figure 1, a frame member for a window comprises an elongate member indicated generally at 10 of T-shaped cross-section. The member 10 has a base 11 and side walls 12 with a top wall 13 formed by a central portion 14 flanked by bevelled side portions 15 each extending between the central portion and a respective side edge 16.

The top wall 13 extends laterally beyond the side walls 12 to form the cross-piece of the T-shape of the cross section and the projecting portions of the under surface of the top wall 13 are formed with respective channels 17. Each channel 17 receives an associated sealing strip indicated generally at 18 and formed by a root 19 received within the channel, a base 20 extending nonnal to the root 19 and connected to the root 19 and an angled sealing portion 21 extending from an edge of the base 20 towards the associated side wall 12.

6 It will be appreciated that the member 10 and the sealing strips 18 are merely schematic examples of very many different members and sealing strips that can be used.

The frame member 10 and the sealing strips 18 are formed from respective plastics materials. They may be formed together by post calibration extrusion. In post calibration extrusion, the frame member 10 is extruded and then passes through calibration, where the form of the hot, soft extrusion is maintained while being cooled. Once the frame member 10 exits the calibration and a cooling stage it passes to a die 10 where the sealing strips 18 are extruded on to the frame member 10. The frame member 10 may be made from a material such as U-PVC and the sealing strips 18 may be made from an elastomeric material. As a result of the co- extrusion, the sealing strips 18 are connected to the associated channel 17 although the connection is not so strong as to prevent the sealing strips 18 being pulled out of the channels if 15 the sealing strips 18 need to be replaced. For the purposes of the joining method to be described below, however, the sealing strips 18 are fixed relative to the frame member 10. The frame member 10 is designed to form the fixed outer frame of a window, but other sections may be used that form a movable leaf frame or form fixed or moving parts of a door. 20 In order to form a fixed outer window frame, four members identical in cross-section to the member 10 are connected together in a square or rectangle. Thisisachieved 7 by mitring the ends of the four frame members 10 at an angle of 45' and then connecting the ends together. A connection between two such ends will now be described with reference to the remaining Figures.

Referring next to Figures 2 and 3, a joint between two frame members I Oa, I Ob is formed as follows. First, the two frame members 10a,10b are placed on a support surface 22 of an apparatus for joining the frame members I Oa, I Ob. As will be seen from Figure 3, the frame members I Oa, I Ob are placed at right angles to one another with their mitred ends close but spaced apart. 10 Each frame member 10a,10b is supported by a first die 23a,23b and a second die 24a,24b. The first dies 23a,23b as seen in Figure 3, are associated with the outer edge of the joint to be formed whereas the second dies 24a,24b are associated with the inner edges of the joint to be formed. 15 Each first die 23a,23b comprises a block 25a,25b having an inner face 26a,26b adjacent the side wall 12a,12b of the associated frame member 10a,10b. Theblock 25a,25b also has an upper face 27a,27b which touches the end of the sealing portion 21a,21b of the associated sealing strip 18a,18b without compressing the sealing 20 portion 21a,21b. A movable die part 28a,28b is connected to the block 25a,25b for up and down movement in a vertical direction. The movable die part 28a,28b includes 8 a projecting portion 29a,29b that overlies the adjacent side portion 15a, 15b of the top wall 13 a, 13b of the associated frame member I Oa, I Ob.

Each second die 24a,24b is formed by a block of rectangular cross section having an inner wall 30a,30b adjacent an associated side wall 12a,12b of the frame member I Oa, I Ob and an upper surface 3 1 a,3 I b that contacts the end of the sealing portion 21a,21b of the associated sealing strip 18a,18b without compressing the sealing portion 2 1 a,2 I b.

As will be seen from Figure 3, the first and second dies 23a,23b,24a,24b are spaced from the mitred edges of the associated frame edges 10a,10b. This spacing is determined by the welding process to be described below.

Next, as seen in Figure 4, a clamping member 32 is brought down on to each of the central portions 14a,14b of the top walls 13a,13b of the frame members 10a,10b to clamp the frame members I Oa, I Ob between the clamping member 32 and the support surface 22. Since the frame members 10a,10b are of plastics material, this results in the depth of the frame members I Oa, 1 Ob being reduced. The effect of this is shown in Figure 4 where it will be seen that the sealing strips 1 8a, 1 8b are compressed against the upper surfaces 27a,27b,3 la,31b of the first and second dies 23a,23b, 24a,24b. The projecfing part 29a,29b of the first dies 23a,23b nevertheless stay in contact with the 9 associated side portions 15a,15b as a result of the ability of the movable die parts 28a,28b to move vertically relative to the block 25a,25b.

Next, a heated TeflonTm coated plate is brought into the gap between the mitred ends.

This plate 33 may be heated to a temperature of between 220'C-260'C and preferably to a temperature of about 24WC. The plate 33 is left in this location for a sufficient time to allow the ends of the frame members 1 Oa, 1 Ob and the ends of the sealing strips 18a,18b to soften to the point at which they can be welded. The plate 33 is then withdrawn and the ends of the two frame members 10a,10b and of the sealing strips 18a,18b (because they are fixed to the frame members 10,10b) are then urged together. The effect of this is to weld the ends together and in forming the weld, the material of the frame members 10a,10b and the sealing strips 18a,18b is pushed outwardly to form a bead of material 34 extending around the join. This is seen in more detail in Figure 6. As seen in that Figure, the projecting portions 29a,29b of the movable die parts 28a,28b and the blocks 25a,25b form respective gaps 35, 36 that constrain the width of the bead; the joints between the side walls 12a, 12b will be similarly constrained as will the joints between the sealing strips 18 a, 1 8b at the inner side of the joint as a result of the action of the second dies 24a,24b. The spacing of the dies 23a23b,24a,24b is chased so that, when the weld is formed, the dies of each pair 23a,23b,24a,24b are spaced to confine the bead 34 to a desired width.

When the weld has cooled, the frame members 10a,10b can be removed and the bead 34 removed by manual use of a router or by a machine.

It has been found that, by maintaining the scaling strips 18a, 1 8b, compressed while the weld is being formed, the bead 34 can be cut back to a point at which it is no higher than the compressed height of the sealing strips 18a, 1 8b. This means that, when the bead 34 is removed, the residual bead does not affect the sealing performance of the sealing strip since the uncompressed sealing portion 21a,21b of each sealing strip 18a,18b is spaced outwardly of the residual bead and thus performs its sealing function.

It has also been found that the arrangement described above with reference to the drawings resists any tendency of the material of the sealing strips 1 8a, 1 8b to migrate into the portion of the bead 34 extending between the outer portions 14a, 14b, of the top wall 15 a, 1 5b, covered by the proj ecting part 29a,29b of the movable die part 2 8 a,2 8b.

This means that, when the bead is removed, there is no unsightly marking from such migrated material. This is a particular problem where the plastics material of the frame member 10a,10b is white and the elastomeric material of the sealing strips 18a,18bisblack. It is believed that this is due to the fact that the movable die parts 28a,28b stay in contact with the frame member 10a, 1 Ob during the formation of the weld and so control the bead 34.

I I It will be appreciated that if the frame members 1 Oa, I Ob are inverted, so that the top walls 13a,13b rest on the support surface 22, corresponding inverted dies 23a,23b,24a,24b will be used except that no separate movable die part will be necessary. This is because the compression at the lower end of the frame members 1 Oa, I Ob is minimal. Nevertheless, it will still be necessary to arrange for the first dies 23 a,23b and the second dies 24a,24b to hold the sealing strips 10 compressed adjacent the join to ensure that the bead can be cut back to a level which is the same as or less than the compressed height of the sealing strips I 8a, I 8b.

It will be appreciated that the apparatus need not just join two frame members 10a,10b together at the same time; it could join together three or four such members simultaneously. In addition, the members need not be of T-shaped cross- section, as shown in Figure 1. They could be of any suitable cross-section such as L- shaped or Z-shaped.

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Claims

1. A method of forming a door or window frame comprising preparing first and second plastics frame members having respective first and second ends, the first frame member carrying a first compressible sealing strip extending to the first end of the first frame member and the second frame member carrying a second compressible sealing strip extending to the first end of the second frame member, heating the first ends of the first and second frame members and the associated ends of the sealing strips and urging the first ends together to form a welded joint between the first and second frame members and between the sealing strips, the sealing strips being held compressed against the associated frame members during the formation of the welded joint.

2. A method according to claim 1 wherein each sealing strip has a portion adjacent the first end of the associated frame member, the method comprising compressing each said portion between a respective die and the associated frame member during formation of said weld, the dies forming a gap therebetween which confines a portion of the weld formed therebetween.

3. A method according to claim 2 and comprising clamping the first and second frame members during formation of the weld, the clamping compressing the sealing strips against the associated dies.

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4. A method according to claim 3 and comprising mounting the first and second frame members on a support and then compressing the first and second frame members down on to the support, to clamp the first and second frame members, said compression compressing the sealing strips against the associated dies.

5. A method according to claim 3 or claim 4 wherein the first and second frame members have respective planar base surfaces which engage said support, the scaling strips being carried on respective frame member surfaces generally parallel to the associated base surfaces and facing the same direction as the base surfaces, the dies being mounted on the support and said clamping compressing the sealing strips between the dies and the associated frame members.

6. A method according to claim 5 and comprising arranging a gap between each sealing strip and the associated die prior to said compression, the gap being taken up by said compression.

7 A method according to claim 5 or claim 6 wherein the dies form at least one additional gap therebetween which confines a portion of the weld formed therebetween.

8. A method according to claim 7 wherein the first and second frame members have respective planar outer surfaces facing in a direction generally opposite to the 14 associated base surfaces, each die having a die part that at least partially overlies the associated outer surface, the die parts forming an additional gap therebetween and the die parts being movable relative to the remainder of the associated dies as the first and second frame members are compressed so that the die parts remain in contact with the associated outer surfaces during formation of the weld.

9. A method according to claim 8 wherein each outer surface has parallel side edges and includes a central portion lying in a plane parallel to the plane of the associated base surface and two edge portions each angled relative to the associated central portion and extending between the central portion and an associated side edge, each die part overlying a respective edge portion.

10. A method according to claim 9 wherein each frame member is of generally T-shaped cross-section with said base surface extending along the foot of the T-shape and the outer surface extending along the upper surface of the cross- member of the T shape, each sealing strip being carried on an under surface of the cross- member of the T-shape, each die forming a gap extending along said edge portion, around the associated side edge and along the associated under surface.

11. A method according to claim 3 or claim 4 wherein the first and second frame members have respective planar outer surfaces which engage said support, the sealing strips being carried on respective frame member surfaces generally parallel to the associated base surfaces and facing in a direction opposite to the outer surfaces, the dies resting on the sealing strips and said clamping compressing the sealing strips between the dies and the associated frame members.

12. A method according to any one of claims 1 to 11 wherein the sealing strips are fixed against movement relative to the associated frame members during formation of the weld.

13. A method according to any one of claims 1 to 12 wherein each sealing strip and the associated frame member are formed by post calibration extrusion.

14. A method according to any one of claims 1 to 13 wherein each sealing strip comprises a root and a sealing portion, the root being received in a channel formed in the associated frame member.

15. A method according to any one of claims 1 to 14 wherein each frame member carries two sealing strips, both sealing strips being compressed during formation of the weld.

16. A method of forming a door or window frame substantially as hereinbefore described with reference to the accompanying drawings.

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17. Apparatus for forming a door or window frame comprising clamping means for clamping first and second frame members on respective supports with respective first ends of the first and second frame members adjacent, means for compressing first and second compressible sealing strips carried by the first and second members respectively and means for heating the first ends of the first and second members and for urging the first ends together to form a welded joint between the first and second frame members and between the compressed sealing strips.

18. Apparatus according to claim 17 wherein the compressing means comprise a die with a die part movable relative to the remainder of the die.

19. Apparatus for forming a door or window substantially as hereinbefore described with reference to the accompanying drawings.

20. A die for forming a door or window frame by the method of claim 8 the die having an end surface for co-operating with an end surface of a second die to form a gap for confining a weld formed between first and second frame members and associated compressible sealing strips supported by the dies, the die including a portion for compressing the sealing strip of the associated frame member and a die part movable relative to the remainder of the die to accormnodate compression of the associated frame member.

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21. A die substantially as hereinbefore described with reference to the accompanying drawings.