GB2105243A

GB2105243A - Forming joints

Info

Publication number: GB2105243A
Application number: GB08123649A
Authority: GB
Inventors: Douglas Harry Meridew Brooks
Original assignee: Blacknell Buildings Ltd
Current assignee: Blacknell Buildings Ltd
Priority date: 1981-08-03
Filing date: 1981-08-03
Publication date: 1983-03-23

Abstract

Two elongate wooden members 2 each have a mitred end face 4, and are each clad with a plastics cover sleeve 6 which extends beyond the end face 4. The wooden members 2 are positioned at 90 DEG to each other so that the end faces 4 are parallel to but spaced from one another by a gap 8. To cement together the two end faces 4 and the internal surfaces 10 of the plastics sleeves 6 a thermoplastic resin is introduced into the gap 8. To retain the unset resin in the gap 8, a suitably shaped restraining frame 12 is located around the gap 8 and the projecting portions of the sleeves 6. In another joint of the invention a hollow restraining frame is located in the gap between the wooden members to support the projecting portions of the cover sleeves. <IMAGE>

Description

SPECIFICATION Non-weld join The present invention relates to a method of forming a joint between two lengths of plastics-covered wood.

The invention is particularly concerned with forming a joint between the constituent members of window, door or the like frames used in the building industry. The various members of these frames may have first been clad by a plastics cover or sleeve prior to being joined.

It has been the practice to join the various members of a wooden frame by dovetailing or mitring them either with or without the use of a conventional adhesive, by screwing or nailing them together, or by a combination of these methods. The joints produced by any of these known methods are found to be substantially rigid.

It is found however that rigid frames can have disadvantages, for example if the frames are to be used in buildings to be constructed or repaired in areas affected by mining subsidence. In these cases it is preferable to have frames possessing joints of a limited resilience.

It is also known to join the members of a plastics coated wooden frame using thermosetting resin such as for example a catalysed polyurethane resin.

It has been found however that the use of thermosetting resins in this method of forming a joint possesses the following disadvantages:~ It is necessary to use a separate ingredient constituting the catalyst. This requires the use of special equipment to feed the resin and catalyst in very accurate proportions, thoroughly mix the ingredients, and then measure a quantity of the mixed material prior to injection into the joint. This equipment requires constant and skilled maintenance if a satisfactory result is to be consistently obtained.

By their very nature thermosetting resins set to infusible materials. Although the equipment used is designed to inject the material into the joint prior to this hardening, it is found that a lesser degree of hardening can occur within the mixing equipment.

This causes a degree of inconsistency in the volume of thermosetting resin injected at each operation, and periodic cleansing of the equipment is required.

Thermosetting resins develop an exotherm by which is meant they progressively gain heat during the setting period. The amount of heat developed will vary with changes in the ambient temperature.

This variation can have an adverse affect on the joint being formed particularly if the heat developed exceeds the softening point of the plastics cover which is part of the joint.

Because of the critical nature of the thermosetting reaction, the degree of adhesion consistency within the joint is not always satisfactory. In addition minimum adhesive requirements to the plastics cover are not always achieved.

Thermosetting resins and their catalysts are often toxic and special handling precautions are required, particularly when using polyurethane resins. During the injection period thermosetting resins are often of low viscosity causing leaks and spillage from small holes and defects in the appropriate portion of the joint. This causes difficulties in cleaning the outside portion of the joint.

It is an aim of the invention to form a joint between two lengths of plastics covered wood in which the aforementioned disadvantages are alleviated.

According therefore to one aspect of the invention there is provided a method of forming a joint between two lengths of plastics-covered wood; said method comprising offering an uncovered end of a first of said lengths to an uncovered end of a second of said lengths so that said ends to be joined spacedly oppose each other to define a gap therebetween surrounding the edges of said gap by a removable restraining frame to enclose the gap, and adhesively bonding the said uncovered ends to each other and to the internal surfaces of the plastics coverings by introducing a thermoplastic resin into the gap and allowing the resin to harden.

According to another aspect of the invention there is provided a method of forming a joint between two lengths of plastics-covered wood; said method comprising offering an uncovered end of a first of said lengths to a lateral exterior surface of the plastics covering of a second of said lengths so that the said end and lateral exterior surface to be joined spacedly oppose each other to define a gap therebetween, surrounding the edges of said gap by a removable restraining frame to enclose the gap, and adhesively bonding the said uncovered end to said lateral exterior surface and to the internal surface of the plastics covering of said first length by introducing a thermoplastic resin into the gap and allowing the resin to harden.

According therefore to another aspect of the invention there is provided a method of forming a joint between two lengths of plastics-covered wood; said method comprising arranging each plastics covering so that it projects beyond its respective member end, offering an uncovered end of a first of said lengths to an uncovered end of a second of said lengths so that said ends to be joined spacedly oppose each other to define a gap therebetween, inserting into the gap a hollow restraining frame which supports the projecting portions of the coverings, and adhesively bonding the said uncovered ends to each other by introducing a thermoplastic resin into the restraining frame and allowing the resin to harden.

The term gap is used in this Specification to define a space having any shape encountered in the formation of joints, and includes the space between two lengths at right-angles to one another.

The method of the invention may include forming one or more holes through the plastics covering or the plastics covering and wood member of at least one of said lengths so as to allow entry of the thermoplastic resin into the gap.

The drawing(s) originally filed were informal and the print here reproduced is taken from a laterfiledformal copy. Theterm"plastics-covered wood" is used in this Specification to mean wood which has a skin of plastics material substantially thicker than would be obtained by painting the wood with a plastcs-based paint.

The preferred thermoplastic resins used in the method of the invention are thermoplastic copolyesters such as polyethylene terephthalate or polybutylene terephthalate each produced by the polyesterification reaction between more than one glycol and/or more than one di-basic acid normally used for the production of thermoplastic monopolyesters. Other suitable thermoplastic resins are other copolyesters such as the polymer of cyclohexane - di - methanol and terphthalic acid with the terephthalic acid partly replaced with other acids.

Also suitable is the glycol-modified version of polyethylene terephthalate copolyester.

It is found that the use of thermoplastic resins does not give rise to the previously mentioned disadvantages encountered when using thermosetting resins. Because thermoplastic resins are more viscous than thermosetting resins, during the injection process into the joint gap the thermoplastic resins are more readily contained within the seams or joints ofthe restraining frame. Also the overall injection and hardening cycle of thermoplastic resins is of shorter duration; for example for a gap volume of 100 ml, the cycle is approximately 1.5 minutes compared with 5.0 minutes for the thermosetting resin.

Finally, the thermoplastic resins can be almost colourless compared with the naturally dark colour of the thermosetting resins. Consequently thermoplas- tic resins can be readily pigmented to match the colour of the plastics coverings and therefore the joint will be of a neater and more consistent appearance.

Further examples of thermoplastic resins suitable for the method of the invention are hot-melt adhesives based on thermoplastics saturated polyester or copolyester resins, or modified copolyamide resins.

Thermoplastic resins which are particularly suitable are the thermoplastic copolyesters based mainly on terephthalic acid whose synthesis uses more than one glycol and/or more than one di-basic acid.

Embodiments of the invention will now be described by way of example with reference to the accompanying illustrative drawings in which: FIGURES 1 to 3 are side elevations in section of three different joints each formed by a method of the invention, FIGURE 3A is a cross-section on the line A-A of Figure 3, FIGURE 3B is a cross-section along the line B-B of Figure 3, FIGURE 4 is a side elevation in section of another joint formed by a method of the invention, FIGURE 4A is a cross-section taken along the line A-A of Figure 4, FIGURES 5 to 18 are side elevations in section of other joints of the invention and FIGURE 19 is a partial perspective view of a part of some of the joints.

Referring to Figure 1, two elongate wooden mem bers 2 each have a mitred end face 4, and are each clad with a plastics cover sleeve 6 which extends beyond the end face 4. The wooden members 2 are positioned at 90 to each other so that the mitred end faces 4 are parallel to but spaced from one another by a gap 8 approximately 1.5 mm wide.

In order to cement the two mitred end faces 4 to one another and to the internal surfaces 10 of the projecting portions of the plastics sleeves 6 a thermoplastic resin is introduced into the gap 8 between the two end faces 4.

With previously proposed methods, there has been a tendency for the resin to ooze out of the gap 8 before the resin had set. This brought about the need to trim off any excess resin material. To reduce this tendency of the resin to ooze out, in the method of the invention a restraining frame is used for each joint being formed; this frame being shaped to form at least a temporary shutter around the gap 8 and the projecting portions of the sleeves 6. This restraining frame is an element separate from the wooden members 2, and is made up of a suitable number of lengths of a section which are joined orjoinable together to form the assembled restraining frame.

Referring to Figure 1, one embodiment of the restraining frame 12 is made of any suitable material, such as aluminium for example, and is of rectangu lar transverse cross-section. This restraining frame 12 is shaped to fit and surround the projecting portions of the cover sleeves 6 so as to enclose the gap 8. The restraining frame 12 is provided with a suitable aperture through which the thermoplastic resin can be introduced into the gap 8 to form therein a permanent element of the joint. It will be noted that in the joint of Figure 1 the projecting ends of the cover sleeves 6 abut one another so that the set thermoplastic resin does not constitute any part of the exterior surface of the joint.

Referring to Figure 2, another joint formed by a method of the invention is the same as the joint of Figure 1 except that the projecting portions of the cover sleeves 6 do not abut one another when the covered wooden members are in their correct joining position.

When in this joining position, the ends 14 of the cover sleeves 6 are spaced from one another to form gaps 16 which are more narrow than the main gaps 8. The restraining frame 12 has the same construction as the aforementioned restraining frame of Figure 1, and the method of forming the joint is the same as the above described method of forming the joint of Figure 1. With the joint of Figure 2 however portions 18 of the set thermoplastic resin constitute the inner and outer external corner surfaces of the joint.

Referring to Figure 3, two elongate wooden members 20 and 22 have end faces 24 and 26 respectively which are perpendicular to the longitudinal axes of the members 20 and 22. These members 20 and 22 have plastics cover sleeves 28 and 30 which project beyond the end faces 24 and 26 to define gaps 32 and 34 respectively. The wooden members and the plastics sleeves are each of square transverse cross-section, with the wooden members and the plastics sleeves each being of the same size as one another. A transverse passage 36 extends through the mid-point of opposite sides of the plastics sleeve 30 and through the aligned part of the wooden member 22. An axial passage 38 extends along the longitudinal axis of the wooden member 22 from the gap 34 to the passage 36.

To assemble the joint, the wooden members 20 and 22 are located at 900 to one another with the projecting ends of the plastics sleeve 28 abutting one side of the plastics sleeve 30. A restraining frame, similarto the frame illustrated in Figures 1 and 2, is located around the end portion of the contacting plastics covered members 20 and 22. This restraining frame 40 has a passage 42 therein which aligns with the transverse passage 36.

A thermoplastic resin is passed along the passage 42 and through the passages 36 and 38 into the gaps 32 and 34, and allowed to harden to secure together the plastics covered wooden members 20 and 22.

When the resin has hardened the restraining frame 40 is removed to leave the joint ready for use.

It will be appreciated that the joint illustrated in Figure 3 could be formed with wooden members and plastics sleeves of rectangularcross-section instead of square cross-section. The joints illustrated in Figures 1 and 2 can be formed from wooden members and plastics sleeves of any cross-section provided that the respective wooden members and plastics sleeves are of the same cross-section and equal size.

Referring to Figure 4, a wooden member 44 has an end face 46 at 900 to the longitudinal axis of the member 44. This member 44 is clad with a plastics cover sleeve 48 which projects beyond the end face 46 to define a gap 50. The member 44 and plastics sleeve 48 are each of square transverse crosssection.

A wooden member 52 is clad with a plastics cover sleeve 54, each having the transverse cross-section illustrated in Figure 4A. To assemble the joint, the members 44 and 52 are located at 900 to one another, and the plastics sleeve 48 is cut so that the sleeve end face 56 abuts the sleeve 54 so as to close the gap 50. A transverse passage 58 extends through the member 52 and sleeve 54 to provide access to the gap 50. A restraining frame 60 is located around the parts of the members 44 and 52 and the sleeves 48 and 54 constituting the joints. This restraining frame 60 is shaped to make an exact fit with the end portions of the sleeves.48 and 54 constituting the joint, and a passage 62 is formed in the restraining frame 60 to align with the transverse passage 58.

To form the joint, a thermoplastic resin is injected through the passages 62 and 58 so as to fill the gap 50. The resin in the gap 50 is allowed to harden, and then the restraining frame 60 is removed to leave the formed joint.

Referring to Figure 5, two elongate wooden members 64 each have end faces 66 which are normal to their longitudinal axes. Each wooden member 64 is clad with a plastics cover sleeve 68 which extends beyond the member end face 66 and has a mitred end edge. Because of this, after the covered wooden members 64 have been positioned as illusrated, the mitred end edges abut one another to provide a continuous joint.

Before the cover sleeves 68 are brought com pletely into contact with one another a restraining frame 70 is located in the gap 72 between the member end faces 66. This restraining frame 70 has two legs 74 and 76 at right-angles to one another, which are dimensioned to make a sliding fit in the projecting portions of the cover sleeves 68, and to abut the end faces 66 when the joint is formed as illustrated. Atransverse passage 78 extends through one of the cover sleeves 68 and the aligned part of the frame leg 74.

When forming the joint, the frame legs 74 and 76 are inserted into the projecting portions of the cover sleeves 68 to which they are preferably joined by means of a suitable adhesive. The components of the joint are dimensioned so that the mitred end edges of the cover sleeve 68 abut one another and the ends of the frame legs 74 and 76 abut the wooden member end faces 66 when the joint is fully assembled. In order to cement the two end faces 66 to one another and to the internal surfaces of the frame legs 74 and 76 a thermoplastic resin is intro duced into the gap 72 through the transverse passage 78.

Figures 6to 16 illustrate modified versions of the joint of Figure 5, and for clarity corresponding components will be given the same reference numerals.

Figure 6 illustrates a joint basically the same as the joint of Figure 5 except that the end edges of the frame legs 74 and 76 are spaced from the wooden member end faces 66.

In the joint of Figure 7, a base 80 extends outwardly from the central part of the restraining frame 70 to be flush with the outer surfaces of the plastics cover sleeves 68.

In the joint of Figure 8, the restraining frame 70 is similar to the frame of Figure 7 except that it is spaced from the end faces 66 of the wooden members 64.

In the joint of Figure 9, the end faces 66 are mitred to define a gap 72 which is smaller than the gaps of Figures 5 to 8. The restraining frame 70 is in the form of a collar having two legs 82 and 84 which are dimensioned to abut the end faces 66 when the joint is fully assembled. A passage 86 extends through the projecting portion of one of the cover sleeves 68 to enable a thermoplastic resin to be introduced into the gap 72 between the two end faces 66.

In the joint of Figure 10 the restraining frame 70 is a collar similar to the collar illustrated in Figure 9, except that it has a base 80 projecting outwardly to be flush with the outer surfaces of the cover sleeves 68.

The internal restraining frames illustrated in Figures 5 to 10 are thin-walled. The joint illustrated in Figure 11 includes a restraining frame in the form of a collar 88 which is the same as the collar illustrated in Figure 9 except that it is thick-walled.

The joint of Figure 12 includes a thick-walled collar 90 which is the same as the collar 88 except that it has an outwardly extending base 80 which is flush with the outer surfaces of the cover sleeves 68.

The joint of Figure 13 includes a thin-walled collar 92 which is the same as the collar of Figure 9 except that its legs 82 and 84 are spaced from the mitred end faces 66 of the timber members 64.

The joint of Figure 14 includes a thin-walled collar O4 which is the same as the collar 92 except that it has an outwardly projecting base 80 which is flush with the outer surfaces of the cover sleeves 68.

The joint of Figure 15 includes a thick-walled collar 96 which is the same as the collar 88 of Figure 11 except that its legs 82 and 84 are spaced from the end faces 66.

The joint of Figure 16 includes a thick-walled collar 98 which is the same as the collar 96 except that it includes an outwardly projecting base 80 which is flush with the outer surfaces of the cover sleeves 68.

Figures 17 and 18 illustrate joints which are similar to the joints of Figures 1 and 2, and for clarity corresponding components will be given the same reference numerals.

Referring to Figure 17, two elongate wooden members 2 each have an end face 4 which is normal to its longitudinal axis. Each wooden member 2 is clad with a plastics cover sleeve 6 which extends beyond the end face 4 and has a mitred end edge.

The wooden members 2 are positioned at 90 to each other so that the end faces 4 are normal to and spaced from one another by a gap 8 with the cover sleeve end edges abutting one another.

In order to cement the end faces 4 to one another and to the internal surfaces 10 of the projecting portions of the plastics sleeve 6 a thermoplastic resin is introduced into the gap 8 through a passage 100 in the projecting portion of one of the plastics sleeves 6.

A restraining frame 12 is shaped to fit and surround projecting portions of the cover sleeves 6 so as to enclose the gap 8. This restraining frame 12 is provided with a suitable aperture through which the thermoplastic resin can be introduced into the passage 100 so that it may enter the gap 8.

In the joint of Figure 17 the projecting end edges of the cover sleeves 6 abut one another so that the set thermoplastic resin does not constitute any part of the exterior surface of the joint.

The joint of Figure 18 is similar to the joint of Figure 17 except that the projecting end edges of the cover sleeves 6 do not abut one another when the joint is assembled. These projecting end edges are spaced from one another to form gaps 16 which are more narrow than the main gaps 8 thereby enabling the set thermoplastic resin to constitute the inner and outer external corner surfaces of the joint.

It will be appreciated that the joints illustrated in Figures 5 to 18 could be formed with wooden members and plastics cover sleeves of any cross-section provided that the respective wooden members and plastics sleeves are of the same cross-section and equal size.

It will be appreciated that the restraining frame used in the joints illustrated in Figures 1 to 4, 17 and 18 can have any suitable shape provided that it fits exactly around and corresponds to the cross-section of the portions of the plastics sleeves adjacent to the joint being formed. This enables the restraining frame to maintain these portions of the wooden members and plastics sleeves in the correct position while the thermoplastic resin is hardening in the gap. Similarly the restraining frame used in the joints illustrated in Figures 5 and 16 can also have any suitable shape provided that it fits precisely in and corresponds to the cross-section of portions of the plastics sleeves adjacent to the joint.

One restraining frame is illustrated by way of example in Figure 19. It will be understood that in the method of this invention the plastics sleeves are not welded together to form an enclosed gap for the reception of the thermoplastic resin.

Claims

1. A method of forming a joint between the lengths of plastics-covered wood; said method comprising offering an uncovered end of a first of said lengths to an uncovered end of a second of said lengths so that said ends to be joined spacedly oppose each other to define a gap therebetween, surrounding the edges of said gap by a removable restraining frame to enclose the gap and adhesively bonding the said uncovered ends to each other and to the internal surfaces of the plastics coverings by introducing a thermoplastic resin into the gap and allowing the resin to harden.

2. A method of forming a joint between two lengths of plastics-covered wood; said method comprising offering an uncovered end of a first of said lengths to a lateral exterior surface of the plastics covering of a second of said lengths so that the said end and lateral exterior surface to be joined spacedly oppose each other to define a gap therebetween, surrounding the edges of said gap be a removable restraining frame to enclose the gap, and adhesively bonding the uncovered end to said lateral exterior surface and to the internal surface of the plastics covering of said first length by introducing a thermoplastic resin into the gap and allowing the resin to harden.

3. A method of forming a joint between two lengths of plastics-covered wood; said method comprising arranging each plastics covering so that it projects beyond its respective member end, offering an uncovered end of a first of said lengths to an uncovered end of a second of said lengths so that said ends to be joined spacedly oppose each other to define a gap therebetween, inserting into the gap a hollow restraining frame which supports the projecting portions of the coverings, and adhesively bonding the said uncovered ends to each other by introducing a thermoplastic resin into the restraining frame and allowing the resin to harden.

4. A method as claimed in any preceding Claim including forming one or more holes through the plastics covering or the plastics covering and wood member of at least one of said lengths so as to allow entry of the thermoplastic resin into the gap.

5. A method as claimed in Claim 1 or Claim 3, in which the uncovered ends of said first and second lengths are offered to one another so that the ends of the plastics coverings abut one another.

6. A method as claimed in Claim 3, in which the ends of the restaining frame abut the respective uncovered ends of the said two lengths.

7. A method as claimed in Claim 3, in which the uncovered ends of the two lengths are offered to one another so that the ends of the plastics coverings abut one another.

8. A joint formed by a method as claimed in any preceding Claim.

9. A joint as claimed in Claim 8 in which the thermoplastic resin is a thermoplastic copolyester.

10. A joint as claimed in Claim 9, in which the thermoplastic resin is polyethylene terephthalate or polybutylene terephthalate.

11. A joint as claimed in Claim 8 in which the thermoplastic resin is a polymer of cyclohexanediemethanol and terephthalic acid with the terephthalic acid partly replaced with other acids.

12. A joint as claimed in Claim 8 in which the thermoplastic resin is a glycol-modified version of polyethylene terephthalate copolyester.

13. A joint as claimed in Claim 8 in which the thermoplastic resin is a hot-melt adhesive based on thermoplastics saturated polyester or copolyester resins, or modified copolyamide resins.

14. A joint as claimed in Claim 8 in which the thermoplastic resin is a thermoplastic copolyester based mainly on terephthalic acid whose synthesis uses more than one glycol and/or more than one die-basic acid.

15. A method of forming a joint substantially as herein described with reference to the accompanying drawings.

16. A joint substantially as herein described and shown in the accomanying drawings.