GB2570893A

GB2570893A - Thermal barrier for a fastener

Info

Publication number: GB2570893A
Application number: GB1802016.4A
Authority: GB
Inventors: James Link Matthew
Original assignee: Valro Manufacturing Ltd
Current assignee: Valro Manufacturing Ltd
Priority date: 2018-02-07
Filing date: 2018-02-07
Publication date: 2019-08-14
Anticipated expiration: 2038-02-07
Also published as: GB201802016D0; GB2570893B

Abstract

The barrier (300, Figs. 5-9) is a flat annular ring for locating between parts of the fastener 100 for attaching an insulation sheets (200, Fig. 4) to a building structure (210, Fig. 4). Such fasteners typically include a plastic insulating tube 110 extending through a hole in a metal plate 120 and through insulation layer 200 for receiving a fixing (e.g. screw), the tube having a lip or ledge (140, Fig. 1) for abutting the plate, the plate abutting the face of the insulation, wherein a waterproof roofing membrane (220, Fig. 4) is adhered to the plate using a heat sensitive adhesive. The heat can melt or warp the plastic tube. The barrier 300 may be plastic e.g. nylon, paper or cardboard, and reduces heat transfer between the plate and tube. It may have a raised collar such that its shape is complementary to the top of the tube. Also claimed is the fastener inc. barrier, a kit of parts, a method of use, and the tube/plate separately. The barrier may be integrally formed with the tube or plate.

Description

THERMAL BARRIER FOR A FASTENER

The present invention relates to thermal insulation of a plastics element of a fastener to reduce heat transfer from an adjacent metal element.

A known fastener for securing insulation and an overlying waterproofing membrane to a structure comprises a metal plate and a plastic tube. The plastic tube passes through a hole in the metal plate and through the insulation and is secured to the structure with a screw fastener passed through the tube. The tube has a lip to hold the metal plate against the insulation to secure it in place and the lip sits within a depression in the metal plate. The membrane is laid over the metal plate and inductive heating activates a heat-activated adhesive on the plate to bond it to the membrane. A problem arises in that heat from the metal plate can warp, melt or otherwise damage the plastic tube, potentially compromising the fastener.

One solution to this problem is to thicken the plastic tube or add sacrificial features to the plastic tube where the tube and metal plate come into contact. Even if these thicker sections are damaged by heat, the rest of the plastic tube is still structurally sound. This solution is flawed since the modified plastic tube is bulky and may not fit correctly against the metal plate. In particular, the lip of the tube may no longer fit or sit correctly within the depression in the metal plate. If the tube protrudes out of the depression, this can damage the membrane, prevent the membrane from being securely attached to the fastener, or interfere with heating equipment. Additionally, in practice, the heating temperature and duration vary, so the damage done to the tube will vary. This can have unexpected consequences that will compromise the fastener .

Another solution is to make the tube from a heat-resistant plastics material or resin. This is prohibitively expensive.

What is needed is an effective but low-cost solution to the problem of damage caused to a plastic tube element of a fastener by a heated metal plate element.

The present invention provides a thermal barrier for a fastener, the fastener of the type comprising a tube and a plate, the plate having a hole for receiving the tube and the tube having a projecting ledge for abutting against the plate to prevent the tube from passing completely through the hole, the plate being heatable to activate a thermally-activated adhesive, wherein the thermal barrier is interposable between the tube and the plate to reduce conduction of heat from the plate to the tube when the plate is heated.

Embodiments of the present invention therefore provide an effective way to reduce heat transfer from the plate, most often a metal plate, to the tube, most often a plastics material tube. By providing a thermal barrier interposable between the tube and the plate, rather than seeking to thicken and/or strengthen the tube, embodiments of the invention can be used with existing low-cost fasteners and minimise the use of expensive materials.

Where the fastener is of the type where an end of the tube adjacent the projecting ledge is sized to fit within a depression in the plate, the thermal barrier is thin to avoid spacing the tube away from the plate to such a degree that the end of the tube protrudes out of the depression in the plate. Advantageously, embodiments of the present invention also avoid the problem of the tube not fitting properly against the plate or within a depression in the plate.

Preferably the thermal barrier is shaped to cover substantially the whole surface of the projecting ledge and/or is shaped to prevent substantially all physical contact between the surface of the projecting ledge and the plate. Advantageously, the thermal barrier reduces heat conduction by preventing direct contact between the plate and the tube.

Preferably, the thermal barrier comprises a flat ring. Such an arrangement is simple to manufacture and has minimal bulk so that the plate and tube can still fit against one another.

In one arrangement, a raised collar is provided on the flat ring. This prevents physical contact between an outer surface of the tube adjacent the projecting ledge and the plate and therefore protects the sides of the tube as well as the projecting ledge.

Preferably, an inner circumference of the flat ring is substantially the same shape as an exterior cross-section of the tube and/or an outer circumference of the flat ring is substantially the same shape as an outer edge of the projecting ledge. This ensures that the thermal barrier can be interposed entirely between the plate and the tube without wasting material.

In one embodiment, the thermal barrier comprises a comanufactured portion of the tube, formed from a material having a lower thermal conductivity than the material forming the rest of the tube. This arrangement permits a tube to be formed to the same size specifications as a normal tube, ensuring a good fit between the tube and the plate but without needing to form the entire tube from an expensive, heatresisting material.

Other aspects of the present invention provide a tube comprising a thermal barrier; a plate comprising a thermal barrier; or a kit of parts comprising a thermal barrier and at least one of a tube and a plate. These aspects of the present invention enable a fastener with a thermal barrier to be quickly and easily assembled.

In another aspect, the present invention provides a method of thermally insulating a tube from a plate, the tube and plate being assemblable to form a fastener, the fastener of the type where the plate has a hole for receiving the tube and the tube has a projecting ledge for abutting against the plate to prevent the tube from passing completely through the hole, the plate being heatable to activate a thermally-activated adhesive, the method comprising interposing a thermal barrier between the plate and the tube.

Advantages and preferred features of this aspect of the invention will be apparent from the forgoing discussion of the other aspects of the invention.

Preferred embodiments of the invention will with reference to the accompanying drawings now be described in which:

Figure illustrates a tubular element of a fastener;

Figure illustrates a plate element of a fastener;

Figure illustrates an assembled fastener including a screw fixing;

Figure 4 illustrates the fastener in use, secured to a structure;

Figure 5 illustrates a thermal barrier;

Figure 6 illustrates thermal barrier on a tubular fastener element;

Figure 7 illustrates thermal barrier on a plate;

Figure 8 illustrates first tubular element moulded from two materials; and

Figure 9 illustrates second tubular element moulded from two materials .

Figures 1 and 2 illustrate the elements of typical fastener used to secure insulation and an overlying membrane to a structure. The assembled fastener

3.

The fastener 100 comprises a tube fixing means 130 such as a screw,

100 is illustrated in Figure

110, and a plate 120. A nail, bolt or rivet is used to secure the fastener to a structure.

The tube 110 is hollow, substantially cylindrical and open at both ends. The tube 110 is typically formed from a plastics material such as polypropylene or polyethylene preferably by moulding or injection moulding. Such materials are susceptible to damage when exposed to high temperatures. The tube 110 comprises a cylindrical tubular member 133 typically 1cm to 2cm in diameter and 1cm to 100cm in length. The tube 110 widens at a proximal end to form a lip or brim 136. A lower surface of the lip 136 forms a projecting annular ledge 140 adjoining and around the tubular member 133. The ledge 140 typically extends away from the side of the tubular member 133 typically at substantially a right angle but the angle between the ledge 140 and the side may also be an obtuse angle up to approximately 135°.

The tube 110 narrows gradually towards a distal end to form a pointed tip 150 to facilitate insertion of the tube 110 into a layer of insulation.

Although this is the typical shape of a tube element 110 of a fastener 100, there are many variations that are known and would be suitable under different conditions. For example, the tubular member 133 and lip 136 each typically have a circular cross-section, but oval, hexagonal or other polygonal crosssections are also conceivable. The external and internal cross-sections may be different such as, for example, a circular external cross-section and a hexagonal internal cross-section.

The plate 120 is formed from a heat conducting material, typically metal, and preferably a material that can be effectively heated by induction such as steel. The plate 120 is formed as a thin sheet having a hole 160, typically located in the centre of the plate 120. The hole 160 is typically circular, but may alternatively be oval or polygonal, preferably being similar to the shape of the tube 110. The plate 120 typically has a circular outer perimeter, although other shapes such as square or oblong are known and generally any relatively wide, flat shape would be suitable.

The plate 120 is shaped, preferably by pressing, to form a depression 170 around the hole 160 and a flat, raised portion 180. As illustrated in the Figures, the upper surface of the plate 120 within the depression 170 around the rim of the hole 160 is typically flat and lies in the plane of the hole 160. Alternatively, the surface around the rim of the hole 160 may be inclined relative to the plane of the hole 160. In general, the inclination of the surface around the rim of the 160 matches the angle between the side of the tubular member 133 and the projecting ledge 140.

Typically, at least the top of the raised portion 180 is provided with a heat-activated adhesive to enable it to be bonded to an overlying membrane, although the adhesive may instead be provided on the underside of the membrane. The adhesive may be applied to the raised portion as a liquid which dries to form an adhesive layer. Alternatively, the adhesive may comprise a layer or film of a material similar to or otherwise compatible with the overlaying membrane so that subsequent heating causes the film and part of the membrane to melt and fuse together, adhering the membrane to the plate 120 .

To assemble the fastener 100, the pointed tip 150 and tubular member 133 of the tube 110 are passed through the hole 160 in the plate 120. The brim 136 of the tube 110 is wider than the hole 160 in the plate 120 to prevent the tube 110 from passing all the way through. Consequently, at least part of the ledge 140 and typically a small region of the adjoining side of the tubular member 133 are in direct contact with the plate 120. The brim 136 of the tube 110 sits fully within the depression 170 in the plate 120 and the top of the brim 136 does not rise above the top surface of the of the raised portion 180. This ensures that an overlying membrane sits flat on the raised portion 180 of the plate 120 and is not distorted or damaged by the tube 110.

When the assembled fastener 100 is ready to be fixed to a structure, the fixing means 130 is passed through the tube 110 from the proximal end and emerges partially from the distal tip 150. A head of the fixing means 130 is retained inside the tube 110 by the narrowing of the tube towards the distal tip

150 and/or by a shelf or projections (illustrated in Figures 8 and 9) inside the tip 150.

Figure 4 schematically illustrates the fastener 100 in use securing insulation 200 to a structure 210 and bonded to an overlying membrane 220. The structure 210 may be part of a roof, ceiling, floor, an interior or exterior wall, or a strut or baton secured to any larger structure.

Typically, the structure is the exterior roof of a building to which a layer of insulation 200 and a water-proofing membrane 220 are to be secured. Depending on the size of the structure 210 and the expected weather conditions, hundreds or even thousands of suitably spaced apart fasteners may be used to adequately secure the insulation 200 and membrane 220 to the structure 210.

An assembled fastener 100 having a tube 110 of an appropriate length is pushed through the insulation, the pointed tip 150 aiding insertion. The fixing means 130 secures the fastener 100 in place to the structure 210. The relatively wide plate 120 sits on top of the insulation 200 and holds the insulation 200 against the structure 210.

The membrane 220 is laid over the plate 120 and the plate 120 is heated through the membrane 220 to activate the heatactivated adhesive provided on either the plate 120 or the membrane 220. The membrane 220 is simultaneously pressed against the raised portion 180 of the plate 120 so that the membrane 220 bonds to the raised portion 180 and is secured to the fastener 100. It is therefore important that the tube 110 does not protrude from the depression 170 in the plate 120 since this could prevent a heating tool, particularly an inductive heating tool, from being positioned correctly against the plate 120, preventing adequate heating and resulting in a less secure or non-existent bond.

Heating is typically achieved by induction heating, but radiant heating may also be used. Induction heating can achieve high temperatures in the plate 120 in a short amount of time without needing to apply direct heat to the top surface of the membrane 220. The plate 120 is a good heat conductor to ensure that it reaches an even temperature to activate the adhesive over the whole bonding area.

Consequently, whichever heating method is used, heat will pass from the conductive plate 120 to the tube 110. The most significant heat flow is via conduction where the tube and the plate are in direct contact.

Figure 5 illustrates a thermal barrier 300 that can be interposed between the plate 120 and the tube 110 for reducing heat flow from the plate 120 to the tube 110. The thermal barrier 300 comprises a flat ring or annulus 310 and, optionally, a collar 320 projecting from the edge of the hole in the annulus 310. The hole in the annulus 310 is sized to fit closely around the tubular member 133 and the outer diameter of the annulus is substantially the same as the diameter of the ledge 140.

The thermal barrier 300 may be placed on the tube 110 from the distal end and slid towards the proximal end where, as illustrated in Figure 6, the annulus 310 covers substantially the whole of the ledge 140. The annulus 310 is depicted as circular to match the typical shape of the ledge 140 but may be oval or polygonal if required to cover the ledge 140. The annulus 310 may optionally extend beyond the ledge 140 and be shaped or deformable to cover the side of the brim 136.

The collar 320 covers the sides of the tubular member 133 adjoining the ledge 140 and extends away from the annulus 310 by a distance at least equal to the thickness of the plate 120 around the edge of its central hole 160. Where the ledge 140 of the tube 110 projects from the sides of the tubular member 133 at a right angle, the collar 320 similarly projects at a right angle away from the annulus 310 so that the thermal barrier 300 is aligned with both surfaces. In general, the angle between the annulus 310 and the collar 320 is the same as the angle between the side of the tubular member 133 and the projecting ledge 140.

Consequently, when the thermal barrier 300 is in place on the tube 110, the annulus 310 prevents direct contact between the ledge 140 and the plate 120 and the collar 320 prevents direct contact between the sides of the tubular member 133 and the plate 120.

The thermal barrier 300 may also be located on the plate 120, as illustrated in Figure 7. In this case, the hole in the annulus 310 is substantially the same size and shape as the hole 160 in the plate 120. Alternatively, the hole in the annulus 310 may be smaller than the hole 160 in the plate 120, or may be partially or entirely filled in, and the thermal barrier 300 is deformable or capable of being pierced so that the tube 110 can be pushed through the thermal barrier 300, creating an appropriately sized hole. In this arrangement, deformation of a previously flat annulus 310 forms the collar 320 for protecting the sides of the tube 110. The outer diameter of the annulus 310 is sufficient that, when the tube 110 is put in place, the barrier 300 prevents contact between the ledge 140 and the plate 120. Alternatively, thermal barriers 300 may be provided on both the tube 110 and the plate 120. The thermal barrier 300 may be located on the tube 110 or plate 120 as part of the manufacturing process, or by an end user just before assembling the fastener 100, or at any time in between.

The annulus 310 and collar 320 of the thermal barrier 300 have a thickness of less than 3mm, and preferably less than 1mm, to ensure that the thermal barrier 300 does not interfere with correct assembly of the fastener 100 or with correct positioning of the tube 110 within the hole 140 of the plate 120. For example, a thin collar 320 will not prevent the tubular member 133 from passing through the hole 160 in the plate 120 and a thin annulus 310 will not raise the top of the brim 136 above the level of the raised portion 180 on the plate 120. Consequently, even with the thermal barrier 300 in place, the brim 136 of the tube 110 remains fully within the depression 170 in the plate 120 and does not protrude above the top of the raised portion 180.

The thermal barrier 300 is made from a material having a sufficiently low thermal conductivity to protect the tube 110 from damage when the plate 120 is heated to between 150°C and 250°C for approximately 20 seconds, this being the typical temperature and duration for inductive heating of a metal plate 120. Suitable materials typically have a thermal conductivity of less than 0.3W/mK. Suitable materials are also heat-resistant and are not susceptible to damage during a single heating such as melting or degradation which would prevent the thermal barrier from functioning. Suitable materials also preferably have low compressibility to ensure consistent thermal resistance when the barrier 300 is pressed between the tube 110 and plate 120.

Typical low-cost but effective materials include nylon, which has a thermal conductivity of around 0.25W/mK, or paper or cardboard, which has a thermal conductivity of around 0.05W/mK. Other suitable materials include: thermoplastic, thermosetting or elastomeric plastic materials such as PETG, polyurethane, polyester, melamine, cellulose, silicone or polyolefin; mineral-based or ceramic materials; or composite materials incorporating nano- or carbon-fibres or glass fillers. The thermal barrier 300 may comprise a single layer or multiple layers of the same or different materials.

When forming the thermal barrier 300 from a plastics material, it can be moulded or otherwise made in the correct shape and size with an annulus 310 and a collar 320 having a good fit either around the tubular member 133 or within the hole 160 in the plate 120. Consequently, the thermal barrier 300 may be placed on the tube 110 or the plate 120 and contact friction alone will be sufficient to hold the thermal barrier 300 in place until the fastener 100 is assembled. Alternatively, or in addition, the thermal barrier 300 may be secured with an adhesive .

When forming the thermal barrier 300 from paper or cardboard, it will typically be cut or stamped as a two-dimensional shape comprising only an annulus 310, but lacking a collar 320. The thermal barrier 300 illustrated in Figure 7 comprises only an annulus 310, for example. Since paper and cardboard are easily deformable and piercable by the tube 110, the hole in the annulus 310 may be smaller than the diameter of the tube 110 or may be filled in and an appropriate sized hole is created by pushing the thermal barrier 300 onto the tube 110 or vice versa. The resulting deformation of a previously flat annulus 310 naturally forms a collar 320 for protecting the sides of the tube 110. The annulus 310 will typically require an adhesive to secure it to the ledge 140 of the tube 110 or to the plate 120. Preferably the adhesive is a pressure-sensitive adhesive applied to one side of the annulus 310. A plurality of thermal barriers 300 may be provided on a sheet or strip of backing material ready to be applied to a tube 110 or plate

120 during manufacture or by an end user prior to assembling the fastener 100 or anywhere in between.

In a thermal barrier 300 lacking a collar 320, there may be physical contact between the interior edge of the hole 160 in the plate 120 and the sides of the tubular member 133 when the fastener 100 is assembled. When the plate 120 is heated, there will be unwanted heat flow to the tube 110. In most circumstances, the contact area is small or zero and the resulting heat flow is low enough that the tube 110 is not damaged, and the flat annulus 310 covering the ledge 140 provides sufficient thermal protection. A collar 320 is only necessary where greater protection is required or the temperatures involved are higher.

A thermal barrier 300 may also be formed by applying a coating to at least part of the tube 110 or plate 120, the coating setting or curing to form a suitable thermal barrier 300 without interfering with the positioning of the tube 110 within the hole in the plate 120. The coating may be applied in any suitable way such as by painting, spraying, dipping or vacuum deposition.

When applied to the tube 110, the coating covers at least the ledge 140 and preferably at least the adjoining sides of the tubular member 133. Optionally, the coating may be applied to substantially the whole of the brim 136 or even the entire tube 110 depending on the application method and cost. When applied to the plate 120, the coating is preferably applied only within the depression 170 around the hole 160. The raised portion 180 is left uncoated so as not to interfere with the adhesion of the plate 120 to the overlying membrane 220.

Figures 8 and 9 illustrate cross-sectional views through a tube 110 which has been multi-material moulded, co-injection moulded, or otherwise co-manufactured to incorporate an integral thermal barrier 300. The thermal barrier 300 portion of the tube 110 is formed from a suitable material to protect the remainder of the tube 110. Suitable materials include polypropylene with polyolefin-based elastomer, or nylon with a polyolefin-based elastomer. A co-manufactured tube 110 can be made to the same dimensions as a standard tube 110 so that the positioning of the tube 110 within the hole 160 and within the depression 170 in the plate 120 is unchanged.

In one arrangement of a co-manufactured tube 110, as illustrated in Figure 8, the whole proximal end of the tube 110 including the brim 136 and a proximal end of the tubular member 133 is formed from a suitable thermal barrier material. In another arrangement, as illustrated in Figure 9, the comanufactured thermal barrier portion 300 is limited to the ledge 140 and optionally the adjoining sides of the tubular member 133. The thermal barrier portion 300 may extend for the full thickness of the tube 110 or only a partial thickness, as illustrated. Other arrangements are possible and may be used depending on factors such as the strength of the different materials and cost.

Claims

CLAIMS :

1. A thermal barrier for a fastener, the fastener of the type comprising a tube and a plate, the plate having a hole for receiving the tube and the tube having a projecting ledge for abutting against the plate to prevent the tube from passing completely through the hole, the plate being heatable to activate a thermally-activated adhesive, wherein the thermal barrier is interposable between the tube and the plate to reduce conduction of heat from the plate to the tube when the plate is heated.

2. The thermal barrier of claim 1 wherein the fastener is of the type where an end of the tube adjacent the projecting ledge is sized to fit within a depression in the plate, wherein the thermal barrier is thin to avoid spacing the tube away from the plate to such a degree that the end of the tube protrudes out of the depression in the plate.

3. The thermal barrier of claim 1 or claim 2 wherein the thermal barrier is shaped to cover substantially the whole surface of the projecting ledge.

4. The thermal barrier of any preceding claim wherein the thermal barrier is shaped to prevent substantially all physical contact between the surface of the projecting ledge and the plate.

5. The thermal barrier of any preceding claim wherein the thermal barrier comprises a flat ring.

6. The thermal barrier of claim 5 further comprising a raised collar on the flat ring.

7. The thermal barrier of claim 6 wherein the raised collar prevents physical contact between an outer surface of the tube adjacent the projecting ledge and the plate.

8. The thermal barrier of any of claims 5 to 7 wherein an inner circumference of the flat ring is substantially the same shape as an exterior cross-section of the tube.

9. The thermal barrier of any of claims 5 to 8 wherein an outer circumference of the flat ring is substantially the same shape as an outer edge of the projecting ledge.

10. The thermal barrier of any preceding claim wherein the thermal barrier has a thermal conductivity of less than

0.3W/mK.

11. The thermal barrier of any preceding claim wherein the thermal barrier has low compressibility.

12. The thermal barrier of any preceding claim wherein the thermal barrier has a thickness less than 1mm.

13. The thermal barrier of any preceding claim wherein the thermal barrier is formed from paper and/or cardboard.

14. The thermal barrier of any of claims 1 to 12 wherein the thermal barrier is formed from nylon.

15. The thermal barrier of any preceding claim wherein the thermal barrier is provided with a pressure-sensitive adhesive .

16. The thermal barrier of any of claims 1 to 11 wherein the thermal barrier comprises a co-manufactured portion of the tube formed from a material having a lower thermal conductivity than the material forming the rest of the tube.

17. The thermal barrier of claim 16 wherein the comanufactured portion comprises at least the surface of the projecting ledge of the tube.

18. A tube for a fastener of the type comprising a tube and a plate, the plate having a hole for receiving the tube and the tube having a projecting ledge for abutting against the plate to prevent the tube from passing completely through the hole, the plate being heatable to activate a thermally-activated adhesive, the tube comprising a thermal barrier according to any of claims 1 to 17.

19. A plate for a fastener of the type comprising a tube and a plate, the plate having a hole for receiving the tube and the tube having a projecting ledge for abutting against the plate to prevent the tube from passing completely through the hole, the plate being heatable to activate a thermallyactivated adhesive, the plate comprising a thermal barrier according to any of claims 1 to 17.

20. A fastener comprising a tube and a plate, the plate having a hole for receiving the tube and the tube having a projecting ledge for abutting against the plate to prevent the tube from passing completely through the hole, the plate being heatable to activate a thermally-activated adhesive, the fastener further comprising a thermal barrier according to any of claims 1 to 17.

21. A kit of parts comprising a thermal barrier according to any of claims 1 to 17 and at least one of a tube and a plate for assembly with the other of the tube and the plate to form a fastener, the fastener of the type where the plate has a hole for receiving the tube and the tube has a projecting ledge for abutting against the plate to prevent the tube from passing completely through the hole, the plate being heatable to activate a thermally-activated adhesive.

22. A method of thermally insulating a tube from a plate, the tube and plate being assemblable to form a fastener, the fastener of the type where the plate has a hole for receiving the tube and the tube has a projecting ledge for abutting

10 against the plate to prevent the tube from passing completely through the hole, the plate being heatable to activate a thermally-activated adhesive, the method comprising interposing a thermal barrier between the plate and the tube.