ATTACHMENT DEVICE

Abstract: An attachment device for securing sections (14, 11) of a tighting layer overlapping each other at edge portions (10, 13) on to a roof and consisting of a plate and a screw (12) for anchoring in the roof before overlapping is effected, whereby the plate secures the section of the tighting layer to the roof structure. According to the invention the side portions are indented so that the width of the plate is at least 25 % less at its mid-portion than at its end portions in order to provide functional side recesses (17, 18) outside each side portion (3, 4), the plate being mounted close to an inner edge of the lower edge portion and the edge portions being brought into contact with each other also via said side recesses. An opening (8, 9) is provided on each side of the mid-portion (5), said openings having an area that is at least 40 % and at most 50 % of the total area of the plate so that the edge portions (10, 13) can be welded together also via the openings. The plate has a flexural resistance of at least 750 N about its longitudinal axis.

Description: Attachment device The present invention relates to an attachment device for securing roofing material to a supporting roof structure, said roofing material comprising a tighting layer formed by sections overlapping each other at edge portions and including meltable bitumen or the like to weld together the sections within the overlapping edge portions, said attachment device consisting of a plate, preferably of metal, and a screw or the like extending through the plate and designed to be anchored in the roof structure before overlapping is effected, whereby the plate presses against the section of the tighting layer to secure it to the roof structure, said plate being oblong with two longitudinal side portions, two transverse end portions and a transverse mid-portion with a central hole for said scre . To effect external insulation of a roof construction, the insulating layer must be secured to the supporting roof structure which may consist of concrete, light concrete, wood or sheet-metal. The insulating layer is covered by a web-shaped tighting, i.e. weatherproof, layer provided with bitumen, applied in sections and welded together at the overlapping edge portions. Oblong rectangular plates are placed along a free edge portion of a section and secured with screws in the supporting roof structure, thereby securing the tighting layer and the insulation together to the roof structure. The edge portion and the plates attached therein are then overlapped by an edge portion of the next section and hot air is supplied to melt the bitumen in the tighting layer so that the edge portions are welded together when the bitumen again has become solid. The overlap joint thus consists of a lower edge portion of a first section and an upper edge portion of a second section. According to current regulations the part of the overlap joint free from the plates must have a minimum width which, according to Swedish regulations, is currently 8 cm. In order to fulfil the requirement of material saving, i.e. the smallest possible width of the overlap joint, the plates are placed as close to the edge line of the edge portion as possible. The screw in each plate is then the weak link in the construction so that stress in the first section results in a break in the edge portion of the section between the screw and its said edge line, this break in turn causing additional breaks at other points of the overlap joint. One proposal for solving this problem has been to make the overlap joint somewhat wider by placing the plates somewhat further, e.g. 1.5-2 cm, from said edge line so that a corresponding inner portion is formed where the two edge portions can be joined together. However, this proposal entails increased material costs as a result of the wider overlap joints. Another problem with the plates used so far is that the tighting layer does not engage with the plates during welding and instead the plates will form weak points in the overlap joint enclosing the plates. Also in this case it has been necessary to make the overlap joints wider in order to reduce said problem, and this has necessitated the use of more material for the tighting layer. The size of the plates has also been limited in order not to aggravate the problem of weak points, but such a reduction in size leads in turn to diminished strength of the tighting layer within the overlap joint. The object of the present invention is to provide a plate enabling sufficient strength to be achieved in the overlap joint, even at the inner part located between the plate screw and the inner section edge, while yet at the same time allowing the overlap joint to be narrow as desired to reduce the material consumption, and also enabling the edge portions of the sections of the tighting layer to be welded together without weak points arising in the welded overlap joints, and also in this case the use of narrower overlap joints and consequently savings in the material used for the tighting, i.e. weatherproof, layer. The attachment device according to the invention is characterized in that the side portions are indented so that the width of the plate is at least 25%, preferably at least 30%, less at the mid-portion than at the end portions in order to provide functional side recesses outside each side portion, whereby the plate being arranged to be mounted adjacent or close to an inner edge of the lower edge portion, and the edge portions also being brought into contact with each other via said side recesses in order to provide an adhesion area primarily between the plate and said inner edge; that a large, uninterrupted opening is arranged on each side of the mid-portion, said openings together having an area that is at least 40%, preferably at least 45%, and at most 50% of the total area of the plate and being arranged to permit the edge portions to be welded together even inside the plate via the openings so that the plate is integrated with the edge portions to form a tight overlap joint; and that the plate has a flexural resistance of at least 750 N about its longitudinal axis. The invention will be described in more detail with reference to the accompanying drawings. Figures 1 and 2 show a side view and top view, respectively, of a plate in an attachment device according to a preferred embodiment of the invention. Figure 3 shows a top view of an overlap joint in a tighting or weatherproof layer, where attachment devices according to the invention are enclosed and integrated with the edge portions of two sections of the tighting layer. Figure 4 shows a section along the line IV-IV in Figure 3. Figures 1 and 2 show a plate, oblong in shape, with two transverse end portions 1, 2, two longitudinal side portions 3, 4 and a transverse mid-portion 5. The end and side portions 1, 2, 3, 4 are relatively narrow, seen in the plane of the plate, without being deformable by normal stresses. Furthermore, the mid-portion 5 is relatively narrow and has a central hole 6 for a screw or the like. Each longitudinal side portion 3, 4 is provided with a ridge 16 and corresponding groove 7, thereby ensuring that the plate has sufficient bending resistance with minimal width of the side portions 3, 4. Uninterrupted openings 8, 9 are provided on each side of the mid-portion 5, these openings being defined by the end portions 1, 2, the side portions 3, 4 and the mid-portion 5. By "uninterrupted opening" is meant that the opening is unitary and thus entirely free of the construction material of the plate, in order to allow free passage. Said portions 1-5 have a minimal width, but are sufficiently wide to ensure that the plate is completely rigid in all directions, while at the same time the two openings 8, 9 are suitably as large as possible. The two openings 8, 9 together thus have an area that is at least 40% and preferably at least 45%, but at most 50% of the total area of the plate. The plate has a flexural resistance of at least 750 N measured at the centre of the plate with the end portions 1, 2 as support points, this being ensured by profiling the relatively narrow side portions 3, 4 by means of said grooves 7. The longitudinal side portions 3, 4 of the plate are indented towards the centre so that the plate has functional side recesses 17, 18 on each side of the central hole 6. The width of the plate is thereby considerably less at the transverse mid-portion 5 than at the transverse end portions 1, 2. To achieve the requisite contact surface for the overlapping edge portions 10, 13 of the sections, the width of the plate is at least 25%, preferably at least 30%, less at the mid-portion 5 than at the end portions 1, 2. The plate is symmetrical, as shown in the drawings, thereby preventing incorrect assembly and the roof-layer needs no instructions as to which long side shall be turned towards the inner edge of the section. The plates are placed within an edge portion 13 of a section 11 of the tighting or weatherproof layer, after which they are secured with screws 12 or the like passing through the central hole 6 of the plate and screwed into the supporting roof structure. The tighting layer normally covers an insulating layer. The edge portion 13 is then overlapped by an edge portion 10 of an adjacent section 14 of the tighting layer so that an overlap zone 15 is formed in which the plates are completely enclosed. The overlap zone 15 may have a width of 12-14 cm. The tighting layer contains bitumen or the like which is caused to melt in the overlap zone 15 by applying hot air so that the two edge portions 10, 13 are caused to adhere to each other and are welded together to form a permanent joint when the bitumen or the like has solidified. Designing the plate with large openings 8, 9 ensures that the two edge portions 10, 13 are also in contact with each other through these openings 8, 9 and are thus welded together within the plate over sufficiently large inner adhesion areas to prevent them from releasing their grip on the inner edges of the plate. The plate is thus integrated with the overlapping edge portions 10, 13 and a stronger overlap joint is obtained which in turn further ensures that it is weatherproof. At the same time the end and side portions 1, 2, 3, 4 of the plate will take up loads over a relatively large area. Designing the plate with relatively large side recesses 17, 18 ensures, as shown in Figure 4, that the two edge portions 10, 13 are also in contact with each other via these side recesses 17, 18 so that they are welded together over sufficiently large adhesion areas immediately outside the longitudinal side portions 3, 4 and particularly over the adhesion area obtained between the plate and the inner edge of the edge portion of the lower section, even if the widest parts of the plate are aligned with or immediately, e.g. 0.1-3.0 mm, inside said inner edge. Sufficient strength is thus also obtained at the inner part, which is located between the screw and the inner edge of the section, while yet at the same time a desired narrow overlap joint is obtained in order to reduce the material consumption. Since the strength is guaranteed, a tight or weatherproof overlap joint is also ensured within the areas for the plates. The plate preferably consists of metal and its length is suitably twice its greatest width. In certain cases the plate may be of plastic.

Claims: C L A I M S 1. An attachment device for securing roofing material to a supporting roof structure, said roofing material comprising a tighting layer formed by sections (14, 11) overlapping each other at edge portions (10, 13) and including meltable bitumen or the like to weld together the sections (11, 14) within the overlapping edge portions (13, 10), said attachment device consisting of a plate, preferably of metal, and a screw (12) or the like extending through the plate and designed to be anchored in the roof structure before overlapping is effected, whereby the plate presses against the section of the tighting layer to secure it to the roof structure, said plate being oblong with two longitudinal side portions (3, 4), two transverse end portions (1, 2) and a transverse mid-portion ( 5) with a central hole (6) for said screw (12), characterized in that the side portions (3, 4) are indented so that the width of the plate is at least 25%, preferably at least 30%, less at the mid-portion ( 5) than at the end portions ( 1, 2) in order to provide functional side recesses (17, 18) outside each side portion (3, 4), whereby the plate being arranged to be mounted adjacent or close to an inner edge of the lower edge portion (13), and the edge portions (10, 13) also being brought into contact with each other via said side recesses (17, 18) in order to provide an adhesion area primarily between the plate and said inner edge; that a large, uninterrupted opening (8, 9) is arranged on each side of the mid-portion (5), said openings (8, 9) together having an area that is at least 40%, preferably at least 45%, and at most 50% of the total area of the plate and being arranged to permit the edge portions (10, 13) to be welded together even inside the plate via the openings (8, 9) so that the plate is integrated with the edge portions (10, 13) to form a tight overlap joint; and that the plate has a flexural resistance of at least 750 N about its longitudinal axis. 2. An attachment device as claimed in claim 1, characterized in that each side portion (3, 4) is provided with a longitudinal ridge (16) and corresponding groove (7), thereby forming a profile increasing the flexural rigidity.

Inventors: RUNDGREN FREDRIK, RUNDGREN, FREDRIK
Applicants: PLAST VERKTYG OCH BESLAG AB K, RUNDGREN FREDRIK, K-PLAST VERKTYG OCH BESLAG AB, RUNDGREN, FREDRIK
Application year: 1995
Main classification: E04D3
IPC codes: E04D5