FIELD OF THE INVENTION

This invention relates to polycarbonate roofs panels adapted for interconnection with so-called sandwich-type panels having outer metal skins.

BACKGROUND OF THE INVENTION

Sandwich-type panels formed by a structure consisting of two sheet metal skins and a filler material are commonly used as roof and wall coverings. Each panel has at opposite ends joints of complementary geometries thus allowing multiple panels to be coupled end to end and fixed to the building structure using screws, which may be visible or concealed. The metal skins are of course opaque so that such a structure is used where light transmission is not an issue.

Also known are light-transmissive polycarbonate panels that are coupled to sandwich-type panels for use on roofs and walls of industrial buildings in general, whereby light can enter the building, while protecting the roof from inclement weather and providing a degree of insulation to the upper part of the building.

EP 3 290 613 discloses a modular polycarbonate panel for roofs of buildings, comprising a cell structure defining a plurality of chambers, such that a first side has at least one tab defining a cavity that is suitable for being coupled to a second panel. A second side of the panel is suitable for being coupled to a third panel and has a projection defining a geometry complementary to the cavity defined by the tab of the first side. The modular panel can be coupled to successive adjacent panels for covering a surface of a roof or enclosure rapidly and safely while reducing the installation time. Fig. 1 shows an arrangement corresponding to the teachings of EP 3 290 613 where a modular polycarbonate panel is configured for coupling to a second sandwich- type panel on one side, and to a third sandwich-type panel on the other side. In further detail, Fig. 1 shows a proprietary polycarbonate panel 10 having a cellular body portion 11, a base 12 of which has a projection 13 on one end and a recess 14 at the opposite end. A projection 15 of generally trapezoidal shape projects upwardly from an upper surface 16 of one end of the panel. The opposite end of the panel supports a jib arm 17 an upper end of which supports a polyhedral tab 18 whose shape may be complementary to that of the projection 15, and such that the respective base angles a and p of the projection 15 and jib arm 17 are substantially identical. This allows multiple panels to be joined end to end, the projection 15 constituting a male connection and the shaped tab 18 constituting a female connector of complementary shape.

Fig. 2 shows the same panel 10 juxtaposed at opposite ends to respective sandwich panels 20 each formed of a central core 21 of insulating material surrounded by upper and lower metal outer layers 22, 22', commonly formed of galvanized steel sheet and constituting upper and lower surfaces of the panel. Each sandwich panel 20 is also provided at opposite end with a respective projection 25 of generally trapezoidal shape and a tab 26, which again may be complementary in shape so as to allow for the mutual juxtaposition of multiple sandwich panels 20.

Flowever, the present invention is concerned principally with the juxtaposition of polycarbonate panels 10 and sandwich panels 20 as shown in Fig. 2. In the case where they have similar or substantially the same contours, it is natural that the male and female connectors be complementary in shape. However, this will generally not be the case when they are made by different manufacturers unless, for example, the manufacturer of the polycarbonate panels 10 wants to retrofit their panels with a specific make of sandwich panel 20. It would clearly be more commercially desirable for the manufacturer of the polycarbonate panels 10 to be able to retrofit their panels for connection to sandwich panels 20 having different contours. In this case, of course, even if the two types of panel have nominally similar projections and tabs, there is no guarantee that they will be complementary in shape. But more generally, unless panels of one type are designed specifically for retrofitting with panels of a different type they will more likely have quite different modes of interconnection rendering them unsuited for mixing and matching.

The need to join polycarbonate panels and sandwich panels is particularly acute when used for roofing applications since the polycarbonate panels may be transparent or translucent to light while the sandwich panels are opaque. It is normal therefore to employ a modular construction where several sandwich panels are interconnected and at suitable intervals polycarbonate panels are interposed and must then be joined to the respective sandwich panels on either side.

KR20100040418 discloses a mounting structure of a roof panel that combines a sandwich panel and polycarbonate panel secured by a fastener, which interconnects the two types of panel. This is not desirable for reasons which will now be explained.

Thus, even apart from the geometrical considerations described above, another no less important concern is that polycarbonate panels and sandwich panels have markedly different rates of thermal expansion and contraction. The rate of thermal expansion of sandwich panels formed of metal and insulating materials is determined principally by the metal skins and is much lower than that of polycarbonate panels. When used in roofing applications, the sandwich panels are fixed by bolts to the building structure but the polycarbonate panels must be free-floating in order to allow unimpeded thermal expansion and contraction. This is not an issue when covering a building structure with metal because the entire structure of the building is then made out of metal and therefore has the same thermal properties.

In some arrangements a bolt passes through the respective coupling tabs of adjacent sandwich and polycarbonate panels and secures the panels to a building structure. However, this may give rise to buckling of the panels owing to the different coefficients of expansion of the two types of the panel. This is apt to cause damage to the panels and may lead to water leakage and other functional failure of the roof or the wall. This drawback is to some extent alleviated by an arrangement such as shown in Fig. 3a where only the sandwich panels are bolted to the fixed building structure while the polycarbonate panels are configured for unimpeded expansion and contraction. Figs. 3b and 3c are enlarged details of the encircled portion of Fig. 3a showing that the sandwich panel 20 is fixed to the building structure (not shown) using a self-tapping screw 31. The polycarbonate panel 10 is not fixed to the building structure but is maintained in abutting relationship with the upward projection 25 of the sandwich panel 20, the adjoining seam being covered by a cap 30 formed of resilient steel. A profiled coupling member 32 formed of corrugated aluminum or steel is secured to an upper end of the projection 25 by the screw 31 and has a downwardly depending leg 33 terminating in a foot 34 to whose lower surface is attached a rubber pad 35. The rubber pad 35 is pressed tight against an upper surface of the polycarbonate panel 10, thereby adhering to the upper surface. By such means, the coupling member 32 joins the sandwich panel 20 to the polycarbonate panel 10, while the profiled cap 30 prevents water leakage.

Further protection against the elements is provided by a sealing joint 36 also formed of rubber that has a resilient socket adapted to grip an upwardly projecting flange 37 at an end of the polycarbonate panel 10. A mating rubber seal 38 is affixed to an end surface of the sandwich panel 20. Side surfaces of the profiled coupling member 32 and of the projection 25 of the sandwich panel 20 are provided with arcuate recesses 39, which accommodate complementary protrusions 39' on opposite inner surfaces of the cap 30 when the latter is snap-fitted to the juxtaposed panels. This applies lateral pressure to the two panels thus forming a water-tight seal owing to the interposing rubber seals.

It is clear that only the coupling element 32 actually retains the two panels in juxtaposed relationship. The cap 30 and the sealing joint 36 play no part in the securing of the two panels.

Fig. 4a shows another known polycarbonate roof panel 10 coupled to a sandwich type panel 20 using a three-part coupling assembly 40, shown in enlarged detail in Fig. 4b. Downwardly projecting joining flanges 41 at opposite ends of the polycarbonate panel 10 engage respective openings in a pair of longitudinal profiles 42 that sit astride the upwardly projecting joining flanges 25 of the sandwich panels 20. An advantage of this arrangement over that of Fig. 3 is that the joining flanges of the polycarbonate panels do not need to be customized to the projections of the sandwich panels. This allows the different types of panels to be mixed and matched, even using panels from different manufacturers. This notwithstanding, there are several drawbacks with the arrangement since the profiles 42 co-operate with a steel support 43 to form a three-part assembly. The support 43 is bolted toward each end to the upwardly projecting flanges 25 of the sandwich panels 20 and is provided with respective cavities 44 at opposite ends. The profiles 42 formed of pre-lacquered steel are disposed inside the respective cavity and are secured thereto by screws 45. Each profile is adapted to engage the joining flange at the respective end of the polycarbonate panel. The sandwich panels 20 and each component of the coupling assembly 40 will thermally expand and contract at the same rate since they are all formed of steel. The polycarbonate panel 10 will thermally expand and contract at a higher rate than steel but is freely supported within the longitudinal profiles 42 thereby allowing it to thermally expand and contract relative to the support without buckling.

Even apart from the relative complexity of the adapter shown in Figs. 4a and 4b, there are other drawbacks. First and more significant is the fact that the sandwich and polycarbonate panels are not in the same plane because a lower surface of the polycarbonate panels is supported on the upwardly projecting flanges of the sandwich panels. Roofs and walls, although primarily roofs, extend along expansive lengths and in many, if not even most, cases the polycarbonate panels cover only a fraction of the length. For example, in a slanting roof, both the upper section closest to the apex and the lower section remote from the apex are covered with sandwich panels only a relatively small intermediate section being covered by the polycarbonate panels. Since the upper surface of the polycarbonate panels is not in the same plane as that of the sandwich panels, this leaves gaps where the different types of panels meet each another and this can be a source of water leakage. Therefore, after constructing the roof, each joint must be sealed along its complete length, which is inconvenient and adds to the cost of construction. Secondly, although the steel guide supports are thin and obviously do not extend along the whole length of the panels, they are visible through the translucent polycarbonate panels. This means that at regular intervals along the length of the skylight the steel guide supports interrupt the continuity of the polycarbonate panels.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an improved adapter for joining sandwich panels to polycarbonate panels or other plastic panels, which addresses the limitations of the prior art. This object is achieved in accordance with different aspects of the invention by a panel system having the features of the respective independent claims.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to understand the invention and to see how it may be carried out in practice, embodiments will now be described, by way of non-limiting example only, with reference to the accompanying drawings, in which:

Fig. 1 shows pictorially a known polycarbonate roof panel adapted for coupling to sandwich type panels;

Fig. 2 shows pictorially the roof panel of Fig. 1 coupled to a sandwich type panel;

Fig. 3a shows pictorially another known polycarbonate roof panel juxtaposed to a sandwich type panel using a profiled sealing member and a coupling element;

Figs. 3b and 3c show enlarged details of the sealing member and coupling element shown in Fig. 3 a;

Fig. 4a shows pictorially another known polycarbonate roof panel coupled to a sandwich type panel using a three-part coupling assembly;

Fig. 4b shows schematically an enlarged view of the three -part coupling assembly shown in Fig. 4a;

Fig. 5a shows pictorially a polycarbonate roof panel coupled to a sandwich type panel using a coupling assembly according to a first embodiment of the invention;

Fig. 5b shows an enlarged detail of a coupling member;

Fig. 5c shows an enlarged detail of the polycarbonate panel;

Fig. 6 shows pictorially a polycarbonate roof panel coupled to a sandwich type panel using a coupling assembly according to a second embodiment of the invention;

Figs. 7a and 7b show pictorially a variation of the first embodiment depicted in

Fig. 5a; and

Figs. 8a and 8b show pictorially a coupling assembly according to another embodiment. DETAILED DESCRIPTION OF EMBODIMENTS

In the following description of some embodiments, identical components that appear in more than one figure or that share similar functionality will be referenced by identical reference symbols. To the extent that the following description relates to known roofing panels, identical reference symbols will also be employed to those shown in Figs. 1 to 4.

Fig. 5a shows a modular panel system 50 according to a first embodiment of the invention comprising a sandwich type panel 10 (constituting a panel of a first type) coupled on opposite sides to respective polycarbonate roof panels 20', 20" (constituting panels of a second type) by respective first and second coupling members 51', 51". Each sandwich panel 10 is fixedly attached to a building structure 52 and has a projection 25 (constituting a male connector) projecting upwardly from an upper surface 22 of the panel toward a first end and a tab 26 (constituting a female connector) of complemen tary shape projecting upwardly at its opposite second end. The sandwich panel 10 may be of similar construction to that described above with reference to Fig. 1 and is therefore not described in detail. The tab 26 is shown schematically projecting upwardly from an edge of the panel bounding the upper surface 22 and the second end of the panel. The tab 26 extends outwardly away from the upper surface so as overlap the adjacent polycarbonate panel. Each of the polycarbonate panels 20', 20" has at least one joining flange 53 toward each end projecting upwardly from the upper surface of the panel. A U-shaped support 54 is secured to the building structure 52 by a screw 55 and serves to support an end of the respective polycarbonate panel 20', 20", while allowing it to thermally expand or contract relative to the sandwich panel 10.

The first coupling member 51' has a planar support member 56 adapted for attachment to the upward projection 25 of the sandwich panel 10. Conveniently this is achieved by means of the same screw 31 that fixes the sandwich panel to the building structure, although it can be secured to the sandwich panel 10 by other means. The support member 56 may be bent to provide a side portion 57 that fits the outer contour of the projection 25 thereby impeding water leakage and rotation of the first coupling member 51'. Projecting downwardly from the support member 56 is a first socket 58 adapted for coupling to the upwardly projecting flange 53 of a first adjacent polycarbonate panel 20'. The support member 56 is preferably formed of material having a similar coefficient of thermal expansion to the sandwich panels 10. This is particularly important when the coupling member extends along the full length of the panel since the support member 56 is then fixed intermittently to the sandwich panels, and if they do not expand and contract in unison, the support member 56 can buckle or tear.

As shown in Fig. 5b, the second coupling member 51" has a body portion 60 of complementary shape to the tab 26 of the sandwich panel 10 into which it may be snugly fitted and optionally secured by a press stud or rivet 61. The body portion 60 has or defines a downwardly projecting second socket 62 adapted for coupling to the upwardly projecting flange 53 of a second polycarbonate panel 20". As shown in Fig. 5c the flange 53 may have a split claw allow it to compress slightly and then expand when push-fitted into the socket 62. The manner in which the flanges 53 of the polycarbonate panels 20 engage the downwardly projecting sockets 62 must be such as to ensure that the result joint is able to withstand mechanical loads applied to the panels. Specifically, strong positive or negative forces that are applied over the wide area of a roof structure caused by wind or suction must not cause the joints to rupture or even partially separate, since this would allow water to seep through the joints. Likewise, positive loads such as snow or the weight of people standing on the roof may cause the polycarbonate panels to bend between purlins under the applied weight. In practice this is avoided by providing at least one notch or tooth on the outer surfaces of the flanges that engage corresponding indents formed on the inner surfaces of the sockets. These are shown more clearly in the enlarged views of Figs. 5b and 5c and are also described and shown in many of our earlier patents such as US Patent No. 8,316,609 titled Modular panel units for constructional purposes and US Patent No. 9,010,056 titled Assembly for securing two juxtaposed panels to a structure so as to allow thermal expansion and contraction. These correspond respectively to Israeli Patent Nos. 183898 and 213693. Use of flanges of this type allows the coupling member to be snap-fitted to the flange simply by pushing the coupling member down on to the upwardly projecting flange. The joint must be sufficiently strong to prevent subsequent separation, other than by relative lateral sliding of the panel and the joint. In some cases, this may require that multiple complementary teeth and indents be provided. Furthermore, the positive coupling action afforded by the notched flanges means that in effect the polycarbonate panels are suspended at their ends by the sandwich panels. The sandwich panels, being partially formed of metal are rigid and are supported by the purlins of the roof structure. If the polycarbonate panels also rest on the purlins, then the support afforded thereby will prevent or at least reduce the natural tendency of the polycarbonate panels to bend under their own weight, particularly when spanning long lengths of roof. This means that if the polycarbonate panels are supported only at their ends on the purlins, the tendency of the polycarbonate panels to bend will be more pronounced as the distance between adjacent purlins increases.

But the invention allows the polycarbonate panels to be supported along their side edges to the abutting sandwich panels, which being rigid offer strong support. In the embodiment of Fig. 5a, the coupling members need to extend the complete length of the panels because in this embodiment, in the absence of a cap that covers the seams between adjacent panels, rain would leak into the roof structure through the seams. In this case, the coupling members are clasped along the complete length of the panels by the sandwich panels, which prevents them from sagging under the weight. This is distinct from the prior art shown in Fig. 3a where the coupling members 30 neither extend the complete length of the panels nor provide positive gripping of the polycar bonate panels.

Preferably, the first and second coupling members 51', 51" are dimensioned so that the respective upper surfaces 16, 22 of the panels are co-planar. This may be achieved by making the sandwich and polycarbonate panels of equal height if they both are supported on their lower surfaces by the building structure. But commonly the polycarbonate panels are of narrower height than the sandwich panels and are supported at their ends. The upwardly projecting flange 53 of the polycarbonate panels must be dimensioned so that it properly engages the sockets 58 and 62. Coupling members 51', 51" of different sizes may be provided to allow this condition to be fulfilled regardless of the height of the upwardly projecting flanges 53.

Typically, the first and second coupling members 51', 51" are dimensioned such that mutually adjacent ends of the panels are in substantial abutting contact as shown in the drawings. Fig. 6 shows a modular panel system 70 according to a second embodiment of the invention comprising a pair of juxtaposed sandwich type panels 10', 10" (consti tuting a panel of a first type) one of which is coupled to a polycarbonate roof panel 20 (constituting a panel of a second type) by a coupling member 71'. The sandwich panels 10' and 10" are not interconnected. There is no need to do so since each is independent ly affixed to the building structure by respective screws 31, but the seam between the two sandwich panels is covered by a cap 71" that prevents water leakage. The poly carbonate roof panel 20 is of identical construction to the panel shown in Fig. 5a and has a respective joining flange 53 as shown in detail in Fig. 5c at or toward each end projecting upwardly from an upper surface 16 of the panel. Each of the sandwich panels 10', 10" has at each end a respective upward projection 72 that constitutes a male connector and projects from the upper surface 22 of the panel.

The coupling member 71' is adapted for attachment to the upward projection 72 of the sandwich panel and has a downwardly projecting socket 73 adapted for coupling to the upwardly projecting flange 53 of the adjacent polycarbonate panel 20. Conceptually, the coupling member 71 ' is of similar design to the coupling member 51 ' shown in 5a in that it has an upper support that is secured to the upward projection 72 of the sandwich panel. As above, this may be done using the same screws 31 that secure the sandwich panels to the building structure 52. Here also the coupling member 71 ' is preferably formed of material having a similar coefficient of thermal expansion to the sandwich panels 10', 10" in order to prevent buckling or fracture caused by uneven rates of expansion or contraction. The support is cantilevered to the upward projection 72 of the sandwich panel and supports the downwardly projecting socket 73. The cap 71" has a cavity 74 shaped for fitting over the upward projection 72 of the sandwich panel 10', 10" and an outer surface of the first coupling member 71'.

Preferably, respective outer surfaces of the upward projection 72 and the socket 73 have matching contours, thereby allowing two sandwich panels or a sandwich panel and a polycarbonate panel to be mutually juxtaposed and for their respective seams to be covered using identical caps 71".

As in the first embodiment, the coupling member 71' and the cap 71" are preferably dimensioned so that the respective upper surfaces 16, 22 of the panels are co- planar. Likewise, the coupling member 71' and the cap 71" are typically dimensioned such that mutually adjacent ends of the panels are in substantial abutting contact as shown in the drawings. Alternatively, a gap may be provided between adjacent panels thus allowing for lateral expansion of the panels.

The same principle of covering the joint with a cap may also be applied to the first embodiment. Thus, Fig. 7 shows a variation of the first embodiment 50 wherein a cap 71 is push-fitted over the joints thereby covering the heads of the bolts 31. Furthermore, since the cap 71 as shown in all its variations in Figs. 6 and 7 extends longitudinally along the complete seam between adjacent panels, it may be configured not only to cover the joint for esthetic purposes but also to seal the joints against water leakage. In such case, the seam between adjacent panels does not need to be watertight along its complete length although the joints do still need to withstand high forces. But this requirement can be met by joining the panels intermittently along their length with coupling members that meet the load requirement. The seam between joints is then susceptible to water leakage, but this is then avoided by the cap which extends along the complete length of the seam. The coupling members are typically formed of metal and the need to provide interlocking with the sandwich panels renders them significantly more expensive than the cap, which is of much simpler construction. Therefore, the arrangement of Fig. 7 reduces costs significantly as compared with that of Fig. 5 a. In this embodiment it is less critical that the support member 56 be formed of similar material to that of the sandwich panels 10, since they do not extend along the complete of the panel and therefore each support member 56 is attached at only a single point to the uprights of the sandwich panels. In cases where the polycarbonate panels span long lengths between successive purlins, extra support can be provided by using additional coupling members on opposite sides of the panels. Since these intermediate coupling members also have complementary notches and indents they interlock positively with the sandwich panels thus providing additional intermediate support even where the polycarbonate panels are not supported by purlins.

In order to ensure a watertight seal, the cap 71 is generally U-shaped having opposing webs 75 formed of resilient material and whose longitudinal rims 76 are rolled so as to facilitate pushing the cap on to the joint, whereby the webs 75 splay apart. They spring back when the rims engage a lower surface 77 (shown in Fig. 5b) of the socket 62 and an outwardly projecting flange 78 formed along the side portion 57 of the support member 56 close to its lower edge. The rims 76 are then secured by the lower surface 77 of the socket 62 and the flange 78 forming a watertight seal. For the sake of clarity, it should be understood that the socket 62 shown in Fig. 5b relates to the embodiment of Fig. 5a which has no cap. But the coupling member in the embodiment of Fig. 7 has a socket of similar construction.

Also shown in Fig. 7a is a mount 80 shown in enlarged detail in Fig. 7b having a base member 81 supporting a generally U-shaped side arm 82. In use, the side arm 82 is first coupled, i.e. push-fitted, to the polycarbonate panel and thereafter the base member 81 is directly screwed to the purlin via the screw 31, which may pass through a pre formed aperture (not shown) in the base member or alternatively may be a self-tapping screw that passes through the base member and through the body of the sandwich panel 10, thereby securing both to the building structure. Alternatively, the base member 81 can be screwed directly to the building structure using short self-tapping screws in a similar manner to the U-shaped support 54 shown in Fig. 5a, which of course serves the same function of supporting the ends of the polycarbonate panels while allowing for thermal expansion or contraction thereof along the length of the panels. In either case, a lower surface of the sandwich panel is preferably provided with a recess like the recess 14 shown in Fig.l for accommodating the base member so that the lower surface of the sandwich panel sits properly on the building structure.

Yet another possibility is to screw the base member 81 to a lower surface of the sandwich panel, which to this end is preferably provided with a recess similar to the recess 14 shown in Fig.l. The sandwich panels with the mounts thus attached thereto are then fixed by the screws 31 to the building structure, thereby indirectly securing also the mounts thereto. The screws 31 in this case pass through the sandwich panels but not the mounts.

In either case, the mounts 80 are preferably metallic and are fixed to successive purlins, thus securing the polycarbonate panels at opposite ends while allowing them to slide within the side arms 82 and thus allow for thermal expansion or contraction of the polycarbonate panels along the length of the panels.

Fig. 8a shows pictorially part of a panel system 85 wherein juxtaposed sandwich panels 10 and polycarbonate panels 20 are joined using a coupling assembly 86 according to another embodiment and shown in slightly greater detail in Fig. 8b. What characterizes the arrangement of Fig. 8a is that identical coupling members 86 are employed for each joint on opposite sides of the polycarbonate panel 20 and that they are adapted for snap-fitting to the juxtaposed panels by a single operative. To this end, each coupling member 86 comprises a support member 87 that supports a socket 88 and is attached to the upward projection 25 of the sandwich panel 10 by a screw 89. The socket 88 has at a lower edge of an outer side surface 90 an inwardly projecting claw 91 that positively engages a corresponding notch or indent in an outer surface of the flange 53 of the polycarbonate panel 20. The socket 88 has an inner side surface 92 that provides mating support to an inner surface of the flange i.e. opposite the notch, whereby the flange 53 is rigidly and positively supported by the coupling member 86. Specifically, engagement of the claw 91 with the indents of the flange 53 retains the polycarbonate panel 20 and prevents it from falling under gravity; while the side surface 92 reduces any tendency of the flange 53 to rotate, which helps to reduce sagging. The upward projection 25 of the sandwich panel 10 and the flange 53 of the polycarbonate panel 20 are provided with respective recesses 93, 93' where they meet the upper surfaces of the respective panels.

The indents 93, 93' serve to engage corresponding shaped lips 94 at the lower rims of the caps 71, thus allowing the caps to be snap-fitted to the adjacent panels. It will be appreciated that even though the coupling members 86 are attached intermittently and do not extend along the full length of the two panels, the indents 93, 93' do indeed extend along the full length of the respective panels. Consequently, the cap 71 seals the joint against water without the need for additional rubber seals, such as required in the prior art construction of Fig. 3b. Furthermore, during construction, the sandwich panels 10 are fixed to the roof structure together with the coupling member 86 using the screws 31. Additionally or alternatively, the screws 89 may be elongated and serve to secure the sandwich panels 10 to the roof structure together with the coupling member 86. In either case, this can be done by a single operative working from above the roof structure. The screws 31 are spaced apart at distances dictated by the spacing between the purlins to provide secure attachment of the sandwich panels 10 to the roof structure. Coupling members 86 are conveniently push-fitted to the polycarbonate panels at spaced-apart locations configured for attachment to the sandwich panels. Once push-fitted on to the polycarbonate panels, the coupling members are clasped by the interlocking indents but can be slid axially along the flanges 53 of the polycarbonate panels. In this manner, they are slid to where the sandwich panels overlap the purlins and a long screw 31 is then inserted through the coupling members 86 and the sandwich panels to secure them to the underlying purlins. In those cases where enhanced rigidity is achieved by interposing additional coupling members intermediate mutually adjacent purlins, the coupling members are secured to the sandwich panels by the shorter screws 89.

The invention also comprises a kit comprising respective a coupling member and a cap for use with the panel systems 50 and 70.

It will further be appreciated that while the invention has been described with particular regard to polycarbonate roof panels, the principles of the invention are applicable to other materials and uses where it is required to provide a watertight joint between panels of markedly different rates of thermal expansion and contraction, without compromising the ability of the resulting structure to withstand high loads cause by wind or other external forces.

In should also be noted that features that are described with reference to one or more embodiments are described by way of example rather than by way of limitation to those embodiments. Thus, unless stated otherwise or unless particular combinations are clearly inadmissible, optional features that are described with reference to only some embodiments are assumed to be likewise applicable to all other embodiments also. Thus, while expanded details of the flanges and sockets are described only with reference to the first embodiment, it will be appreciated that the same considerations apply to all embodiments in order to withstand high loads and avoid water leakage through the joints.