BACKGROUND OF THE INVENTION Fastening screws are widely used in any number of applications. Typically, they are used for attaching an element to a substrate, the screws being designed to securely hold the same.

Although screws are widely used, they normally are not used wherein a relatively leak resistant arrangement is required between the assembled components.

Thus, the shank of a screw having threads thereon forms a helicoidal thread which extends through the components and this usually renders the assembly somewhat susceptible to leaking.

There are certain situations wherein such leaking is not acceptable and such situations would include the attachment of building or roof panels to an underlying substrate. Building panels for use as roof and fascia portions of building structures are well known in the art. Many such building panel structures are arranged to have an interlocking relationship at their edges to orient the building panel structures relative to another and also to protect against the entry of moisture. However, the attachment of these panels has suffered from the possibility of moisture penetration through conventional fastening screws. Many building panel structures are designed for aesthetic appearance and an interlocking relationship, but do not provide for the development of structurally self sufficient wall and roof portions which will support uniformly distributed loads without any additional structure.

There have been attempts in the past to devise fasteners which are leak resistant. Thus, various types of screws having washers associated therewith have been employed. These washers have been usually manufactured of a fibrous or polymeric material.

It is known that wind and other forces produce vibration tending to cause such a screw to work loose by causing the washer to act as a lever transmitting forces to the screw head. In order to overcome this, it has been proposed in the art to form an integral assembly of a screw and a roofing washer which tends to make it more difficult for the screw to work loose. However, such integral assemblies are relatively expensive to manufacture and often special tools are required for their installation.

They still remain susceptible to the problem of leakage. Thus, when the conventional sealing washer is pressed by the screw head in order to prevent water from seeping through the apertures, the peripheral region of the sealing washer normally extends outwardly past the peripheral edge of the screw and thus is not covered or protected by the head. The peripheral region is thus exposed to the elements including the air and solar rays which tend to drastically reduce its effective service life.

In addition, such screw fasteners generally do not have an aesthetically appealing outward appearance. This is particularly so when deformation and cracking of the washer occurs after prolonged exposure to environmental elements such as the sun and air borne pollution. Thus, after the fastener has been driven into the structural member, the washer will often crack and deform and pieces will break off allowing moisture to easily leak into the assembled structure.

It has also been proposed to provide a screw wherein an elastomeric washer is mounted under a conventional metal washer with both washers being adapted to be sandwiched between the screw head and the panel being attached. However, since roofing panels tend to flex under forces exerted thereon such as wind or the weight of snow, the elastomeric washer tends to remain compressed in its original configuration and subsequently water can infiltrate between the screw head and the metallic washer.

SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide an improved fastening device which is easy to manufacture and provides easy assembly of the components while maintaining a leak resistant connection.

According to one aspect of the present invention, there is provided a washer assembly for use with a screw having a shaft and a screw head, the screw head having a recess formed on an underside thereof, the washer assembly comprising first and second washer members, the first washer member being formed of a resilient material, the second washer member being formed of a material less resilient than the material forming the first washer member ; the first washer member having a centrally located aperture sized to receive the screw shaft, the first washer member having an upper section, a lower section, and an intermediate section between the lower and upper sections ; the washer assembly being characterized by the upper section having an upper section diameter sized to at least partially fit within the recess of the screw head ; the intermediate section having an intermediate section diameter less than the upper section diameter ; the lower section having a lower section diameter larger than the upper section diameter ; the second washer member having a second washer member aperture extending therethrough, the second washer member aperture having an aperture diameter at least substantially equal to the intermediate section diameter and less than the upper section diameter.

According to a further aspect of the present invention, there is provided a washer and screw assembly comprising a screw having a shaft and a screw head, the screw head having a recess formed on an underside thereof, the washer assembly comprising first and second washer members, the first washer member being formed of a resilient material, the second washer member being formed of a material less resilient than the material forming the first washer member, the first washer member having an upper section, a lower section, and an intermediate section between the upper and lower sections, the washer and screw assembly being characterized by the first washer member being placed on the shaft of the screw whereby the upper section fits partially within the recess of the screw head, the intermediate section having an intermediate section diameter less than the upper section diameter, the lower section having a lower section diameter larger than the upper section diameter, the second washer member fitting between the upper section and the lower section.

BRIEF DESCRIPTION OF THE DRAWINGS Having thus generally described the invention, reference will be made to the accompanying drawings illustrating an embodiment thereof, in which : Figure 1 is an exploded perspective view of a screw and washer assembly attaching a first member to a substrate ; Figure 2 is a top plan view thereof ; Figure 3 is a side elevational view thereof ; Figure 4 is a side elevational view, partially in section, of a first washer member of the washer assembly ; Figure 5 is a top plan view of the first washer member of Figure 6, Figure 6 is a partial side cross sectional view of the screw and washer assembly used in Figure 1 in a non-compressed position ; and Figure 7 is a partial sectional view of the screw and washer assembly of Figure 1 in a compressed condition.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the drawings in greater detail and by reference characters thereto, there is illustrated in the Figures a screw and washer assembly generally designated by reference numeral 10 and which screw and washer assembly 10 is used to secure a panel having a corrugation 82 to a substrate 84 (Figure 3). The arrangement shown is that typically used in construction for securing such panels.

The screw and washer assembly includes a first washer member generally designated by reference numeral 12 as best seen in Figures 4,6 and 7 and to which reference will now be made. First washer member 12 is characterized by having an upper section 14, a lower section 16, and an intermediate section 18 between upper section 14 and lower section 16.

Upper section 14 includes an annular side wall 22 and a top wall 24. Between annular side wall 22 and top wall 24, there is provided a chamfered surface 26.

A bottom wall of upper section 14 extends inwardly to meet an intermediate section side wall 30.

Lower section 16 has an annular side wall 34, a relatively flat bottom wall 36, and a sloping top wall 38 extending between intermediate section side wall 30 and side wall 34 of lower section 16.

The screw and washer assembly also includes a second washer member which is best seen in Figures 1,6 and 7 and which is generally designated by reference numeral 42. Second washer member 42 has an annular side wall 44, a top wall 46 which is of a sloping convex configuration, and a concave bottom wall 48. An aperture is centrally located in second washer member 42.

First washer member 12 is formed of a resilient material, and is preferably formed of an elastomeric material such that the same can be compressed and it also has a memory such that when it is compressed, it will be resiliently biased against the compressing force. Second washer member 42 is of a less resilient material than first washer member 12 and in a preferred embodiment, is of any suitable metallic material which is preferably resistant to corrosion.

Screw 50 has a screw head 52 which has a concave upper surface 54 and a convex lower surface 56. The arrangement is such that there is provided a lower recess 58 defined by convex surface 56 and which extends to the peripheral edge 59 of screw head 52. A recess 60 is provided in upper surface 54 for receiving the head of a screw driver or other tool.

Screw 50 has an upper shaft portion 64 adjacent screw head 52 and a lower shaft portion 66 having threads 68 formed thereon. Upper shaft portion 64 preferably is not provided with screw threads.

In use, second washer member 42 is placed over upper section 14 of first washer member 12 such that it will seat within the recess defined by intermediate section 18. As will be noted, upper section 14 has a diameter greater than the diameter of the aperture in second washer member 42. Thus, second washer member 42 is retained in position between upper section 14 and lower section 16. Preferably, the aperture in second washer member 42 is sized such that the same will seat snugly against intermediate section side wall 30.

Annular side wall 22 of upper section 14 is preferably of a height which is at least slightly greater than the distance between convex lower surface 56 and a plane defined by the peripheral edge 59 of screw head 52. Thus, when upper section 14 is placed within lower recess 58 of screw head 52, there is a slight compressive force acting thereon.

It will also be noted that second washer member 42 has a diameter which is slightly greater than the diameter of lower section 16 of first washer member 14 and is also greater than the diameter of screw head 52.

Figure 7 illustrates the screw and washer assembly in a tightened position and wherein peripheral edge 59 of screw head 52 will contact concave upper surface 54 of second washer member 42. However, the compressed upper section 14 prevents the over tightening of the screw and prevents the lower section 16 from being unduly deformed while enabling a proper sealing.