Abstract:
A nail having an elongate shank, a head at one end of the shank and a tip portion at the other end. A lateral step is formed in the shank at a location spaced from both the head and the tip so as to divide the shank into a relatively small diameter penetrating portion which is adjacent the tip, and a relatively large diameter gripping portion which is adjacent the head. Any of a variety of gripping features, such as ribs or teeth, could be provided on the gripping portion to assist its grip within a member to which the nail is to be secured.

Description:
FIELD OF THE INVENTION 
     This invention relates to nails for fastening one member to another, and is particularly although not exclusively concerned with fastening sheet or plank cladding to a support. A nail according to the invention is especially suited for fastening cladding to a steel or other metal support, and it will be convenient to hereinafter describe the invention with particular reference to that type of application. It is to be understood however, that a nail in accordance with the invention can be used in other applications. 
     Reference in this specification to &#34;cladding&#34; is to be understood as embracing any sheet or plank material suitable for forming internal or external linings for walls or other structures. Examples of such materials are timber, plaster-board and HARDI-PLANK (Trade Mark), but this is not an exhaustive list of examples of applicable materials. 
     BACKGROUND OF THE INVENTION 
     Cladding is commonly fastened to a metal frame by means of screws because of the ability of screws to firmly grip within the metal frame. Screws of the self-drilling type are generally used because of their convenience, but they are relatively expensive. Nails have not been thought to be appropriate for securing cladding to a metal frame because of their relatively low pull-out resistance when driven through a hard material. 
     OBJECTS OF THE INVENTION 
     It is an object of the present invention to provide a nail which grips firmly within a Lard material, such as metal, into which it is driven. It is a further object of the invention to provide such a nail which is suited for use with a power driven tool such as a pneumatic, gas, electric or powder operated driving tool. It is to be understood however, that the nail could be used with other types of power driven tools. 
     SUMMARY OF THE INVENTION 
     When a nail is driven through a member, the hole thereby formed in that member results from rupture and/or resilient distortion of that part of the member containing the hole. In the case of a member composed of relatively soft material, the hole forming mechanism is predominantly resilient distortion of the material, and consequently the material surrounding the hole tends to press back against the shank of the nail to provide a firm grip on the nail. In the case of a member composed of a relatively hard material, the hole forming mechanism is predominantly rupture of the material, and that may result in a hole larger than the shank of the nail which formed the hole. At least, there is minimum tendency for the material surrounding the hole to move back against the nail shank. 
     A nail according to the present invention overcomes the aforementioned difficulty by having a stepped shank. That is, the shank has a penetrating portion which is remote from the head of the nail and a gripping portion which is between the head and the penetrating portion and which has a cross-sectional size greater than that of the penetrating portion. The arrangement is such that the penetrating portion creates a hole within the member into which the nail is driven, and the gripping portion is subsequently forced into that preformed hole to grip firmly with the member. The hole is enlarged as the gripping portion is driven into it, but the material distortion necessary for that enlargement is not significant, and as a consequence results predominantly from resilient deformation rather than rupture. 
     It is generally preferred that the nail has a pointed or otherwise formed tip portion which facilitates initial penetration of the nail into a member. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Embodiments of the invention are described in detail in the following passages of the specification which refer to the accompanying drawings. The drawings, however, are merely illustrative of how the invention might be put into effect, so that the specific form and arrangement of the various features as shown is not to be understood as limiting on the invention. In the drawings, like reference characters designate like or corresponding parts throughout the several views, and: 
     FIG. 1 is a side elevation view of a nail according to one embodiment of the invention. 
     FIG. 2 is a view showing the tip portion of the nail of FIG. 1 penetrating cladding to be attached to a support. 
     FIG. 3 is a view similar to FIG. 2 but showing the nail extending through both the cladding and the support. 
     FIG. 4 is a view similar to FIG. 3 but showing the nail fully driven through the cladding and support so as to hold the cladding against the support. 
     FIG. 5 is a cross-sectional view taken along line 5--5 of FIG. 1. 
     FIG. 6 is a view similar to FIG. 1 but showing another embodiment of the invention. 
     FIG. 7 is an enlarged cross-sectional view taken along line 7--7 of FIG. 6. 
     FIG. 8 is a view similar to FIG. 6 but showing still another embodiment of the invention. 
     FIG. 9 is a view similar to FIG. 1 showing yet another embodiment of the invention. 
     FIG. 10 is a view similar to FIG. 1 showing still another embodiment of the invention. 
     FIG. 11 is a perspective view of a tip portion of a nail according to the invention, wherein the tip is of diamond form. 
     FIG. 12 is a cross-sectional view taken along line 12--12 of FIG. 11. 
     FIG. 13 is a view similar to FIG. 11 but showing a chisel point tip portion. 
     FIG. 14 is a cross-sectional view taken along line 14--14 of FIG. 13. 
     FIG. 15 is a view similar to that of FIG. 1, showing however an additional embodiment wherein the different component parts of the nail are denoted by primed (&#39;) reference characters; and 
     FIG. 16 is a view similar to that of FIGS. 1 and 15, showing however a further embodiment of the present invention wherein the different component parts of the nail are denoted by double-primed (&#34;) reference characters. 
    
    
     DETAILED DESCRIPTION 
     The nail shown in FIGS. 1 to 5 of the drawings has a shank 1 and a head 2, which in the example shown is formed with a flat side 3 so as to be adapted for use in the cartridge system of a powered driving tool. The invention is applicable to nails which are not so adapted and which have heads of a form different to that shown. In particular, the invention is applicable to nails having heads other than flat sided heads. 
     In the particular example shown, the shank 1 is generally cylindrical and has three portions, a tip portion 4, a penetrating portion 5, and a gripping portion 6. The tip portion 4 is of pointed conical form, and although that has been found to be a most satisfactory form, other forms such as diamond or chisel points may also be used. A conical form is generally preferred because it exhibits little tendency to shear the material through which it is driven, whereas diamond and chisel points are generally less satisfactory in that regard. Also, a conical point exhibits less tendency to be deflected laterally when it first strikes the surface of the member into which it is to be driven. 
     Tests have indicated that use of a conical tip portion form rather than one of diamond or chisel form, results in approximately 15% improvement in nail grip. A particularly satisfactory conical tip has an included angle A (FIG. 1) within the range 30° to 40° inclusive, and an angle of 35°, or thereabouts, is preferred. It is nevertheless possible to achieve acceptable results with an angle in the range 25° to 120°. The same range of included angles is applicable to both diamond and chisel points, and any other point configuration which may be adopted. 
     The penetrating portion 5 of the shank 1 is immediately adjacent the tip portion 4, and the length of the portion 5 can be selected to suit requirements. That length is preferably such that in the case of attachment of cladding 7 to a metal frame (FIGS. 2 to 4), the penetrating portion 5 passes completely through the frame member 8 before the gripping portion 6 engages that member (FIG. 3). Stated another way, the length of the penetrating portion 5 is prefereably no less than the thickness of the member 8 through which it is to pass and within which the gripping portion 6 is intended to grip. 
     It is also preferred that the penetrating portion 5 is of substantially constant cross-sectional size throughout its length, however, it could be slightly tapered as shown in FIG. 15. 
     The gripping portion 6 has a diameter larger than that of the penetrating portion 5, and is selected to achieve the required result--namely, a firm grip within the member 8. It is generally preferred to adopt a particular relationship between the thickness (T) of the member 8 and the height (H) of the step 9 formed between the two shank portions 5 and 6 (see FIGS. 1 and 2). Satisfactory results have been achieved with a difference in diameter between the gripping portion 6 and the penetrating portion 5 which is roughly equivalent to the thickness (T) of the member 8. It is thought that the pull-out stength of the nail will diminish if the difference in diameter is increased substantially above the thickness of the member in which the nail is to grip. 
     It is preferred that the gripping portion 6 is of substantially constant cross-sectional size throughout its length, although it could be slightly tapered, particularly over the section immediately adjacent the penetrating portion 5, as shown, for example, in FIG. 16. In the particular arrangement shown, the gripping portion 6 has a substantially constant diameter, and stepped portion or chamfer 9 slopes away from the penetrating portion 5. The angle B (FIG. 1) at which the step 9 slopes can be selected to suit requirements, but an angle of roughly 45° has been found to be satisfactory. 
     The length of the gripping portion 6 will be selected to suit requirements, but will usually be no less than the combined thicknesses of the cladding 7 and the member 8. 
     It is to be understood that neither of the shank portions 5 and 6 needs to have a smooth surface as is indicated by FIGS. 1 to 4 of the drawings. The surface of either or each of those portions 5 and 6 may be roughened, provided with grooves, or otherwise treated to suit requirements. FIGS. 6 and 7 of the drawings show one such form of treatment in which the surface of the shank portion 6 is provided with a gripping feature in the form of alternating grooves 10 and ribs 11 which extend longitudinally of the shank 1. Such surface treatment may assist in achieving a strong grip with an object into which the nail is driven. 
     The cross-sectional shape shown by FIG. 7 is an exemplified shape, and is not to be understood as the only shape which may be adopted for a grooved shank. Furthermore, the grooves 10 could be arranged angularly relative to the longitudinal axis of the shank 1 rather than being parallel to that axis as shown. It is also possible to have grooves extending circumferentially of the shank 1, rather than longitudinally thereof. Still further, the grooves 10 need not be continuous, but could be interrupted, and an example of an interrupted arrangement is shown in FIG. 8. 
     Although FIGS. 6 and 8 show the grooves 10 in the gripping portion 6 of the shank 1, it is to be understood that they may be provided also in the penetrating portion 5. Alternatively, they may be provided in the penetrating portion 5 only. 
     FIG. 9 shows another embodiment of the invention in which a series of teeth 12 extend along the gripping portion 6 so as to act as a gripping feature. Each tooth 12 extends circumferentially around the gripping portion 6, and is spaced from each two adjacent teeth 12 in the axial direction of the shank 1. It is to be understood that the teeth 12 may have a form different to that shown in FIG. 9. Also, each tooth 12 need not extend as a continuous ring around the gripping portion 6, but could be divided into two or more circumferentially spaced parts. 
     Still another embodiment is shown by FIG. 10. According to that embodiment, the gripping feature is formed by a series of angularly extending ribs 13 provided on the gripping portion 6. Each rib 13 extends angularly relative to the longitudinal axis of the shank 1 so as to follow a helical path. The angle of the helix can be selected to suit requirements, but an angle within the range 45° to something less than 90° is usually preferred. The number of ribs 13 can be also selected to suit requirements. 
     Each of the embodiments shown in the drawings has a conical tip portion 4. As previously indicated, other forms could be adopted for the tip portion, including a diamond form or a chisel form. FIGS. 11 and 12 show an exemplified diamond form having four flat surfaces 14, each of which is arranged substantially at right-angles to each two adjacent surfaces 14. FIGS. 13 and 14 show an exemplified chisel form having two oppositely facing flat surfaces 15. 
     According to yet another possible modification of the nail according to the invention, an adhesive may be applied to the gripping portion 6 and arranged to be activated as a consequence of driving that portion 6 into a member. By way of example, the adhesive may be activated by friction generated heat as the nail penetrates a member. Alternatively, the adhesive may be captured in globules which break as the nail is driven into a member and therefore result in spreading of the adhesive. Other arrangements are clearly possible. In each case the intention is to result in automatic exposure of an adhesive which subsequently hardens to assist in maintaining a grip between the nail and the member into which it is driven. 
     A nail according to the invention has been found to be highly effective for securing cladding to a metal section. In particular, the nail has high pull-out stength when embedded in such a section. 
     Various alterations, modifications and/or additions may be introduced into the constructions and arrangements of parts previously described without departing from the spirit or ambit of the invention as defined by the appended claims.