Fastener

Disclosed is a fastener comprising a central elongate shank extending between first and second ends. The first end of the shank has a tapered point. The second end a head has an annular shoulder disposed towards the second end. The fastener further comprises an opposed pair of spines extending helically along the shank and a plurality of hooks extending from each of the pair of opposed spines. Also disclosed is a protrusion extending axially with the shank from the head deformable into an anti-friction washer upon impact by a fastener driver.

BACKGROUND OF THE INVENTION

1. Field of Invention

The present invention relates to fasteners in general and in particular to an improved fastener that is resistant to removal or pull-out.

2. Description of Related Art

Fasteners, such as nails, are well known for the purpose of securing articles of wood, plastic and the like together. Nails are elongate pin-shaped, sharp objects of hard metal or alloy having a sharpened end and a blunted or flared driving end.

Nails are typically driven into the work piece by a hammer, a pneumatic nail gun, or a small explosive charge or primer. A nail holds materials together by friction in an axial direction and shear strength laterally. Fasteners, such as nails, which are applied by an axial force are advantageously quick and easy to use. One limitation of nails, however is their reliance upon the friction between the nail on the wood surface to retain the nail in the material. Accordingly, nails may be prone to being axially displaced within the material which is also known as being pulled out.

Screws are also well known fasteners, however it is well known that screws are more difficult and time consuming to apply as they are required to be twisted or torque into the material. In particular, many screws are required to be axially rotated a plurality of times while being driven into the material. This is both time consuming and labor intensive. Screws also typically have a single helical thread extending therearound.

Other attempts to provide fasteners having improved pull out performance have provided circumferential rings or ridges around the shank of the nail or spiraled planar surfaces surrounding the shank of the nail, also referred to as screw-shank nails. Such attempts have similarly been limited in the resistance of the nail to pull out as the nail does not engage a surface area of the material into which it is applied that is a significantly larger than the circumference of the nail itself.

SUMMARY OF THE INVENTION

According to a first embodiment of the present invention there is disclosed a fastener comprising a central elongate shank extending between first and second ends. The first end of the shank has a tapered point. The second end has a head having an annular shoulder disposed towards the second end. The fastener further comprises an opposed pair of spines extending along the path of a double-alpha helix along the shank and a plurality of hooks extending from each of the pair of opposed spines.

The plurality of hooks may have sharpened tips oriented towards the second end of the shank. The spines and the hooks may be formed from a planar member defining a double-alpha helix plane around the shank. The plurality of hooks may be curved out of the double-alpha helix plane of the spines. The tips of the plurality of hooks may be disposed to opposed alternating sides of the spines. The plurality of hooks may have flexible tips.

The spines may extend radially from the shank. The spines may have a constant angle of inclination about the shank. The spines may include a directional self-tapping blade oriented at an angle corresponding to the angle of inclination about the shank proximate to the first end of the shank. The spines may extend 360 degrees around the shank between the first and second ends of the shank. The spines may extend less than 360 degrees around the shank between the first and second ends of the shank.

The fastener may further include a protrusion extending axially with the shank from the head. The protrusion may be frangibly connected to the head. The protrusion may be formed of a more ductile material than the head. The protrusion may be deformable into an anti-friction slip washer upon impact by a fastener driver. The washer may be separable from the head upon rotation of the shank and head.

DETAILED DESCRIPTION

Referring toFIG. 1, a fastener according to a first embodiment of the invention is shown generally at10. The fastener10has an elongate central shaft or shank12extending between a first or sharpened end14and a second or driving end16. The fastener10includes first and second spines18and20extending therealong. The first and second spines18and20are located to opposed sides of the shank12and spiral around the shaft along a double-alpha helix path as will be more fully described below. The first and second spines18and20each include a plurality of protrusions or hooks30having pointed ends oriented towards the driving end16of the fastener.

The shank12may have a round cross section, as are common in the art although it will be appreciated that other cross-sections may also be useful, such as, by way of non-limiting example, oval, square or rectangular. In embodiments having a non-round cross section, the cross section shape may twist around the shank in correspondence with the first and second spines such that the location of the spine on the cross-sectional shape will remain constant along the length of the shank. Optionally, the cross section may remain at a constant radial orientation around the shank while the spines twist therearound along a double-alpha helix path.

The path of each spine has an angle of inclination, generally indicated at23relative to an axis24of the shank12. The angle of inclination23of the spines18and20is constant along the length of the shank. As illustrated, a path of each of the first and second spines18and20curves around the fastener by 360 degrees from the sharpened end14to the driving end16although it will be appreciated that the first and second spines18and20may twist about the shank12by other rotation angles as well. Preferably, the twist of the first and second spines18and20about the shank will be limited to 360 degrees such that the first or second spine18or20does not overlap upon itself. Accordingly, the angle of inclination23of the spines18and20will be selected so as to permit each of the spines to rotate around the shank by up to 360 degrees along a double-alpha helix path depending upon the length of the fastener10. As utilized herein, a double-alpha helix path is defined as the path of a pair of paths twisting about the central shank in a continuous right-hand spiral with a smooth constant angle on opposite sides of the shank.

Each spine18and20may also include a directional self-taping blade40comprising a planar member42extending radially from the shank12. The planar member42is oriented relative to the shank12at an angle corresponding to the angle of inclination23of the spines18and20so as to form a path in the material into which the fastener10is to be inserted for the first and second spines18and20to follow. Each directional self-taping blade40includes a leading edge44being angled away from the sharpened end14of the fastener. The leading edge44may optionally be sharpened so as to facilitate insertion of the fastener through the material. As illustrated inFIGS. 4,5and6, the leading edge44may be formed between side blade surfaces48. The side blade surfaces48may be continuations with sharpened tip surface49as illustrated. The leading edge44may be angled by an angle relative to the axis24of the shank generally indicated at46. The leading edge angle46may correspond to the angle of the sharpened portion of the shank and be selected to facilitate ease of insertion of the fastener into a material as is commonly known. As described above, the directional self-taping blade40cuts a path into the material along a double-alpha helix path about a bore formed by the shank12for the first and second spines18and20to follow.

The driving end16includes a flattened head portion17and an annular shoulder19as are conventionally known. The fastener10may also include a protrusion or nipple22extending axially from the head portion17. The protrusion22may be of a softer material or have less material hardening treatment than the remainder of the fastener such that the protrusion22is operable to be sheared off of the head portion17. The protrusion22may also be attached to the head portion17by a frangible portion. Upon impact by a hammer or the like, the protrusion22will be flattened and sheared from the head portion17so as to form a slip washer25on the surface thereof as illustrated inFIG. 2. The slip washer25formed by the protrusion22will reduce the friction between the head portion17of the fastener10and a driving surface, such as a pneumatic nail gun, hammer, or the like it is driven into a material. It will therefore be seen that the slip washer will therefore reduce the torque imparted to the head portion17and will therefore be particularly useful for applications where the fastener10is inserted by the use of a nail gun and the like. It will be appreciated that for applications where the fastener10is to be driven by a hammer, that the slip washer may not be necessary due to the repeated impacts of the hammer on the head portion17of the fastener being for a shorter duration therefore less prone to friction or exertion of a torque on the head.

The fastener10may be formed of any known means such as machining, forging or casting. The fastener10may be formed of any suitable metal, such as, by way of non-limiting example, mild steel, iron, stainless steel, copper, titanium, or alloys. In particular, one method of forming the present fastener10may to be form, by pressing, stamping, extruding from a roll of wire or otherwise forming the shank12with opposed side plates50extending radially therefrom as illustrated inFIG. 3. Thereafter, excess material or notches52may be removed, by cutting, grinding, stamping, pressing or otherwise so as to form the hooks30in the side plates50as illustrated inFIGS. 3 and 4. The head portion17and protrusion22may then be formed in driving end16by a press or other means as illustrated inFIG. 5. Before, after or concurrently with forming the head portion and nipple, the fastener10may be twisted about the shank12so as to provide the required twist to the first and second spines18and20. The fastener10may also be formed with a twisting side plates50thereabout along a double-alpha helix path wherein the spines18and20and the hooks30are formed in the side plates along the double-alpha helix path. Optionally, the fastener10may be formed to have the side plates50and thereafter the side plates and fastener twisted to follow the double-alpha helix path before the spines and hooks are formed therein.

Turning now toFIGS. 6 and 7, the hooks30and spines are formed of a common side plate50as described above. The hooks may be formed to have a rearwardly inclined triangular shape having leading and trailing edges,37and39, respectively, and first and second distal pointed ends,34and36, respectively. The spines18and20and hooks30are aligned along and extend radially from the shaft along a longitudinal path32. The spines and hooks therefore define a plane33extending radially from the shank12along the path32as illustrated inFIG. 7. It will therefore be appreciated that the path of travel32and plane33follow a double-alpha helix path along the shank12. As illustrated inFIG. 6(showing the fastener10before a twist is applied to spiral the spines) the first pointed ends34of the hooks30may be displaced to a first side of the plane33while the second pointed ends36may be displaced to a second opposed side of the plane33. The first and second pointed ends34and36are alternated along the first and second spines18and20. Additionally,FIG. 7shows the alternating protrusion orientation in greater detail wherein the first and second pointed ends34and36are disposed to alternating sides of the plane33. The first and second ends may be arcuately curved out of the plane33such that the majority of the protrusions are aligned therewith. The offset to the hooks30may be formed during forming of the hooks30or at any other time.

The trailing edge39of the hooks30may be inclined from radial to the shank12in a direction towards the driving end16of the fastener. Once imbedded within a material, the rearwardly inclined hooks30will resist pull out of the fastener and the head portion17and will resist further insertion of the fastener thus securing the fastener therein. As illustrated inFIG. 2wherein the fastener10is embedded through first, second, third and fourth boards,8a,8b,8cand8d, respectively, the hooks30will resist any pull out movement of the fastener as indicated generally at64. In any movement of the fastener in direction64relative to one of the boards8a,8b,8cor8dwill cause the hooks30to engage with that board and draw the hooks out of the plane33in directions60and62. This will further serve to embed the fastener within the material as the fastener is attempted to be drawn backwards. Similarly, if any of the boards8b,8cor8dare drawn downward in directions generally indicated at66, such as by prying between the boards, the hooks30will also be drawn out of plane33in directions60and62to further engage in that board. It will be seen that the first board8ais maintained fixed with the fastener10by the head portion17which will bear upon the top surface of the first board. Therefore, any movement between the boards8a,8b,8cand8dwill cause a corresponding movement between the fastener and at least one of those boards and will therefore further engage the hooks30in that board.

Thus it will be seen that any attempt to remove the fastener10from the boards or to pry the boards apart from each other will server to further engage the hooks30within the boards and more securely secure them to each other. Such a fastener may be useful for constructions in locations susceptible to natural disasters and may therefore be useful as a tornado, hurricane or earthquake fastener (T.H.E Fastener).