Threaded – headed fastener – or washer making: process and apparat – Apparatus for making headed fastener – e.g. – nail – rivet – etc. – Header means
Reexamination Certificate
2002-10-04
2004-01-13
Tolan, Ed (Department: 3725)
Threaded, headed fastener, or washer making: process and apparat
Apparatus for making headed fastener, e.g., nail, rivet, etc.
Header means
C470S034000, C470S110000, C470S121000, C470S192000
Reexamination Certificate
active
06676528
ABSTRACT:
The present invention relates to a tool for the manufacture of an offset head nail, said nail comprising a shank and a head, said head being placed with its centre being offset to the centre of the shank, wherein said tool is one of a set of at least two tools acting mutually on a blank for a nail, said tool comprising a front side with a reception opening and a top side to be used when forming the head, said reception opening being shaped to form an impression in the blank and to fixate said blank during the forming of a head on the blank. The invention further relates to a use of the aforementioned tool.
Nails with offset heads are used in nail guns, where a strip of nails is used for shooting multiple times before reloading a new strip of nails. The strip of nails has closely adjacently assembled nails, said nails having nail heads which are offset to one side. The offset is necessary in order to have a large head surface freely exposed for shooting off the nail, although the nails, as mentioned, are closely assembled. Nails of this type are known as D-heads and offset heads.
Nails with offset heads etc. are manufactured by mainly the same method as nails without offset heads, i.e. a wire clamped between two oppositely placed tools with an exposed end of the wire outside the tools. The exposed end is then flattened by force, whereby the head is formed. The exposed end is bent before the head forming process, when offset head nails are made. In this way, the material is already offset to one side, when the head is formed.
This process, however, suffers from the drawback that a small portion of the head is not always completely offset and extends slightly in the direction opposite the general offset. This creates problems when the nails are assembled to a strip. Also, fewer nails per length of strip can be assembled. This means that the user of the nail gun must reload more often with a new strip. When the nails are closely assembled, the nail heads are overlapping each other leaving only a small surface exposed for shooting of the nail, said surface being offset from the shank of said nail. Hence, when the surface is impact by the firing of the nail gun, the force introduced is correspondingly offset from the shank. When the nail is shot, the reaction from the object, into which the nail is shot, is concentrated to the centre axis of the shank. The distance between the centre axis of the shank and the offset force on the nail head results in a significant moment of force being introduced on the nail. The nail must have the necessary strength to carry said moment of force. The critical part of the nail, in this respect, is the transition between the nail head and the shank.
An attempt has been made to overcome the problem concerning the small un-offset portion. This has been achieved, but has, however, created a new problem. The small un-offset portion has apparently been removed by constructing the tools with an opening just below the head, said opening having a cross section on the side opposite the direction of the offset, whose cross section is smaller than the related cross section of the wire, whereby the material causing the small un-offset portion is displaced and hence removed. Also, one of the tools apparently has an upper side, which is raised slightly relative to the other tool in order to move more material in the direction of the offset. Such a nail is severely weakened at the critical transition between the head and the shank. For reference, see attached
FIGS. 18
a
and
18
b
displaying a nail according to the prior art. When the nails are weakened, they have a tendency to cause malfunction in the nail gun. To solve this, the shooting force has to be reduced. When the shooting force is reduced, the use of the nail gun is limited.
Similar strength problems are known from nails with heads, which are not fully offset, but have a reduced un-offset portion.
The object of the present invention is to provide a tool for the manufacture of improved nails with offset heads, where the aforementioned drawbacks of the nails are avoided.
Novel and inventive aspects of the tool, according to the invention, comprise that the reception opening comprises a protruding section by the top side for forming an impression in the shank of said nail, said impression being placed adjacent to the head and mainly to a side, which is opposite the direction in which the head is to be offset, and that the protruding section comprises at least one substantially flat or convex surface for forming at least one substantially flat or concave section on said nail, said flat or convex section being placed substantially parallel to the longitudinal axis of the reception opening.
In this way, a high strength is provided of the nail in the transition between the shank and the head. The high strength is obtained by the protruding section of the tool with the at least one substantially flat or convex surface, said flat or convex surface resulting in a smaller reduction of the area of the cross section by the impression of the nail, than the prior art, and further by the shape of the flat or convex surface, which allows a large amount of the material, which is displaced when the impression is formed, to remain in the side of the shank which is opposite the direction of the offset. When a large amount of material remains in that location, the moment of inertia is largely maintained in the transition between the shank and the head, which is of great importance to maintain strength against the moment of force. Improved strength is obtained both for nails with full head offset as well as nails with a partial head offset.
The protruding section bends the blank further in the direction of the offset, whereby a full offset head may be obtained, i.e. without a small portion of the head being offset and extending slightly in the direction opposite the offset. Also, due to the protruding section, a very firm grip around the blank is obtained. When the tool is used on a continuous manufacturing apparatus, the protruding section also has the positive effect that an effective grip is obtained well before the forming of the head. This is important, since the free end of the blank, which is to become the head, must be bent before the head is formed in order to obtain the offset head. The effective grip assures that the end of the blank may be bent without risk of unwanted displacement of the blank.
The dimensions of flat or convex surface and the sides of the reception opening by said flat or convex surface may preferably be provided in a way, such that the area of the cross section of the shank of the nail by the flat or concave section will be substantially corresponding to the adjacent part of the shank.
Hereby it is obtained that the material of the blank is allowed to yield sideways when the impression is made. This enables the main part of the material to remain in a desired location for high strength of the nail, instead of mainly yielding in the directions of the longitudinal axis of the nail.
The flat or convex surface and the sides of the reception opening by said flat or convex surface may be provided with two grooves, said grooves being placed near the ends of the at least one flat or convex surface, said grooves having an extension with a radius larger than the radius of the part of the reception opening, said part which is not to be engaged in the forming of the impression in the nail.
Such grooves and the location of such grooves result in a displacement of the material of the blank to preferred locations, said locations resulting in a high moment of inertia of the nail in the transition between the head and the shank. To obtain a high moment of inertia in the desired direction, a high amount of material must remain in the side opposite the direction of the offset of the head of the nail.
The sides of the reception opening by the flat or convex surface may comprise areas, said areas having an extension with a radius smaller than the radius of the part of the reception opening, said part which is not to
Enkotec A/S
Pitney Hardin Kipp & Szuch LLP
Tolan Ed
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