Expanded – threaded – driven – headed – tool-deformed – or locked-thr – Externally threaded fastener element – e.g. – bolt – screw – etc. – Pilot end having means enhancing fastening or installation
Reexamination Certificate
1998-11-19
2001-01-23
Saether, Flemming (Department: 3627)
Expanded, threaded, driven, headed, tool-deformed, or locked-thr
Externally threaded fastener element, e.g., bolt, screw, etc.
Pilot end having means enhancing fastening or installation
C411S387800, C411S417000
Reexamination Certificate
active
06176664
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to fastening screws of the self-drilling/self-tapping kind having a drilling tip at the terminal end of the threaded shank.
BACKGROUND OF THE INVENTION
Fastening screws of the foregoing kind are manufactured in a variety of forms, and it is generally the case that different forms are adopted for penetration into metal and timber respectively. Fastening screws intended to drill through sheet metal have a drilling tip which has substantially the same characteristics in terms of shape and function as the end of a conventional drill bit for drilling metal (see the attached FIGS.
1
and
2
). The end portion of the fastening screw at which the drilling tip is formed is not threaded and is very much like a conventional drill bit except that the flutes are straight rather than helical. The length of the non-threaded end portion varies, but is generally significantly greater than the diameter of that portion.
A fastening screw intended for penetration into timber has an entirely different drilling tip, and a typical example is shown by the attached
FIGS. 3 and 4
. The major features of the wood screw is that it has a tapered end portion which terminates in a pointed terminal end, and the thread extends along that end portion substantially up to the terminal end or tip. Also, a single flute is provided in the drilling tip rather than two as in the case of a fastening screw intended to drill through sheet metal. Continuation of the thread through the tapered end portion is an important feature because it enables the thread to bite into the timber early in the penetration process and thereby pull the screw into the timber. That reaction between the thread and the timber assists the drilling operation by requiring minimum endwise pressure on the fastener.
A problem arises when a fastening screw designed to drill through metal is required to penetrate into timber, for example when the screw is being used to fasten a metal sheet to a timber support. Under those circumstances the screw typically penetrates both the metal sheet and the timber without difficulty until the threaded portion of the fastener shank reaches the timber surface. The thread does not bite into the timber as with the fastener of
FIGS. 3 and 4
, but tends to ride over the timber surface. Substantial endwise force is then required to drive the fastener further into the timber and achieve self-tapping without significant stripping of the internal thread so formed.
Because of the foregoing problem it is not uncommon for tradesmen to use fastening screws of the kind shown by
FIGS. 3 and 4
for securing metal sheet to timber. Substantial endwise force is required to initiate penetration through the metal, but less effort is required for penetration and tapping into the timber for the reason previously stated. The drilling tip of such fasteners is not suited for cutting into metal and tends to leave a burr as the fastener penetrates through the metal sheet. Such burrs are unsightly and are dangerous because of their jagged nature. They also promote corrosion of the metal sheet and can tend to cause the roof to leak, because the sealing washer is prevented by such burrs from sitting firmly against the roof surface.
OBJECTS OF THE INVENTION
It is an object of the present invention to overcome or minimise the aforementioned difficulties by providing a fastening screw which cuts cleanly through metal and which requires minimum endwise force to form a mating thread within timber. It is another object of the invention to provide an improved method and apparatus for forming a fastening screw.
SUMMARY OF THE INVENTION
According to the present invention there is provided a fastening screw having an elongate shank, and a drilling tip and a head provided at respective opposite ends of said shank, said drilling tip having a cutting edge for cutting through metal and a flute extending longitudinally of said shank a thread being formed on said shank and extending over a portion of the section of the shank in which the flute is formed.
The drilling tip is designed to efficiently cut into metal and for collection and removal of swarf created during penetration of the drilling tip into a metal/timber component. The thread formed on the shank preferably extends over a substantial part of that portion of the shank in which said flute is formed. It is preferred that the fluted portion of the shank is tapered so as to be generally of frusto-conical form.
It is preferred that the drilling tip cutting edge extends outwards from the shank axis and angularly towards the head end of the shank, while the flute extends from the cutting edge towards the head end of the shank. The shank preferably has a parallel portion and a tapered portion which are adjacent the head and the drilling tip respectively of the fastener, the flute extends along at least part of the tapered portion, and a thread is formed on the shank so as to extend along both the parallel portion and the tapered portion of the shank.
The thread may not extend along the full length of either portion of the shank, but preferably extends along at least a substantial part of the tapered portion. It is further preferred that the thread extends without interruption across the junction between the two portions of the shank.
The drilling tip preferably includes two cutting edges and two flutes, each of which extends longitudinally from a respective one of the cutting edges. Each cutting edge may be located on a respective one of two opposite sides of the shank axis, and each may be arranged and angularly disposed in generally the same manner as the corresponding cutting edges of a conventional drill bit for drilling through metal.
According to another aspect of the invention there is provided a method of forming a fastening screw from a screw preform having a cylindrical elongate shank and a head at one end of the shank, including the steps of deforming said preform by means of a material displacement operation to create a drilling tip at an end portion of said shank opposite to said head, said drilling tip having at least one cutting edge for cutting through metal and a flute extending from said edge toward said head, applying a thread to said shank which extends over a portion of the section of the shank in which the flute is formed.
The end portion of the shank remote from the head may be subjected to a stamping, forging, or other material displacement operation to create a drilling tip configuration having at least one angularly disposed cutting edge and a flute extending from that cutting edge towards the head end of the shank. A portion of waste material may extend between the cutting edge and the terminal end of the preform shank, and that waste can be removed in any appropriate manner to leave the cutting edge exposed at a thereby newly created terminal end of the fastener. The thread may be formed on the shank after or during removal of the aforementioned waste material, and it is preferred that a thread rolling operation is used for that purpose.
The present invention further provides a die for forming a threaded fastening screw of the kind described above, from a screw preform having a cylindrical elongate shank and a head at one end of the shank, by a thread rolling operation, said die including a ramp surface for removing a portion of shank material from the terminal end of said shank opposite said head, to expose a cutting edge.
It is further preferred that each thread rolling die is formed so that a portion of the shank adjacent the drilling tip cutting edge is formed with a taper so as to reduce in diameter (or cross sectional size) in a direction away from the fastener head. That tapered portion includes at least part of the drilling tip flute. The thread preferably extends along at least a substantial part of the tapered portion so as to terminate close to the cutting edge of the drilling tip.
Formation of the tapered portion and/or the thread on that portion may result in removal of an outer portion of the drilling tip cutting edg
Lowe Hauptman & Gilman & Berner LLP
Saether Flemming
W A Deutsher Pty Ltd
LandOfFree
Fastening screw and method of forming same does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Fastening screw and method of forming same, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Fastening screw and method of forming same will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2437695