U.S. patent number 3,703,843 [Application Number 05/103,637] was granted by the patent office on 1972-11-28 for fastener with improved thread construction.
This patent grant is currently assigned to MSL Industries, Inc.. Invention is credited to Richard C. Laverty.
United States Patent |
3,703,843 |
Laverty |
November 28, 1972 |
FASTENER WITH IMPROVED THREAD CONSTRUCTION
Abstract
A fastener having a shank divided into first and second portions
respectively located adjacent a head end and a tapered pointed end
with the first portion having a single thread formed thereon of
uniform pitch. A multiple of parallel threads of similar uniform
pitch are formed on the second portion of the shank and one of the
threads on the second portion is a continuation of the thread on
the first portion. All of the threads have a substantially uniform
minor diameter while the major diameter of the upper single thread
portion is greater than the major diameter of the lower multiple
thread portion.
Inventors: |
Laverty; Richard C.
(Schaumburg, IL) |
Assignee: |
MSL Industries, Inc.
(N/A)
|
Family
ID: |
22296224 |
Appl.
No.: |
05/103,637 |
Filed: |
January 4, 1971 |
Current U.S.
Class: |
411/413 |
Current CPC
Class: |
F16B
25/0057 (20130101); F16B 25/0031 (20130101); F16B
25/0068 (20130101) |
Current International
Class: |
F16B
25/00 (20060101); F16b 025/00 (); F16b
039/30 () |
Field of
Search: |
;85/46,41,48,47 ;151/22
;10/1R ;52/700,362,363 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Britts; Ramon S.
Claims
I claim:
1. A fastenting element including a shank with a head on one end
and a tapered point on the opposite end, said shank being divided
into first and second portions; a continuous thread of uniform
pitch on said shank extending substantially between said ends with
said portions each having a plurality of thread convolutions; and
at least one additional parallel thread of similar uniform pitch
intermediate said continuous thread only on said second portion of
said shank, said threads having a common minor diameter throughout
the length of both portions, said continuous thread having a major
diameter on said first portion which is greater than the major
diameter of said threads on said second portion, and the major
diameters of said threads on said second portion being
substantially uniform.
2. A fastener element as defined in claim 1, in which said second
portion has a double thread and said first portion has a single
thread.
3. A fastener as defined in claim 1, in which said second portion
has a triple thread and said first portion has a single thread.
4. A fastener element as defined in claim 1, in which said second
portion is located adjacent said tapered point and said first
portion is located adjacent said head.
Description
BACKGROUND OF THE INVENTION
The present invention relates generally to threaded fasteners and
more particularly to an improved fastener for use with materials,
such as particle board.
In recent years, the increased cost in natural wood, plaster and
various other building materials heretofore utilized has required
the construction industry to look to other types of materials to
reduce the cost of buildings. Thus, the use of dry wall Gypsum
board in place of the conventional plaster in buildings has been
rather extensive. In addition, particle board, masonite, etc., are
being used as building materials.
While the substitute materials for the heretofore known types of
building materials have found a remarkable degree of commercial
success, difficulties have been encountered in providing a secure
connection between the above mentioned materials and supporting
structure. In various uses, the Gypsum board, particle board,
masonite, etc. are secured to a supporting structure, such as a
wood or metal base, by the use of self-tapping screws that form
their own openings.
Because of the tendency for the above mentioned materials to
disintegrate under the pressure of the screw threads, difficulties
have been encountered in obtaining the necessary holding power
between such materials and supporting structure, such as metal.
SUMMARY OF THE INVENTION
The present invention contemplates a self-tapping screw which is
capable of forming its own opening and produces easy initial entry
and greater holding power after the screw has been fully inserted
into the structure. The screw has a first multiple thread portion
which accommodates easy initial entry into a workpiece and
partially forms threads in the more dense material. Thereafter, a
second portion of the screw enlarges one of the multiple threads in
the workpiece while the multiple thread portions provide easy entry
into the supporting structure. All of the above is accomplished by
a simple and inexpensive screw which can easily be deformed by
utilizing conventional roll thread dies to deform a circular shank
of uniform diameter.
The fastener element of the present invention includes a shank
having a head upon end and a tapered point on the opposite end and
the shank divided into first and second portions respectively
located adjacent the opposite ends. A continuous thread of uniform
pitch is produced on the shank and extends between the opposite
ends. At least one additional parallel thread of similar uniform
pitch is formed on the second portion of the shank to produce
multiple parallel threads along the lower portion of the shank and
a single thread along the upper portion of the shank, that is a
continuation of one of the multiple parallel threads.
All of the threads on both portions of the shank have a
substantially uniform minor diameter while the single continuous
thread on the upper portion has a larger major diameter than the
major diameter of the lower twin threaded portion.
With this arrangement, the lower portion of multiple threaded
portion initially forms a multiple thread in an opening which is
produced by the screw as it enters the workpiece, such as a
particle board. Thereafter, the single threaded portion, which has
a thread formed as a continuation of one of the multiple threads on
the lower portion, increases the major diameter of one of the
multiple threads since it has a greater major diameter.
The single threaded portion has considerably more spacing between
adjacent thread portions thereby requiring less deformation of the
particle board. However, because of the larger major diameter of
the thread in the upper portion and the common minor diameter of
all of the threads on the shank, increased holding power will
result from such a thread construction.
In one specific embodiment, the multiple thread portion utilizes a
twin parallel thread while an alternate embodiment utilizes a
triple parallel thread on the lower portion of the screw. In each
embodiment, the single thread on the upper portion of the screw is
a continuation of one of the lower threads.
BRIEF DESCRIPTION OF SEVERAL VIEWS OF DRAWINGS
FIG. 1 is a side elevation of a screw constructed in accordance
with the present teachings;
FIG. 2 is a fragmentary sectional view showing the screw retaining
a workpiece on a supporting structure; and
FIG. 3 is a fragmentary side elevation similar to FIG. 1 showing a
slightly modified form of the invention.
DETAILED DESCRIPTION
While this invention is susceptible of embodiment in many different
forms there is shown in the drawings and will herein be described
in detail one specific embodiment, with the understanding that the
present disclosure is to be considered as an exemplification of the
principles of the invention and is not intended to limit the
invention to the embodiment illustrated.
Referring to the drawings, FIG. 1 shows a screw 10 having an
enlarged head 12 on one end of a shank 14 and a tapered point 16
adjacent the opposite end of the shank. The shank 14 is threaded in
accordance with the teachings of the present invention and includes
a continuous thread 20 extending between the head end 12 and the
tapered pointed end 16. The thread 20 has a first portion 20a on
the upper end of the screw adjacent the head 12 and a second
portion 20b adjacent the tapered point or second portion of the
shank. An inspection of FIG. 1 reveals that the thread portions 20a
and 20b, respectively defined on the first and second portions of
the shank 14 have a common substantially uniform minor diameter a
while the first or upper thread portion 20a has a greater major
diameter c than the major diameter b of the second or lower thread
portion 20b. Also, each portion has a plurality of thread
convolutions as is shown in FIG. 1.
In addition, the lower or second portion of the shank 14 of the
screw 10 has a second parallel thread 22 that has a similar uniform
pitch and is located between or intermediate the continuous thread
portion 20b. The two threads 20b and 22 cooperate to define
parallel twin threads along the lower or second portion of the
shank and the thread portion 20a defines a single thread along the
upper or first portion of the shank that is a continuation of one
of the double or twin parallel threads.
The screw 10 of the present invention is formed by utilizing a
blank having a uniform diameter which is deformed by rolling to
produce the finished screw. Since the same amount of metal is
deformed along the entire length of the shank and the minor
diameter of the thread is substantially uniform along the length of
the shank, the major diameter of the single threaded portion is
larger than the major diameter of the double or multiple threaded
portion adjacent the pointed end.
When inserting the screw through a workpiece, such as a particle
board or Gypsum board, and attaching the workpiece to a support,
such as a metal stud, the double threaded portion provides easy
entry into the material to form the hole and the double or multiple
thread portion allows the screw to be inserted with a minimum
amount of torque being applied thereto. As the double threaded
portion is inserted past the upper surface of the workpiece, the
single threaded portion enlarges the major diameter of one of the
multiple threads formed in the workpiece while the thread portion
begins its travel into the support to produce a multiple threaded
opening in the support.
The larger pitch or wider spacing between respective turns of the
thread on the upper portion having a larger major diameter results
in a deepening of one of the double threads in the workpiece to
further compact the interior of the workpiece and the substantial
increment between the major and minor diameters of the thread
produces considerably greater holding power after the screw is in
its fully inserted position, shown in FIG. 2. Since only one of the
double threads initially formed in the workpiece is enlarged, the
higher degree of holding power is achieved without removing or
disintegrating the material between respective helixes of the upper
thread.
Thus, it will be seen that the present invention provides a simple
and efficient manner for increasing the holding power of a screw,
particularly used for connecting a workpiece to a support and
wherein the workpiece and the support are formed of different
materials. The double threaded portion on the lower end of the
screw provides for easy, rapid screw entry through the Gypsum board
and the metal stud, while the upper single threaded portion attains
a higher degree of holding power without disintegrating the
material adjacent the opening.
A slightly modified form of the present invention is shown in FIG.
3, in which a shank 30 having a head (not shown) on one end thereof
and a pointed tip 32 on the opposite end thereof, is provided with
a single threaded portion 32 along the upper portion of the screw
and a triple threaded portion 34 along the lower portion of the
screw with one of the triple threads being a continuation of the
single thread along the upper portion. Again, the major diameter of
the single thread along the upper portion of the shank is greater
than the major diameter along the lower multiple thread defined on
the lower portion of the shank while the minor diameters of the two
threads are the same.
In the modified embodiment of the invention, the threads are again
produced by rolling a uniform, diameter shank and the increment
between the major diameters b and c, is larger than the increment
between these diameters in the FIG. 1 embodiment.
Various other modifications will come to mind without departing
from the spirit of the present invention. For example, any multiple
of threads could be used for the lower portion of the screw so long
as one of the parallel threads continues into the upper portion and
has a larger major diameter along the upper portion of the shank.
In addition, while the head 12 has been shown as being of the flat
type, having a kerf 40 for receiving a driving element, such as a
screwdriver, various heads, such as the oval head, round head, pan
head and Fillister head could be substituted without departing the
spirit of the invention. In addition, the screw need not
necessarily have a tapered point adjacent the opposite end thereof.
However, in its specific embodiment, the screw is preferably of the
tapered point type with the thread extending down to the point so
that the screw will form its own hole and need not have a
pre-drilled hole formed in the workpiece and/or the support.
* * * * *