U.S. patent application number 11/711067 was filed with the patent office on 2008-08-28 for spiral-grooved arrow shaft.
Invention is credited to Todd A. Kuhn.
Application Number | 20080207362 11/711067 |
Document ID | / |
Family ID | 39716555 |
Filed Date | 2008-08-28 |
United States Patent
Application |
20080207362 |
Kind Code |
A1 |
Kuhn; Todd A. |
August 28, 2008 |
Spiral-grooved arrow shaft
Abstract
The present invention is a spirally grooved arrow shaft that
imparts axial rotation to an arrow assembly. The shaft has a
plurality of substantially identical, helical, longitudinal
channels along its outer surface extending down a substantial
portion of the arrow shaft along its primary axis. The channels may
consist of a plurality of grooves cut into the outer surface of the
arrow shaft. Alternatively, the channels may be formed from a
plurality of raised-fins or raised members that extend radially
outward from the surface of the shaft. The invention is compatible
with all contemporary arrowheads and vanes provided that all
aerodynamic surfaces present on these devices urge rotation of the
arrow assembly in the same direction as the spiral channels.
Inventors: |
Kuhn; Todd A.; (North East,
MD) |
Correspondence
Address: |
Todd Kuhn
171 Springfield Drive S.
North East
MD
21901
US
|
Family ID: |
39716555 |
Appl. No.: |
11/711067 |
Filed: |
February 27, 2007 |
Current U.S.
Class: |
473/586 |
Current CPC
Class: |
F42B 10/24 20130101;
F42B 6/04 20130101 |
Class at
Publication: |
473/586 |
International
Class: |
F42B 6/04 20060101
F42B006/04 |
Claims
1. An arrow shaft including: a first end; a second end; and at
least one helical channel disposed on the outer surface of said
arrow shaft; and wherein said at least one helical channel begins
at said first end of said arrow shaft and spirals down the
longitudinal axis of said arrow shaft toward said second end; and
wherein all said channels spiral in the same rotational direction
giving the appearance of a turbine.
2. An arrow shaft according to claim 1, wherein said helical
channels consist of grooves in the smooth outer surface of said
arrow shaft.
3. An arrow shaft according to claim 1, wherein said helical
channels are formed between raised helical ridges in the smooth
outer surface of said arrow shaft; wherein said helical ridges are
integral with the outer surface of said arrow shaft; and wherein
said helical ridges extend radially outward from the outer wall of
said arrow shaft.
4. An arrow shaft according to claim 1, wherein said channels are
close together around said body so that they contact each other
down their entire helical length said helical channels are disposed
close together around said arrow shaft so that said helical
channels are adjacent to each other down their entire helical
length.
3. An arrow shaft according to claim 1, wherein there are between
about three and about ten said channels located symmetrically about
the circumference of said arrow shaft.
4. An arrow shaft according to claim 1, wherein there are eight
said channels.
5. An arrow shaft according to claim 1, wherein said channels
terminate partially down a portion of the axial length of said
arrow shaft.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to the field of archery.
Specifically, the invention relates to the arrow shaft component of
arrow devices.
[0003] 2. Description of the Prior Art
[0004] The flight path of an arrow assembly must be predictable in
order for an archer to strike an intended target. The arrow should
not float or drift from the path along which it was aimed.
[0005] Prior art arrow assemblies have relied upon the aft or
forward end to provide this guidance. The most ancient of these
technologies is the uniformly spaced application of two, three, or
even more feathers, also referred to as fletches or vanes, about
the aft end of the arrow assembly. These fletches steer the arrow
assembly from behind like the rudder of a ship. The arrow assembly
is essentially pushed through the air. This pushing can cause the
flight path of the arrow assembly to wander as the arrow assembly
is affected by random influences such as crosswind, oscillating
vibration of the arrow shaft, and asymmetries between the arrow
vanes' mass or installation position. One recent improvement is the
vane of Kuhn (U.S. Pat. No. 6,695,727) that employs vanes whose
geometry imparts an axial rotational spin on the arrow assembly
during flight
[0006] The use of aerodynamic influences at the forward end of an
arrow assembly has been less deliberate in the prior art until
recently. So-called field point arrowheads are very simple devices
that are commonly used for target practice. Field point arrowheads
taper from a maximum diameter, equal to approximately the diameter
of the arrow shaft, down to a point at the forwardmost end. This
prior art arrowhead has a negligible aerodynamic effect as the
arrow assembly flies towards its intended target.
[0007] Broadhead arrowheads were invented to increase effective
hunting penetration and success potential. Typically two to four
flat, triangular blades are arranged around the forward pointed
tip. These broad, flat blades have a pronounced aerodynamic effect
that can radically affect the overall stability of the arrow in
flight and significantly reduce the precision of flight. Typical
incarnations of such broadheads are described in the patents of
Newnam (U.S. Pat. No. 5,636,845) or Musacchia (U.S. Pat. No.
4,621,817). One recent improvement is the broadhead of Kuhn (U.S.
Pat. No. 6,663,518) that employs blades whose deliberate,
aerodynamically active geometry imparts an axial rotational spin on
the arrow assembly during flight. Such inventions are improvements
over the fletching technologies because they provide steering from
the leading end of the arrow. Asymmetries encountered during flight
tend to be damped out by the trailing rotational inertia of the
shaft. One drawback of these technologies is that the arrowheads
can be easily damaged and may be rendered useless after a single
shot. Manufacturing tolerances must also be strict in order to
produce a product that has consistent aerodynamic qualities.
[0008] Spin-stabilization is clearly a desirable feature for any
successful arrow assembly. Unfortunately, the competing aerodynamic
effects of the aft end and forward end enhancements described above
can render each other unsuccessful. Furthermore, individual archers
may prefer features found in certain vanes or arrowheads; such
features may not be included in commercially available products.
The prior art lacks teaching of a spin-stabilizing arrow shaft as a
part of an arrow assembly. Such a shaft could be assembled with an
archer's choice of vanes and arrowhead while still providing
adequate spin stabilization to promote accurate flight.
SUMMARY OF THE INVENTION
[0009] The present invention is a spirally grooved arrow shaft that
imparts axial rotation to an arrow assembly. The shaft has a
plurality of substantially identical, helical, longitudinal
channels along its outer surface extending down a substantial
portion of the arrow shaft along its primary axis. The channels may
consist of a plurality of grooves cut into the outer surface of the
arrow shaft. Alternatively, the channels may be formed from a
plurality of raised fins or raised members that extend radially
outward from the surface of the shaft. The invention is compatible
with all contemporary arrowheads and vanes provided that all
aerodynamic surfaces present on these devices urge rotation of the
arrow assembly in the same direction as the spiral channels.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 shows an oblique longitudinal view of the present
invention.
[0011] FIG. 2 shows a cross-sectional view of a first embodiment of
the present invention. The cross-section is perpendicular to the
major axis of the arrow shaft.
[0012] FIG. 3 shows a cross-sectional view of a second embodiment
of the present invention. The cross-section is perpendicular to the
major axis of the arrow shaft.
DETAILED DESCRIPTION OF THE INVENTION
[0013] With reference to FIGS. 1 through 3, arrow shaft 1 of the
invention comprises a typically cylindrical body of substantially
uniform diameter with a first end 2 and a second end 3. Shaft 1 is
typically symmetrical about the longitudinal axis and may be
manufactured from any suitable structural material known in the art
such as steel, aluminum, carbon fibers, plastic or a composite of
materials. Any arrowhead known in the art may be attached by
typical attachment means (not depicted) to first end 2. Typically,
such an attachment means comprises a female-threaded socket that is
press-fitted or glued into first end 2 of arrow shaft 1. This
socket mechanically engages the arrowhead to arrow shaft 1. Any
fletches known in the art may be attached to second end 3 by
typical attachment means known in the art such as gluing.
[0014] At least one helical channel 4 begins at first end 2 of
arrow shaft 1 and spiral down the longitudinal axis of arrow shaft
1 toward second end 3. Helical channels 4 are integral to arrow
shaft 1 and disposed on the outer surface of arrow shaft 1. Field
tests suggest that a right-handed spiral pitch equal to one turn in
twenty-four inches of shaft length down the longitudinal axis works
well, but other pitches and left-handed spirals are also envisioned
within the scope of the invention.
[0015] In a first embodiment, helical channels 4 are formed either
by cutting or extruding grooves of v-shaped or square cross section
into the smooth outer surface of arrow shaft 1, although other
groove geometries would be obvious to one of ordinary skill in the
art. Helical channels 4 are defined as grooves if the minimum
diameter of the channeled portions of arrow shaft 1 does not exceed
the nominal maximum diameter of arrow shaft 1. Helical channels 4
do not penetrate entirely through the wall of arrow shaft 1. In the
preferred embodiment, helical channels 4 are only cut through the
gel coat and outer layer(s) of the formed arrow shaft 1.
[0016] In a second embodiment, helical channels 4 are formed
between raised helical ridges 5 of v-shaped or square cross section
that are integral with the outer surface of arrow shaft 1. Other
ridge geometries would be obvious to one of ordinary skill in the
art. Helical channels 4 are defined as the space between a pair of
ridges 5 if the maximum diameter of the ridged portions of arrow
shaft 1 exceeds the nominal maximum diameter of arrow shaft 1.
Helical ridges 5 are formed by extrusion with or physical
application onto the smooth outer surface of arrow shaft 1. Helical
ridges 5 extend radially outward from the outer wall of arrow shaft
1.
[0017] Helical channels 4 may spiral down substantially the entire
axial length of arrow shaft 1, or they may terminate partially down
a portion of the axial length of arrow shaft 1. In the preferred
embodiment, helical channels 4 terminate between about three and
about five inches short of second end 3. This provides a smooth
surface of arrow shaft 1 for the physical application of
fletches.
[0018] All helical channels 4 spiral in the same rotational
direction giving the appearance of a turbine. In the preferred
embodiment, helical channels 4 are disposed close together around
arrow shaft 1 so that they are adjacent to each other down their
entire helical length.
[0019] In the preferred embodiment there are between about three
and about ten helical channels 4 located symmetrically about the
circumference of arrow shaft 1. There are optimally about eight
helical channels 4 located symmetrically about the circumference of
arrow shaft 1. Too few helical channels 4 will not provide enough
rotational torque to produce the desired axial flow turbine
aerodynamic effect. Too many helical channels 4 must be so narrow
or small that their aerodynamic effect becomes inconsequential as
their aggregate surface approaches that of a smooth arrow
shaft.
[0020] One of the features of this invention is its ability to
produce stabilized arrow assembly flight without the use of
fletches or tail fins (or feathers). The rotation induced in the
arrow assembly by the aerodynamically designed arrow shaft is
sufficient to stabilize the arrow in flight. Eliminating or
reducing the size of the fletches in fact improves flight
characteristics because the rotational drag normally induced by the
fletches is avoided. It should be noted, however, that all
embodiments of the arrow shaft of the invention can be used with
fletches as well.
[0021] While various embodiments of the present invention have been
described above, it should be understood that they have been
presented by way of example only, and not limitation. Thus, the
breadth and scope of the present invention should not be limited by
any of the above-described exemplary embodiments, but should be
defined only in accordance with the following claims and their
equivalents.
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