Note: Descriptions are shown in the official language in which they were submitted.
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ELASTIC PROJECTILE PROPULSION SYSTEMS AND METHODS
CROSS-REFERENCE
[0001] This application claims the benefit of U.S. Provisional Application No.
61/867,383, entitled ELASTIC PROJECTILE PROPULSION SYSTEM, filed on
August 19, 2013, and 61/946,736, entitled ELASTIC PROJECTIVE PROPULSION
SYSTEM, filed March 1, 2014, which applications are incorporated herein by
reference.
BACKGROUND
[0002] The present disclosure relates to a compact propulsion systems that
deploys
stored elastic energy to propel a projectile, and more particularly to a
compact
propulsion system for launching an arrow and other flying projectiles.
[0003] Prior methods of launching arrows and other projectiles have deployed
elastic
energy stored in springs, such as leaf springs in a bow, torsion springs and
coil
springs, rubber tubes and bands, as well as the elastic energy stored in a
stretched
launching cord. Various combinations of these elements are known, some of
which
include a series of pulleys to extend and direct the launching cord in a
generally
serpentine path. See, for example, U.S. Patent 2,515,205 A to Fieux for
Catapult
Device for Launching Aerial Machines, issued July 18, 1950.
[0004] However, the prior systems have limitations. While metal springs are
more
reliable over a range of temperatures than rubber springs, the higher mass of
the metal
springs imposes a velocity limitation.
[0005] Bow systems are not compact (typically having a width of at least 12
inches
(30.48 centimeters) or more at a widest point), and require large loading
force
(crossbows typically having 125 - 200 lbs (56.7 - 90.72 kilograms) of draw
weight),
which is overcome by adding heavy, bulky and complicated levers and ratchets,
thereby increasing size and weight of the device.
[0006] Additionally, bow systems are limited in the ability to reabsorb stored
energy
without sustaining damage to the bow during launch. Hence, bow systems require
a
minimum arrow weight be matched proportionately to a draw force of a bow in
order
to dissipate energy away from the bow during launch and ensure functionality
without
incurring damage to the bow system. Widely adopted industry standards
recommend
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that a bow never be deployed to launch without an arrow ("dry fired") and have
set a
minimum ratio of arrow weight to draw force which, in turn, imposes a velocity
limitation.
[0007] The devices disclosed herein provide a propulsion configuration that
can
overcome the above limitations.
SUMMARY
[0008] An aspect of the disclosure provides a propulsion device comprising a
rigid
elongated barrel member having a forward (distal) launching end and an
opposing
(proximal) stock connecting end, a pair of forward (distal) spring members
each
mounted to connect at a distal end thereof on opposing sides of the barrel
adjacent the
forward (distal) launching end, each forward (distal) spring having a distal
end
connected to the barrel opposite the moveable proximal end, a pair of rear
(proximal)
spring members, each mounted to connect to the barrel at a proximal end
thereof on
opposite sides of the barrel adjacent the proximal stock end, a pair of
moveable fore
pulley blocks, each coupled to the proximal moveable end of each forward
spring
member and at least one proximal moveable pulley block, connected to the
distal
moveable end of each rear spring member, a launching cord having each of the
opposing ends and engaging both the distal and proximal moveable pulley blocks
on
opposing sides of the barrel to provide a pair of moveable, counter acting
block and
tackle pulleys to couple the elastic energy stored in the distal and proximal
spring
members when a launch cord center is drawn in a proximal direction toward the
stock
connecting end of the barrel. Components made from elastic materials are
resilient
and enable the component to spring back into a predetermined shape after a
deforming force is removed.
[0009] A second aspect of the disclosure provides a method of propelling a
projectile,
such as an arrow. The method comprises the steps of providing a propulsion
device,
providing a projectile having a forward (distal) end and a rear (proximal) end
opposite
the forward end, resting the projectile on a barrel to engage a center of a
launching
cord at the rear (proximal) end of the projectile, drawing the center of the
cord and
attached projectile in the rearward (proximal) direction to tension the
launching cords
engaged in the adjacent moveable pulley blocks attached to the distal and
proximal
spring members on both opposing sides of the barrel and in turn extend each of
the
distal and proximal spring members toward the other, releasing the launching
cord
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and projectile to provide a mutual and simultaneous transfer of energy from
the
tensioned springs and launching cord to the projectile. Alternatively, the
linear
projectile, such as an arrow, may be secured within the device after the
launch cord
has been fully tensioned, and thereafter, the user releases the draw on the
projectile
(e.g., by pulling the trigger, releasing the launch cord, etc.), which causes
a transfer of
energy from the tensioned springs and launch cord to the projectile.
[0010] An aspect of the disclosure is directed to propulsion devices. Suitable
propulsion devices, comprise: a) an elongated barrel member forming a cavity
having
an elongated barrel member proximal end and an elongated barrel member distal
end,
where the elongated barrel member proximal end engages a mounting stock, b) a
pair
of forward spring members each having a forward spring member proximal end and
a
forward spring member distal end, the pair of forward spring members
positioned
within the cavity of the elongated barrel member wherein the distal ends of
the
forward spring members connect to a corresponding moveable brace and the
proximal
ends of the forward spring members connect to a moveable pulley blocks, c) a
pair of
rearward spring members, each having a rearward spring member proximal end and
a
rearward spring member distal end, the pair of rearward spring members
positioned
within the cavity of the elongated barrel member wherein the distal end of the
rearward spring members connects to the moveable pulley blocks and the
proximal
ends of the rearward spring members connects to the corresponding moveable
braces,
d) at least one pair of forward pulleys, each forward pulley coupled to the
forward
spring member proximal ends and at least one rearward pulley, connected to
each of
the rearward spring member distal ends, and e) a launching cord having a first
end
and a second end which can attach at either the forward moveable pulley blocks
or the
rearward moveable pulley blocks and traverse a serpentine path around pulleys
to
engage both the forward pulleys and rearward pulleys. In at least some
configurations,
the pair of forward pulleys and the rearward pulley are configurable to
comprise a
counteracting block and tackle pulley which couples an elastic energy stored
in the
forward spring members and the rearward spring members when the launch cord is
drawn rearward toward the stock connecting end of the barrel. Additionally, a
rail can
be provided and interiorly positioned in the barrel member. The rail can also
be
configurable to vertically move while remaining stationary horizontally.
Additionally,
a cocking mechanism and/or trigger assembly can be provided. Propulsion
devices
are configurable such that they have a width of 12 inches or less. In some
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configurations, the launching cord is wrapped three or more times around the
distal
pulley. Additionally, the forward spring members and the rearward spring
members
are combined in parallel banks, wherein each bank engages one or more moveably
pulley blocks.
[0011] Another aspect of the disclosure is directed to linear archery systems.
The
linear archery systems comprise: a) an elongated barrel member forming a
cavity
having an elongated barrel member proximal end and an elongated barrel member
distal end, where the elongated barrel member proximal end engages a mounting
stock, b) one or more of a forward spring member each of the one or more
forward
spring members having a forward spring member proximal end and a forward
spring
member distal end, the one or more forward spring members positioned within
the
cavity of the elongated barrel member wherein the distal end of the one or
more
forward spring members connects to a moveable brace and the proximal ends of
the
forward spring members connect to a moveable pulley block, c) one or more
rearward spring members, each of the one or more rearward spring members
having a
rearward spring member proximal end and a rearward spring member distal end,
the
one or more rearward spring members positioned within the cavity of the
elongated
barrel member wherein the distal end of the one or more rearward spring
members
connects to the moveable pulley blocks and the proximal ends of the rearward
spring
members connects to the corresponding moveable brace, d) one or more forward
pulleys, each of the one or more forward pulleys coupled to at least one of
the one or
more forward spring member proximal ends and at least one rearward pulley,
connected to the rearward spring member distal end, and e) a launching cord
having a
first end and a second end which can attach at either the forward moveable
pulley
blocks or the rearward moveable pulley blocks and traverse a serpentine path
around
pulleys to engage both the forward pulleys and rearward pulleys. In at least
some
configurations, the pair of forward pulleys and the rearward pulley are
configurable to
comprise a counteracting block and tackle pulley which couples an elastic
energy
stored in the forward spring members and the rearward spring members when the
launch cord is drawn rearward toward the stock connecting end of the barrel.
Additionally, a rail can be provided that is interiorly positioned in the
barrel member.
The rail is also configurable to vertically move while remaining stationary
horizontally. Additionally, a cocking mechanism and/or trigger assembly can be
provided. Configurations of the systems have a width of 12 inches or less.
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Additionally, the launching cord is wrapped three or more times around the
distal
pulley.
[0012] Still another aspect of the disclosure is directed to self-arresting
propulsion
systems. The self-arresting propulsion systems comprise: a) an elongated
barrel
member forming a cavity having an elongated barrel member proximal end and an
elongated barrel member distal end, where the elongated barrel member proximal
end
engages a mounting stock, b) a pair of forward spring members each having a
forward spring member proximal end and a forward spring member distal end, the
pair of forward spring members positioned within the cavity of the elongated
barrel
member wherein the distal end of the forward spring members connect to a
corresponding moveable brace and the proximal ends of the forward spring
members
connect to a moveable pulley block, c) a pair of rearward spring members, each
having a rearward spring member proximal end and a rearward spring member
distal
end, the pair of rearward spring members positioned within the cavity of the
elongated
barrel member wherein the distal end of the rearward spring members connect to
the
moveable pulley block and the proximal end of the rearward spring members
connects
to the corresponding moveable brace, d) a pair of forward pulleys, each
forward
pulley coupled to one of the forward spring member proximal ends and at least
one
rearward pulley, connected to the rear ward spring member distal end, and e) a
launching cord having a first end and a second end which can attach at either
the
forward moveable pulley blocks or the rearward moveable pulley blocks and
traverse
a serpentine path around pulleys to engage both the forward pulleys and
rearward
pulleys, wherein the pair of forward pulleys and the rearward pulley comprise
a
counteracting block and tackle pulley which couples an elastic energy stored
in the
forward spring members and the rearward spring members when the launch cord is
drawn rearward toward the stock connecting end of the barrel. Additionally, a
rail
interiorly positioned in the barrel member can be provided. The rail can be
configurable to vertically move while remaining stationary horizontally. Some
configurations will include a cocking mechanism and/or trigger assembly. As
with
other configurations, the systems have a width of 12 inches or less. The
launching
cord is wrapped three or more times around the distal pulley.
[0013] Yet another aspect of the disclosure is directed to methods of
operating a
system according to any of the configurations disclosed. The methods comprise
the
steps of: providing a propulsion device, drawing the launching cord in the
rearward
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direction to tension the launching cord and extend each of the forward spring
member
and rearward spring members towards each other, and releasing the launching
cord to
provide a mutual and simultaneous transfer of energy from the tensioned
springs and
launching cord. Additionally, the method can include providing a linear
projectile,
and placing the linear projectile in the barrel of the propulsion system to
engage the
launching cord, wherein the steps of providing the linear projectile and
placing the
linear projectile in the barrel of the propulsion system is performed after
the step of
drawing the launching cord.
INCORPORATION BY REFERENCE
[0014] All publications, patents, and patent applications mentioned in this
specification are herein incorporated by reference to the same extent as if
each
individual publication, patent, or patent application was specifically and
individually
indicated to be incorporated by reference, for all purposes and as if repeated
in total in
the present application. Additional references of interest include U.S.
Patents
4,050,438A to Pfotenhauer issued September 27, 1977 for SPRING TYPE
PROJECTING DEVICE; 4,169,456A to Van House issued October 2, 1979 for
SHORT LIMB ARCHERY BOW; 4,411,248A to Kiveson issued October 25, 1983
for CATAPULT CONSTRUCTION; 4,703,744A to Taylor et al. issued November 3,
1987 for APPARATUS FOR SHOOTING A PROJECTILE; 5,243,955A to Farless
issued September 14, 1993 for MECHANICAL SHOOTING APPARATUS;
5,673,677A to Wing issued October 7, 1997, for PROJECTILE LAUNCHING
APPARATUS; 7,578,289B2 to Norkus issued August 25, 2009 for COMPOUND
ARCHERY BOW WITH EXTENDED INVERTED STROKE; and PCT Publication
W02012/150387A1 to Lamine published November 8, 2012 for SPEARGUN FOR
UNDERWATER FISHING.
BRIEF DESCRIPTION OF THE DRAWINGS
[0015] The novel features of the invention are set forth with particularity in
the
appended claims. A better understanding of the features and advantages of the
present invention will be obtained by reference to the following detailed
description
that sets forth illustrative embodiments, in which the principles of the
invention are
utilized, and the accompanying drawings of which:
[0016] FIG. 1A is a top plan view of a propulsion system which includes an
outer
frame, and FIG. 1B is the same view omitting the outer frame, whereas, FIG. 1C
is a
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side elevation view including the outer frame, and FIG. 1D is the same view as
FIG.
1C again omitting the outer frame;
[0017] FIG. 2 is a perspective view of the launching cord as it is wrapped
between
the distal and proximal pulleys within their respective moveable pulley blocks
but
without the distal moveable pulley blocks;
[0018] FIG. 3A is side elevation view of the device in a retracted spring
position,
whereas FIG. 3B is a side elevation view in an extended spring position or
projectile
launch ready state; FIG. 3C is a close-up side view of the sliding trigger
assembly
including the outer frame; FIG. 3D is a close-up front cross-sectional view of
the
sliding trigger assembly including the outer frame;
[0019] FIG. 4 is perspective partial view of the springs in the extended
position or
projectile launch ready state;
[0020] FIG. 5 is a more detailed perspective view of the moveable pulley
mechanism
attached to the springs in the extended position or projectile launch ready
state;
[0021] FIG. 6 is a partial enlarged perspective view of FIG. 4 and FIG. 5 that
includes the nock of arrow projectile, adjacent the distal moveable pulleys
attached to
the springs in the retracted position;
[0022] FIG. 7A is an top plan view of the outer frame as it connects to the
fixed
braces, shown in the extended spring position or projectile launch ready
state, whereas
FIG. 7B depicts the top plan view with the outer frame omitted to better
depict the
fixed and moveable brace connections to the springs in the extended position,
and
FIG. 7C illustrates the top plan view with the outer frame omitted to better
depict the
fixed and moveable brace connections with springs in a position during
retraction, and
FIG. 7D illustrates the top plan view with the outer frame omitted to better
depict the
springs in the retracted position;
[0023] FIGS. 8A-C are schematic diagrams of the cord, pulley blocks, pulleys
and
springs representing alternative configurations tested in comparative
examples;
[0024] FIGS. 9A-H are isolated views of rail mechanisms, such as shown in
FIGS. 1
and 7;
[0025] FIGS. 10A-C are front and isometric views that depict the positions of
the
grip as configured in an integrated cocking mechanism;
[0026] FIGS. 11A-F are partial side and top views of the passive safety
mechanism;
[0027] FIGS. 12A-H are partial side and top views detailing the anti-dry-fire
mechanism;
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[0028] FIGS. 13A-D are side and isometric views illustrating the auto-
retractable
foot claw mechanism;
[0029] FIGS. 14 A-C illustrate the adjustable stock; wherein FIGS. 14A-B are
partial
side views detailing the full range adjustability, and FIG. 14C is a detailed
proximal
view of the components of the stock release mechanism;
[0030] FIGS. 15A-B are isometric, close-up, views of launch cord tensioning
terminals; and
[0031] FIGS. 16A-B are top views of an arrow retaining system with springs
extended and arrow loaded, and springs retracted arrow unloaded.
DETAILED DESCRIPTION
[0032] Referring to FIGS. 1 through 16, wherein like reference numerals refer
to like
components in the various views, there is illustrated therein a new and
improved
device for an elastic projectile propulsion system, generally denominated /00
herein.
The elastic projectile propulsion system is a linear archery system. The
elastic
projectile propulsion system /00 can be described as a launching device or
launcher.
Spatial orientation references 'proximal' and 'distal' have been labeled in
the figures
as "P" and "D", respectively, where proximal is situated nearest the user and
distal is
situated furthest from the user. The systems and devices position the launch
cord
between moveable pulleys.
[0033] The various described embodiments described herein provide multiple
benefits, which include for example, stable elastic metal or composite springs
which
are deployable with a reduced inertial burden imposed by the spring mass on
the
velocity of the projectile such as an arrow, as the elastic projectile
propulsion system
/00 couples the force and travel distance of multiple springs utilizing
moveable
pulleys and an attached launch cord to simultaneously accelerate the launch
cord and
attached projectile at a velocity that exceeds the velocity of each individual
spring
moving simultaneously within the system. In addition, the elastic projectile
propulsion
system /00, which is a launching device, can be very narrow (e.g. 12 inches
(30.48
centimeters) or less in width), light-weight (e.g., 9 pounds (4.08kg) or less
in weight),
compact (e.g., having a volume of 500 cubic inches (8,193 cubic centimeters),
or
less). As an example of this benefit, in the comparison to competitive
shooting
crossbows, a high velocity arrow flight is achieved without a bulky, wide and
heavy
bow limbs. As well, the stable metal or composite springs within the elastic
propulsion system /00 provide more reliable elastic performance under a range
of
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temperate weather conditions compared to propulsion devices utilizing rubber
elasticity, which is known to have elastic performance that varies with a wide
range of
temperate weather conditions.
[0034] Additionally, the embodiments described provide for a self-arresting
propulsion system which allows the safe use of lighter weight arrows than
usable in
currently available bows and crossbows, which generally follow industry
guidelines
that limit arrow weight to 5 grains of arrow weight per pound of bow draw
force. As
will be appreciated by those skilled in the art, lighter arrows can attain
much higher
velocities than heavier arrows when launched at the same draw length and force
(e.g.,
power stroke). The propulsion system /00 is capable of safely launching
projectiles
such as arrows that are less than 5 grains of arrow weight per pound of draw
force.
Still another advantage to the configurations provided herein is that there is
very low
draw weight, which is less than 125 lbs. This enables the user to directly
cock the
device and does not require a cocking device employing significant mechanical
advantage. As will be appreciated by those skilled in the art, most crossbows
range
from 125-200 lbs (56.7 - 90.72 kilograms) of draw weight and require a cocking
assist
either as a separate device or as an integrated component in order to gain a
mechanical advantage.
DEVICES AND SYSTEMS
[0035] Turning now to FIG. 1A, a top plan view of an elastic projectile
propulsion
system /00 is illustrated which includes an elongated outer frame ///, where
the
length is greater than the width. FIG. 1B is the same view of an elastic
projectile
propulsion system /00 omitting the outer frame. FIG. 1C is a side elevation
view of
the elastic projectile propulsion system /00 including the elongated outer
frame ///.
FIG. 1D is the side elevation of the elastic projectile propulsion system /00
omitting
the outer frame. In accordance with the present disclosure, the elastic
projectile
propulsion system /00 has an elongated outer frame /// having a cavity therein
with
an interior surface and an exterior surface, an elongated center rail member
110
having a distally positioned forward launching end 110a and a proximally
positioned
opposing stock connecting end 110b. Elongated center rail member 110 is
configurable to connect to a portion of the interior surface of the elongated
outer
frame ///, along a length of a bottom of the inner wall of the elongated outer
frame
///. The connection between the elongated outer frame /// and the elongated
center
rail member 110 can be in a stationary position, as illustrated in FIG. 1A and
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FIG. 1C. One or more fixed braces 220, 230 can be provided to connect to the
elongated outer frame 111 on the interior surface and perpendicular to the
inner walls
of elongated outer frame 111, each of the fixed braces 220, 230 are
positionable at
opposing ends of the elongated outer frame 111, e.g. at a proximal position
and a
distal position in a stationary position, as illustrated in FIGS. 1A-D.
[0036] Elongated center rail member 110 and fixed braces 220, 230 can be
formed
integrally with elongated outer frame 111 in a fixed position to form a rigid
and
robust barrel structure or housing. A pair of forward spring members 120, 120'
positioned distally, are mountable to connect to a fixed brace 220 via
moveable braces
127a, 127'a at a distal spring end 120a, 120'a thereof on opposing sides of
the
elongated center rail member 110 adjacent a distally positioned forward
launching
end 110a, each of the forward spring members 120, 120' having a proximal
spring
ends 120b, 120'b opposite the distal spring ends 120a, 120'a. Likewise, a pair
of rear
spring members 130, 130' positioned proximally, are mountable to connect to
fixed
brace 230 via moveable brace 137a, 137'a at proximal spring ends 130a, 130'a
thereof on opposite sides of the elongated center rail member 110 adjacent the
proximally positioned opposing mounting stock 160 connecting end 110b, with
distal
spring ends 130b, 130'b opposite the proximal spring ends 130a, 130'a. Each of
the
forward spring members 120, 120' and the rear spring members 130, 130' is
connectable to a member of a moveable pulley block or block and tackle system
140
(shown in more detail in FIG. 2, FIG. 5, FIG. 6 and FIGS. 15A-B) that deploys
the
proximal moveable pulley blocks 135, 135' and distal moveable pulley blocks
125,
125', and that includes a launch cord 150. It should be noted that distal
moveable
pulley blocks 125, 125' are comprised of top moveable pulley block linkages
125a,
125'a and the lower linkage portion of moveable brackets 127b, 127'b and are
connected to hold the pulley wheels 126a, 126b, 126'a, 126'b via pulley wheel
axels
129, 129', as illustrated in FIG.6. In addition, moveable pulley blocks 135,
135' are
comprised of top moveable pulley block linkage 135a,135'a and bottom moveable
pulley block linkages 135b, 135'b and are connected to hold the pulley wheels
via
pulley wheel axels 139, 139' as illustrated in FIG. 15A-B.
[0037] For a handheld device, as shown in FIG. 1D, it is also preferable to
deploy a
hand grip 161 or support or mounting stock 160 at the proximal end of the
elongated
center rail member 110. While the device may be configured to extend and
release the
launch cord 150 directly by hand, a launch cord release latch 170 can also be
used
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which is activated by trigger 180 which is connected to elongated center rail
110 via
trigger assembly 185. Further, the diameter of the distal moveable pulley
blocks 125,
125', and the proximal moveable pulley blocks 135, 135' is no wider that the
forward
spring members 120, 120' and rear spring members 130, 130' to keep the elastic
projectile propulsion system 100 compact (e.g., having a diameter from 1/4
inch to 3/4
inch). Pulleys or sheaves, which are a grooved wheel as part of a pulley block
can
include bearings, not shown, to reduce friction, or be provided without
bearings.
[0038] FIG. 2 is a perspective view of the launch cord 150 as it is wrapped
between
the distal pulleys and the proximal pulleys within their respective moveable
pulley
blocks (without illustrating the distal moveable pulley blocks). As
illustrated at least
one proximal pulley 136, 136' is connected or coupled via proximal moveable
pulley
blocks 135, 135' to a distal spring end of each rear spring members via
moveable
braces 137b, 137'b and at least one distal pulley 126a, 126b and 126'a, 126'b
is
coupled or connected to the proximal spring end via distal moveable pulley
blocks of
each of the forward spring members (distally positioned) . A launch cord 150
has a
launch cord first end 150a and a launch cord second end 150b (opposing launch
cord
ends) engaging both the proximal moveable pulleys 136, 136' within blocks 135,
135'
and the distal pulleys 126a, 126b and 126'a, 126'b within their respective
moveable
pulley blocks (not pictured) and on opposing ends of the tackle system to
provide a
pair of counter acting block and tackle pulleys to couple the elastic energy
stored in
the forward spring members and rear spring members, when a launch cord center
150c is drawn rearward (proximal).
[0039] Coupling each moveable pulley block and an associated pulley(s) to move
with a spring overcomes an inertial burden of metal springs by adding a force
of
multiple cooperating springs without excess friction. Moreover, it is
preferable to
provide three wraps of a launch cord 150 between distal pulleys 126a, 126b,
and
proximal pulley 136 and three wraps of launch cord 150 between proximal pulley
126'a, 126'b and proximal pulley 136', as illustrated in FIG. 2 (which omits
the
springs that are attached to each moveable pulley block). The springs and
pulleys of
this configuration are also shown schematically in FIG. 8C.
[0040] The combination of multiple launch cord wraps between pulleys that move
in
cooperation with the springs on release of the launch cord and the projectile
enables a
large launch velocity by simultaneously improving the speed at which the force
of the
launch stroke is transferred to the projectile and facilitates a compact,
light-weight,
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robust and reliable design. First, it should be understood that the launch
velocity will
be proportional to the product of the launching force and launch stroke, which
is the
distance over which the force is applied. Second, it should now be understood
that the
velocity will also be proportional to the speed at which the launching force
can be
applied. However, coil springs have not been favored for archery propulsion by
those
skilled in the art because coil springs have been at a compromise between
these
factors, as increasing the launch force and or stroke through larger or more
powerful
springs is limited by proportional increase in spring mass and inertia.
Although
elastomers or rubber materials provide a high energy to mass density, the
materials
are not reliable below 40 F (4.4 degree Celsius). Further, the materials can
degrade
or crack from repeated use and environmental exposure, and are subject to
physical
damage from other materials they may contact. Metal and composite coil springs
are
generally more reliable than elastomers or rubber materials when used in these
conditions.
[0041] FIG. 3A is side elevation view of the device in a retracted spring
position,
whereas FIG. 3B is a side elevation view in an extended spring position or
projectile
launch ready state. FIG. 3C is a close-up side view of the sliding trigger
assembly
including the outer frame and FIG. 3D is a close-up front cross-sectional view
of the
sliding trigger assembly including the outer frame. When the projectile 10,
such as an
arrow, is launched the distal moveable pulley blocks 125, 125' connected to
moveable
braces 127b, 127'b are pulled in a distal direction via forward spring members
120,
120' and the proximal moveable pulley blocks 135, 135' connected to moveable
braces 137b, 137'b are pulled in a proximal direction via rear spring members
130,
130'. Thus, as shown in FIG. 3A in the refracted spring position the distal
moveable
pulley blocks 125, 125'are separated from the moveable pulley blocks 135, 135'
by a
distance, first distance L1, which upon loading or extending as shown in FIG.
3B,
decreases from the first distance L1 to a lesser distance, second distance L2.
The
launch strokes is (L1-L2)x where x is a number of launch cords traverses or
wraps
between opposing the distal moveable pulley blocks 125, 125' and proximal
moveable pulley blocks 135, 135', which includes the addition of the launch
cord
center 150c when in the loading or extending position as shown in FIG. 3B. In
this
example, L1-L2 = 7.5 inches and is multiplied by 4 (3 pulley wraps plus the
addition
of 1 to account for the leverage of the center cord 150c) and thus produces a
launch
stroke of 30 inches.
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[0042] Multiple parallel springs can be employed to engage each distal
moveable
pulley blocks 125, 125' or proximal moveable pulley blocks 135, 135', as shown
in
FIGS. 3A-3B via a connection to moveable braces 127b, 127'b and/37b, 137'b,
respectively.
[0043] As illustrated in FIGS. 3A-D, the launch cord release latch 170 and
hand grip
161 can be attached to a moveable trigger assembly 185 that can travel along
the
length of the elongated center rail 110. As shown in FIG. 3C and 3D, at the
top
corners of trigger assembly 185 are roller mounts 186a, 186'b and 187a, 187'b
(186a
not show in these partial figures) that extend up through slits that run the
length of the
bottom of the elongated outer frame 111. Launch cord release latch 170, 170'
extend
through the same two slits running the length of elongated outer frame 111 on
either
side of elongated center rail 110. Attached to the ends of roller mounts 186a,
186'b
and 187a, 187'b are rollers 186, 186' and 187, 187'(186 not show in these
partial
figures) that travel within the channel guide shape on either side of the
elongated
center rail 110. This configuration allows the launch cord release latch 170,
hand grip
161 and trigger assembly to travel the length of elongated center rail 110 in
both a
proximal and distal direction while staying permanently attached to elongated
center
rail 110. This mechanism provides a method of drawing and releasing the launch
cord
150 via the grip 161 for either cocking or uncocking the device. As shown in
FIG.
3A-3C, the trigger assembly 185 is permanently attached to a latch hook 181
that can
connect and disconnect from the stationary latch pin 162 that is permanently
attach to
the mounting stock 160.
[0044] FIG. 4 is perspective partial view of the springs in the extended
position or
projectile launch ready state. FIG. 5 is a more detailed perspective view of
the
moveable pulley mechanism attached to the springs in the extended position or
projectile launch ready state. FIG. 6 is a partial enlarged perspective view
of FIG. 4
and FIG. 5 that includes the nock of arrow projectile 10, adjacent the distal
moveable
pulleys attached to the springs in the retracted position. The launch or power
stroke
can be increased by multiple wraps between the pulleys in the distal moveable
pulley
blocks 125, 135 associated with opposing springs. However, as the springs move
simultaneously upon the release of the launching cord, back to the rest or
equilibrium
position, while an inertial limitation still exists, the contribution of each
spring to the
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launch velocity is additive, which combined with a large power stroke rated by
multiple pulley wraps can overcome these inertial spring barriers and greatly
increase
the launch velocity of a projectile such as an arrow 10. Further, additional
springs can
be added in a parallel configuration to each of the moveable braces connected
to the
moveable pulley blocks, as shown in the second embodiment of FIGS. 3-6, to
provide
additional force, without significant increase in physical dimensions, other
than the
minor height increase transverse to the elongated center rail member 110.
[0045] As shown in FIG. 5, it also preferable that the moveable braces 127b,
127'b
that connect to the proximal ends of forward spring members 120, 120' are
connected
by bridge 225, that extend over and traverse the elongated center rail member
110.
Bridge 225 also extends over any projectile such as an arrow 10..
[0046] As shown in FIG. 6, the launch cord center 150c is removably attachable
to a
nock 300 of projectile such as an arrow 10 and projectiles for release at the
time of
flight. The nock 300 is a notch in the rearmost end of the arrow which serves
to keep
the arrow in place on the string, or launch cord 150, as the bow is drawn.
However, in
the case of complicated projectiles the launch cord 150 may be coupled to the
projectile through a more elaborate intermediate assembly (not shown) that
runs with
the elongated center rail 110, and the projectile launches from the
intermediate
assembly. Hence, the elongated center rail 1/0 can be deployed to guide the
projectile. In the case of arrow projectiles, the track can be configured
minimally, but
particularly not to interfere with the flight of the arrow wings. In the case
of other
projectiles, the elongated center rail 110 can be more substantial, and need
not be
linear.
[0047] As discussed with respect to FIGS. 3-6, forward spring members 120,
120'
and rear spring members 130, 130' may be combined in a parallel bank, each
baffl(
engaging one or more moveable pulley blocks, but preferably four metal or
composite
coil springs in each forward spring members 120, 120'and three metal or
composite
coil springs are deployed in each rear spring member 130, 130'. The spring
tension
within the forward spring members and rear spring members should be balanced
with
the mechanical advantage of the associated pulleys so that the forward spring
members and rear spring members retract simultaneously throughout launch. When
using uniform spring dimensions for each spring, determining the balance can
be done
by matching the number of launch cord 150 connections to each moveable pulley
block with the number of springs in each spring member, while the springs are
in the
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extended position. As an example, shown in FIG.5, in the spring extended
position, 3
launch cords connections are made at each of the moveable pulley blocks
attached to
rear spring members 130, 130', thus each spring member contains 3 springs.
Similarly, 4 launch cord 150 connections are made at both moveable pulley
blocks
attached to forward spring members 120, 120', thus each spring member contains
4
springs. Alternatively, different spring dimensions in the forward and read
spring
members can be used to achieve balance with the pulley advantage. The spring
members are optionally metal or composite coil springs. Springs are preferably
deployed in tension, but a configuration with at least some of the springs in
a
compression mode is possible.
[0048] Further, to the extent some launching devices deploy metal or other
torsion
springs that work to displace a pulley that directs a launch cord, their
performance can
likely be improved by adding a second moveable pulley or moveable pulley block
connected to a compression or tension spring to wrap the launch cord back to
the
torsion spring member before it engages the projectile.
[0049] FIG. 7A is an top plan view of the outer frame as it connects to the
fixed
braces, shown in the extended spring position or projectile launch ready
state, whereas
FIG. 7B depicts the top plan view with the outer frame omitted to better
depict the
fixed and moveable brace connections to the springs in the extended position,
and
FIG. 7C illustrates the top plan view with the outer frame omitted to better
depict the
fixed and moveable brace connections with springs in a position during
retraction, and
FIG. 7D illustrates the top plan view with the outer frame omitted to better
depict the
springs in the retracted position.
[0050] Additionally, moveable braces 127a, 127'a and moveable brace 137a,
137'a
can be used to allow free travel through fixed braces 220, 230, respectively,
which are
firmly attached to the inner walls at opposing ends of elongated outer frame
111 and
elongated center rail 110. One or more bumpers 128, 128', are mounted to the
distal
ends of moveable braces 127a, 127'a located on the distal face of fixed brace
220,
and bumpers 138, 138' mounted to proximal ends of moveable brace 137a, 137'a
located on the proximal face of fixed brace 230, as illustrated in FIGS. 7A-D.
In the
extended position, forward spring members 120, 120' forces draw the moveable
braces 127a, 127'a in a proximal direction, thus pulling the one or more
bumpers 128,
128' firmly against the distal face of fixed brace 220 which is attached to
elongated
outer frame 111, and simultaneous the rear spring members 130, 130' forces
draw the
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moveable brace 137a, 137'a in a distal direction, thus pulling the bumpers
138, 138'
firmly against the proximal face of fixed brace 230 which is attached to
elongated
outer frame ///, as show in FIGS. 7A-B. During the process of retracting,
forces in
forward spring members 120, 120' move the moveable braces 127b, 127'b in the
distal direction until a stopping point at which the launch cord center 150c
is held
stationary, in turn, disengaging the nock 300 as projectile such as an arrow
10
continues to travel in a distal launch direction. Simultaneously, forces in
rear spring
members 130, 130' move the moveable brace 137b, 137'b in a proximal direction
until a stopping point at which launch cord 150 is held stationary. Forces not
imparted
to the projectile 10, continue to travel through forward spring members 120,
120' and
rear spring members 130, 130'. Forward spring members 120, 120' continue
moving
in the distal direction and, in turn, push the moveable braces 127a, 127'a
though fixed
brace 220, thus moving the bumpers 128, 128' in a distal direction away from
fixed
brace 220 (attached to distal end of the elongated outer frame 111), and
simultaneously to rear spring members 130, 130' continue moving in the
proximal
direction and, in turn, push the moveable brace 137a, 137'a through fixed
brace 230,
thus moving the bumpers 138, 138' in a proximal direction away from fixed
brace
230 (attached to the proximal end of the elongated outer frame 111) . One or
more
bumpers 128, 128' and moveable braces 127a, 127'a continue moving in a distal
direction until counter-acting forces within forward spring members 120, 120'
reach
equilibrium and arrest their distal travel progress, thus moving them back in
a
proximal direction and returning one or more bumpers 128, 128' to their
initial
position, flush against the distal face of fixed brace 220, and simultaneously
the
bumpers 138, 138' and moveable brace 137a, 137' a continue moving in a
proximal
direction until counter-acting forces within rear spring members 130, 130'
reach
equilibrium and arrest their proximal travel progress thus moving them back in
a
distal direction and returning the bumpers 138, 138' to their initial position
flush
against the proximal face of fixed brace 230, a steady state, in the retracted
spring
position, as illustrated in FIG. 7C and FIG. 7D. Hence, these configurations
allow
excess forces not imparted to the projectile such as an arrow /0 to be
reabsorbed and
resolved within the system without sustaining damage to the system.
[0051] FIGS. 8A-C are schematic diagrams of the cord, pulley blocks, pulleys
and
springs representing alternative configurations tested in comparative examples
with
the illustrations showing only the pulley blocks on one side of the center
rail,
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including the associated symmetric half of the launching cord. Further,
pulleys that
rotate about a common axis or axle of a single pulley block are shown in FIGS.
8A-C
as vertically spaced apart to better illustrate the launching cord path and a
launch cord
first end 150a forming a terminal connection of half the launch cord 150.
Projectile
such as an arrow 10 points in the direction it is launched by forward spring
members
120 and rear spring members 130. FIG. 8C corresponds to an embodiment of FIG.
1
and FIG. 2. It should be noted that the configurations in FIG. 8A and FIG. 8B
both
deploy two pulley blocks 125, 135 and in each of two pulley wheels 126a, 126b
and
136a, 136b, respectively, so that the launch cord makes four wraps between the
pulleys. In FIG. 8A, however, only the proximal pulley block 135 is moveable
as
attached to the springs, as the forward or distal pulley blocks 125 has been
attached in
a fixed point of the distal end of elongated center rail 110. FIG. 8C is as
shown in
FIGS. 1A-B, with only three pulley wheels utilized in the two moveable pulley
blocks. Two pulley wheels 126a, 126b were placed in a distal moveable pulley
blocks
125 attach to the proximal ends of the forward spring members 120 and one
pulley
wheel 136 in the moveable pulley block 135 attached to the proximal spring (at
the
distal spring end), and the string or launch cord 150 ends terminated directly
to the
proximal springs 130. The bow string or launch cord 150 now traveled around
three
pulley wheels on either side of the center rail.
[0052] Comparative test results revealed that the configuration illustrated in
FIG. 8C
generated superior arrow velocity and the results are discussed in more detail
in the
TESTING section below. However, a summary of the results concluded that
associating each moveable pulley blocks 125, 135 to move individually with a
tensioned spring members, forward spring members 120, and rear spring members
130, respectively, or elastic member in the opposing direction of the opposing
pulleys
in the block and tackle configuration provided a higher launch velocity than
if one set
of pulleys was not moveable or was fixed to the stationary part of the
embodiment, or
the end of the launching cord was attached to a fixed position with respect to
the
elongated center rail member 110. As each wrap of the launch cord 150 around a
pulley 126, 136 introduces friction, it is desirable to minimize the pulley
wraps of the
launch cord 150, while still obtaining the additive release power and stroke
distance
of opposing springs: forward spring members 120, and rear spring members 130.
[0053] FIGS. 9A-H are isolated views of rail mechanisms, such as shown in
FIGS. 1
and 7. FIG. 9A-C are depicted with a large diameter projectile such as an
arrow 10,
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and FIG. 9D-E are depicted with a smaller diameter projectile such as an arrow
10.
As illustrated in FIGS. 9A-H, the elongated center rail 110 can be configured
with the
addition of an over-molded center rail 112 to raise or lower arrows of varying
diameters in order to keep the projectile such as an arrow 10 and arrow nock
300 in
alignment with launch cord center 150c. An over-molded center rail 112 is
nested on
top of the elongated center rail 110 and configured such that the over-molded
center
rail 112 can raise and lower while remaining in parallel alignment with
elongated
center rail 110 in order to accommodate arrows of varying diameters. On
adjacent
sides of the over-molded center rail 112, angled notches have been positioned
at the
proximal 112b, center and distal 112a areas of over-molded center rail 112.
Each of
the notches 112c, 112'c, 112d, 112'd and 112e, 112'e of over-molded center
rail 112
rest upon pins 113 that are mountable into and along adjacent sides of over-
molded
center rail //2. Notches 112c, 112'c rest upon pins 113a, 113'a, notches 112d,
112'd
rest upon pins 113, 113' and notches 112e, 112'e rest upon pins 113b, 113 'b.
FIG.
9F-H are a close up view of the mechanism used to adjust the over-molded
center rail
112. At the proximal end of the over-molded center rail 112, an adjustment
screw 114
is mounted to the over-molded center rail 112 through grommet 116. The distal
end of
adjustment screw 114 connects to clevis end 117. A slotted linkage 119 then
connects
over-molded center rail 112 to the clevis end 117 such that the slotted end of
the
linkage is captured within the clevis end 117 via a clevis pin 118. When the
adjustment screw 114 is rotated clockwise it draws the over-molded center rail
112 in
the proximal and upward direction, as the angled notches in over-molded center
rail
112 travel over the pins 113 mountable in the sides of over-molded center rail
112, as
shown in FIG. 9H..
[0054] FIGS. 10A-C are front and isometric views that depict the positions of
the
hand grip as configured in an integrated cocking mechanism. Additionally, the
hand
grip 161 may be configured in two moveable pieces, moveable hand grips 161,
161'
attached to trigger assembly 185 with two hinges 183, 183', as depicted in
FIG. 10A-
C, to aid in the cocking or uncocking the device. A scope mount 201 may also
be
attached to elongated outer frame 111 to mount a scope 200.
[0055] FIGS. 11A-F are partial side and top views of the passive safety
mechanism.
Additionally, the mechanisms within the trigger assembly 185 can be configured
to
passively activate a safety mechanism (which prohibits the deployment of the
propulsion system) during the cocking process, as depicted in FIGS. 11A-F. In
order
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for trigger 180 to release the launch cord release latch 170, 170' (and deploy
the
propulsion system), trigger 180 must rotate around its axis pin 182, which
rotates the
top of trigger 180 in a distal direction away from contact with pin 175 that
is
connected to the launch cord release latch 170, 170'. When safety pin 174 is
moved
into the proximal position (SAFE position), beyond ball stud 176 and into the
safety
pin catch groove in the top of trigger 180, trigger 180 is not able to rotate
into a
position to allow launch cord release latch 170, 170' to deploy the propulsion
system,
as shown in FIG. 11E. Safety pin 174 is mounted to the end of a first toggle
arm 173a
which is joined in a perpendicular position to a second toggle arm 173b in a
ridged
fashion. Both toggle arms are pivotable on axis pin 172 at the point where the
first
toggle arm 173a and second toggle arm 173b are joined. When the second toggle
arm
173b is moved upward it moves the attached safety pin 174 into a SAFE position
via
the first toggle arm 173a. The pin 175 of launch cord release latch 170, 170'
is
positioned below the second toggle arm 173b. Launch cord release latch 170,
170' is
mounted within trigger assembly 185 via axis pin 171 so that launch cord
release latch
170, 170' may tilt backward (proximally) when the top of launch cord release
latch
170, 170' makes contact with the launch cord center 150c and moves in a distal
direction beyond the launch cord center 150c, during the cocking process. As
launch
cord release latch 170, 170' tilts backward its pin 175 moves upward thus
moving the
second toggle arm 173b upward, and thus moves safety pin 174 into a SAFE
position,
as illustrated in FIG. 11C. Safety pin 174 can then be manually moved in a
distal
direction, out of the SAFE position, in order to allow trigger 180 to be
actuated (and
deploy the propulsion system).
[0056] In another configuration a launch cord release latch 170, 170' as shown
in
FIG. 11, is deployable to hold the launch cord 150 with attached projectile,
such as an
arrow (not shown) and at least one of the springs in the extended position -
until
released by a trigger 180. The springs can be metal or composite coil springs,
preferably tension springs, but can also be elastic materials, such as rubber
tubing and
the like. Forward spring members 120, 120' and rear spring members 130, 130'
are
mounted parallel to elongated center rail member 110; however, as will be
appreciated by those skilled in the art, the forward spring members 120, 120'
and rear
spring members 130, 130' can be mounted in different orientations, with the
attached
moveable pulley blocks deployed to redirect the launch cord 150 to propel the
projectile such as an arrow 10 along the center rail direction without
departing from
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the scope of the disclosure. Further, it should be appreciated that elastic
energy is
generally stored in the launching cord, as well as the springs. Hence, nothing
precludes all or part of the launching cord from being formed of a rubber or
elastomer
such as a band or tubing, although this might only be desired in isothermal
warm
environments.
[0057] FIGS. 12A-H are partial side and top views detailing the anti-dry-fire
mechanism. To further enhance safety, a mechanism can be added to ensure that
the
propulsion system cannot be deployed without an arrow nocked in the launch
cord, as
illustrated in FIGS. 12A-H. In the instant configuration, a string catch 164
is mounted
via hinge to the top of mounting stock 160. In the absence of a projectile
such as an
arrow 10 connected by its nock 300 to launch cord center 150c, string catch
164 is
allowed to rest on the launch cord center 150c in a position that is able to
arrest the
travel of the launch cord center 150c from full deployment, as depicted in
FIG. 12C.
The distal end of string catch 164 is shaped in an angle that is slight
proximal and
downward to ensure that string catch 164 does not prohibit the cocking
process.
During the cocking process, the angular shape of the distal end on string
catch 164
encourages string catch 164 to pivot upward from its hinge mount, allowing the
launch cord center 150c to move in a proximal direction, past string catch
164,
without significant interference. Additionally, as shown in FIG. 12G, a push
arm 165
is connected to the underside of string catch 164 via a hinge connection. The
push arm
165 extends downward and rests on top of the latch hook 181. During the de-
cocking
process and in the absence of a projectile such as an arrow 10, when latch
hook 181 is
lifted upwards, push arm 165 is also pushed upwards, which in turn lifts
string catch
164 upwards and thus out of contact with launch cord center 151c as it travels
down a
distal path. This mechanism ensures that the string catch 164 is prohibited
from
interfering with the launch cord center 150c during de-cocking, even when a
projectile such as an arrow /0 is not engaged by its nock 300 to launch cord
center
150c.
[0058] The trigger assembly 185 is configured to attach to the mounting stock
160 via
a latch hook 181 installed into the trigger assembly 185. The latch hook 181
interfaces
with a corresponding stationary latch pin 162 that is located in the lower
portion of
the mounting stock 160, as shown in FIG. 12C. This mechanism allows the
trigger
assembly 185 and associated launch cord release latch 170, 170' to secure the
launch
cord center 150c in a fixed position at the proximal end of the elastic
projectile
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propulsion system 100 during the fully cocked or launch-ready state. The latch
hook
181 may be disengaged from the corresponding stationary latch pin 162 in
mounting
stock 160 allowing the trigger assembly 185 to move freely in the distal
direction
while de-cocking the device, as illustrated in FIG. 12G.
[0059] FIGS. 13A-D are side and isometric views illustrating the auto-
retractable
foot claw mechanism. In another configuration, the elastic projectile
propulsion
system 100 may include a foot claw 221 to aid in the cocking process, as
illustrated in
FIGS. 13A-D. In the present execution, the foot claw 221 is attached through
the
spring wall 220 via two foot claw mounts 222, 222'. On the proximal end of
each of
the foot claw mounts 222, 222' coil springs 223, 223' are attached to keep the
foot
claw 221 in the retracted position against the elongated outer frame 111. This
configuration allows the foot claw to increases accessible foot space during
use, and
then, when not in use, the foot claw space is minimized to reduce potential
interference with other operations of the elastic projectile propulsion system
100.
[0060] FIGS. 14 A-C illustrates the adjustable stock; wherein FIGS. 14A-B are
partial side views detailing the full range adjustability, and FIG. 14C is a
detailed
proximal view of the components of the stock release mechanism. As depicted in
FIG. 14A-C, an adjustable shoulder stock may be included in the elastic
projectile
propulsion system 100. A shoulder stock 231 is attached to the proximal ends
of two
of the stock mounting rods 232, 232'. The distal ends of the stock mount rods
232,
232' are mounted through holes in mounting stock 160, elliptical holes in each
of the
release buttons 233, 233' and holes in the spring wall 230, as to allow the
stock
mounting rods 232, 232' to extend in a proximal direction or retract toward
mounting
stock 160. On the surface of each of the stock mounting rods 232, 232',
running the
length of each rod, is a series of banded notches. As illustrated in FIG. 14C,
the
release buttons 233, 233' are inset mounted into either side of mounting stock
160,
and can pivot on axis bolts 235, 235' within the inset pattern of mounting
stock 160.
The release buttons 233, 233' are maintained in their opposing, extreme
positions of
travel via two coil springs 234, 234' such that their outer edges each extend
beyond
either edge of mounting stock 160. In this position, the inner edge of each
elliptical
hole within each release buttons 233, 233' is encouraged into notches on the
side of
each of the stock mounting rods 232, 232'. In this position the stock mounting
rods
are prohibited from extending or retracting. Both release buttons 233, 233'
can be
pressed inward at the same time in order to allow each of the stock mounting
rods
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232, 232' to be extended or released. This configuration allows the stock to
be
adjusted to fit users with varying physical needs and allows the stock to be
minimized
during non-use in order to minimize potential interference with transportation
or
storage of the elastic projectile propulsion system 100.
[0061] FIGS. 15A-B are isometric, close-up, views of launch cord tensioning
terminals. It should be understood that the launch cord 150 first end 150a and
second
end 150b can be attached to the proximal ends of the forward spring members,
but
preferably the distal ends of the rear spring members 130, 130'. In at least
some
configurations, the launch cord first end 150a and launch cord second end 150b
are
attached to two respective launch cord tensioning mechanisms located below the
at
least one proximal pulley 136, 136' and the bottom of the proximal moveable
pulley
block linkages 135b, 135'b, which allow the launch cord 150 to be tensioned in
fine
increments, as depicted in FIG. 15 A-B. The launch cord tensioning mechanism
is
comprised of cord end spools 151, 151' and ratchets 152, 152' which are
mounted in
fixed positions to pulley wheel axels 139, 139', such that they rotate when
the top of
pulley wheel axels 139 or 139' are turned with a screw driver. Pawls 153, 153'
attach
to pulley block linkage pins 134, 134' and engage ratchets 152, 152' in a
manner that
allows cord end spools 151, 151' to maintain launch cord tension after pulley
wheel
axels 139, /39'are tightened.
[0062] The moveable pulley blocks are attachable to either the distal or
proximal
spring members that deploy a plurality of pulleys be configured such that each
pulley
in the block rotate independently of the others.
[0063] However, alternatively, each wrap of the launching cord can connect
multiple
pulleys that are attached to the spring ends, each moveable pulley block
having a
single pulley.
[0064] FIGS. 16A-B are top views of an arrow retaining system with springs
extended and arrow loaded, and springs retracted arrow unloaded. Additionally,
the
elastic projectile propulsion system /00 can be configured to launch arrows of
widely
varying lengths and arrows that are shorter that the length of the draw or
power stroke
of the device, as illustrated in FIG. 16A-B. When arrow retaining spring 115,
attached within elongated outer frame 111, is located at the mid-point between
the
launch cord release latch 170, 170' and distal spring wall 220, the arrow
retaining
spring 115 maintains contact with the projectile such as an arrow 10
throughout the
entire power stroke of launch cord 150. The configuration ensures that arrow
point
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10a of projectile such as an arrow 10 will exit the hole in spring wall 220
without
making contact with spring wall 220. The result is that shorter, lighter
weight arrows
may be safely launched and can attain higher arrow velocity than longer,
heavier
arrows without any other modifications to the elastic projectile propulsion
system
/00.
METHODS
[0065] Methods include operation of the devices disclosed above. In practice,
a user
obtains a linear projectile, such as an arrow, mounts the projectile in the
barrel of the
device to engage the launch cord. Once the projectile is secured within the
device, the
user draws the projectile in a rearward direction to tension the launch cords
and
extend each of the forward springs and rearward springs. Thereafter, the user
releases
the draw on the projectile (e.g., by pulling the trigger, releasing the launch
cord, etc.),
which causes a transfer of energy from the tensioned springs and launch cord
to the
projectile. Alternatively, the linear projectile, such as an arrow, may be
secured within
the device after the launch cord has been fully tensioned, and thereafter, the
user
releases the draw on the projectile (e.g., by pulling the trigger, releasing
the launch
cord, etc.), which causes a transfer of energy from the tensioned springs and
launch
cord to the projectile.
TESTING
[0066] Various configurations of the propulsion mechanism were tested to
determine
superior arrow velocity, as illustrated in FIG. 8A-8C. In all tests, the power
stroke
was 30" for launching a 1 oz. (28.35 grams) arrow 33.5 inches (85.09
centimeters) in
length, with the arrow flight velocity subsequently measured with a
RADARCHRONO brand Doppler radar velocity sensor meter.
[0067] As shown in FIG. 8A, the propulsion mechanism was configured so that
the
front pulleys 126a, 126b were held stationary as the distal moveable pulley
blocks
125 were attached to a distal, fixed part of the center rail. The forward
spring
members 120, 120' and rear spring members 130, 130' were connected into series
attached to the proximal moveable pulley blocks 135. The velocity result of
one test
was 163 ft/sec (4968 centimeters/second).
[0068] The embodiment of FIG. 8B used the same four springs (two springs being
positioned on each side of the elongated center rail 110) as in FIG. 8A,
however,
forward spring members 120 were attached to the distal end of elongated center
rail
110 with the distal moveable pulley blocks 125 (containing two pulley wheels)
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attached to the proximal end of forward spring members 120, 120'. The string
ends
were terminated directly to the forward springs just under the distal moveable
pulley
blocks 125. Initial spring tension was the same as the example described with
respect
to FIG. 8A. The launch cord 150, or bow string, traveled around four pulley
wheels in
each moveable pulley block. The three flight test results were:
1) 197 ft/sec (6005 centimeters/second),
2) 199 ft/sec (6066 centimeters/second),
3) 196 ft/sec (5974 centimeters/second).
[0069] Variances in velocity were likely due to minor adjustments made to the
arrow
rest between each test.
[0070] The propulsion mechanism was also configured as shown in FIG. 8C as
shown in FIGS. 1A-B, with only three pulley wheels utilized in the two
moveable
pulley blocks. Two pulley wheels 126a, 126b were placed in a distal moveable
pulley
blocks 125 attach to the proximal ends of the distally positioned, forward
spring
members 120 and one pulley wheel 136 in the moveable pulley block 135 attached
to
the proximal spring (at the distal spring end), and the string or launch cord
150 ends
terminated directly to the proximal springs 130. The bow string or launch cord
150
now traveled around three pulley wheels on either side of the center rail. The
velocity
result of 'test one' was 210 ft/sec (6401 centimeters/second). Initial tension
in the bow
string or launch cord was increased further by visibly removing slack from the
launch
cord. While initial tension was not measured, it did not appear to separate
the
extension spring coils. The velocity result of 'test two' was 228 ft/sec (6949
centimeters/second). Initial tension was then further increased in the bow
string or
launch cord 150 so that the initial tension was taken from the spring,
separating the
coils no more than 1/8". The velocity result of this test was 246 ft/sec (7498
centimeters/second).
[0071] While the highest velocities achieved during tests peaked at 339ft/sec
(1.033e+004 centimeters/second) utilizing a 270 grain arrow at 30 inch (76.2
centimeters) draw length and 781bs (35.38 kilograms) draw force, it was
discovered
that some energy was lost in the launch cord 150 being stretched. It is
assumed that
solely utilizing a more robust launch cord 150 will result in greater
velocities.
[0072] As well, it was discovered after velocity testing concluded that
utilizing the
same spring wire and outer diameter design with a slight increase in spring
length
resulted in the ability to generate equal or more energy in the power stroke
with a
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significant decrease in draw length. For example, the same spring design used
in all
the tests was increased in length by 0.9" and resulted in the ability to
decrease the
draw length by 6" while generating a ¨2% increase in power stroke foot-pounds,
all
with the same 78 lbs (35.38 kilograms) draw force. This was achieved by
increasing
the initial tension in the springs via tightening of the launch cord which
increased the
total amount of force that was distributed over the length of the shortened
draw
stroke. It was also realized that the addition of more pulleys and resulting
increase in
pulley ratio would allow the use of shorter, more powerful springs to
distribute their
force over similar or greater draw lengths. It is reasonable to believe that
future tests
are likely to reveal increases in arrow speeds as shorter, lighter arrows
matched to the
reduced draw length, with a slight increase in power stroke force will result
in more
velocity. As well, overall device length can be reduced by a shorter draw
length,
consistent with a more compact and maneuverable design.
[0073] Testing of the shock absorbing system described above was conducted to
assess damage caused to the entire system including the elastic projectile
propulsion
system /00 as a result of launching a projectile such as an arrow /0 not
meeting
minimum current standards of weight to draw force ratio. The commonly followed
industry standard, set and maintained by the International Bowhunting
Organization
(IB0), is prescribed in a ratio that states an arrow typically weighs at least
5 grains
per every one pound of draw force (for bows generating arrow velocities above
290
feet per second (8839 centimeters/second)). Testing was performed with arrows
weighing a little as 270 grains (30" in length) at a draw force of 78 pounds
(35.38
kilograms), resulting in a testing ratio of approximately 3.5 grains per one
pound of
draw force (generating arrow speeds significantly above 290 feet per second
(8839
centimeters/second)). Though testing was not conducted to the point of
failure,
repeated launches did not result in any observed damage to the elastic
projectile
propulsion system /00. While dry fire tests (without an arrow) were not
performed, it
is believed that parameters of the described shock absorbing system are
capable of
being adjusted to achieve dry fire without damage to the elastic projectile
propulsion
system /00. The demonstrated ability of the propulsion system /00 to reabsorb
stored
energy not imparted to the arrow upon release and thus launch lighter arrows
at equal
draw forces compared to conventional bow systems provides an advantage in the
ability to increase arrow velocity without increasing draw force or causing
corresponding damage to the system.
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[0074] While preferred embodiments of the present invention have been shown
and
described herein, it will be obvious to those skilled in the art that such
embodiments
are provided by way of example only. Numerous variations, changes, and
substitutions will now occur to those skilled in the art without departing
from the
invention. It should be understood that various alternatives to the
embodiments of the
invention described herein may be employed in practicing the invention. It is
intended that the following claims define the scope of the invention and that
methods
and structures within the scope of these claims and their equivalents be
covered
thereby.
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