U.S. patent application number 12/719888 was filed with the patent office on 2010-09-16 for breech seal for air gun.
Invention is credited to Thomas Gore.
Application Number | 20100229844 12/719888 |
Document ID | / |
Family ID | 42729669 |
Filed Date | 2010-09-16 |
United States Patent
Application |
20100229844 |
Kind Code |
A1 |
Gore; Thomas |
September 16, 2010 |
BREECH SEAL FOR AIR GUN
Abstract
A barrel break air gun includes a pair of opposed, generally
planar faces defining a narrow gap between the breech and the
barrel. The barrel face includes a circular groove concentric with
the barrel bore that receives an annular seal, and a recessed
annular land defined between the circular groove and the barrel
bore. The annular seal may be either an o-ring nominally disposed
within the circular groove, or an annular urethane washer that is
slightly radially-compressed when placed into the circular groove
such that the inner diameter of the washer projects slightly away
from the barrel face prior to closing the barrel breech. In one
embodiment featuring the annular washer, the washer's internal
diameter is slightly smaller than the maximum skirt dimension of an
air gun pellet, such that the pellet's skirt is retained by the
washer upon closing the barrel breech.
Inventors: |
Gore; Thomas; (South Lyon,
MI) |
Correspondence
Address: |
QUINN LAW GROUP, PLLC
39555 ORCHARD HILL PLACE, SUITE # 520
NOVI
MI
48375
US
|
Family ID: |
42729669 |
Appl. No.: |
12/719888 |
Filed: |
March 9, 2010 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61160702 |
Mar 16, 2009 |
|
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|
Current U.S.
Class: |
124/80 |
Current CPC
Class: |
F41B 11/642 20130101;
F41B 11/73 20130101 |
Class at
Publication: |
124/80 |
International
Class: |
F41B 11/34 20060101
F41B011/34; F41B 11/00 20060101 F41B011/00 |
Claims
1. An air gun comprising: a receiver having a breech face and
defining a gas port configured for exhausting a compressed gas
therethrough; a barrel defining a bore extending along a
longitudinal axis of said barrel and including a barrel face
disposed opposite said breech face, wherein said bore is in fluid
communication with said gas port for receiving the compressed gas;
said barrel defining a circular groove disposed concentrically
about and radially offset from said bore and recessed a depth from
said barrel face; a seal at least partially disposed within said
circular groove and in sealing engagement with said breech face of
said receiver for sealing said bore and said gas port between said
barrel and said receiver; and an annular land disposed adjacent and
concentrically about said bore between said circular groove and
said bore and recessed from said barrel face a depth less than said
recessed depth of said circular groove.
2. An air gun as set forth in claim 1 wherein said seal includes a
durometer greater than or equal to 40 and less than or equal to
90.
3. An air gun as set forth in claim 2 wherein said seal includes an
o-ring seal.
4. An air gun as set forth in claim 2 wherein said seal includes a
washer.
5. An air gun as set forth in claim 4 wherein said washer includes
a thickness greater than a difference between said depth of said
circular groove relative to said barrel face and said depth of said
annular land relative to said barrel face.
6. An air gun as set forth in claim 5 wherein said washer defines
an outer diameter greater than an outer diameter of said circular
groove.
7. An air gun as set forth in claim 6 wherein said washer defines a
radially inner surface having a diameter that is less than a
diameter of said bore of said barrel.
8. An air gun as set forth in claim 7 wherein said radial inner
surface of said washer includes at least one surface feature for
contacting a pellet disposed in said bore and configured for
providing a consistent breakaway force between the pellet and said
bore.
9. An air gun as set forth in claim 4 wherein said washer includes
a cylindrical body disposed within said circular groove and a
flange extending radially inward from said body adjacent said
annular land.
10. An air gun as set forth in claim 9 wherein said body includes a
length along said longitudinal axis that is greater than said depth
of said circular groove relative to said barrel face.
11. An air gun as set forth in claim 10 wherein said flange
includes at thickness greater than said depth of said annular land
relative to said barrel face.
12. An air gun as set forth in claim 9 wherein said flange defines
a radially inner surface having a diameter that is less than a
diameter of said bore of said barrel.
13. An air gun as set forth in claim 12 wherein said radial inner
surface of said flange includes at least one surface feature for
contacting a pellet disposed in said bore and configured for
providing a consistent breakaway force between the pellet and said
bore.
14. An air gun comprising: a receiver having a breech face defining
a gas port configured for exhausting a compressed gas therethrough;
a barrel defining a bore extending along a longitudinal axis of
said barrel and including a barrel face disposed opposite said
breech face, wherein said bore is in fluid communication with said
gas port for receiving the compressed gas; said barrel defining a
counterbore disposed concentrically about and adjacent said bore of
said barrel; and a seal at least partially disposed within said
circular counterbore and in sealing engagement with said breech
face of said receiver for sealing said bore and said gas port
between said barrel and said receiver; wherein said seal includes a
cylindrical body extending along said longitudinal axis and a
second flange disposed at a second end of said cylindrical body and
extending radially inward from said cylindrical body to a radial
inner surface having a diameter less than a diameter of said
bore.
15. An air gun as set forth in claim 14 wherein said counter bore
extends a depth along said longitudinal axis relative to said
barrel face and said second flange includes a thickness along said
longitudinal axis relative to said barrel face that is less than
said depth of said counterbore.
16. An air gun as set forth in claim 15 wherein said radial inner
surface of said second flange includes at least one surface feature
for contacting a pellet disposed in said bore and configured for
providing a consistent breakaway force between the pellet and said
bore.
17. An air gun as set forth in claim 16 wherein said seal includes
a first flange disposed at a first end of said cylindrical body
between said barrel face and said breech face, and extending
radially outward from said cylindrical body.
18. An air gun as set forth in claim 17 wherein said seal includes
a durometer greater than or equal to 40 and less than or equal to
90.
19. An air gun comprising: a receiver defining a gas port
configured for exhausting a compressed gas therethrough; a barrel
defining a bore extending along a longitudinal axis of said barrel
and including a barrel face, wherein said bore is in fluid
communication with said gas port for receiving the compressed gas;
and a seal in sealing engagement with said barrel face and said
receiver for sealing said bore and said gas port, and defining an
interior diameter less than a diameter of a projectile for engaging
at least a portion of the projectile and retaining the projectile
in place until fired.
20. An air gun as set forth in claim 19 wherein said seal includes
a durometer greater than or equal to 40 and less than or equal to
90.
21. An air gun as set forth in claim 20 wherein said barrel defines
a counterbore disposed concentrically about and adjacent said bore
of said barrel, with said seal at least partially disposed within
said counterbore.
22. An air gun as set forth in claim 20 further comprising loading
mechanism configured for urging the projectile into a secured
position within said seal.
23. An air gun as set forth in claim 22 wherein the loading
mechanism is disposed inline with said longitudinal axis, with said
seal configured for sealing against a barrel face of said loading
mechanism.
24. An air gun as set forth in claim 23 wherein said seal defines a
port adjacent and in fluid communication with said gas transfer
port.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit if U.S. Provisional
Patent Application Ser. No. 61/160,702, filed on Mar. 16, 2009, the
disclosure of which is hereby incorporated by reference.
TECHNICAL FIELD
[0002] This invention relates to air guns and, particularly, to a
barrel and breech seals for such air guns.
BACKGROUND OF THE INVENTION
[0003] Known barrel break air guns fire projectiles using
compressed air that is delivered to a gas transfer port disposed in
the gun breech, immediately rearward of a projectile, such as a
pellet, disposed in the barrel proximate to the breech. The barrel
is pivotally connected to the breech, such that the barrel can be
"broken" to expose the rearward extent of the barrel's bore in
order to receive the pellet, whereupon the pellet is retained in
the rearward extent of the barrels' bore by static friction until
firing.
[0004] The opposed generally planar faces of the breech and the
barrel are typically sealed by an o-ring disposed in a concentric
groove machined on one of the faces, such as the rearward face of
the barrel. Upon pivoting the barrel into a closed position, in
general alignment with the axis of the gas transfer port of the
breech, the o-ring is slightly axially compressed between the
opposed breech and the barrel faces to achieve an air-tight seal
between the breech and the barrel. Thus, when the air gun is fired,
for example, by triggering the release of a spring-driven piston
within a compression tube defined within the breech, or other
suitable source of compressed gas, a volume of highly-compressed
gas is directed through the gas transfer port and into the barrel.
The effectiveness of the breech seal plays a significant role in
the efficiency of the air blast that is delivered into the barrel
bore, which, in turn, determines the air gun's muzzle velocity and
firing performance.
[0005] In order to achieve a greater muzzle velocity without
increased air loss through the breech seal, the prior art has
sought to generate an increase in the gas flow rate through the gas
transfer port by increasing the port's cross-sectional area, with
the correlative effect of reducing the peak pressure achieved
behind the projectile seated in the barrel bore to reduce air
losses through the breech seal. This approach has been known to
slightly improve muzzle velocities over a stock breech. However,
the use of an increased port cross-sectional area often generates
increased physical shock as the piston slams into the end of the
compression bore due to a reduction in piston back-pressure, such
that the air gun is more difficult to shoot accurately, and with
reduced smoothness. Further, an increased port cross-sectional area
appears to more gradually ramp up the pressure achieved behind the
seated projectile, such that the static friction retaining the
projectile in the barrel bore proximate the breech is overcome well
before peak pressure is achieved, thereby further mitigating the
performance increase that might otherwise be achieved from an
increased gas flow rate.
SUMMARY OF THE INVENTION
[0006] An air gun includes a receiver. The receiver includes a
breech face, and also defines a gas port configured for exhausting
a compressed gas therethrough. The air gun further includes a
barrel defining a bore extending along a longitudinal axis of the
barrel. The barrel includes a barrel face disposed opposite the
breech face. The bore is in fluid communication with the gas port
for receiving the compressed gas. The barrel defines a circular
groove disposed concentrically about and radially offset from the
bore. The circular groove is recessed a depth from the barrel face.
A seal is at least partially disposed within the circular groove.
The seal is in sealing engagement with the breech face of the
receiver for sealing the bore and the gas port between the barrel
and the receiver. The barrel further includes an annular land
disposed adjacent and concentrically about the bore, between the
circular groove and the bore. The annular land is recessed from the
barrel face a depth less than the recessed depth of the circular
groove.
[0007] In another aspect of the invention, an air gun is provided.
The air gun includes a receiver having a breech face. The receiver
further defines a gas port configured for exhausting a compressed
gas therethrough. The air gun further includes a barrel defining a
bore extending along a longitudinal axis of the barrel. The barrel
includes a barrel face disposed opposite the breech face. The bore
is in fluid communication with the gas port for receiving the
compressed gas. The barrel defines a counterbore disposed
concentrically about and adjacent the bore of the barrel. The air
gun further includes a seal at least partially disposed within the
circular counterbore. The seal is in sealing engagement with the
breech face of the receiver for sealing the bore and the gas port
between the barrel and the receiver. The seal includes a
cylindrical body. The cylindrical body extends along the
longitudinal axis. The seal includes a second flange that is
disposed at a second end of the cylindrical body, and extends
radially inward from the cylindrical body to a radial inner
surface. The radial inner surface includes a diameter less than a
diameter of the bore.
[0008] In another aspect of the invention, an air gun is provided.
The air gun includes a receiver. The receiver defines a gas port
that is configured for exhausting a compressed gas therethrough.
The air gun further includes a barrel. The barrel defines a bore
extending along a longitudinal axis of the barrel. The barrel
includes a barrel face. The bore is in fluid communication with the
gas port for receiving the compressed gas. The air gun further
includes a seal. The seal is in sealing engagement with the barrel
face and the receiver. The seal seals the bore and the gas port.
The seal also defines an interior diameter that is less than a
diameter of a projectile. The interior diameter engages at least a
portion of the projectile for retaining the projectile in place
until fired.
[0009] The above features and advantages and other features and
advantages of the present invention are readily apparent from the
following detailed description of the best modes for carrying out
the invention when taken in connection with the accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 is an enlarged, partial view in longitudinal
cross-section of a single-shot break barrel air gun incorporating a
first exemplary breech seal in accordance with an aspect of the
invention.
[0011] FIG. 2 is an enlarged cross-sectional view of the first
exemplary breech seal, with the breech closed.
[0012] FIG. 3 is an enlarged cross-sectional view of a second
exemplary breech seal, in accordance with another aspect of the
invention.
[0013] FIG. 4 is an enlarged cross-sectional view of a modified
washer seal, prior to installation in the barrel face.
[0014] FIG. 5 is an enlarged cross-sectional view of a third
exemplary breech seal incorporating the modified washer seal of
FIG. 4, in accordance with another aspect of the invention.
[0015] FIG. 6 is an enlarged cross-sectional view of an alternative
embodiment of a barrel incorporating the third exemplary breech
seal shown in FIG. 5.
[0016] FIG. 7 is an enlarged cross-sectional view of a fourth
exemplary breech seal, in accordance with yet another aspect of the
invention.
[0017] FIG. 8 is an enlarged cross-sectional view of a fifth
exemplary breech seal in an alternative embodiment of the air
gun.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0018] Referring to FIGS. 1 and 2, a break barrel air gun 10
includes a receiver 12 defining an internal compression chamber 14
for generating a quantity of compressed gas upon powered
translation of a piston 16 within the chamber 14. The piston 16 may
be powered by a coil spring, a gas spring, compressed gas, or some
other power source suitable for the air gun 10. A barrel 18 is
pivotally mounted on an end of the receiver 12, such that a barrel
face 20 defined on a rearward end of the barrel 18 is pivoted away
from a breech face 22, which is defined on a forward rend of the
receiver 12, to provide access to a breech 24, whereby a pellet 26
can be loaded into the breech 24. When closed to place the barrel
face 20 in general parallel-spaced opposition with the breech face
22, a barrel bore 28, which extends along a longitudinal axis 33,
is placed in general axial alignment with a gas transfer port 30
that is defined in the breech face 22, by which compressed air is
delivered from the compression chamber 14 to the barrel bore 28
upon firing. Alternatively, as is shown in FIG. 8, the gas transfer
port 30 may be disposed perpendicularly relative to the
longitudinal axis 33 of the barrel bore 28, and may not extend
through the breech face 22.
[0019] As best seen in FIG. 2, the air gun 10 includes a first
exemplary breech seal 32 in accordance with the invention.
Specifically, the barrel face 20 includes a circular groove 32 that
is generally concentric with and radially offset from the barrel
bore 28. The circular groove 34 is adapted to receive a seal 32,
which is at least partially disposed within the circular groove 32.
The seal 32 is in sealing engagement with the breech face 22 of the
receiver for sealing the barrel bore 28 and the gas port 30 between
the barrel 18 and the receiver 12. As shown in FIG. 2, the seal 32
may include an o-ring seal 36. A recessed annular land 38 is also
defined on the barrel face 20 between the circular groove 34 and
the barrel bore 28. The annular land 38 is disposed adjacent and
concentrically about the barrel bore 28. The maximum depth of the
annular land 38, relative to the barrel face 20, is less than the
nominal depth of the circular groove 34 relative to the barrel face
20. In other words, the annular land 38 is recessed from the barrel
face 20 a depth that is less than the depth the circular groove 34
is recessed from the barrel face 20. While the annular land 38 may
be formed generally orthogonal to the bore axis, in the first
breech seal 32, the annular land is provided with a radial draft
angle by which the land depth increases slightly with increasing
distance from the bore axis.
[0020] The first breech seal 32 is believed to provide an expansion
area that temporarily receives the high forces of compressed air
flow through the gas transfer port 30. These forces are allowed to
divert dynamically radially away from the pellet 26 seated in the
barrel bore 28 and are believed to improve the effectiveness of the
o-ring seal 36 by radially elastically deforming the o-ring seal 36
and, hence, increasing the seal's axial compression between the
opposed barrel face 20 and breech face 22. Further, the first
breech seal 32 is believed to dynamically absorb a portion of these
forces, thereby modulating piston back pressure to significantly
reduce the likelihood that the piston 16 will slam into the end of
the compression chamber 14, and increasing air gun smoothness. By
way of example, in a constructed embodiment of the first air gun
10, the use of the stepped breech seal pocket achieved improved
muzzle velocities of as much as thirteen percent, depending on
pellet caliber.
[0021] Referring to FIG. 3, a second exemplary breech seal 40 in
accordance with another aspect of the invention includes the
circular groove 34 and annular land 38 in the barrel face 20 as in
the first breech seal of FIGS. 1 and 2. The second breech seal 40
includes an annular washer 42 having outer diameter 44 that is
greater than an outer diameter of the circular groove 34. In other
words, the annular washer 42 is sized such that the annular washer
42 is slightly radially-compressed when placed into the circular
groove 34, such that the radially-innermost portion of the annular
washer 42 projects slightly away from the barrel face 20 prior to
closing the breech 24. Additionally, the annular washer 42 includes
a thickness measured along the longitudinal axis 33 that is greater
than the difference between the recessed depth of the circular
groove 34 and the recessed depth of the annular land 38 relative to
the barrel face 20. Having the thickness of the washer 42 greater
than the difference between the recessed depths relative to the
barrel face 20 ensures that the washer 42 extends beyond the barrel
face 20. While the invention contemplates use of any suitable seal
material, the seal may advantageously be formed from an elastomer
such as a urethane material, or of rubber, preferably having a
durometer of at least about 40, and preferably having a durometer
less than about 90. The annular washer may advantageously be
stamped or cut from sheet stock, molded, or cast depending upon
material choice.
[0022] In accordance with another aspect of the invention, the
washer's radial inner surface 46 includes diameter that is less
than a diameter of the barrel bore 28, which is slightly smaller
than the maximum skirt dimension of the pellet 26, such that the
pellet skirt 48 is retained by the washer's radially inner surface
46 upon closing the breech 24. In accordance with yet another
aspect of the invention, the washer's radially inner surface 46 is
provided with a contour or other surface feature to customize
initial pellet retention upon closing the breech, and/or the pellet
breakaway force. Thus, in a constructed embodiment, the radially
inner surface 46 retains the pellet skirt 48 slightly closer to the
barrel side of the washer's thickness, to improve pellet release
circumferential contact between the washer and the pellet skirt
upon closing of the breech, it will be appreciated that the
invention contemplates other configurations for the washer's
central bore, for example, by which to achieve three-point contact
with the pellet's skirt. The washer's central bore may
alternatively be provided with surface features, such as ribs or a
threadform, to achieve a repeatable breakaway force notwithstanding
nominal variation in skirt dimensions.
[0023] Referring to FIGS. 4 and 5, a third exemplary breech seal 50
in accordance with another aspect of the invention likewise
includes the circular groove 34 and annular land 38 in the barrel
face 20 as in the first and second breech seals 32, 40. In the
third breech seal 50, the annular washer 52 is formed with a
generally cylindrical body 54 and a radially-inward flange 56 which
projects slightly axially away from the cylindrical body 54 to
thereby project slightly toward the opposed breech face 22 when the
washer's cylindrical body 54 is received in the barrel face's
circular groove 34. The cylindrical body 54 includes a length along
the longitudinal axis 33 that is greater than the depth of the
circular groove 34 relative to the barrel face 20. The flange 56
includes a thickness measured along the longitudinal axis 33 that
is greater than the depth of the annular land 38 relative to the
barrel face 20. The flange 56 defines a radially inner surface 58
having a diameter that is less than the diameter of the barrel bore
28. Upon closure of the breech 24, the washer's radial flange 56
flexes axially to improve the quality of the seal, while also
radially contracting slightly to more securely retain the pellet
skirt 48. As in the second breech seal 40, the radially inner
surface 58 of the washer's radial flange 56 is provided with a
suitable contour and/or surface feature to provide a consistent
pellet retention force, such as a threadform (not shown), and to
nominally position the pellet skirt at a desired depth relative to
the barrel face 20.
[0024] Referring to FIG. 6, the third breech seal 50 is shown in
with an alternative embodiment of the barrel 100. The alternative
embodiment of the barrel 100 includes an outer portion 102 and an
inner portion 104. The outer portion 104 defines the annular groove
34, and includes a nut 106 disposed within the annular groove 34
and rotationally fixed about the longitudinal axis 33. The inner
portion 104 includes a threaded end 108, and is slideably disposed
within the outer portion 102. The threaded end 108 is in threaded
engagement with the nut 106 to secure the inner portion 104
relative to the outer portion 102. The inner portion 102 defines
the bore 28. Accordingly, in the configuration shown in FIG. 6, the
inner portion 104 of the barrel 18 may be replaced, such as for
example, to change the caliber of the air gun. The threaded end 108
of the inner portion 104 cooperates with the outer portion 102 to
define the circular groove 34. As such, the third breech seal 50 is
disposed within the circular groove 34, between the outer portion
102 and the inner portion 104 of the barrel 100. As shown in FIG.
5, the annular washer 52 is formed with a generally cylindrical
body 54 and a radially-inward flange 56 which projects slightly
axially away from the cylindrical body 54 to thereby project
slightly toward the opposed breech face 22 when the washer's
cylindrical body 54 is received in the barrel face's circular
groove 34. The cylindrical body 54 includes a length along the
longitudinal axis 33 that is greater than the depth of the circular
groove 34 relative to the barrel face 20. The flange 56 includes a
thickness measured along the longitudinal axis 33 that is greater
than the depth of the annular land 38 relative to the barrel face
20. The flange 56 defines a radially inner surface 58 having a
diameter that is less than the diameter of the barrel bore 28. Upon
closure of the breech 24, the washer's radial flange 56 flexes
axially to improve the quality of the seal, while also radially
contracting slightly to more securely retain the pellet skirt 48.
As in the second breech seal 40, the radially inner surface 58 of
the washer's radial flange 56 is provided with a suitable contour
and/or surface feature to provide a consistent pellet retention
force, such as a threadform (not shown), and to nominally position
the pellet skirt at a desired depth relative to the barrel face
20.
[0025] Referring to FIG. 7, a fourth exemplary breech seal 60 in
accordance with another aspect of the invention includes a
counterbore 62 defined in the barrel face 20. The counterbore 62 is
disposed concentrically about and adjacent the barrel bore 28. It
will be appreciated that a circular groove and annular land as in
the first, second, and third breech seals 32, 40, 50 may also be
used in place of the simple counterbore 62 as seen in FIG. 7. The
fourth breech seal 60 includes an annular washer 64 that includes a
generally cylindrical body 66 that extends along the longitudinal
axis 33, a radially-outward first flange 68 on one end of the
cylindrical body 66 that overlies at least a portion of the barrel
face 20 concentric with the counterbore 62, and a radially-inward
second flange 70 on the other end of the cylindrical body 66 that
projects radially inwardly to mechanically capture the pellet skirt
48. The first flange 68 is disposed between the barrel face 20 and
the breech face 22. The second flange 70 has an inner diameter that
is less than the diameter of the barrel bore 28, which is slightly
less than the nominal skirt diameter of the pellet 26, such that
the pellet skirt 48 is elastically retained within the washer's
second flange 70 prior to firing. As in the second and third breech
seals 40, 50, the inner surface 72 of the washer's second flange 70
preferably includes a contour to help retain the pellet skirt at a
predetermined depth relative to the barrel face 20. The counter
bore 62 extends a depth along the longitudinal axis 33 relative to
the barrel face 20, and the second flange 70 includes a thickness
along the longitudinal axis 33 relative to the barrel face that is
less than the depth of the counterbore 62. Accordingly, the depth
of the counterbore 62 and the second flange 70 may be sized to
substantially equal a length of the pellet 26, so as to engage both
a body of the pellet and the pellet skirt 48 (as shown), or
alternatively, may be sized so as to only engage the pellet skirt
48.
[0026] Referring to FIG. 8, a fifth alternative embodiment of the
breech seal is shown generally at 120. The fifth breech seal 120 is
shown in an alternative embodiment of the air gun 122. More
specifically, the fifth breech seal 120 is shown in an inline bolt
action air gun. The inline bolt action air gun 122 includes a
loading mechanism 124 for loading the projectile, i.e., the pellet
26. The loading mechanism 124 includes an inline bolt 126, which
moves axially along and inline with the longitudinal axis 33 to
move the pellet 26 into position within the breech of the barrel
18. The air gun 122 includes a receiver 128, which defines a gas
port 30. The gas port 30 is configured for exhausting a compressed
gas therethrough, into a firing chamber disposed behind the pellet
26, between the pellet 26 and a barrel face 130 of the loading
mechanism 124.
[0027] The barrel 18 defines a bore 28, which extends along the
longitudinal axis 33 of the barrel 18. The bore 28 is in fluid
communication with the gas port 30 for receiving the compressed
gas. The fifth breech seal 120 is in sealing engagement with the
barrel face 130 and the receiver 128 for sealing the bore 28 and
the gas port 30. The fifth breach seal 120 defines an interior
diameter 132 that is less than an outer diameter 134 of the pellet
26. The smaller interior diameter 132 of the fifth breech seal 120
engages at least a portion of the pellet 26, and retains the pellet
26 in place until fired. Preferably, the fifth breech seal 120
includes a durometer greater than or equal to 40 and less than or
equal to 90, so as to be able to flex as the pellet 26 is loaded
into a secured position by the bolt 126 of the loading mechanism
124, while still maintaining sufficient rigidity to secure the
pellet 26 in place until gas pressure behind the pellet 26 is
sufficient to fire the pellet 26.
[0028] As shown, the barrel may define a counterbore 62 disposed
concentrically about and adjacent the bore of the barrel. The fifth
breech seal 120 is at least partially disposed within the
counterbore 62. However, it should be appreciated that the air gun
122 need not include the counterbore 62, and the fifth breech seal
120 may be disposed in abutting engagement with, i.e., immediately
adjacent to, the breech face 22 of the barrel 18. As described
above, the loading mechanism 124 is configured for urging the
pellet 26 into a secured position within the seal 120, in
preparation for firing. When the loading mechanism 124 is
positioned in a firing position, the fifth breech seal 120 is
configured for sealing against the barrel face 130 of the loading
mechanism 124, i.e., against an end of the bolt 126 facing the
pellet 26. The seal may defines a port 138 adjacent and in fluid
communication with the gas transfer port 30, through which the
compressed gas flows.
[0029] In accordance with yet another aspect of the invention, in
each of the second, third, fourth and fifth breech seals 40, 50,
62, 120 through suitable selection of the washer's/washer flange's
internal diameter and contour, and the washer material's durometer,
the pellet breakaway force can be set such that the piston 16
finishes its movement within the compression chamber 14 and comes
to a complete stop at roughly the same time that the pellet 26
breaks from the washer. Thus, these breech seals 40, 50, 62, 120
advantageously permit the use of larger compression springs and
pistons with greater mass, without generating unwanted piston slam.
Further, the resulting improved seal quality permits use of larger
caliber projectiles with a given breech, thereby lowering air gun
cost and weight by allowing use of a smaller frame.
[0030] While the best modes for carrying out the invention have
been described in detail, those familiar with the art to which this
invention relates will recognize various alternative designs and
embodiments for practicing the invention within the scope of the
appended claims.
* * * * *