U.S. patent application number 11/583784 was filed with the patent office on 2008-04-24 for firearm bolt assembly with fully-supported bolt face.
Invention is credited to Jesse S. Gomez, Robert Bernard Iredale Clark, Paul Leitner-Wise.
Application Number | 20080092733 11/583784 |
Document ID | / |
Family ID | 39316677 |
Filed Date | 2008-04-24 |
United States Patent
Application |
20080092733 |
Kind Code |
A1 |
Leitner-Wise; Paul ; et
al. |
April 24, 2008 |
Firearm bolt assembly with fully-supported bolt face
Abstract
An improved bolt carrier for a firearm is provided that improves
the overall reliability and performance of the firearm bolt
assembly. The bolt carrier includes a bolt with a body having a
number of lugs extending therefrom. The bolt includes an extractor
recess sized and configured to avoid any undercut of the lugs
adjacent the recess. The bolt also includes an extractor pivotably
engaged in a recess formed in the bolt. The extractor has a pair
nipples on flanges configured to engage a pair of integrally
buffered springs disposed on a tapered spring well on either side
of a firing pin bore extending through the bolt.
Inventors: |
Leitner-Wise; Paul;
(Alexandria, VA) ; Iredale Clark; Robert Bernard;
(Bodmin, GB) ; Gomez; Jesse S.; (Fredericksburg,
VA) |
Correspondence
Address: |
Reed Smith, LLP
Suite 1400, 3110 Fairview Park Drive
Falls Church
VA
22042
US
|
Family ID: |
39316677 |
Appl. No.: |
11/583784 |
Filed: |
October 20, 2006 |
Current U.S.
Class: |
89/138 ;
89/33.01 |
Current CPC
Class: |
F41A 15/14 20130101;
F41A 3/26 20130101 |
Class at
Publication: |
89/138 ;
89/33.01 |
International
Class: |
F41A 15/00 20060101
F41A015/00 |
Claims
1. A bolt for a firearm, the bolt comprising: an elongate body
having a proximal end and an opposite distal end along a
longitudinal axis, said body defining a generally cylindrical
portion and a firing pin bore along said longitudinal axis between
said proximal and distal ends, said body further including a number
of bolt lugs adjacent said distal end integrally connected to and
radially extending from said body about said longitudinal axis,
said bolt lugs including at least a first bolt lug and an adjacent
second bolt lug; a recess formed in said body extending between
said first and second bolt lugs wherein the first and second bolt
lugs are not undercut by the recess; said body further defining a
pair of spring wells, a spring disposed within each of said spring
wells; and an extractor residing within said recess pivotably
coupled to said body.
2. The bolt of claim 1, wherein said extractor comprises: a first
portion for releasably engaging a cartridge extending between said
first and second bolt lugs; a second portion having a pair of
oppositely disposed flanges extending therefrom, and a body
extending between said first portion and said second portion.
3. The bolt of claim 2, wherein said first portion of said
extractor includes a guide flange extending therefrom.
4. The bolt of claim 2, wherein each of said pair of flanges of the
second portion includes a spring stabilizing nipple engaging a
corresponding one of said springs to bias said extractor to a first
position.
5. The bolt of claim 1, wherein each of said spring wells includes
a spring bearing surface, said spring bearing surface positioned
proximate said firing pin bore, said spring wells oppositely
disposed about said firing pin bore wherein the spring wells are
parallel to one another and perpendicular to the longitudinal axis
of the firing pin bore.
6. The bolt of claim 5, wherein each of said spring wells is
tapered.
7. The bolt of claim 5, wherein the spring has a base coil larger
than the rest of the spring coils.
8. The bolt of claim 7, wherein each of said springs is integrally
buffered.
9. The bolt of claim 1, wherein: said body includes an extractor
bearing portion within said recess adjacent said distal end, said
bearing portion including a mating surface, said mating surface
defining a curved plane extending substantially parallel to an
outer surface of said cylindrical body portion; and said extractor
includes a bottom surface configured to engage said mating surface
in form fitting relation.
10. The bolt of claim 9, wherein the mating surface defines a flat
plane, and said extractor includes a bottom surface configured to
engage said mating surface in form fitting relation.
11. An extractor for extracting a cartridge in an autoloading
firearm, the extractor comprising: a first portion for releasably
engaging a cartridge; a second portion having oppositely disposed
flanges extending therefrom; a spring stabilizing nipple extending
from the underside of each of said flanges; a body extending
between said first portion and said second portion, said body
having a pin bore therethrough to pivotably couple said extractor
to a firearm bolt.
12. A bolt carrier assembly for a firearm, the bolt carrier,
comprising: a bolt having a cylindrical body defining a firing pin
bore therethrough; said cylindrical body having an extractor
recesses for accommodating an extractor pivotably coupled to said
bolt, said extractor defining a pair of flanges extending
therefrom, said flanges having a spring stabilizing nipple
extending therefrom; and a pair of integrally buffered springs
oppositely disposed about said firing pin bore within said bolt,
wherein each of said nipples engages a corresponding one of said
springs.
13. The bolt carrier assembly of claim 12, wherein said body
includes an outer surface thereabout and a proximal end and distal
end along a longitudinal axis; and a number of lugs extending
radially from said body about said longitudinal axis such that a
first and second lug adjacent the extractor recess are not
undercut.
14. The bolt carrier assembly of claim 12, wherein said bolt
includes a parallel pair of tapered spring wells on either side of
a firing pin bore, each of said spring wells defining a
longitudinal axis perpendicular to the longitudinal axis of the
bolt.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to firearm bolt assemblies and
more particularly to the improved design of a bolt and extractor
for use therewith.
BACKGROUND OF THE INVENTION
[0002] The M-16 automatic rifle has been a standard weapon of
choice for the U.S. Military. The M-16 family of weapons includes
semi-automatic counterparts which are popular with the civilian
sector. The structure and mechanisms of these weapons, and
improvements and variations thereto, have been the subject of many
patents over the years. U.S. Pat. Nos. 2,951,424 and 3,198,076 to
Stoner provide early examples of the M-16 type of weapon. In recent
years, many variations and modifications of the M-16 family have
evolved.
[0003] Generally, the M-16 family of automatic and semi-automatic
rifles is based on a gas-operated bolt carrier system. The bolt
carrier system includes a multi-lug bolt that interlocks, within
the receiver, with a barrel extension engaged to the rifle barrel
for firing each round of ammunition. The bolt also includes a
spring-loaded extractor configured to releasably engage a cartridge
as it is placed in the firing chamber. When the rifle is fired, the
interlocked bolt receives the recoil force that is transmitted from
the face of the bolt to its lugs. The lugs in turn transmit the
recoil force to corresponding lugs of the barrel extension. Once
the round is fired, the bolt unlocks from the barrel extension and
the bolt carrier recoils. As it recoils, the extractor pulls the
expended cartridge from the firing chamber. The cartridge is then
ejected, as is well known in the art, to allow chambering of
another round by the bolt assembly. This process may then be
repeated as often as desired by the shooter until the last
cartridge is expended.
[0004] As used herein, "gun" or "firearm" refers to a completely
assembled weapon including not only a receiver operable to fire
rounds of ammunition, but also any other structure normally
associated with the given weapon. Also as used herein, a "receiver"
includes a barrel extension, barrel interface, or any other part or
assembly of a gun or firearm that has one or more surfaces
configured to engage lugs of a breech bolt.
[0005] The design of the bolt carrier and bolts used in such
weapons has been the subject of previous patents. For example, U.S.
Pat. No. 5,351,598 to Schuetz discloses a new type of bolt for an
automatic weapon. A portion of some of the lugs on the front face
of the bolt have been removed to allow easier chambering of short,
low pressure pistol cartridges in an M-16 rifle.
[0006] U.S. Pat. No. 6,182,389 to Lewis discloses a bolt with a
body having a number of lugs extending therefrom, as well as an
extractor pivotably engaged in a recess formed in the bolt, the
extractor having a pair of flanges configured to engage a pair of
springs disposed on either side of a firing pin bore extending
through the bolt.
[0007] While the prior art has addressed some of the deficiencies
in the design of bolts and bolt carriers of automatic and
semi-automatic rifles, there still exists many problems in the use
of such assemblies. It is well known that the bolts are subject to
failure due to the extreme stresses and temperatures to which they
are subjected from repeated firing of the gun. This problem is
particularly focused with respect to the lugs projecting from the
main body of the bolt. As described above, the lugs are used to
transfer the force from the firing of the cartridge to the barrel
of the rifle. This problem is exacerbated further by the fact that
automatic and semi-automatic rifles typically employ an
unsymmetrical locking system in order to accommodate the extractor.
The lack of symmetry of the load bearing portion of the bolt
results in an uneven stress distribution among the lugs. Thus, the
lugs of bolts for rifles are subject to structural failure due to
the repeated high stresses induced by firing the rifle.
[0008] One of the common structural failures occurs at the lugs
adjacent to the recess formed in the body of the bolt to
accommodate the extractor. In forming this recess, the adjacent
lugs are typically undercut and weakened relative to the other
lugs.
[0009] These failures limit the overall reliability of the weapon,
sometimes represented as Mean-Time-Between-Failure (MTBF). By
reducing the frequency of these failures, maintenance-actions for
the gun are correspondingly reduced and overall reliability is
improved.
[0010] Another problem known in the art involves the extractor that
is typically coupled to a bolt of an automatic or semi-automatic
rifle. The extractor is known to malfunction, thus causing a
jamming of the rifle due to the spent cartridge remaining in the
firing chamber. As previously described, the extractor is typically
spring-loaded. In the prior art extractors, the spring has a
relatively short length due to the small amount of space between
the outer surface of the bolt and the firing pin bore defined by
the bolt for receiving the firing pin. The short length of the
spring makes it much more difficult to control and maintain the
tension to ensure it remains at the proper setting.
[0011] While the prior art devices attempt to address some of the
problems with bolts and bolt carriers for rifles, there are still
problems existing in the art requiring a need for a bolt that
effectively addresses those problems. The present invention is
directed toward providing various improvements to bolt carriers and
bolts for automatic and semi-automatic rifles, and addresses the
problems and the shortcomings of the prior art in a novel and
unobvious way.
SUMMARY OF THE INVENTION
[0012] The present invention addresses the foregoing shortcomings
in the design of bolt carriers and bolts for automatic and
semi-automatic rifles. In accordance with one aspect of the present
invention, a bolt for a firearm includes an elongated body having a
proximal end and an opposite distal end along a longitudinal axis.
The body defines an intermediate portion having an outer surface. A
number of bolt lugs are integrally connected to the outer surface
of the intermediate portion and extend radially from the body about
the longitudinal axis. Each of the bolt lugs has an end face
adjacent the distal end of the body and an opposite bearing face.
Each lug also has a pair of sidewalls extending between the end
face and the bearing face.
[0013] In accordance with another aspect of the present invention,
the bolt includes an elongate body having a proximal end and an
opposite distal end along a longitudinal axis. The body defines a
generally cylindrical body portion having an outer surface and a
firing pin bore extending between the proximal and distal ends. The
body further includes a number of fully radiused bolt lugs
positioned adjacent the distal end integrally connected to the
body. The bolt lugs radially extend from the body about the
longitudinal axis. The bolt lugs include at least a first bolt lug
and an adjacent second bolt lug. An extractor-accommodating recess
is formed in the body between the first bolt lug and the adjacent
second bolt lug without undercutting either of said first and
second bolt lugs.
[0014] In a further aspect of the invention, the bolt body further
defines a pair of tapered spring wells oppositely disposed about
the firing pin bore in the recess and oriented such that their
longitudinal central axes are parallel. An integrally dampened
spring is disposed within each of the spring wells, and an
extractor is configured to reside in the recess and be pivotably
coupled to the body. The extractor includes a first portion
extending between the first and second bolt lugs, and an extractor
body extending to a second portion. The second portion of the
extractor body has a pair of oppositely disposed flanges extending
therefrom. Each of the flanges contains an integrally formed nipple
or spring stabilizing pin to engage the corresponding one of the
springs to bias the extractor between a first and second position
to releasably engage a cartridge. As used in this specification,
radiused means that care has been taken to round off the corners of
the embodiments of the present invention in order to ensure a more
even stress distribution.
[0015] In another aspect of the present invention, an
integrally-dampened spring sized and configured to minimize lateral
movement within the spring wells is disposed within each of the
spring wells.
[0016] In another aspect of the present invention, a bolt carrier
for a firearm is provided. The bolt carrier comprises a
conventional bolt carrier for an autoloading weapon system of the
M-16/AR15 family having a bolt defining a firing pin bore
therethrough and an extractor pivotably coupled to the bolt. A pair
of nippled flanges extend from the extractor. The flanges engage a
corresponding integrally dampened spring positioned on opposite
sides of the firing pin bore within the bolt.
[0017] It is one object of the present invention to provide an
improved extractor for a bolt used in a firearm that reduces or
prevents extractor failures.
[0018] It is another object of the present invention to provide an
improved lug design for a bolt that reduces or prevents structural
failure of the bolt.
[0019] It is yet another object of the present invention to provide
a reliable and safe design of a bolt and bolt carrier used with a
firearm.
[0020] It is yet another object of the present invention to provide
an integrally dampened extractor spring for a bolt used in a
firearm that reduces or prevents spring failures.
[0021] These and other objects of the present invention will be
more apparent from the following description of the figures and
preferred embodiments.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] FIG. 1 is a diagrammatic cross-sectional side view of one
embodiment of the present invention.
[0023] FIG. 2 is a three dimensional illustration of the bolt, the
integrally buffered spring and the extractor of one embodiment of
the present invention.
[0024] FIG. 3 is a top view of the bolt illustrated in FIG. 2.
[0025] FIGS. 4A, 4B, 4C and 4D are different views of the extractor
illustrated in FIG. 2.
[0026] FIG. 5 is a cross-sectional view of the bolt depicted in
FIG. 2 in the direction of A.
[0027] FIG. 6A is an illustration of a spring according to one
embodiment of the present invention.
[0028] FIG. 6B is a cross-sectional view of the bolt depicted in
FIG. 2 showing a pair of tapered spring wells containing integrally
dampened springs.
[0029] FIG. 7 is an end view of the bolt depicted in FIG. 2.
[0030] FIG. 8 is an end view of the barrel interface of the rifle
depicted in FIG. 1.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0031] For the purposes of promoting an understanding of the
principles of the invention, reference will now be made to the
embodiments illustrated in the drawings and language will be used
to describe the same. It should be understood that no limitation of
the scope of the invention is intended by the illustrations;
alterations and further modifications of the illustrated device and
such further applications of the principles of the invention as
illustrated herein being contemplated and fully expected to fall
within the scope of the invention.
[0032] A firearm according to one embodiment of the present
invention is depicted in FIG. 1 and designated generally as 10.
Firearm 10 has barrel 12 and magazine 14. Magazine 14 is
configured, as is well-known in the art, to feed cartridges 52 to a
cartridge chamber through cartridge chamber interface 18. The
cartridge chamber is defined by receiver 20. Receiver 20 includes
trigger assembly 22 with spring-loaded trigger 24, spring-loaded
hammer 26, and firing pin 28. Receiver 20 also defines a cavity
configured to house bolt carrier 32. Bolt carrier 32 includes a
bolt 34 residing therein. Bolt 34 defines firing pin bore 36 for
receiving firing pin 28 therethrough. Bolt 34 also includes a
spring-loaded extractor 42 pivotably coupled thereto. Extractor 42
has guide flange and is pivotably coupled by pivot pin 48 to bolt
34. Barrel 12 is coupled to barrel extension 50. Barrel extension
50 defines a firing chamber therein for receiving a cartridge 52
chambered by bolt carrier 32.
[0033] Referring now to FIGS. 2, 3 and 5, further description of
bolt 34, shown removed from bolt carrier 32, is provided. Bolt 34
defines an elongate body having a proximal end 54 and an opposite
distal end 56 along longitudinal axis L. Bolt 34 includes
integrally formed stem 58 adjacent proximal end 54. Circumferential
flanges 60 are integrally formed with stem 58. The flanges 60 form
a groove 62 therebetween for receiving a sealing ring (not shown).
Bolt 34 is also formed with a neck portion 64 extending from the
flanges 60 to cylindrical body portion 66. Cylindrical body portion
66 defines a first bore 68 and a second pin bore 70 therethrough.
Cylindrical body portion 66 also defines an outer surface 72
thereabout and a cartridge bearing surface 74 at distal end 56.
[0034] The outer surface 72 of the bolt 34 has a lug bearing
portion 76 adjacent distal end 56. Body portion 66 of bolt 34 also
defines extractor recess 78. The extractor recess 78, formed on the
outer surface 72, is in communication with firing pin bore 36 and
is configured to receive extractor 42 therein. An extractor bearing
portion 80 resides within extractor recess 78 adjacent distal end
56 and is integrally formed with body portion 66. Extractor bearing
portion 80 is configured to engage an underside 82 of extractor 42.
In a preferred embodiment, extractor bearing portion 80 includes a
mating surface 84 (see FIG. 2) defining a curved plane
substantially parallel to the outer surface 72 of the bolt 34 such
that cartridge bearing face 74 is circular. The underside 82 of
extractor 42 is also preferably curved so that it engages bearing
portion 84 in a form fitting engagement. In another embodiment,
underside 82 of extractor 42 and mating surface 84 define a
substantially flat plane.
[0035] Referring now to FIGS. 2 and 4A-4C, extractor 42 includes a
guide flange 44 at first portion 90, extractor flanges 92 at second
portion 94, and an extractor body 96 extending therebetween.
Extractor recess 78 is positioned on cylindrical body portion 66
such that first portion 90 of extractor 42 substantially coincides
with distal end 56 of bolt 34. Lip 98 of extractor 42 is then
biased between a first and second position to removably retain a
cartridge (not shown) in cartridge recess 100 (see FIG. 5) formed
at distal end 56. At the underside 82 of each of the flanges 92 of
extractor 42 is a spring stabilizing pin or nipple 102 designed to
engage an integrally dampened extractor spring 104.
[0036] Cartridge recess 100 includes cartridge bearing face 74. The
retained cartridge resides within cartridge recess 100 such that
the end of the cartridge bears against bearing face 74 to transfer
the load from firing the cartridge to the bolt 34. Extractor mating
surface 84 defines a portion of the circumference of cartridge
bearing surface 74.
[0037] Preferably, the circumference of cartridge bearing surface
74, including the portion defined by mating surface 84, is circular
and cartridge bearing surface 74 receives the entire circular end
portion of the retained cartridge in bearing engagement. In another
embodiment, mating surface 84 and underside 82 of extractor 42
define a flat plane, and the circular end of the retained cartridge
is not fully received in bearing engagement against cartridge
bearing surface 74. A portion of the end of the cartridge projects
above mating surface 84. In the preferred embodiment, the
co-extensive bearing surface reduces and more evenly distributes
the stress on the bolt lugs created during firing and extraction of
the cartridge. Extractor 42 also includes pin receiving portion 110
extending therefrom. Pin receiving portion 110 defines extractor
bore 112 therethrough. Extractor bore 112 is configured to align
with pin bores 70 when extractor 42 is positioned within extractor
recess 78. Pivot pin 114 is extended through pin bores 70 and
extractor bore 112 to pivotably engage extractor 42 to bolt 34.
[0038] Referring to FIG. 2 and FIG. 6B, extractor recess 78 is
provided with a pair of spring wells 116. Spring wells 116 are
formed in body portion 66 on opposite sides of firing pin bore 36.
The central axes of the spring wells 116 are parallel to one
another and are perpendicular to the longitudinal axis of the bolt.
Spring wells 116 are each configured to receive an extractor spring
104 therein as more clearly illustrated in FIG. 2. The spring wells
116 are preferably tapered, and are sized and configured to receive
a spring 104 that is preferably sized and configured with a
slightly larger base coil 105 in order to minimize lateral movement
of the spring 104 inside the well 116. (See FIGS. 6A and 6B).
Referring to FIG. 6B, the larger base coil 105 allows the spring to
be captured at the bottom of the spring well; the buffer dampens
spring bounce; and the tapered spring well minimizes spring contact
with the walls under distortion. In a preferred embodiment, the
base coil is about 5% larger in diameter than the rest of the
spring coils. When extractor 42 is engaged to bolt 34 as described
above, each one of the nipples 102 on the flanges 92 engages a
corresponding spring 104 positioned in a spring well 116. The
preferred dimensions, in inches, of a spring and spring well
according to one embodiment of the present invention are shown in
FIG. 6B. The degree of taper of the spring well 116 is shown as an
angle .theta.. Angle .theta. is preferably in the range from about
2 to about 6 degrees, more preferably, about 4.sup.0. In a
preferred embodiment, each spring 104 contains an integral buffer
120. The springs 104 are configured to pivotably bias extractor 42
radially inward to allow lip 98 to engage the rim of a cartridge.
However, springs 104 must have the requisite flexibility to allow
movement of extractor lip 98 radially outward to eject a
cartridge.
[0039] The positioning of integrally dampened springs 104 inside
the tapered spring wells 116 provides many advantages over prior
art bolt designs. Lateral movement of the springs is decreased not
only by the larger-base coil design of the springs 104 and the
tapered spring wells 116, said lateral movement is further
decreased by the engagement of the springs by the extractor nipples
102 on the underside 82 of the flanges 92 of extractor 42.
Vibrational motion of the spring is further dampened by use of an
integral buffer 120. The integral buffer 120 can be made with any
material known in the art. The buffer material should be heat
resistant to at least 500 degrees Fahrenheit; leaving no chance of
burning from the heat generated by the rifle.
[0040] Referring now to FIG. 7, lug bearing portion 76 includes a
number of bolt lugs 130a, 130b; 132a, 132b; 134a, 134b; and 136. To
spread the recoil forces as evenly as possible, the bolt preferably
has an odd number of lugs spaced, with the exception of the lugs
adjacent to the extractor recess, equidistant apart. For example,
the bolt depicted in FIG. 7 has seven lugs. Each bolt lug radially
extends about the longitudinal axis of the bolt. Lugs 130a, 130b
are collectively designated as lug pair 130 and extend opposite
each other. Lugs 132a, 132b are designated as lug pair 132 and
extend radially opposite each other. Finally, lug pairs 134a, 134b
are designated as lug pair 134 and likewise extend radially
opposite each other. Bolt lug 136 has no paired lug and extends
radially opposite extractor 42, which is positioned between
adjacent first lug 130a and second lug 134b.
[0041] Each adjacent pair of bolt lugs defines a gap 138
therebetween. The first lug 130a and the second lug 134b are
adjacent to one another and define an extractor gap 140. Extractor
gap 140 is configured to receive the first portion 90 of extractor
42. Each lug 130a, 132a, 134a, 136, 130b, 132b, and 134b defines a
corresponding end face 142a, 142b, 142c, 142d, 142e, 142f and 142g
(collectively designated as end face 142), respectively and a pair
of sidewalls 144. In the prior art, first lug 130a and second lug
134b are most susceptible to failure because they are undercut by
the extractor recess in order to accommodate the first portion 90
of the extractor 42. In a preferred embodiment of the present
invention, first lug 130a and second lug 134b are not undercut by
the extractor recesses as the mating surface 84 does not extend
under the plain of the sidewall 144 of the first lug 130a and
second lug 134b.
[0042] Receiver 20 also includes barrel extension 50 as illustrated
in FIG. 1. Barrel extension 50 is configured to interlock with lug
portion 76 of bolt assembly 32 during firing of the firearm. Barrel
extension 50 includes a barrel receiving end opposite a bolt
receiving end. Adjacent the barrel receiving end is a connecting
portion which is configured to engage barrel 12 as is known in the
art.
[0043] The bolt receiving end includes extension lugs 212. (See
FIG. 8). Extension lugs 212 define receiving gaps 214 therebetween.
Feed ramp 216 is defined proximate a pair of adjacent extension
lugs 212 to facilitate insertion of a cartridge and lug portion 76
through bolt receiving end 204. Each extension lug 212 defines an
interlock face which engages a corresponding one of the lug bearing
faces of the bolt lugs.
[0044] In operation, bolt carrier 30 moves in a reciprocal fashion
along longitudinal axis L when rounds are fired from firearm 10 in
a conventional automatic or semi-automatic manner. This operation
is well-known in the art. U.S. Pat. No. 2,951,424 to Stoner, U.S.
Pat. No. 3,198,076 to Stoner, and U.S. Pat. No. 5,351,598 to
Schuetz provide further information pertinent to this process and
are incorporated herein in their entireties. Generally, the
operation begins with a cartridge from magazine 14 being fed into
cartridge recess while bolt 34 is in the open position, as shown in
FIG. 1. Bolt 34 then slides forward in the direction indicated by
arrow B to position the cartridge in firing chamber 16. As bolt 34
moves forward, the lug pairs 130, 132, 134, and lug 136 of lug
portion 76 pass by the extension lugs 212 of barrel extension 50 in
interdigiting fashion through receiving gaps 214. Likewise, guide
flange 44 passes through a receiving gap 214. Simultaneously,
extension lugs 212 pass through a corresponding gap 138 or 140 of
lug portion 60.
[0045] After the lugs of bolt 34 and barrel extension 50 have
passed in interdigiting fashion, bolt carrier 32 continues to move
in the direction of arrow L, causing the bolt 34 to rotate about
axis L and interlock the bolt 34 in a closed position. (See FIG.
1). Lug portion 76 rotates in interlock chamber 210 of barrel
extension 50 as is well known in the art, causing the bolt 34 to
interlock with the barrel extension 50. Once the bolt 34 is
interlocked with barrel extension 50, the cartridge in firing
chamber 16 may be fired by pulling trigger 24. The pulling motion
on trigger 24 rotates the hammer 26 from an engaged cocked
position, as shown in FIG. 1, to an unengaged position. Hammer 26
rotates to strike firing pin 28. Firing pin 28 moves within firing
pin bore 36 of bolt 34 to strike the cartridge in firing chamber
16, causing the cartridge to fire.
[0046] After firing a cartridge, bolt 34 is rotated to unlock from
barrel extension 50 and bolt carrier 32 recoils back in receiver 20
in a direction opposite arrow L to an open position, as shown in
FIG. 1. As the bolt carrier 32 recoils, ejector pin 40 in shaft 38
is driven towards distal end 56 until it engages the spent
cartridge held in cartridge recess by lip 98 of extractor 42. The
operation of ejector pins is well-known in the art, and will not be
discussed in detail herein. The ejector pin 40 ejects the spent
cartridge by rotating the cartridge away from the cartridge recess.
The rotation of the cartridge causes extractor 42 to rotate about
pivot pin 114 from its first position, compressing springs 104. The
extractor 42 rotates sufficiently to disengage lip 98 of extractor
42 from the rim of the cartridge. Once the cartridge is released
from lip 98, springs 104 again bias extractor 42 to return to its
first position. When the next cartridge is chambered, the extractor
42 again rotates from its biased first position to allow the lip 98
to engage a cartridge and releasably retain it in the cartridge
recess. This operation is repeated at the discretion of the shooter
to consecutively load and fire cartridges. It should be understood
the present invention contemplates the use of other ejector systems
known to those skilled in the art.
[0047] The firing of a cartridge in firing chamber 16 causes a
recoil force in the direction opposite arrow L. Bolt lug pairs 130,
132, 134 and lug 136 bear against a corresponding interlock face of
the extension lugs 212. Thus, a load bearing relationship is formed
between lug pairs and the extension lugs. The force from firing the
cartridge is transferred from lug portion 76 of the bolt 34 to the
extension lugs 212. This force has been known to create large shear
stresses at the interface between the bolt lug pairs and
cylindrical body portion 66. Rapid and/or repeated firing of the
cartridges is known to cause fatigue failure of the bolt lugs at
this interface. The problem becomes even more severe due to the
unsymmetrical pattern created by the lug pairs 130, 132, 134 and
unpaired lug 136. The lack of symmetry results in an unbalanced
stress distribution among the bolt lugs. As a result, first bolt
lug 130a and second bolt lug 134b share a disproportionate burden
of the load.
[0048] As clearly illustrated by FIG. 6 of U.S. Pat. No. 6,182,389,
the disclosure of which is incorporated herein in its entirety, not
only do the first and second lug bolt lugs bear a disproportionate
burden of the load, they also have an extractor undercut that
further structurally weakens them leading to a high failure rate.
On the other hand, and as clearly illustrated in FIGS. 2 and 7
herein, the first and second bolt lugs of the preferred embodiment
of the present invention are not undercut to accommodate the
extractor. Moreover, the lug portion 76 is fully radiused in order
to have a more even stress distribution.
[0049] The present invention also contemplates bolt lug patterns
that vary from the pattern illustrated in FIGS. 2-7. In one
embodiment, the bolt 34 is provided with five bolt lugs in lieu of
the seven bolt lugs depicted in FIG. 7. Another embodiment
contemplates nine bolt lugs. Other embodiments contemplate more or
less bolt lugs as would occur to one skilled in the art.
[0050] It has also been found that the above-described
configuration of extractor 42 and bolt 34 is particularly
advantageous. The addition of flanges 92 to extractor 42 allows the
springs 104 to be positioned on either side of firing pin bore 36.
Referring to FIG. 4C, it can be observed that addition of spring
stabilizing nipples 102 to the flanges 92 of extractor 42 helps to
stabilize the spring against lateral motion leading to more
reliable operation. The prior art springs are more susceptible to
fatigue failure given their excessive lateral motion inside the
spring wells 116. Additionally, the dampening of the springs using
buffers 120 also reduces spring vibration thus providing more
reliable operation of the extractor 42.
[0051] Preferably, the springs 104, extractor 42 and bolt 34 are
manufactured from a metal material suitable for use in firearms
using techniques known to those skilled in the art. Furthermore, it
is preferred that bolt 34 and extractor 42 be formed from a single,
unitary piece of metal; however, in alternate embodiments, bolt 34
and extractor 42 may be made by coupling two or more separate
components as would occur to one skilled in the art. Also, it is
contemplated that extractor 42, bolt 34, and springs 104 may be
formed from different materials suitable for their intended
purpose.
[0052] While the invention has been illustrated and described in
detail in the drawings and foregoing description, the same is to be
considered as illustrative and not restrictive in character, it
being understood that only the preferred embodiments have been
shown and described and that all changes and modifications that
come within the spirit of the invention are desired to be
protected.
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