Note: Descriptions are shown in the official language in which they were submitted.
CA 02558836 2006-09-05
TRIGGER MECHANISM FOR FIREARMS WITH SELF-LOADING ACTIONS
BACKGROUND OF THE INVENTION
This invention relates to firearms and weapons in general, and in particular
to a
trigger mechanism particularly intended for firearms with self-loading
actions.
Self-loading actions are those where the next round loads after a round has
been
discharged, whether semi-automatic or automatic. Once the firearm is cocked,
the
operator must only pull the trigger to fire a round and load the next
available round
from a magazine, belt or other storage device. As long as there is ammunition
available the firearm will be ready to fire the next time the operator pulls
the trigger.
Self-loading firearms operate either in open-bolt or closed-bolt fashion. This
refers to
the position of the bolt and carrier. The bolt houses the firing pin and locks
together
with the barrel during firing. It is responsible for holding the case of the
bullet in the
chamber of the barrel and withstand the considerable pressure and recoil that
occur.
The carrier holds, guides and locks/unlocks the bolt from the barrel. It is
the motion
of the bolt and carrier, as a result of expanding gas from the fired bullet,
that causes
the firing mechanism to be reset and the next round to be loaded from the
magazine
into the ready to fire position.
Typically a closed-bolt rifle is more accurate than an open-bolt rifle. The
drawback of
a closed-bolt rifle is the occurrence of "cook-off' under extended heavy rates
of fire.
"Cook-off' is the condition where the heat of the barrel and chamber of the
rifle
initiate the next loaded round without the trigger being pulled. This is a
dangerous
condition where the rifle may fire without the intent of the operator. An open-
bolt rifle
avoids this, and thus can operate at prolonged higher rates of fire.
In the prior art, at least one mechanism allows the firearm to operate in a
closed-bolt
mode or open-bolt mode. However, while switching from open-bolt mode
(automatic)
to closed-bolt mode, there is a loud mechanical motion of the carrier to the
closed-
bolt position. This noise and motion is considered undesirable from the
operator's
standpoint in terms of sound signature while trying to maintain stealth, and
potential
surprise/confusion over the motion of the carrier.
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SUMMARY OF THE INVENTION
The invention provides a novel trigger mechanism incorporating unique fire
control
logic. "Logic" in this context refers to the behavior of the weapon depending
on
various conditions, or more specifically, the chain of events that comprise a
full cycle
of the weapon from pulled trigger through to the home position.
One aspect of the invention is that it allows the firearm to operate in a
closed-bolt
mode during semi-automatic fire (when accuracy is desirable) and operate in an
open-bolt mode (when high heat conditions exist) to avoid possible cook-offs.
The
mode change occurs when the first round is discharged after the selector has
been
moved instead of when the selector switch is moved, and thus there is no
undesirable noise or motion as in the prior art.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention will now be described in greater detail with reference to the
accompanying drawings of a preferred embodiment of the trigger mechanism, in
which:
Fig. 1 is a cut-open perspective view of relevant portions of a representative
rifle
embodying the trigger mechanism, with the rifle barrel, gas chamber, firing
pin and
other typical components removed for clarity;
Fig. 2 is a generally corresponding cut-open side view;
Fig. 3 is a generally corresponding exploded perspective view;
Fig. 4 is a perspective view of the auto-sear;
Figs. 5A and 5B are opposite side perspective views of the hammer;
Figs. 6A and 6B are lower and upper perspective views of the trigger;
Fig. 7 is a perspective view of the disconnect;
Fig. 8 is a perspective view of the disconnect in combination with the
trigger;
Fig. 9 is a perspective view of the carrier sear;
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Figs. 10A and 10B are upper and lower perspective views of the auto-sear;
Fig. 11 is a cross-section showing the safety sear and carrier sear together;
Figs. 12A, 12B and 12C are various perspective views of the auto-disconnect;
Fig. 13 is a perspective view of the selector;
Fig. 14A is a side view of the selector, and Figs. 14B-D are various cross-
sectional
views thereof;
Fig. 15 shows the primary components for closed-bolt operation, and the home
position of the closed-bolt operating cycle;
Fig. 16 shows Step 1 of the closed-bolt operating cycle;
Fig. 17 shows Step 2 of the closed-bolt operating cycle;
Fig. 18 shows Step 3 of the closed-bolt operating cycle;
Fig. 19 shows Step 4 of the closed-bolt operating cycle;
Fig. 20 shows Step 5 of the closed-bolt operating cycle (the home position
again);
Fig. 21 shows Step 1 of the open-bolt operating cycle;
Fig. 22 shows Step 2 of the open-bolt operating cycle;
Fig. 23 shows Step 3 of the open-bolt operating cycle;
Fig. 24 shows Step 4 of the open-bolt operating cycle;
Fig. 25 shows the selector moved from the automatic mode (open-bolt operation)
to
the semi-automatic mode (closed-bolt operation), to begin the transition from
open-
bolt to closed-bolt;
Fig. 26 shows the trigger depressed, initiating a semi-automatic cycle from
automatic
mode;
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Fig. 27 shows the safety sear and carrier sear held down and away from the
carrier
when the trigger is released, after one round has been fired, so that the
firearm is
now in the closed-bolt configuration;
Fig. 28 shows the selector moved from the semi-automatic mode (closed-bolt
operation to the automatic mode (open-bolt operation), to begin the transition
from
closed-bolt to open-bolt; and
Fig. 29 shows the weapon part way through the automatic cycle, with the
trigger
remaining depressed and the firearm therefore continuing to cycle until the
trigger is
released or ammunition is depleted.
DETAILED DESCRIPTION
Referring now to the accompanying drawings, the preferred embodiment will be
described in detail. It should be understood that this is an example of the
invention
only, and that other embodiments and variations are possible within the scope
of the
invention.
Figs. 1-3 show the primary components of the trigger mechanism, embodied in a
rifle
1. For simplicity, many conventional elements of the rifle are not
illustrated, other
than the receiver 2, grip 3, trigger guard 4, and carrier 5. The main
components for
operation of the invention are the auto-sear 6, the hammer 7, the trigger 8,
the
disconnect 9, the carrier sear 10, the safety sear 11, the auto-disconnect 12,
and the
selector 13.
The preceding main components of the preferred embodiment will be described
first,
followed by a description of closed-bolt operation, then open-bolt operation,
then the
mechanism which integrates the two modes of operation and permits switching
between them.
Components of the Preferred Embodiment
Auto-sear
Fig. 4 shows the auto-sear 6. The purpose of the auto-sear is to prevent the
hammer
from moving unless the carrier is in its fully forward position. The auto-sear
is acted
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on in a clockwise direction by a spring 19, so that surface 18 engages a notch
25 in
the hammer unless rotated by the carrier. Thus a round cannot be fired unless
the
bolt is locked with the barrel. In fully automatic mode, the auto-sear is the
only
element preventing the hammer from moving while the trigger is depressed, i.e.
it is
the mechanism that releases the hammer and once the carrier is fully forward,
to fire
the round.
The auto-sear pivots around a pivot axis 15, provided by a auto-sear pin 16 in
the
receiver 2 (see Figs. 1-3). The carrier 5 contacts the surface 17 and rotates
the auto-
sear forward (counter-clockwise when viewed from the left side as in Fig. 2),
disengaging it from the hammer. Until the auto-sear is so rotated by the
carrier, the
surface 18 sears with a notch in the hammer, blocking rotation of the hammer.
Hammer
Figs. 5A and 5B show the hammer 7. The hammer rotates on a hammer pin 20
mounted in the receiver and so that surface 21 strikes the firing pin,
transferring
energy stored in the hammer spring 22 (see Figs. 2 and 3) to the firing pin
with
sufficient energy to initiate the primer in the ammunition, thus firing the
round.
The carrier also pushes back against surface 21 as it moves backwards, to
reset the
hammer against the hammer spring. Surface 23 sears with the disconnect to
interrupt the semi-automatic cycle after one round while the trigger remains
pulled.
(The disconnect is cammed out of interference in full automatic mode and thus
does
not engage this surface and allows the cycle to continue.) Surface 24 engages
the
trigger. The trigger interferes with the rotation of the hammer by engaging
this notch
when the trigger is not pulled. The auto-sear engages surface 25. When the
carrier is
not in the fully forward position, the auto-sear is able to interfere with the
rotation of
the hammer by engaging this notch. The hammer is acted on in a counter-
clockwise
direction by a spring.
Tri er
Figs. 6A and 6B show the trigger 8. The trigger of course controls the
selected firing
cycle of the weapon. It interferes with the motion of the hammer when not
depressed. In automatic mode it provides the pivotal input to move the carrier
sear to
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disengage it from the carrier. The trigger also provides a support for the
disconnect
which limits the semi-automatic cycle to one round only per depression of the
trigger.
While in safe mode the movement of the trigger is prohibited. Immobilizing the
trigger
either by selecting the safe mode or by the default function of a grip safety
(not
shown), prevents the weapon from being able to cycle.
The trigger rotates on trigger pin 31. The operator's finger pulls on surface
32 to fire
the weapon. The edge 33 sears with the hammer. It engages a notch in the
hammer
interfering with its ability to rotate. The surface 34 is cut away to allow
retention of
the pivot axis pin by means of a spring wire engaging a groove in the pin. The
surface 35 acts against the safety sear / carrier sear sub-assembly to
disengage the
sears from the carrier during automatic mode open-bolt operation. The pocket
36
exists for a spring to provide a separating force between the trigger and
disconnect.
The slot 37 houses and aligns the disconnect.
Disconnect
Fig. 7 shows the disconnect 9, and Fig. 8 shows the disconnect in combination
with
the trigger 8.
The purpose of the disconnect 9 is to interrupt the firing cycle to allow only
one round
to be fired in semi-automatic mode. While the trigger is depressed, the
disconnect is
presented in interference to the hammer. Since the disconnect is spring loaded
with
respect to the trigger, the hammer pushes the disconnect out of the way as the
carrier pushes the hammer back, resetting the mechanism. As the hammer reaches
the fully reset position the disconnect engages the hammer, preventing it from
moving forward. As the trigger is released the disconnect releases the hammer
but
not prior to the trigger engaging the hammer and thus preventing the weapon
from
firing. This is the fundamental principle behind the operation of semi-
automatic mode
in a fully automatic capable weapon.
The disconnect and the trigger both pivot on the trigger pin 31 (see Figs. 1-
3). Edge
42 engages the hammer in the fully reset position and when the trigger is
depressed,
thus presenting this edge in interference with the corresponding surface on
the
hammer. When the selector is in full automatic mode, it contacts surface 43 on
the
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disconnect to prevent motion of the disconnect, effectively removing or
"disconnecting" it from its ability to engage the hammer. Since the disconnect
cannot
engage the hammer, the weapon will continue to cycle rounds until ammunition
has
been depleted or until the trigger is released. Notch 44 allows for clearance
with the
selector when the selector has been moved to the semi-automatic position. This
allows the disconnect to move with the trigger as it is depressed, presenting
the
disconnect in interference with the hammer. A pocketed spring 45 acts on
surface to
rotate the disconnect counter-clockwise with respect to the trigger (see Fig.
8).
Fig. 8 shows the trigger and disconnect in section. The trigger 8 blocks the
counter-
clockwise rotation of the disconnect at point 46. Effectively the disconnect
can move
clockwise a small distance against the spring force to allow engagement with
the
hammer.
Carrier Sear
Fig. 9 shows the carrier sear 10, whose purpose is to hold the carrier in the
rearward
position. The carrier sear pivots about pivot pin 51 (see Figs. 1-3) and
engages a
notch in the bottom of the carrier and holds it in the rearward position when
the
weapon is in automatic mode and the trigger is released. When the trigger is
pulled,
it cams the carrier sear to disengage it from the carrier and initiate the
automatic
cycle.
Surface 52 is cut away to allow retention of the pivot axis pin by means of a
spring
wire engaging a groove in the pin. Surface 53 sears with the carrier to
interrupt the
automatic cycle. When the trigger is depressed, this surface disengages from
the
carrier and the automatic cycle begins. Slot 54 houses and aligns the safety
sear 11.
Pocket 55 houses a spring that separates the safety sear from the carrier
sear.
Surface 56 is blocked by the selector when in safe mode to prevent any
downward
motion of the carrier sear, thus preventing forward movement of the carrier in
open-
bolt mode, and thus accidental preventing firing (in addition to the selector
then also
blocking movement of the trigger).
Safety Sear
Figs. 10A and 10B are perspective views of the safety sear 11, and Fig. 11
shows
the safety sear and carrier sear together in cross-section. The safety sear
pivots
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about pivot pin 51, i.e. on the same pin and axis as the carrier sear, and
holds the
carrier in a rearward position in the event of incomplete charging action.
This
prevents a round from being chambered, since the point at which the safety
sear can
engage the carrier precedes the picking up of a new round or the subsequent
engagement of the carrier sear. The carrier sear engages a notch in the bottom
of
the carrier and holds it in the rearward position when the weapon is in
automatic
mode and the trigger is released. When the trigger is pulled, it cams the
carrier sear
to disengage it from the carrier and initiate the automatic cycle.
Edge 62 sears with a notch in the bottom of the carrier. When the trigger is
depressed it pushes against surface 63 to rotate the safety sear away from the
carrier. The safety sear will travel a short distance until it hits the
carrier sear, at
which point both will continue to move as a pair away from the carrier,
preventing
either from engaging the carrier. Surface 64 is acted on by a pocketed spring
65
within the carrier sear to separate the two, moving the safety sear counter-
clockwise
with respect to the carrier sear. Surface 66 is engaged by the auto-disconnect
in
semi-automatic mode to capture both the safety sear and the carrier sear down
and
away from the carrier.
Auto-disconnect
Figs. 12A-12C show various views of the auto-disconnect 12, which pivots about
auto-disconnect pin 71 and whose purpose is to hold the safety sear and
carrier sear
away from the carrier when the weapon is in semi-automatic mode. The auto-
disconnect is free to engage the safety sear in semi-automatic mode. This
occurs
once the trigger is depressed and the safety sear over-travels the auto-
disconnect,
capturing it. At this point the carrier sear is moving with the safety sear as
a single
unit.
Surface 72 engages the safety sear as the safety sear over-travels the auto-
disconnect. It prevents the safety sear and subsequently the carrier sear from
rising
under the influence of their respective springs. Groove 73 holds a spring wire
that
influences the safety sear in the counter-clockwise direction. Surface 74 is
cammed
by the selector when switched to automatic mode, to release the safety sear
and
carrier sear, allowing either of them to engage the carrier as conditions
permit.
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Surface 75 is cut away to allow retention of the pivot axis pin by means of a
spring
wire engaging a groove in the pin.
Selector
Figs. 13A and 13B show the selector 13, which pivots in hole 81 and whose
purpose
is to control the mode in which the firing mechanism operates. The operator
moves
the selector arm 82, sweeping it through a 90° arc with detents to
select one of three
specific operating modes: safe, semi-automatic or automatic. The selector
accomplishes this by presenting material in interference or slots/grooves to
allow
movement of various components, as can be seen from Figs. 14A - 14D. There are
several different slots of different shape and orientation along the body of
the
selector depending on which component it is interacting with. The arm 82 at
one end
of the body is the lever by which the operator selects the mode. There is
another arm
that attaches to the selector on the opposite end of the cylinder to retain it
in the
receiver of the firearm. This allows for ambidextrous manipulation of the
selector.
(Note that there is only one selector arm 82 shown in the drawings. The second
is
attached during assembly of the firearm, to retain the selector in the
receiver and to
provide for operation from either side of the weapon.) A portion 83 of the cam
track
interfaces with the auto-disconnect in safe mode. This ensures that the auto-
disconnect is cammed out of engagement with the safety sear and allows it to
rise
and the selector to rotate into the safe position. Recess 84 allows the auto-
disconnect to be moved by its spring to engage the safety sear, thus capturing
it in
semi-automatic mode. Surface 85, like surface 83, ensures that the carrier and
safety sear can rise to engage the carrier in automatic mode. Surfaces 86 are
both
positioned to interfere with motion of both the trigger and the carrier sear
when the
selector is in the safe position. Conversely gap 87 allows motion of the
carrier sear,
allowing the trigger to be pulled.
Closed-Bolt Operation
This section describes how the invention operates in a manner analogous to a
traditional closed-bolt weapon, i.e. when in closed-bolt mode.
When a self-loading weapon cycles, there are many moving parts that interact
with
each other to ensure that the firing mechanism is reset and the next available
round
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of ammunition is loaded and ready to be fired. When a weapon is firing on
fully
automatic, this cycle continues repeatedly as long as the trigger is pulled
until the
source of ammunition has been depleted. The energy for all of these actions
comes
from expanding gases tapped from the barrel of the gun when a round is fired.
The cycle will stop when interrupted, either by the operator releasing the
trigger or, in
the case of a semi-automatic firearm, after only one round despite maintaining
a
depressed trigger. It is important to understand that the cycle is still ready
to continue
in either case, as long as ammunition is present, when the operator again
depresses
the trigger.
The difference between closed-bolt and open-bolt operation is defined by the
position of the carrier and bolt when the cycle is interrupted. In a closed-
bolt system
the interruption occurs when the carrier is in the forward position and the
bolt is
locked with the barrel and a round is in the chamber. When the trigger is
pulled the
only internal moving parts are the trigger and the released hammer as it
strikes the
firing pin. This explains why closed-bolt operation is inherently more
accurate, since
the number of moving parts prior to the initiation of the round is minimized.
Fig. 15 shows the mechanism in its closed-bolt home position, with the trigger
8, the
selector 13, the disconnect 9, the hammer 7, the auto-sear 6, the firing pin
90, and
the carrier 5. In this position, the weapon has been cocked and is ready to
fire. The
firing mechanism has been reset and there would be a round in the chamber.
Fig. 16 shows Step 1 of the operating cycle, which is immediately after the
trigger 8
has been pulled. The hammer 7 is just starting to move counter-clockwise under
the
force of its spring. Note that since the carrier 5 is in the forward position,
the auto-
sear 6 is disengaged from the hammer, allowing it to move. (In semi-automatic
mode
the safety sear serves as a safety device, preventing the hammer from striking
the
firing pin if the carrier is not fully forward and thus the bolt being locked.
It is a
potentially dangerous situation if a round is fired without the bolt being
locked.)
Fig. 17 shows Step 2 of the operating cycle. The hammer 7 strikes the firing
pin 90,
initiating the round.
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Fig. 18 shows Step 3 of the operating cycle. The carrier 5 travels rearward as
the
round is fired. Notice that the trigger 8 is still depressed and thus the
disconnect 9
latches onto the hammer 7 as it is pushed back by the carrier. In addition,
since the
carrier is positioned to the rear, the auto-sear 6 has now re-engaged the
hammer as
well.
Fig. 19 shows Step 4 of the operating cycle. The trigger 8 remains depressed
and
the carrier 5 has traveled forward, loading another round. The disconnect 9
prevents
the hammer 7 from moving once the auto-sear 6 is disengaged by the carrier 5.
The
disconnect has thus interrupted the cycle, allowing only one round to be
fired.
From the Step 4 position, Step 5 is back to the home position of Fig. 15
again. As the
trigger 8 is released, its leading edge engages the notch 24 (see Fig. 5B) in
the
hammer prior to the disconnect releasing the hammer. The mechanism is now once
again ready to fire another single round for each depression of the trigger.
Open-Bolt Operation
This section describes how the invention operates in a manner analogous to a
traditional open-bolt weapon, i.e. in automatic mode.
As explained above, the difference between closed-bolt and open-bolt operation
is
defined by the position of the carrier and bolt when the firing cycle is
interrupted. In
an open-bolt system the carrier is in the rearward position. When the trigger
is pulled
the carrier is released and travels forward. As the carrier travels forward it
pushes a
round into the chamber (something the closed-bolt cycle had accomplished
before
pulling the trigger). This is beneficial in high rates of fire since the
rounds are not
exposed to the heat of the chamber except directly before the firing pin
initiates the
round. Keeping a round out of a hot chamber prevents the possibility of cook-
off, as
explained above. The downside of open-bolt operation is that there is a
significant
movement of mass within the firearm between the time the trigger is pulled and
when
the round is actually fired. As a result the point of aim may move before the
round is
fired, thus making it inherently less accurate. In situations of fully
automatic fire, this
level of inaccuracy is overwhelmed by the repeated motion of the carrier and
recoil of
full automatic fire and is thus considered acceptable.
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Fig. 20 shows the mechanism in the home position of the operating cycle, in
which
the weapon has been cocked and is ready to fire. The firing mechanism is
reset. The
difference from the closed-bolt cycle is that the carrier 5 is to the rear and
no round is
loaded in the chamber. As will be explained later below, the carrier does not
move to
the rear as soon as the selector 13 is switched from semi-automatic to
automatic.
Instead, it remains forward until the first round is fired.
Fig. 21 shows Step 1 of the operating cycle. As the trigger 8 is depressed, it
cams
the carrier sear 10 out of engagement with the carrier 5. The carrier is just
beginning
its forward motion, propelled by a typical recoil spring (not shown). In
addition, the
trigger disengages from the hammer 7. Note that at this point the over-travel
of the
carrier and the engagement of the auto-sear are preventing the hammer from
moving.
Fig. 22 shows Step 2 of the operating cycle. As the carrier 5 travels forward,
the bolt
strips a round from the magazine (conventional and therefore not shown),
loading it
into the chamber and subsequently locking with the barrel. When the carrier is
fully
forward, it disengages the auto-sear 6 from the hammer 7.
Fig. 23 shows Step 3 of the operating cycle. The hammer 7 rotates forward
under
the force of its spring 22 (not shown in this view; see Fig. 2) and strikes
the firing pin
90, initiating the round.
Fig. 24 shows Step 4 of the operating cycle. The carrier 5 travels to the
rear,
resetting the trigger mechanism. Note that the auto-sear 6 has re-engaged the
hammer 7. At this point if the trigger 8 remains pulled, the cycle will go to
Step 2 and
continue to cycle from Step 2 to Step 4 until all ammunition has been
exhausted or
the trigger is released.
From the Fig. 24 position, Step 5 of the operating cycle is back to the Fig.
20 home
position. When the trigger is released, the carrier sear interrupts the cycle
and the
mechanism stops in the home position. Otherwise, the carrier sear remains in
the
Fig. 21 position, and the weapon fires again as soon as the carrier is fully
forward to
disengage the auto-sear and allow the hammer to fly forward.
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Integration of Open-Bolt and Closed-Bolt Operation
Introduction
It is a particular advantage of aspects of the invention that the firearm can
operate as
an open-bolt firearm in fully automatic mode, or as a closed-bolt firearm in
semi-
automatic mode. The integration of the two different operating modes and the
operating logic will now be described.
In the invention, the bolt position change is effected after the first round
has been
fired, subsequent to the mode change: Thus there is no motion of the carrier
upon
mode selection, either from closed bolt to open bolt, or vice versa.
The dual-mode operation is achieved primarily by virtue of the auto-disconnect
12
and its interaction with the safety sear 11. It should be noted that the
safety sear
provides a protective function that prevents a round from being chambered if
the
carrier sear 10 has not engaged the carrier 5.
Note that the operative surfaces of the safety sear could be integrated into
the carrier
sear, i.e. in a single piece, if for some reason the presence of the safety
sear is
considered obsolete or redundant. However, the preferred embodiment
advantageously contemplates having these as two separate components.
Safety Sear Function
The safety sear is free to rise, separating from the carrier sear, when it is
not being
acted on by the trigger. This happens due to a pocketed spring between the
two, as
described above. The purpose of the safety sear is to prevent possible
accidental
chambering of a round if an operator pulls back on the charging handle of the
firearm, but not quite far enough back to engage the carrier sear. The carrier
assembly may have moved back far enough to engage the next round in the
magazine, so that if the operator releases the charging handle, a round will
be
chambered and the bolt will close, despite the selector being set to the open-
bolt
mode. If this occurs after a prolonged high rate of fire, the chamber of the
weapon
will be hot and the potential for cook-off exists - something the open-bolt
mechanism
is designed to avoid. The safety sear, however, being shorter, can engage the
carrier
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to hold it back even if the carrier is not pulled back far enough to engage
the carrier
sear.
From the stage shown in Fig. 20, the firearm will fire in automatic mode when
the
trigger is pulled and will cycle normally. The safety sear is never presented
to the
notch in the carrier. Since the safety sear directly interacts with the
trigger and
subsequently sweeps the carrier sear away from the carrier, the safety sear is
removed from any possible interference before the cycle starts.
In semi-automatic operation, the auto-disconnect 12 engages the lower arm of
the
safety sear 11, whereas in automatic operation, the auto-disconnect has been
rotated by the selector and thus cannot engage the safety sear. The surface 35
on
the trigger raises to cam the safety sear in this area when the trigger is
depressed,
so that it can be engaged by the auto-disconnect when in semi-automatic
operation.
Automatic to Semi-Automatic Transition
In Fig. 20, the firearm is in the automatic home position, in which the auto-
disconnect
remains cammed out of the way by the selector. Note that the carrier is to the
rear in
the open-bolt configuration.
In Fig. 25, when the selector 13 is moved to the semi-automatic mode (closed-
bolt
operation), the auto-disconnect 12 is allowed to rotate counter-clockwise
under the
force of its spring to be in position to be ready to interfere with the safety
sear 11.
In Fig. 26, when the trigger 8 is depressed, initiating a semi-automatic
cycle, the
safety sear 11 snaps past the auto-disconnect 12.
In Fig. 27, the safety sear 11 and carrier sear 10 are held down and away from
the
carrier 5 even when the trigger 8 is released, after one round has been fired.
Note
that now the firearm is in the closed-bolt configuration.
The difference between this and a regular semi-automatic cycle is the initial
movement and subsequent capture of the safety sear and carrier sear,
effectively
removing them from participating in the action thereafter.
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Semi-Automatic to Automatic Transition
In Fig. 27, the firearm is in semi-automatic mode. The selector has not yet
been
switched to the automatic mode (open-bolt). Note that the carrier 5 is
forward, in the
closed-bolt configuration.
In Fig. 28, the selector 13 has been moved to the automatic mode. Note the
movement of the auto-disconnect 12 and subsequent release of the safety sear
11
and carrier sear 10 combination. It should be stressed that the arm of the
auto-
disconnect where it contacts the selector does not touch the carrier sear. The
motion
of the carrier sear and safety sear are only a result of their spring driving
them
upwards once the auto-disconnect has released them
Fig. 29 is part way through the automatic cycle, with the trigger 8 remaining
depressed. The firearm will continue to cycle in this state until the trigger
is released
or ammunition is depleted.
From the Fig. 29 position, as the trigger 8 is released, the firearm returns
to the
automatic (open-bolt) home position of Fig. 20.
Summary
It can thus be seen that the invention advantageously allows the weapon to be
easily
switched between closed-bolt semi-automatic operation, and open-bolt automatic
operation, without the disadvantage of noise or significant mechanical
movement at
the time of changing the mode of operation. The carrier 5 does not move until
the
first round is fired after operating the selector 13 to change the mode.
The above description is of a preferred embodiment, by way of example only.
Those
knowledgeable in the field of the invention will understand that there are
many
possible variations within the scope of the invention. The scope of the
invention
therefore is not limited to the above description, but instead is defined by
the
following claims.
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