Patent Abstract:
Machine guns having detachable barrels and methods of operating the same are disclosed. An illustrated example firearm includes a housing; a removable barrel; a latch to releasably secure the barrel in the housing, the latch having a released state and a secured state; and a carrying handle movable between a rest position and a carry position. The carrying handle cooperates with the latch such that the latch can only be moved into the released state to permit removal of the barrel when the carrying handle is at least substantially in the carry position.

Full Description:
RELATED APPLICATIONS 
   This patent is a continuation of U.S. patent application Ser. No. 11/496,535, which was filed on Jul. 31, 2006, which is a continuation of U.S. application Ser. No. 11/027,935, which was filed on Jan. 3, 2005, which is a continuation of International Patent Application Serial No. PCT/EP2003/005926, which was filed on Jun. 5, 2003, the disclosures of the parent applications are incorporated herein by reference. 

   FIELD OF THE DISCLOSURE 
   This disclosure related generally to firearms, and, more particularly to, machine guns having detachable barrels, a latch to facilitate the attachment and removal of a barrel, and a foldable carrying handle mounted near the latch. 
   BACKGROUND 
   Positional terms such as “rear” or “top”, “right” or “left” are used in this patent with reference to a weapon positioned in a shooting position, That is, with reference to a weapon positioned to shoot “forward” (i.e., away from the shooter), in a generally horizontal plane. 
   Conventional light weight machine guns often have a carrying handle that is mounted near the rear end of the barrel, (i.e., in proximity to the gun&#39;s center of gravity). The handle can be moved between a rest position and a working position. In the rest position, the carrying handle is folded down and rests against the jacket of the machine gun. In its working position, the carrying handle protrudes upwards from the machine gun and is positioned to serve for transporting the gun. 
   In general, such machine guns should be as light as possible and be able to handle long rounds and a high overall number of shots. Each shot fired produces heat and the gun barrel may become over-heated during use. To address this issue, these machine guns usually have devices that allow one to quickly exchange one barrel for another. 
   Such devices are usually designed as latches that snap into place. After the latch is opened, the barrel can be removed, for example, with asbestos-clad gloves or by means of a heat-insulated manual handle (see CH 116,607). Subsequently, a new barrel is inserted, and the latch is closed again. In its closed position, the latch should be firmly locked and hold the barrel in its proper position during the next round of firing. 
   There are several disadvantages with the above described prior art design. First, if the asbestos-clad gloves are not within easy reach or if there is a failure, the machine gun operator may inadvertently use his free hand to remove the hot barrel and injure himself. Second, in the excitement of a fight, it is easy to forget about the need to always carefully check and make sure that the latch is properly locked. If the latch is not properly locked, it could unexpectedly open, thereby permitting the barrel to fall out of the gun. One could conceive of a separate safety catch that would only allow the gun to fire when the latch has properly snapped into place. However, such a safety catch would disable the weapon if the barrel becomes loose and, at any rate, would be very complicated and, thus prone to failure. 
   It would also be possible to equip the snap-in latch with a secondary latch. However, such a secondary latch would require additional operations to exchange a barrel and, thus, delay and complicate the exchange process. 
   Detachable barrels on machine guns with carrying handles are known in the prior art. For example, U.S. Pat. No. 2,131,716 illustrates a device for removal and/or insertion of a barrel that can be provided in addition to a carrying handle on a machine gun. However, the actuation of the device shown in U.S. Pat. No. 2,131,716 is independent from the position of the carrying handle and/or can only occur when the carrying handle is in position B (see FIG. 2 of U.S. Pat. No. 2,131,716). 
   A transversally arranged eccentric rod used to hold a barrel of an automatic firearm in a detachable connection is known from U.S. Pat. No. 2,423,854. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a side view of an example universal machine gun equipped with an example barrel exchange latch mechanism. 
       FIG. 2  is a longitudinal cross-sectional view of the example barrel exchange latch mechanism shown in its ready-to-shoot state in which a barrel exchange is precluded, with portions shown in block diagram form. 
       FIG. 3  is a longitudinal cross-sectional view of the example barrel exchange mechanism of  FIG. 2 , but shown in its release position in which a barrel exchange is permissible. 
       FIG. 4  is an enlarged view of the check plate that rests on the end of the eccentric bar in the example barrel exchange mechanism of  FIGS. 1-3 . 
   

   DETAILED DESCRIPTION 
     FIG. 1  illustrates an example machine gun (e.g., a US M60), which is equipped with an example barrel exchange latch mechanism  3  and an exchangeable barrel  1 . Other than the inclusion of the barrel exchange mechanism  3 , the remainder of the illustrated machine gun is largely conventional. Those portions of the weapon not described in the following are well known to persons of ordinary skill in the art. 
   To enable the removal of the barrel  1 , the weapon of  FIG. 1  is further provided with a removable gas piston device  5 . The gas piston device  5  is typically removed to exchange the barrel  1  for a new barrel (which, although not separately shown, is identical to the barrel shown in  FIG. 1 ) when the barrel  1  become hot from use. 
   The machine gun of  FIG. 1  also includes a carrying handle  7 . The carrying handle  7  is mounted on the machine gun such that it can be folded between a rest position and a carrying position.  FIG. 1  illustrates the handle  7  in an example carrying position. In this position, the carrying handle  7  may obstruct the line of sight. In such an example, the handle  7  should be folded down to the rest position before shooting. 
   When removing a hot barrel  1 , the user actuates the barrel-exchange latch mechanism  3 , grabs the barrel  1  with an insulated glove, (e.g., an asbestos-clad glove), and pulls the barrel  1 , along with the bipod  9 , forward in the direction of firing. In this process, the gas piston device  5  is separated into two parts, with one part remaining on barrel  1  and the other part remaining on the machine gun. 
     FIG. 2  is a cross-sectional view of the example barrel-exchange latch mechanism  3  of  FIG. 1 . Note that in  FIG. 1  the machine gun points to the right, while in  FIGS. 2 and 3 , the machine gun points to the left. 
   As shown in  FIG. 2 , the exchangeable barrel  1  of the illustrated weapon comprises an expanded rear end  11 . The rear end  11  is in communication with the magazine and is inserted into the front of a fitting borehole in the jacket/housing  41  of the machine gun. 
   The upper part of the rear end  11  includes a recess  13 . A transversally extending eccentric bar  15  is mounted in the gun jacket  41  near the recess  13 . The eccentric bar  15  is rotatable. In the position illustrated in  FIG. 2 , the rear part of the eccentric bar  15  protrudes into the recess  13  of the barrel  1 . This engagement between the eccentric bar  15  and the barrel  1  prevents the barrel from moving forward, (i.e., blocks the barrel from being removed). Thus, when the eccentric bar  15  is in the position of  FIG. 2 , the weapon is in a ready-to-shoot position. 
   A handling device  14  (e.g., a lever) is located on the end of the eccentric bar  15  and shown in  FIGS. 2 and 3  in block diagram form. 
   A slider  17  is located within a cavity defined in the housing  41  above the eccentric bar  15 . The slider  17  is longitudinally movable and is pushed to the back by a spring  19 . The slider  17  includes a slider block  43  on the bottom and a slider lug  23 , which extends the slider  17  towards the front. The slider lug  23  can emerge from the housing/jacket  41 . In the illustrated example, the slider lug  23  is formed in one piece with the slider block  43 . A transversally extending recess  21 , which opens forward, is disposed in the upper side of the eccentric bar  15 . 
   In the position shown in  FIG. 2 , the slider block  43  sits in the recess  21 . The slider block  43 , which forms a part of the slider  17 , interacts with the recess  21  of the eccentric bar  15  to substantially prevent the eccentric bar  15  from turning clockwise beyond the position shown in  FIGS. 2 and 3 . When the slider lug  23  and, thus, the slider block  43 , are moved sufficiently forward against the force of the spring  19  (i.e., by pivoting the eccentric bar  15  with the handling device  14 ), the eccentric bar  15  turns counter-clockwise from the position shown in  FIG. 2  and exits the recess  13 . As a result, the barrel  1  can be pulled out of the housing  41  toward the front of the weapon. If the handling device  14  connected with the eccentric bar  15  is subsequently released, the eccentric rod  15  and the slider block  43  return to the position shown in  FIGS. 2 and 3  under the influence of the spring  19 . A new barrel may then be pressed from the front into the borehole in the jacket  41 . 
   When a new barrel is so inserted, it rotates the eccentric bar  15  counter-clockwise against the force of the spring  19 . When the new barrel is sufficiently inserted, the eccentric bar  15  snaps back into the position shown in  FIG. 2 . When the eccentric bar  15  snaps back into the position of  FIG. 2 , the slider lug  23  re-enters the jacket  41 , and the barrel  1  is completely fit into the borehole. A sloping edge/camming surface on the top of the rear end  11  of the barrel  1  facilitates this snap-in procedure. 
   Further toward the front, the barrel  1  has a gas borehole (not shown) that extends radially from the bottom and connects to a gas channel  33  located within a gas discharge element  35 . An axial gas discharge element  37  is attached in a well known fashion to the open end of the radial gas discharge element  35 . The angular gas channel  33  continues to the rear in this gas discharge element  37 . The gas discharge channel  33  ends in a plug-in block  39  which is structured as a piston. This plug-in block  39  is detachably inserted from the front into a gas cylinder  27 . The gas cylinder  27  includes a movable gas piston  29 . This piston  29  transfers its backward movement to a rod assembly  31  which, in turn, transfers its movement to a closure mechanism (not numbered) to initiate unlocking of the bolt head of the breech. The bolt head and breech mechanism are partially shown in  FIG. 3 . For more details of this structure, the interested reader is referred to U.S. patent application Ser. No. 11/027,934, which is hereby incorporated by reference in its entirety. 
   To release the eccentric bar  15  from the recess  13  in the rear end  11  of the barrel  1 , the lever  14  coupled to the eccentric bar  15  is used to rotate the eccentric bar  15  counter-clockwise. After the eccentric bar  15  exits the recess  13 , the barrel  1  can be pulled forward and out of the machine gun. Concurrently, the plug-in block  39  of the gas piston device  5  is pulled out of the gas cylinder  27 . The illustrated gas cylinder  27  may be implemented as an expendable part that can be exchanged at any time. 
   As shown in  FIG. 2 , a horizontal axle  45  is attached to the housing/jacket  41  just in front of, and beneath, the slider  17 . The axle  45  is the support pivot for the carrying handle  7 . Attached to the bottom of the carrying handle  7  is a stop block  25 . The stop block  25  faces the slider  17 , and lies directly in front of the slider lug  23  when the carrying handle  7  is folded down in the ready-to-shoot state as shown in  FIG. 2 . When the stop block  25  is in this position, it prevents the slider lug  23  from exiting the jacket  41  and, thus, prevents the slider  17  from moving forward. The handle  7  may be structured with a snap-in connection, wherein the slider lug  23  fixes the carrying handle  7  in its ready-to-shoot position by a spring-biased engagement in a recess in the stop block  25 . 
   When the carrying handle  7  is rotated up to the position shown in  FIG. 3  (e.g., for transporting the weapon as the shooter changes his/her position), the stop block  25  swivels past the slider lug  23  and releases it for forward longitudinal movement. (The stop block  25  is not visible in  FIG. 3  because it lies before the plane of the drawing.) The barrel  1  can only be exchanged when the carrying handle  7  is in this position (i.e., the position of  FIGS. 1 and 3 ). In the ready-to-shoot position shown in  FIG. 2 , the barrel  1  may not be exchanged because the eccentric bar  15  may not be turned out of the recess  11  because it rests, through the slider  17  and the slider lug  23 , against the stop block  25  of the carrying handle  7 . The eccentric bar  15  can only be turned when the stop block  25  is not located in front of the slider  17  and the slider lug  23  is, thus, free to move forward (i.e., when the handle  7  is in the position shown in  FIG. 3 ). This approach provides added security because the barrel  1  may only be exchanged when the carry handle  7  is rotated up, into a position obstructing the gun operator&#39;s view (i.e., where the weapon is not in a ready-to-shoot fire state). 
     FIG. 4  is an enlarged top view of the end of the eccentric bar  15 . This top view is from the right side of the machine gun; thus, in this drawing, the direction of shooting is to the right. 
   To limit the range through which eccentric bar  15  can turn, a check plate  47  is mounted in a recess  51  in the jacket  41 . This check plate  47  is sized to allow the eccentric bar  15  to turn only between its two end positions in the shortest path and prevents the eccentric bar  15  from turning beyond these end positions. 
   The check plate  47  is associated with two snap-in devices  49  in the recess  51  of the jacket  41 . These snap-in devices  49  may be implemented by, for example, spring-mounted snap-in balls. The snap-in devices  49  stop the check plate  47  and, thus, limit the rotation of the eccentric bar  15  in each of its two end positions. 
   From the foregoing, persons of ordinary skill in the art will appreciate that the illustrated example machine gun has a barrel  1  which can be exchanged as quickly as in conventional firearms, but in a safer and more reliable fashion. To this end, the illustrated example device  3  that permits exchanging of the barrel  1  can only be brought into the release position when the carrying handle  7  is in the carrying position. Furthermore, the illustrated device  3  is simpler, or at least not more complex, than what is known in the art. 
   In the illustrated example, the eccentric bar  15  cannot extend beyond its end positions or, at least, cannot exceed them substantially. A person of ordinary skill in the art will appreciate that the illustrated example uses a locking piece  25  to prevent the eccentric bar  15  and the carrying handle  7  from unexpectedly moving from one end position towards the other. This locking piece  25  stops the eccentric bar  15  and the carrying handle  7  in an end position. The eccentric bar  15  and the carrying handle  7  can be moved beyond the stopped position through the exertion of additional force. This not only ensures the usability of the machine gun both in the rest and in the ready-to-shoot position, but it also avoids any situation where the eccentric bar  15  is wrongly turned with the barrel  1  removed so that a new barrel  1  cannot be simply inserted. 
   While the mechanism in the illustrated example prevents the end positions of the eccentric bar  15  from being exceeded, it does not prevent the possibility of the eccentric bar  15  being heavily stressed during a rush operation and possibly damaged as a result. Therefore, the illustrated example utilizes a check plate  47  on the eccentric bar  15  in order to absorb such stress in the end position and, thus, relieve the mechanism of that stress and the potential for damage. 
   A person of ordinary skill in the art will appreciate that the carrying handle  7  of the illustrated example is also used as a safety device. In particular, the illustrated carrying handle  7  guarantees that the machine gun can only shoot when the inserted barrel  1  is fully locked in place. When the carrying handle  7  is in its ready/carry position, it is not possible to aim the machine gun since the carrying handle  7  is directly in the gun operator&#39;s field of view and, therefore, it is difficult to shoot. This decreases the likelihood of a shot being fired from a misassembled weapon. 
   A person of ordinary skill in the art will further appreciate that the illustrated example helps the gun operator avoid injury during the changing of a hot barrel  1 . During the exchange of the barrel  1 , the gun operator usually has one hand on the carrying handle  7 . In order to exchange the barrel  1 , the operator grabs the hot barrel  1  at a heat-insulated handle or using some protective gear, (e.g., an asbestos-clad glove), while his other hand holds the carrying handle  7 . As a result, the temptation to assist with the other hand—and injure it, while doing so—is reduced. 
   In a further example, the machine gun has a carrying handle  7  that can only be brought into its rest position when the device  3  that releasably secures the barrel  1  is in its ready position. However, it is preferred that, during the transfer of the carrying handle  7  from its position of use (i.e., the carry position) to its rest position, the device  3  that releasably secures the barrel  1  is pressed into its ready position. As a result should the aforementioned device  3  become stiff to operate, (e.g., due to some dirt), it can still be brought into its locked position by means of the carrying handle  7  without facing the risk that the barrel  1  is not properly locked in. 
   In a preferred example, a weapon jacket/housing  41  defines a longitudinal borehole that receives the rear end  11  of the barrel  1 . The rear end  11  of the barrel  1  has a transversally extending recess  13 . Also, the weapon jacket  41  carries a transversally running eccentric bar  15  that can turn to—with the barrel  1  inserted—engage or disengage in the recess  13 . The carrying handle  7  is operatively coupled with the eccentric bar  15  when the eccentric bar  15  is engaged with the recess  13 , but is uncoupled from the eccentric bar  15  when the eccentric bar  15  is disengaged from the recess  13 . 
   An operation lever  14  is mounted on the eccentric bar  15 , and may be used to turn the eccentric bar  15 . The lever  14  must be long enough to ensure that the unlocking of the device  3  that releasably secures the barrel  1  is easily possible, even after an accumulation of dirt and rust. Furthermore, the recess  13  can be fabricated in a simple and inexpensive fashion so that the costs related to an exchangeable barrel  1  are minimized. Should the exchangeable barrel  1  be dirty, the recess  13  can be wiped off, without any extraordinary effort, by hand or with a piece of rag. 
   In the illustrated example, a slider  17  is pressed into engagement with the eccentric bar  15  by a spring  19 . The slider  17  can be pushed back away from the eccentric bar  15  when the carrying handle  7  is in its use/carry position. However, when the carrying handle  7  is in the rest position, it blocks the slider  17  from being pushed back. Thus, due to the slider  17 , the eccentric bar  15  is automatically blocked and cannot be released as long as the carrying handle  7  is in its rest position. Therefore, the gun operator can always be sure that the barrel  1  of his machine gun is secured in its proper place by observing the position of the carrying handle  7 . 
   A person of ordinary skill in the art will appreciate that the illustrated example latch can be used, for example, in a delayed recoil repeater gun, whose breech block is locked in the manner of the Swiss assault rifle 57 or the German G3. Furthermore, it is particularly advantageous to use the latch with gas-pressure repeater guns because, during the exchange of the barrel  1 , the connection between the barrel  1  and the gas channel  33  must also be separated, which is easy to do because the barrel  1  is inserted into its retaining borehole from the front in the direction of the centerline of the borehole. 
   A person of ordinary skill in the art will further appreciate that it is especially advantageous for an extension to be mounted on the barrel  1  between its muzzle and its rear end  11 . In the illustrated example, the extension comprises a gas borehole in communication with the barrel  1 . The gas borehole includes a free end that is offset backwards, and which extends parallel to the barrel  1  and ends in a plug-in block  39 . Furthermore, it is advantageous if the machine gun includes a gas channel  33  that is open in the forward direction and that, with the barrel  1  inserted, can be closed by the plug-in block  39 . The plug-in block  39  may only loosely be inserted into the gas channel  33 . However, it is also possible, and under certain circumstances advantageous, to equip the plug-in block  39  with sealing rings and insert it into the gas channel  33  so that it seals it off, especially in the case of small or weak cartridges, in which the developed gas quantity is relatively small. 
   Although certain example methods, apparatus and articles of manufacture have been described herein, this patent covers all methods, apparatus and articles of manufacture fairly falling within the scope of the appended claims either literally or under the doctrine of equivalents.

Technology Classification (CPC): 5