Abstract:
Grenade launchers for attachment to gas-operated service rifles and carbines such as the M16 and M4 are improved by providing them with a trigger assembly that enables the shooter to deliver repeated hammer strikes to the primer of the loaded grenade without having to open the breach to reset the hammer and signals final aim indication via added trigger pull force.

Description:
BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   This invention relates broadly to grenade launcher attachments for gas-operated automatic and semi-automatic rifles. More particularly, it concerns improved trigger assemblies for the grenade launcher attachments. 
   2. Description of the Prior Art 
   Grenade launchers for attachment to gas-operated service rifles and carbines such as the M16 and M4 are known firearms devices, e.g. see U.S. Pat. Nos. 3,641,145 and 6,281,145. A need exists for such launchers to have a trigger assembly that allows the operator to deliver repeated hammer strikes to the primer of the loaded cartridge without having to open the breach to reset the hammer. The state of the art in grenade launchers is the M203 that has a firing mechanism that is cocked when the weapon is locked shut. It can only be released to strike the primer of the loaded cartridge one time without opening the breach and closing it again thereby resetting the hammer. 
   There have been many double-acting trigger assemblies for firearms previously designed that allow trigger pull to cock and trip the hammer repeatedly, e.g., see U.S. Pat. Nos. 3,965,603; 4,285,152; 5,160,795 and 5,400,537. 
   It has also been known to construct trigger assemblies for firearms wherein an increased pressure is required at the end of the trigger stroke to provide a clear tactile indication to the shooter that the hammer is in pending release to fire the weapon, e.g. see U.S. Pat. Nos. 4,974,356 and 6,571,502. 
   The present invention provides further improvements in the construction of grenade launchers for attachment to rifles and their trigger assemblies. 
   OBJECTS 
   A principal object of the invention is the provision of improvements in construction of grenade launchers for attachment to service rifles, including carbines, such as the M16A2 and M4. 
   Further objects include: 
   1. Improvements in the construction of grenade launchers for attachment to rifles by providing added signal trigger pull force mechanically within the trigger assembly via its mechanical design. 
   2. Improvements in the construction of grenade launchers for attachment to rifles comprising a trigger assembly that allows the operator to deliver repeated hammer strikes to the primer of the loaded cartridge without having to open the breach to reset the hammer. 
   3. The provision of rifle attached grenade launchers that are easier to operate then their predecessors and have improved probability of hitting a target upon firing. 
   4. The provision of improved trigger assemblies for rifle attached grenade launchers that help shorten the length and reduce the weight of the grenade launchers. 
   Other objects and further scope of applicability of the present invention will become apparent from the detailed descriptions given herein; it should be understood, however, that the detailed descriptions, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent from such descriptions. 
   SUMMARY OF THE INVENTION 
   The stated objects are accomplished in accordance with the invention by the provision of improved grenade launchers that basically include a receiver structured for attachment to a service firearm, a barrel depending from the receiver, a breech at the rear of the barrel and a hand-grip enclosing at least a portion of the barrel. 
   The improvement in the new grenade launchers is in improved trigger assemblies comprising a frame depending from the receiver proximal of the grenade launcher breech and defined by a forward vertical portion, a rearward vertical portion and a central cavity therebetween. Left and right cover-plates are removeably fitted to the frame. 
   A trigger guard depends from the frame and is fitted with a trigger pivot. 
   A trigger defined by an upper end and a lower end is pivoted at its lower end on the trigger pivot and configured at its upper end with a cocking notch and a ledge that extends integrally and proximally from the cocking notch. 
   A trigger spring is fitted between the trigger and the frame to bias the upper end of the trigger toward the forward vertical portion of the frame. 
   A hammer defined by an upper end and a lower end has the upper end pivoted to the frame and there is a lever-arm extending integrally and upwardly from the hammer&#39;s upper end. Further, the lower end of the hammer is configured with a vertical recess. 
   A spring plunger is carried in a bore in the receiver to engage the lever arm on the hammer to bias the lower end of the hammer around the hammer pivot toward the breech of the grenade launcher barrel. 
   A critical element of the new trigger assemblies is a link of triangular shape defined by a major leg, a first minor leg, a second minor leg and a link nose at the junction of the major and first minor legs. This link is pivoted to the hammer within its vertical recess mentioned above for limited rotation of the link in a vertical plane. 
   A link spring is carried on the lower end of the hammer to urge the link nose downward by rotation of the link. 
   Finally, a firing pin is reciprocally carried in the forward vertical portion of the frame to be impacted for firing of the grenade launcher by the lower end of the hammer. 
   Advantageously, the new grenade launchers include a trigger spring protected in a two-part telescoping capsule with its first part fitted into the trigger guard and its second part fitted into the hammer. Also, a set screw is carried by the frame to limit the forward travel of the trigger. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A more complete understanding of the invention can be obtained by reference to the accompanying drawings in which: 
       FIG. 1  is a left side elevation of a grenade launcher of the invention attached to a gas-operated carbine. 
       FIG. 2  is a closer left side elevational view of the grenade launcher of  FIG. 1  focused on the trigger assembly. 
       FIG. 3  is an even closer left side elevational view of the grenade launcher of  FIG. 1  in which the cover plates have been removed from the trigger assembly. 
       FIG. 4  is a left side sectional view taken along the centerline of the grenade launcher. In this and the remaining figures, there is no showing of parts of the rifle to which the grenade launcher is attached. 
       FIG. 5  is a left side sectional view with the trigger pulled slightly to the rear. 
       FIG. 6  is a left side sectional view similar to  FIG. 5  that shows the trigger traveling to the rear with the link pivoting as necessary to keep its front rounded nose into the mating surface on the trigger. 
       FIG. 7  shows the end of the first stage of the trigger travel wherein the link has rotated until the surface above and behind its pivot point has contacted a ledge in the hammer. 
       FIG. 8  is a close-up view of the trigger position in  FIG. 7 . 
       FIG. 9 , compared to  FIG. 7 , shows the trigger rotation position thru the second-stage of the trigger travel. 
       FIG. 10  is an enlarged, close-up view of the trigger assemply in the position of  FIG. 9 . 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   In the attached drawings, the numerals with an arrowhead lead-lines refer to major structural units, numerals with plain lead-lines refer to specific parts and in all figures, the same numerals specify identical elements. 
   Referring initially in detail to  FIG. 1 , the grenade launcher  2  constructed in accordance with the invention is attached to the gas-operated rifle  4  comprising rifle receiver assembly  6 , rifle barrel  8  and rifle hand-guard  10 . 
   The grenade launcher  2  generally comprises barrel  12 , hand-grip  14 , breech  15 , receiver  16  and trigger assembly  18 . The receiver  16  is attached to and depends from the rifle hand-guard  10 . For loading grenades and unloading spent casings (not shown), the barrel  12 , hand-grip  14  and breech  15  pivot to the left side away from the receiver  16  and trigger assembly  18 . 
   Referring to  FIG. 2 , the trigger assembly  18  includes the trigger  20 , trigger guard  22 , trigger pivot  24  carried by the trigger guard  22 , frame  26  from which the trigger guard  22  depends, a pair of left and right cover-plates  28  (right not shown) releasably fixed to the receiver  16 . 
   Referring to  FIG. 3  shown without cover-plate  28 , the trigger assembly  18  further includes hammer  30 , cocking notch  31  in front of ledge  33  at the top of trigger  20 , link  32 , trigger spring  34  and hammer spring plunger  36 . 
   Referring to  FIG. 4 , the trigger  20  has pulled link  32  about the link pivot pin  38  slightly to the rear with the link nose  40  settled into the cocking notch  31 . Also shown are trigger spring  42 , link spring  43 , hammer pivot pin  46 , trigger travel adjustment set screw  48  and firing pin  50 . The trigger spring  42  is protected in a two-part telescoping capsule  44  with its first part  44 A fitted into the trigger guard  22  and its second part  44 B is fitted into the trigger  20 . 
   The set screw  48  limits the forward travel of the trigger  20  to keep link  32  from dropping down behind the ledge  33  on top of the trigger  20  which is the surface that engages the link  32  and causes the hammer  30  to retract. 
   Referring to  FIG. 5 , this shows the trigger pulled further to the rear so the hammer  30  disengages the firing pin  50  while the link  32  pivots as necessary to keep link nose  40  in contact with the cocking notch  31  of trigger  20 . 
     FIG. 6  shows another intermediate position of travel of trigger  20  and the position of link  32  as the trigger  20  is pulled further rearward. 
     FIG. 7  shows the end of the first-stage of rearward travel of trigger  20  wherein the link travel limit surface  52  comes into contact with the stop ledge  54  on hammer  30  as link  32  rotates about link pivot pin  38 . 
     FIG. 8  shows a close-up view of end of the first-stage of rearward travel of trigger  20  as shown in  FIG. 7 . 
     FIGS. 9 &amp; 10  show the second-stage of rearward travel of trigger  20 . Now that the link  32  can no longer rotate relative to the hammer  30 , the continued rearward travel of the trigger  20  causes the link nose  40  to slide up the cocking notch  31  of the trigger  20 . When the link nose  40  finally clears the cocking notch  31 , the hammer  30  is released to travel forward powered by springs that have been compressed in hammer spring plunger  36  during the first-stage of trigger travel. 
   In preferred embodiments of the invention, the force required to pull the trigger to the end of the first stage is approximately 5 pounds. The load thereafter immediately increases to approximately 8 pounds just before the hammer is released. This three-pound difference provides a clear tactile indication to the shooter that the hammer is in pending release so the final aim can be made just before the weapon is fired. Trigger assemblies of the invention thus provide the gunner with improved hit probability over those that do not provide the tactile feel of impending release. 
   One of the major features of trigger assembly  18  is that it accomplishes its task within a very small front to back length of the weapon. This enables moving the base of the cartridge to the rear by approximately 1.5 inches relative to the current M203 grenade launcher. Moving the cartridge to the rear makes the weapon easier to operate because the shooter doesn&#39;t have to reach so far forward to load it, but also reduction in the weight of the launcher by ⅓ and to move its center of mass to the rear as well. The new compact trigger assembly in accordance with the invention has made this possible.