US 3893369 A
The pistol comprises a bolt provided with ribs extending transversely to the bolt axis and adapted to engage in and disengage from corresponding mating grooves provided in the receiver breech upon a slight rotation of said bolt with respect to said receiver breech. A locking link provided between the bolt and the bolt carrier is caused, upon firing, to rotate in such a direction that said link holds said bolt urged against the receiver breech, with said ribs engaged in the mating grooves. Once the inertial force of said bolt carrier has failed, the residual pressure of exhaust gases applies a force to said bolt which causes the bolt to rotate with respect to said receiver breech so as to disengage said ribs from the associated grooves in said receiver breech.
Description (OCR text may contain errors)
July 8, 1975 United States Patent [191 Benelli  INERTIA DEVICE FOR RETARDING THE 2,466,902 4/1949 Lochhead 89/182 UNLOCKING OF A BOLT ASSEMBLY Primary Examiner-Stephen C. Bentley  inventor. Giovannl Benellr, Urbmo, Italy Attorney Agent, or Firm Amster & Rothstein  Benelli S.p.A. Divisione Armi,
 ABSTRACT The pistol comprises a bolt provided with ribs extending transversely to the bolt axis and adapted to en in and disengage from corresponding mating g Italy  Filed: Feb. 23, 1973 gage 21 Appl. No.. 334,976 moves provided in the receiver breech upon a slight rotation of said bolt with respect to said receiver breech. A
, upon firing, to rotate in such a direcwith said ribs engaged in the mating 268 U 1 ou 09 4 M 44 aww mgu
m cc a T FUh l. ll
39 1g grooves. Once the inertial force of said bolt carrier has failed, the residual pressure of exhaust gases applies a  Field of Search 182, 183, 89/184, 190, l94, 195, 196, 197
force to said bolt which causes the bolt to rotate with 56] R f ren Cited respect to said receiver breech so as to disengage said UNITED STATES PATENTS ribs from the associated grooves in said receiver breech.
l,39l,496 9/1921 89/183 2,247,011 6/1941 Browning.............................. 89/!84 2 Claims, 7 Drawing Figures INERTIG DEVICE FOR RETARDING THE UNLOCKING OF A BOLT ASSEMBLY This invention relates to automatic firing and defense pistols. Automatic firing and defense pistols heretofore known of the kind having a fixed barrel and a recoiling bolt carrier are limited in use to very low pressure ammunition. This kind of weapons is provided with a striking bolt assembly. In operation the barrel is stationary, whereas the bolt carrier recoils due to the pressures developed by the gases on the cartridge cases.
This system generally accepted in almost all of the automatic firing and defense pistols, has the advantage of being simple in construction and accurate in firing; however, this system is suitable only where the pressures are not very high, otherwise it is necessary to reinforce the locking of the bolt assembly by means of strong recoil springs or increase the bolt carrier inertia, in which case the bolt carrier would become very heavy, which results in the pistol being difficult to operate and of considerable weight. The above drawbacks practically show the reasons why the fixed barrel and recoiling bolt carrier system is generally employed with short-barrel weapons and low muzzle velocity of bullets.
It is the object of this invention to overcome these drawbacks.
The automatic firing and defense pistol according to the present invention is characterized in that it comprises a bolt provided with ribs extending transversely to the bolt axis and adapted to engage in and disengage from corresponding mating grooves provided in the re ceiver breech upon a slight rotation of said bolt relative to said receiver breech, and a link one end of which is articulated in a cavity provided in said bolt and the other end of which in subjected to the pressure exerted thereon by said bolt carrier under the bias of a preloaded spring, the contact of said link with said bolt and bolt carrier being established in such locations relative to the pistol axis that, upon firing, the force applied to said link by said bolt carrier due to the inertia of the latter and the force applied to said link by said bolt due to the exhausted gases will generate a torque which causes said link to rotate in such a direction that said link holds said bolt urged against the receiver breech, with said ribs engaged in the mating grooves which are provided in the receiver breech whereas, once the inertial force of said bolt carrier has failed, the residual pressure of exhaust gases applies a force to said bolt which causes the bolt to rotate relative to said receiver breech so as to disengage said ribs from the associated grooves provided in said receiver breech.
By means of the above arrangement a retarded unlocking of the bolt after firing is obtained without the necessity of using strong recoil springs or a very heavy bolt carrier for increasing the inertia thereof.
This invention will readily become apparent upon reading the following specification of one embodiment of the invention given by way of example only and therefore not limitative, taken in connection with the accompanying drawing, wherein:
FIG. I is a diagrammatic, fragmentary, axial sectional view of a pistol in accordance with the invention, with the bolt assembly in a locking position and therefore ready for firing;
FIG. 2 is a sectional view similar to FIG. 1, showing the pistol after firing;
FIG. 3 is a sectional view similar to FIG. 1 and 2, showing the pistol with the bolt assembly in an unlocking position;
FIG. 4 is a fragmentary. axial sectional view ofthe receiver breech of the pistol shown in FIGS. 1 to 3;
FIG. 5 is a fragmentary cross-section of the receiver breech taken along the line 55 of FIG. 4;
FIG. 6 is a side elevational view of the bolt assembly of the pistol of FIGS. l to 3; and
FIG. 7 is a cross-section of the bolt assembly taken along the line 77 of FIG. 6.
As can be seen from FIGS. 1 to 3, the automatic pistol comprises a fixed barrel 1, rigidly connected to a receiver breech l0 and a receiver 9 so as to form an unitary body therewith. A bolt assembly 3 has an outer semicylindrical portion at its bottom provided with two crescent ribs 7 (see FIGS. 6 and 7) exactly aligned with two mating grooves 8 provided in the receiver breech 10 (see FIGS. 4 and 5). These crescent ribs 7 have inclined surfaces 12 adapted to cooperate with corresponding inclined surfaces 11 provided in the grooves 8.
A bolt carrier 2 fastened to a stop element 5 by means ofa splined coupling (not shown) carries at one end a cylindrical spring housing 15 for receiving a preloaded spring 6 which bears at one end against the bottom of the spring housing and at the other end against a washer 16 received on a spring guide rod 17 extending from an abutment surface 18 of the receiver breech 10, the spring 6 holding the washer 16 against said abutment surface 18.
The bolt assembly 3 has a spherical cavity provided therein, which houses a spherical end of a locking link 4, the other end of which bears against the upper wall of the bolt carrier 2 and also against the stop element 5 by being held in engagement with the latter by the force of the spring 6. Assuming that the weapon is charged and ready for firing, then, under these conditions, the link 4 is inclined about 45 relative to the bolt axis and the link exerts on the bolt a thrust which causes the latter to be held-down with the crescent ribs 7 in firm engagement in the mating grooves 8 of the receiver breech l0 and, at the same time, against the bottom of the cartridge case 20 of the cartridge introduced into the barrel 1. The bolt 3 has a through hole 21 provided therein (see FIG. 7), in which a firing pin 13 is received which is intended to cooperate with a hammer 14, only fragmentarily shown.
The pistol so described operates as follows:
At the time that the firing pin 13 (FIG. 2) is struck by the hammer 14, the firing pin reaches the cartridge detonator causing the explosion of the charge and the bolt carrier 2 tends by its own inertia to maintain its position relative to the other parts of the weapon which recoil against the hand of the shooter.
To the maintenance of this position also the preloaded spring 6 contributes.
If the receiver and barrel assembly 1-9-10 is taken as reference, then the inertia of the bolt carrier and stop element assembly 2-5 results in a force acting on the link 4 in a location where it is in contact with the bolt carrier and stop element assembly 2-5. Simultaneously, the action of gases on the bolt results in a force acting on the fulcrum of the link 4.
These two forces form a torque which, with the link 4 being supposed free, would cause the link to rotate in counterclockwise direction about its gravity center.
Due to the constraints of the mechanical system according to this invention the resultant, will be a force tending to hold-down the bolt 3 with the crescent ribs 7 in engagement within the mating grooves 8 of the receiver breech 10.
Therefore, at the most dangerous time that the forces developed by the propelling gases of the cartridge case violently eject the bullet, the system provides for an extremely stiff locking of the bolt assembly.
This condition continues as long as the inertial force of the bolt carrier-stop element assembly 2-5 is present. Once this force has failed. the only force acting on the system is that due to the residual gas pressure acting in the direction of the longitudinal axis of the barrel.
As the bolt is recoiled by the high pressure developed by the residual gases, it is no longer held-down by the link 4, which now is no longer subjected to the force generated by the bolt carrier inertia and the bolt, therefore. due to the mutual action of inclined surfaces 12 of the ribs 7 provided on the bolt, and the mating inclined surfaces 11 of the grooves 8 provided in the receiver breech 10, it slightly pivots upwards, with the crescent ribs 7 disengaging from the mating grooves 8 of the receiver breech l0, and therefore, it recoils together with the bolt carrier and stop element assembly, thereby causing the cartridge case to be ejected from the pistol. The recoil spring 6 then returns the bolt forward together with the bolt carrier, thereby introducing a new cartridge in the barrel; in such a manner the weapon will be again with the bolt in locked position and ready for firing.
From the above description it will be readily apparent that the bolt cannot unlock until the recoil move ment tends to terminate. Therefore, the system attains the object to provide a positive bolt locking for the fraction of time necessary for the bullet to be ejected from the barrel.
What i claim is:
I. An automatic firing and defense pistol comprising a fixed barrel having an axis;
a bolt carrier axially aligned with said barrel and located adjacent thereto;
said bolt carrier including a stop element extending transversely to said axis;
a bolt assembly slidably mounted within said bolt carrier. said bolt assembly having a plurality of projecting ribs. and said ribs having faces inclined with respect to said axis;
a receiver breech attached to said barrel and including a plurality of grooves corresponding to and providing mating engagement with said ribs prior to firing of the pistol;
a link having one end pivotally mounted on an end of said bolt assembly remote from said barrel and the other end of said link freely bearing against said stop element;
a preloaded spring associated with said barrel and applying a bias to said stop element thereby exerting a thrust force on said link to maintain engagement of said ribs;
said link having an inclination of approximately 45 to said axis prior to firing. and said link temporarily maintaining said inclination and rib engagement upon firing due to inertia force of said bolt carrier and stop element; and
said link movable to be axially aligned with said barrel due to force of residual gases following firing thereby allowing disengagement of said ribs and sliding movement of said bolt assembly.
2. An automatic firing and defense pistol according to claim 1 wherein said ribs are two in number and have a transverse crescent configuration.