Title:
BOLT ACCELERATOR FOR RECOIL OPERATED GUN
United States Patent 3757636
Abstract:
A single barrel gun has a short recoil system of operation and a bolt accelerator which includes the barrel drive spring and barrel buffer spring as a part of its operating mechanism.
US Patent References:
Automatic firearm
Herlach et al. - February 1930 - 1746471
Automatic or self-loading gun
Gebauer et al. - December 1934 - 1985493
ACCELERATOR FOR THE BOLT CARRIER OF AN AUTOMATIC GUN
Stoner - May 1970 - 3512449
Automatic firearm
Herlach et al. - February 1930 - 1746471
Automatic or self-loading gun
Gebauer et al. - December 1934 - 1985493
ACCELERATOR FOR THE BOLT CARRIER OF AN AUTOMATIC GUN
Stoner - May 1970 - 3512449
Application Number:
05/245508
Publication Date:
09/11/1973
Filing Date:
04/19/1972
View Patent Images:
Export Citation:
Primary Class:
Other Classes:
89/198, 89/177
International Classes:
F41A3/82; F41A5/08; F41A15/12; F41A25/10; F41A25/12; F41A3/00; F41A5/00; F41A15/00; F41A25/00; F41D5/02
Field of Search:
89/169,162,177,178
Primary Examiner:
Borchelt, Benjamin A.
Assistant Examiner:
Jordan C. T.
Claims:
What is claimed is
1. An at least partly self acting gun which comprises, in combination:
2. A gun according to claim 1 wherein:
3. A gun according to claim 1 wherein:
4. A gun according to claim 1 wherein:
5. A gun according to claim 1 wherein:
6. A gun according to claim 5 wherein
7. A gun according to claim 6 wherein:
1. An at least partly self acting gun which comprises, in combination:
2. A gun according to claim 1 wherein:
3. A gun according to claim 1 wherein:
4. A gun according to claim 1 wherein:
5. A gun according to claim 1 wherein:
6. A gun according to claim 5 wherein
7. A gun according to claim 6 wherein:
Description:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to automatic and semiautomatic guns which are recoil operated.
2. Description of the Prior Art
Recoil operated, single barrel guns, utilizing the Browning short recoil system of operation, are well known, and are described in some detail in "The Machine Gun" Vol. IV, by G.M. Chinn, 1955, published for the Department of the Navy by the U.S. G.P.O. Most of these guns utilize a rigid mechanical device to accelerate the bolt from the barrel during recoil movement. When fired on a relatively stiff mount, these guns develop a relatively high instantaneous recoil force.
BRIEF SUMMARY OF THE INVENTION
It is, therefore, an object of this invention to provide a recoil operated, single barrel gun, having a short recoil system of operation, and an inherently lower recoil force than conventional guns of this type.
Another object is to provide a gun of this type having an operating cycle which is relatively insensitive to fluctuations in ammunition performance.
A feature of this invention is a gun having a short recoil system of operation and a bolt accelerator which includes the barrel drive spring and the barrel buffer spring as a part of its operating mechanism.
BRIEF DESCRIPTION OF THE INVENTION
FIG. 1 is a side view in longitudinal cross-section of the essential structure of a gun embodying this invention;
FIG. 2 is an aft end view of the gun of FIG. 1;
FIG. 3 is a view in cross-section taken along plane 3--3 of FIG. 1;
FIG. 4 is a view in cross-section taken along plane 4--4 of FIG. 1;
FIG. 5 is a partial view in cross-section taken along plane 5--5 of FIG. 4;
FIG. 6 is a view in cross-section rotated 90°, taken along plane 6--6 of FIG. 3;
FIG. 7 is a detail top view of the feed drive cam plate of the gun of FIG. 1;
FIG. 8 is a schematic diagram of the accelerator of the gun of FIG. 1, at the instant of firing; and
FIG. 9 is a schematic diagram of the accelerator of FIG. 2, during recoil.
DESCRIPTION OF THE PREFERRED EMBODIMENT
1. Introduction
The gun shown in FIG. 1 utilizes the barrel extension 10, in lieu of the receiver 12, as the structural housing in which most of the other components of the gun operate. The barrel extension supports the barrel extension buffer package 20 housed within the receiver 12 which functions as a gun cradle. The barrel extension supports the feeder 16 and the feeder drive 18 in all directions, except the longitudinal, wherein support is provided by a rearward extension of the receiver. The barrel extension contains the bolt and sear buffer package 22, actuates the accelerator lever 24, and provides a barrel support 26, tracks 28 for the bolt package and locking surfaces 30 for the bolt. Thus the weight which conventionally goes into the supporting structure of the receiver is incorporated in the recoiling mass, thereby lowering the energy of recoil which must be absorbed by the barrel buffer assembly.
2. Gun Cycle
To start a cycle of operation the solenoid 32 is energized. This moves the sear release 34 transversely to the right as seen in FIG. 2. This motion drives a cam surface 36 against the sear 38. The sear is swung about its pivot 40 compressing its spring 42 to withdraw its tail 44 from a notch 46 in the bolt carrier 48 to release the bolt carrier, which is driven forward by the bolt drive spring 50. This is the start of the counter-recoil stroke. The bolt body 54 moves forward and by means of a spring 56 loaded rammer 58, strips the round 60, located on the feed tray in the feeder 16, from its link and rams it into the chamber 62 of the barrel 64. The bolt body 54 is driven by the bolt carrier 48 and is cammed into a locked position by a stud 66 riding in a cam (not shown) in the bolt body. The forward motion of the bolt carrier 48, after it has locked the bolt body, is enough to provide dwell travel during the recoil stroke. (This dwell is required to allow for chamber pressure decay.) The last gun function in the counter-recoil stroke is the firing pin release. The firing pin 70 strikes the primer and fires the round. This starts the recoil cycle of the barrel 64 and barrel extension 10. The accelerator lever 24 is pivoted on the barrel extension by a pivot stud 72, and, at the instant of firing, rests against a stop lug 74 located on the barrel extension. It is held in this position by the action of the barrel recoil spring 130. As the pivot stud 72 pushes the accelerator aft, the accelerator rotator-buffer spring guide 76 restrains the upper end of the accelerator. This restraint is a spring-loaded restraint because the accelerator rotator-buffer spring guide is attached to the buffer package 20. This action causes the accelerator lever to rotate clockwise about the pivot stud 72. A roller 78 on the lower end of the accelerator lever pushes against the front surface 80 of the bolt carrier 48 and accelerates the bolt carrier aft. The stud 66 on the bolt carrier cams the bolt body 54 to the unlocked position. The bolt carrier continues to be accelerated aft by the accelerator after unlock until the barrel support 26 strikes the spring guide 76. The barrel extension continues aft until it is halted by the buffer package while the bolt body is carried aft by the bolt carrier. The extractor 82, pivotally mounted and spring loaded in the bolt body, extracts the fired case 60 from the chamber 62 and carries it aft until the ejector 84 strikes the case and drives it laterally from the gun. The ejector 84 is spring loaded, pivoted lever, and is actuated by a cam surface 86 on the bolt carrier. The aft end of the lever is struck by the recoiling bolt carrier cam surface 86 to pivot the lever so that its front end strikes the fired case and ejects it from the gun. The bolt body continues to recoil aft until it hits the bolt buffer plate 88 of the preloaded bolt buffer spring package 22. The buffer stops the bolt and reverses its direction.
To halt the cycle the solenoid 32 is de-energized. The sear release 34 moves to the left and releases the sear 38. The sear snaps into the notch 46 of the bolt body and halts its forward motion. The sear 38 is mounted on a sear buffer plate 90 that transmits the sear load to the rear of the bolt buffer spring 92, thereby limiting the load on the sear 38.
3. Feeder
The feeder 16 is driven by a feed drive cam plate 94 attached to the barrel extension and having two cam tracks 96 and 98. The cam plate recoils and counter-recoils with the barrel extension. The cam motion, during both recoil and counter-recoil, is transmitted via two cam followers 100 and 102 journalled to two levers 104 and 106 that alternately drive via spring loaded plungers 108 and 110 a drive wheel 112 in a clockwise direction. The drive wheel 112 is attached to a shaft 114 that rotates the feeder sprocket 116. The belt of ammunition is pulled through the feeder 16 by the sprocket 116. Outer guides for the ammunition are provided by the feeder housing 118. At the ramming position, spring-loaded depressors 120 hold the round downward in the rammer slot 122 of the feeder tray portion of the feeder housing 118.
4. Feeder Drive
The feed drive cam plate 94 is attached to the barrel extension 10 and recoils and counter-rcoils with the extension. Lever 106 is mounted on the drive shaft. Cam follower 102 is positioned in cam 98. Lever 104 is mounted on the drive shaft. Cam follower 100 is positioned in cam 96. When the barrel extension recoils, lever 104 is swung clockwise by cam 96. Lever 104's plunger 108 is engaged with surface 126 on the drive wheel. As the lever swings, it rotates the drive wheel 112 clockwise. This action completes the first half of the feeder action. During the same recoil of the barrel extension, lever 106 is rotated counter-clockwise by cam 98. Lever 106 plunger 110 snaps behind surface 128 on the drive wheel. When the barrel extension counter-recoils, lever 106 rotates clockwise as directed by cam 98. This action drives the drive wheel clockwise, thereby completing the feeding motion. During barrel extension counter-recoil lever 104, directed by cam 96 swings counter-clockwise. Plunger 108 snaps behind surface 115. This positions lever 106 for the next cycle.
5. Bolt Assembly
The rotating lock type, bolt assembly of the gun is shown in FIGS. 1 and 4. Four locking lugs 124 are provided on the generally cylindrical bolt body 54. To permit the use of four lugs, the rammer 58 and extractor 82 are located forward of the lugs and are designed to fit within the outside dimensions of the lugs. This permits the extractor and rammer to enter the barrel extension through the same spaces as are provided for the locking lugs. The rammer is spring-loaded, so that it can be depressed as it enters the barrel extension.
The locking and unlocking action is provided by the stud 66 of the bolt carrier 52 which travels in a cam on the bolt body 54. This cam includes a straight portion at the front of the cam, allowing initial bolt carrier travel that does not effect the locks. This provides time for chamber pressure decay before unlocking. When the stud leaves the straight portion and enters the aft helical portion of the cam, it rotates the bolt body and unlocks the bolt, after which the bolt carrier 48 pulls the bolt body rearward. On the counter recoil stroke the locking lugs are held in respective tracks 126 in the barrel extension thereby precluding rotation of the bolt body. The stud bearing on the cam tries to rotate the head during the entire counter-recoil stroke. When the lugs 124 reach the forward ends of the tracks in the barrel extension, the bolt body is free to rotate and the lugs pass in front of the locking surfaces 30 to lock the bolt in the battery position.
6. Bolt Buffer and Sear Mechanism
The bolt buffer spring 92 performs two functions. It buffs the bolt at the end of the bolt recoil stroke; and buffs the sear when the bolt is stopped in its counter-recoil stroke.
When the bolt strikes the buffer plate 88, the buffer spring compresses, reverses the direction of the bolt and sends it forward. When the solenoid is de-energized, the sear 38 inter engages the bolt body. The sear 38 pulls forwardly on the sear buffer plate 90 and the sear buffer plate compresses the buffer spring. This action buffs the bolt to a stop.
To release the bolt, the solenoid is energized. This actuates the sear release. The sear release pivots the sear out of engagement with the bolt body, allowing the bolt to go forward into battery and to strip and fire the next round.
7. Barrel and Barrel Extension Buffer-Bolt Accelerator
The spring-biased accelerator mechanism is shown schematically in FIGS. 8 and 9. The barrel (barrel extension) 10 of the recoil operated automatic cannon is mounted to slide along the barrel axis in the gun receiver 12. The barrel 10 is pushed forward by a single acting barrel recoil spring 130 and the double acting barrel buffer spring 14, the two springs being connected in series by a buffer guide 132 which slides concentrically with the barrel bore axis.
The accelerator lever 24 is pivoted at 72 to the barrel 10 and the roller 78 on its lower end can bear on the bolt assembly drive surface 80. The upper end of the accelerator lever 24 is connected to the buffer spring guide 132 by a pin 134 and slot 136 linkage which accommodates the change in center distance between the pin 134 and the accelerator pivot 72 as the accelerator lever rotates on its pivot 72 with the barrel. Rotation of the accelerator 24 is limited in the clockwise direction by the abutment between the surface 138 of the buffer spring guide 132 and the surface 140 of the barrel. In the counterclockwise direction, rotation of the accelerator is limited by abutment between the lower end of the accelerator lever 24 and the stop lug 74 on the barrel.
In FIG. 8 the mechanism is shown in the position which exists at the instant of firing. All parts of the mechanism are at rest, or nearly at rest. The barrel 10 is held forward by the barrel recoil spring 130 holding the lower end of the accelerator lever 24 against the stop lug 74 of the barrel. The buffer spring guide 132 is positioned in the receiver 12 by the double acting barrel buffer spring 14. A gap G exists between the bolt assembly drive surface 80 and the accelerator lever roller 78.
Upon firing, the bolt assembly 52, and the barrel 10 begin recoiling together, and the accelerator lever starts to rotate clockwise about its pivot 72 on the barrel, the accelerator being restrained at its upper end by the link 134/136 and the buffer spring guide 132. After a time delay, which is determined by the size of the gap G, the accelerator strikes the bolt assembly drive surface 80, thereby imposing upon the bolt 52 an accelerating force which is determined primarily by the preload of the barrel buffer spring 14 and the proportions of the accelerator lever, the force developed by the barrel recoil spring 130 being lower than that of the buffer spring 14.
As the barrel continues to recoil the barrel recoil spring 130 and the buffer spring 14 are both compressed, and the resulting force applied to the bolt assembly 52 causes it to accelerate away from the barrel 10 as shown in FIG. 9. The acceleration continues until the surface 140 of the barrel abuts the surface 138 of the buffer spring guide 130, after which the bolt continues aft independently of the barrel. Continuing action of the buffer spring 14 brings the barrel 10 to a stop, reverses its direction, and returns all components of the mechanism except the bolt 52 to the battery position, as shown in FIG. 8. The bolt driving spring 50 then returns the bolt assembly 52 to battery position to initiate another cycle of the mechanism.
The spring-biased accelerator mechanism has been described as applied to a short recoil automatic gun in which the barrel is free to return to battery before the return of the bolt assembly. Should a barrel hold back feature be desired it can be provided by any of several means, without interfering with the objectives of this invention. Such means would preferably retain the barrel with respect to the buffer spring guide in such position that surfaces 138 and 140 remain in close proximity to each other, and such that the hold back feature is buffered with respect to the gun receiver or cradle by means of the barrel buffer spring.
Several details of the construction of the device can be varied without effect on its overall function. For example, the barrel recoil spring, described as operating in series with the barrel buffer spring, could operate in parallel, that is, between the barrel and the receiver. The link 134/136 may be replaced by any of several connecting means which will provide the relative connection between the accelerator and the buffer spring guide. The bolt drive spring could operate between the bolt assembly and receiver, rather than between the bolt assembly and barrel extension. Similarly, the pivot of the accelerator could be placed on the spring guide and a link similar to link 134/136 used to connect the accelerator to the barrel. (Note that the term "barrel" as used includes all parts which are fixed to the barrel, such as barrel extension, etc.) The functions of the stops for the springs may be replaced in any manner which provides proper limits for the motion of the accelerator. The delay provided by the gap G can be obtained, for some types of bolt assemblies, by a similar functional gap elsewhere in the bolt assembly.
1. Field of the Invention
This invention relates to automatic and semiautomatic guns which are recoil operated.
2. Description of the Prior Art
Recoil operated, single barrel guns, utilizing the Browning short recoil system of operation, are well known, and are described in some detail in "The Machine Gun" Vol. IV, by G.M. Chinn, 1955, published for the Department of the Navy by the U.S. G.P.O. Most of these guns utilize a rigid mechanical device to accelerate the bolt from the barrel during recoil movement. When fired on a relatively stiff mount, these guns develop a relatively high instantaneous recoil force.
BRIEF SUMMARY OF THE INVENTION
It is, therefore, an object of this invention to provide a recoil operated, single barrel gun, having a short recoil system of operation, and an inherently lower recoil force than conventional guns of this type.
Another object is to provide a gun of this type having an operating cycle which is relatively insensitive to fluctuations in ammunition performance.
A feature of this invention is a gun having a short recoil system of operation and a bolt accelerator which includes the barrel drive spring and the barrel buffer spring as a part of its operating mechanism.
BRIEF DESCRIPTION OF THE INVENTION
FIG. 1 is a side view in longitudinal cross-section of the essential structure of a gun embodying this invention;
FIG. 2 is an aft end view of the gun of FIG. 1;
FIG. 3 is a view in cross-section taken along plane 3--3 of FIG. 1;
FIG. 4 is a view in cross-section taken along plane 4--4 of FIG. 1;
FIG. 5 is a partial view in cross-section taken along plane 5--5 of FIG. 4;
FIG. 6 is a view in cross-section rotated 90°, taken along plane 6--6 of FIG. 3;
FIG. 7 is a detail top view of the feed drive cam plate of the gun of FIG. 1;
FIG. 8 is a schematic diagram of the accelerator of the gun of FIG. 1, at the instant of firing; and
FIG. 9 is a schematic diagram of the accelerator of FIG. 2, during recoil.
DESCRIPTION OF THE PREFERRED EMBODIMENT
1. Introduction
The gun shown in FIG. 1 utilizes the barrel extension 10, in lieu of the receiver 12, as the structural housing in which most of the other components of the gun operate. The barrel extension supports the barrel extension buffer package 20 housed within the receiver 12 which functions as a gun cradle. The barrel extension supports the feeder 16 and the feeder drive 18 in all directions, except the longitudinal, wherein support is provided by a rearward extension of the receiver. The barrel extension contains the bolt and sear buffer package 22, actuates the accelerator lever 24, and provides a barrel support 26, tracks 28 for the bolt package and locking surfaces 30 for the bolt. Thus the weight which conventionally goes into the supporting structure of the receiver is incorporated in the recoiling mass, thereby lowering the energy of recoil which must be absorbed by the barrel buffer assembly.
2. Gun Cycle
To start a cycle of operation the solenoid 32 is energized. This moves the sear release 34 transversely to the right as seen in FIG. 2. This motion drives a cam surface 36 against the sear 38. The sear is swung about its pivot 40 compressing its spring 42 to withdraw its tail 44 from a notch 46 in the bolt carrier 48 to release the bolt carrier, which is driven forward by the bolt drive spring 50. This is the start of the counter-recoil stroke. The bolt body 54 moves forward and by means of a spring 56 loaded rammer 58, strips the round 60, located on the feed tray in the feeder 16, from its link and rams it into the chamber 62 of the barrel 64. The bolt body 54 is driven by the bolt carrier 48 and is cammed into a locked position by a stud 66 riding in a cam (not shown) in the bolt body. The forward motion of the bolt carrier 48, after it has locked the bolt body, is enough to provide dwell travel during the recoil stroke. (This dwell is required to allow for chamber pressure decay.) The last gun function in the counter-recoil stroke is the firing pin release. The firing pin 70 strikes the primer and fires the round. This starts the recoil cycle of the barrel 64 and barrel extension 10. The accelerator lever 24 is pivoted on the barrel extension by a pivot stud 72, and, at the instant of firing, rests against a stop lug 74 located on the barrel extension. It is held in this position by the action of the barrel recoil spring 130. As the pivot stud 72 pushes the accelerator aft, the accelerator rotator-buffer spring guide 76 restrains the upper end of the accelerator. This restraint is a spring-loaded restraint because the accelerator rotator-buffer spring guide is attached to the buffer package 20. This action causes the accelerator lever to rotate clockwise about the pivot stud 72. A roller 78 on the lower end of the accelerator lever pushes against the front surface 80 of the bolt carrier 48 and accelerates the bolt carrier aft. The stud 66 on the bolt carrier cams the bolt body 54 to the unlocked position. The bolt carrier continues to be accelerated aft by the accelerator after unlock until the barrel support 26 strikes the spring guide 76. The barrel extension continues aft until it is halted by the buffer package while the bolt body is carried aft by the bolt carrier. The extractor 82, pivotally mounted and spring loaded in the bolt body, extracts the fired case 60 from the chamber 62 and carries it aft until the ejector 84 strikes the case and drives it laterally from the gun. The ejector 84 is spring loaded, pivoted lever, and is actuated by a cam surface 86 on the bolt carrier. The aft end of the lever is struck by the recoiling bolt carrier cam surface 86 to pivot the lever so that its front end strikes the fired case and ejects it from the gun. The bolt body continues to recoil aft until it hits the bolt buffer plate 88 of the preloaded bolt buffer spring package 22. The buffer stops the bolt and reverses its direction.
To halt the cycle the solenoid 32 is de-energized. The sear release 34 moves to the left and releases the sear 38. The sear snaps into the notch 46 of the bolt body and halts its forward motion. The sear 38 is mounted on a sear buffer plate 90 that transmits the sear load to the rear of the bolt buffer spring 92, thereby limiting the load on the sear 38.
3. Feeder
The feeder 16 is driven by a feed drive cam plate 94 attached to the barrel extension and having two cam tracks 96 and 98. The cam plate recoils and counter-recoils with the barrel extension. The cam motion, during both recoil and counter-recoil, is transmitted via two cam followers 100 and 102 journalled to two levers 104 and 106 that alternately drive via spring loaded plungers 108 and 110 a drive wheel 112 in a clockwise direction. The drive wheel 112 is attached to a shaft 114 that rotates the feeder sprocket 116. The belt of ammunition is pulled through the feeder 16 by the sprocket 116. Outer guides for the ammunition are provided by the feeder housing 118. At the ramming position, spring-loaded depressors 120 hold the round downward in the rammer slot 122 of the feeder tray portion of the feeder housing 118.
4. Feeder Drive
The feed drive cam plate 94 is attached to the barrel extension 10 and recoils and counter-rcoils with the extension. Lever 106 is mounted on the drive shaft. Cam follower 102 is positioned in cam 98. Lever 104 is mounted on the drive shaft. Cam follower 100 is positioned in cam 96. When the barrel extension recoils, lever 104 is swung clockwise by cam 96. Lever 104's plunger 108 is engaged with surface 126 on the drive wheel. As the lever swings, it rotates the drive wheel 112 clockwise. This action completes the first half of the feeder action. During the same recoil of the barrel extension, lever 106 is rotated counter-clockwise by cam 98. Lever 106 plunger 110 snaps behind surface 128 on the drive wheel. When the barrel extension counter-recoils, lever 106 rotates clockwise as directed by cam 98. This action drives the drive wheel clockwise, thereby completing the feeding motion. During barrel extension counter-recoil lever 104, directed by cam 96 swings counter-clockwise. Plunger 108 snaps behind surface 115. This positions lever 106 for the next cycle.
5. Bolt Assembly
The rotating lock type, bolt assembly of the gun is shown in FIGS. 1 and 4. Four locking lugs 124 are provided on the generally cylindrical bolt body 54. To permit the use of four lugs, the rammer 58 and extractor 82 are located forward of the lugs and are designed to fit within the outside dimensions of the lugs. This permits the extractor and rammer to enter the barrel extension through the same spaces as are provided for the locking lugs. The rammer is spring-loaded, so that it can be depressed as it enters the barrel extension.
The locking and unlocking action is provided by the stud 66 of the bolt carrier 52 which travels in a cam on the bolt body 54. This cam includes a straight portion at the front of the cam, allowing initial bolt carrier travel that does not effect the locks. This provides time for chamber pressure decay before unlocking. When the stud leaves the straight portion and enters the aft helical portion of the cam, it rotates the bolt body and unlocks the bolt, after which the bolt carrier 48 pulls the bolt body rearward. On the counter recoil stroke the locking lugs are held in respective tracks 126 in the barrel extension thereby precluding rotation of the bolt body. The stud bearing on the cam tries to rotate the head during the entire counter-recoil stroke. When the lugs 124 reach the forward ends of the tracks in the barrel extension, the bolt body is free to rotate and the lugs pass in front of the locking surfaces 30 to lock the bolt in the battery position.
6. Bolt Buffer and Sear Mechanism
The bolt buffer spring 92 performs two functions. It buffs the bolt at the end of the bolt recoil stroke; and buffs the sear when the bolt is stopped in its counter-recoil stroke.
When the bolt strikes the buffer plate 88, the buffer spring compresses, reverses the direction of the bolt and sends it forward. When the solenoid is de-energized, the sear 38 inter engages the bolt body. The sear 38 pulls forwardly on the sear buffer plate 90 and the sear buffer plate compresses the buffer spring. This action buffs the bolt to a stop.
To release the bolt, the solenoid is energized. This actuates the sear release. The sear release pivots the sear out of engagement with the bolt body, allowing the bolt to go forward into battery and to strip and fire the next round.
7. Barrel and Barrel Extension Buffer-Bolt Accelerator
The spring-biased accelerator mechanism is shown schematically in FIGS. 8 and 9. The barrel (barrel extension) 10 of the recoil operated automatic cannon is mounted to slide along the barrel axis in the gun receiver 12. The barrel 10 is pushed forward by a single acting barrel recoil spring 130 and the double acting barrel buffer spring 14, the two springs being connected in series by a buffer guide 132 which slides concentrically with the barrel bore axis.
The accelerator lever 24 is pivoted at 72 to the barrel 10 and the roller 78 on its lower end can bear on the bolt assembly drive surface 80. The upper end of the accelerator lever 24 is connected to the buffer spring guide 132 by a pin 134 and slot 136 linkage which accommodates the change in center distance between the pin 134 and the accelerator pivot 72 as the accelerator lever rotates on its pivot 72 with the barrel. Rotation of the accelerator 24 is limited in the clockwise direction by the abutment between the surface 138 of the buffer spring guide 132 and the surface 140 of the barrel. In the counterclockwise direction, rotation of the accelerator is limited by abutment between the lower end of the accelerator lever 24 and the stop lug 74 on the barrel.
In FIG. 8 the mechanism is shown in the position which exists at the instant of firing. All parts of the mechanism are at rest, or nearly at rest. The barrel 10 is held forward by the barrel recoil spring 130 holding the lower end of the accelerator lever 24 against the stop lug 74 of the barrel. The buffer spring guide 132 is positioned in the receiver 12 by the double acting barrel buffer spring 14. A gap G exists between the bolt assembly drive surface 80 and the accelerator lever roller 78.
Upon firing, the bolt assembly 52, and the barrel 10 begin recoiling together, and the accelerator lever starts to rotate clockwise about its pivot 72 on the barrel, the accelerator being restrained at its upper end by the link 134/136 and the buffer spring guide 132. After a time delay, which is determined by the size of the gap G, the accelerator strikes the bolt assembly drive surface 80, thereby imposing upon the bolt 52 an accelerating force which is determined primarily by the preload of the barrel buffer spring 14 and the proportions of the accelerator lever, the force developed by the barrel recoil spring 130 being lower than that of the buffer spring 14.
As the barrel continues to recoil the barrel recoil spring 130 and the buffer spring 14 are both compressed, and the resulting force applied to the bolt assembly 52 causes it to accelerate away from the barrel 10 as shown in FIG. 9. The acceleration continues until the surface 140 of the barrel abuts the surface 138 of the buffer spring guide 130, after which the bolt continues aft independently of the barrel. Continuing action of the buffer spring 14 brings the barrel 10 to a stop, reverses its direction, and returns all components of the mechanism except the bolt 52 to the battery position, as shown in FIG. 8. The bolt driving spring 50 then returns the bolt assembly 52 to battery position to initiate another cycle of the mechanism.
The spring-biased accelerator mechanism has been described as applied to a short recoil automatic gun in which the barrel is free to return to battery before the return of the bolt assembly. Should a barrel hold back feature be desired it can be provided by any of several means, without interfering with the objectives of this invention. Such means would preferably retain the barrel with respect to the buffer spring guide in such position that surfaces 138 and 140 remain in close proximity to each other, and such that the hold back feature is buffered with respect to the gun receiver or cradle by means of the barrel buffer spring.
Several details of the construction of the device can be varied without effect on its overall function. For example, the barrel recoil spring, described as operating in series with the barrel buffer spring, could operate in parallel, that is, between the barrel and the receiver. The link 134/136 may be replaced by any of several connecting means which will provide the relative connection between the accelerator and the buffer spring guide. The bolt drive spring could operate between the bolt assembly and receiver, rather than between the bolt assembly and barrel extension. Similarly, the pivot of the accelerator could be placed on the spring guide and a link similar to link 134/136 used to connect the accelerator to the barrel. (Note that the term "barrel" as used includes all parts which are fixed to the barrel, such as barrel extension, etc.) The functions of the stops for the springs may be replaced in any manner which provides proper limits for the motion of the accelerator. The delay provided by the gap G can be obtained, for some types of bolt assemblies, by a similar functional gap elsewhere in the bolt assembly.