US3535980A

US3535980A - Automatic,burst firing,gun

Info

Publication number: US3535980A
Application number: US787069A
Authority: US
Inventors: Robert E Chiabrandy; George H Bloom
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1968-12-26
Filing date: 1968-12-26
Publication date: 1970-10-27
Anticipated expiration: 1987-10-27
Also published as: DE1965145A1; FR2027161A1

Description

United States Patent Inventors Robert E. Chiabrandy;

. George H. Bloom, Burlington, Vermont Appl. No. 787,069 Filed Dec. 26, 1968 Patented Oct. 27, 1970 Assignee General Electric Company a corporation of New York AUTOMATIC, BURST FIRING, GUN

Bomheim et a1 2,962,935 12/1960 Hepperle 89/157UX Primary E.raminerBenjamin A. Borchelt Assistant Examiner-Stephen C. Bentley Attorneys-Bailin L. Kuch, lrving M. Freedman. Harry C.

Burgess, Frank L. Neuhauser and Oscar B. Waddell ABSTRACT: An automatic, burst firing howitzer is provided having a single tube or gun barrel, and two alternatively and sequentially utilized firing chambers which reciprocate with the tube in recoil and counterrecoil. A loading system is provided to load cartridges sequentially into the respective firing chamber approximately at the nadir of its recoil travel, which travel may vary in extent in response to the particular elevation of the tube and the powder charge fired. The loading system includes a hydraulic cylinder and spring system for continuously monitoring the recoil velocity of the chambers and for traversing the cartridge in the appropriate direction and with the appropriate velocity to fully chamber the cartridge at or near said nadir.

' Pitnted 0. 27, 1910 3,535,980

INVENTORS;

ROBERT E. CHIABRANDY, GEORGE H. aLoogn,

/ THEIR ATTORNEY.

Patented Oct. 27,1970

Sheet INVENTORSI ROBERT E. CHIABRANDY,

I GEORGE H. BLOOM,

I/ITHEIR ATTORNEY.

Patented Qct.27, 1970 3.535.980

lNVENTORS- ROBERT E. CHIABRANDY. GEORGE H. BLOOM;

BY I

/ mam ATTORNEY.

Patented Oct. 27, 1970 3,535,930

Sheet "3' of 5 INVENTORs: ROBERT E. CHIABRANDY,

luv llt llllllllllll mm m 8 S 4. N 4 NM Mm GEORGE H. BLOOM,

THEIR ATTORNEY.

v llllll l 1 o- Fm Q0 E N9 on I AUTOMATIC, BURST FIRING, GUN

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to rapid firing artillery; and especially to an artillery piece adapted to fire 'a rapid burst of rounds, e.g., a burst firing howitzer.

2. Prior Art The conventional heavy artillery piece includes a barrel assembly and a breech mechanism mounted on a recoil support mechanism. The distance of the recoil travel is mainly a function of the recoil impulse generated by the charge of powder fired to project the projectile from the weapon. It is also, inter alia, a function of the angle of elevation of the barrel assembly. Conventional weapons designed for relatively rapid fire usually fire fixed ammunition, i.e., the projectile is fixed to its powder canister. Thus, for a given type of ammunition, the powder charge fired will be substantially uniform, and the recoil impulse will be substantially uniform. The minor variation which might be caused by changes in the angle of elevation can be compensated for by changing the stiffness of the recoil buffer system. Thus, in fixed ammunition firing weapons, the distance of recoil travel is substantially invariable, i.e., subject to a variation of less than 10 percent. Historically, a round of ammunition was loaded into the breech after the breech mechanism had completed its counterrecoil travel and was in battery, i.e., in its firing, forwardmost position. This requires a firing cycle wherein the time spent in recoil and counterrecoil is wasted as far as loading is concerned. In an cffort to shorten the firing cycle, some automatically loaded weapons have provided for an initiation of the loading operation while the weapon is traveling in counterrecoil. However, these weapons have required an invariable distance of travel, i.e., the point at which the magazine shifted the round to the breech loading device was fixed. Such a system works quite well for relatively lightweight weapons, such as the 75mm AA gun and lighter weapons. which fire fixed ammunition.

However. in a weapon which fires semifixed ammunition the distance of travel is not invariable. Semifixed ammunition permits the canoneer to withdraw the projectile from the powder canister and to change the quantity of powder contained therein. The variable quantity of powder fired will provide a variable recoil impulse.

In a 105mm howitzer firing semifixed ammunition, a variation of recoil impulse of :1 may be encountered. With an ideal spring recoil system, a variation of recoil travel of 25:1 would result. However, by use of preloaded spring-hydraulic bufiers, this can be reduced to a 4:1 variation of recoil travel, e.g., 72 to 17 inches. A skilled gun crew can start loading about the time the weapon commences counterrecoil. that is before it reaches battery. However, conventional loading devices could not, since they would not have an invariable point at which to shift from the magazine to the breech loading mechanism.

A related problem is that the fuzes and rotating bands on many projectiles are quite sensitive to acceleration. It is desirable to chamber the roundat as low a relative velocity between the round and the breech as possible. For this reason also, it is desirable to chamber the round at or about the nadir or the point of maximum recoil travel. at which point the velocity of the breech will be zero.

SUMMARY OF THE INVENTION It is an object of this invention to provide an ammunition loading system for automatically, rapidly loading a relatively heavy artillery piece with semifixed ammunition; which ammunition may be acceleration-sensitive with respect to its fuze and rotating band.

Consequently, it is an object of this invention to provide an ammunition loading system which is especially adapted to automatically chamber each round at substantially the nadir of the recoil travel, wherever, and whenever such nadir occurs.

A feature of this invention is the provision of an ammunition loading system which continually monitors the recoil velocity ofgthe breech and continually traverses the round to be chambered in the appropriate direction and at an appropriate velocity with respect to the breech so that the round will be chambered at the nadir of the recoil travel.

BRIEF DESCRIPTION OF THE DRAWINGS These and other objects, features and advantages of the invention will be apparent from the following specification thereof taken in conjunction with the accompanying drawing inlwhich:

FIG. 1 is a view in perspective of a representative howitzer embodying this invention;

FIG. 2 is a side in elevation of the tipping parts of the howitzer of FIG. 1;"

FIG. 3 is a top plan view of the tipping parts of FIG. 2;

FIG. 4 is a rear view in elevation of the tipping parts of FIG.

FIG. 5 is a front view in elevation of the tipping parts of FIG. 2;

FIG. 6 is a side view in elevation, in partial cross section, of the hydrospring chambering mechanism;

FIG. 7 is a rear view, in cross section of FIG. 6, taken along the plane 7-7;

FIG. 8 is a detail side view in elevation of chamber indexing mechanism; and

FIGS. 9 and 10 are velocity-displacement diagrams illustrating loading under high and low recoil conditions. respectively.

DESCRIPTION OF THE PREFERRED EMBODIMENT A rapid-fire howitzer embodying this invention is illustrated in the drawing. When compared to conventional mm howitzers. the open trails of this weapon are longer. the azimuth axis is forward of the elevation trunnions, and a rotary magazine is affixed to the cradle assembly and placed above the breech. The weapon has a two-chambered indexing breech and a variable displacement ramming stroke.

The two-chambered breech, which is fixed fore and aft to a breech support, recoils with the firing barrel. which is located axially ahead of the lower chamber. These parts recoil and counterrecoil on the cradle ways. A rammer and tray assembly, which is not rigidly attached to the recoiling parts, travel on a center rod. A top carriage supports the tipping parts at the elevation trunnion and by means of elevating ball screws. The top carriage is rotatably supported by the bottom carriage, to which are attached a firing pedestal, firing trails, and the torsion bar wheel suspension.

The weapon has four major components: the recoiling parts. the cradle assembly, the top carriage, and the bottom carriage.

A. Recoiling Pans Asembly The recoiling parts assembly consists of a breech 12, a tube 14, a breech support assembly 16, an extractor assembly 20, a main cam 22 having two diametrically spaced apart cycloidal cam slots 23, intersected fore and aft by two diametrically spaced apart longitudinal return slots 230, a recoil brake 24 and a recuperator 26.

The breech I2 is a member with a generally elliptical cross section. It has two

chambers

28, 29 whose internal dimensions and rifling are similar to the same length of conventional tube. This breech 12 rotates on the cam 22, which in turn is supported by, and keyed to, a center rod 32. Both the breech and the cam are free to slide on the center rod during recoil. Two

cam followers

34, 36, diametrically opposite, are fastened to the inside of the breech to engage the cam slot 23.

Prime structural support for the breech comes from the fore and aft sections of the breech support structure 16. On the front end of the breech around both chambers, are the gas seals 38, 40 which are of the ring seal type. Adjacent each bore on the front end of the breech is a respective finely machined tapered centered hole 42 (one not shown) and a pin 45 to assure tube-to-breech alignment while firing.

lower chamber of the breech assembly, which is the firing chamber, and is supported circumferentially by a section at the front of the breech support assembly 16. The tube is attached to the breech structure by uninterrupted threads and locked to prevent rotation by the use of a locking key.

The rectangular breech support assembly 16 supports the breech 12 on the sliding bearing surfaces at both the front and rear. The sides of this assembly provide the runners 48 that ride in the cradle ways 52, during recoil and counterrecoil. The aft end of this rectangular structure develops into the breech plate assembly 54. The breech plate 54 is placed immediately to the rear of the breech. Its section is sufiiciently great to withstand the loads created by the firing impulses. This plate also keeps the round chambered when the weapon is in counterrecoil. Axially behind the lower chamber of the breech and hinged and locked to the breech plate is the horizontal-swing breechblock 56, which has an interrupted thread. (This breechblock is only used when a misfire is to be removed.)

The extractor assembly 20 consists of two, individually hinged U-shaped hinged plates 60. Each fits into a respective recessed cutout 64 on the rear face of the breech. Each plate has a set of arms which straddle the respective chambered round and bear against 180 degrees of the extractor plate rim of the round to insure a good bearing area during extraction.

The two main cam slots 23 are cut into the periphery of the main cam 22 which is a tubular member. The inside diameter of the cam tube houses a ratchet ann 68 that engages teeth 70 on the center rod 32 only during counterreeoil (skipping over the teeth during recoil). The cam slot configuration is that of a modifiied cycloid (with respect to time, not displacement). This cam slot is designed to produce minimum roller loads at high zones of fire by reducing the angular and linear accelerations of the breech and recoiling parts respectively.

Two hydrospring counterrecoil buffers mount on the forward end of the breech support assembly. They are symmetrically placed about the firing tube, and act against the cradle assembly. The recoil brake 24 is also mounted on the breech support assembly [6 and is located below the tube 14. Two hydraulic lines connect it to the recuperator 26. The recuperator has a free floating piston which provides recoil throttling action, and is nitrogen charged. Both of these hydraulic members have been made part of the recoiling parts to lower their center of mass and increase their weight. The barrel centerline is coincident with the center of mass of the recoiling parts.

The round 30 is on a loading tray 102. with the base. or rear portion. of the round held against a ram 74 spaced aft of the recoiling breech 12. In the event of low zone firing in a representative howitzer. the breech moves back approximately l8 inches. The round. positioned inches to the rear of the breech, must therefore. move forward to be chambered. A hydraulic cylinder [06, positioned at the center of the breech is acted upon by the force created by the hydraulic fluid, acting on the piston 108 and passing through an orifice therein H0. in low zone (i.e.. low recoil velocity pressure differential across the piston is low. Thus, the force against the piston is low. A gear rack 112 is formed as an extension of the cylinder, and recoils therewith. in moving rearward, it is engaged with and rotates a gear set 114 mounted in a housing 118 which is loaded by a spring I16, and which housing is formed as an extension of the piston 108. The ram 74 has a rack 120 which is engaged by the gear set 114, so that the ram moves forward a related distance. The ratio of recoil travel to ram travel is set by the gear ratio. The chambering of the round is determined by the balance between the hydraulic parameters, particularly the orifice coefficient the spring 116, and the gear ratio discussed above.

As eounterrecoil begins, the reverse occurs. The breech 12 carries the rack 112 forward causing the ram 74 and tray 102 to move aft. As the breech retums to battery, the ram returns to its neutral position. The gear housing is returned to its neutral position by action of the preloaded spring 1 16.

In the event of high zone firing, the breech moves back at higher velocity. The hydraulic fluid in the cylinder creates pressure against the forward face of the piston, forcing it to accelerate aft. This motion is transmitted directly to the housing 118 in which the gear set 1 14 is carried through the piston rod 122. This rearward motion, with respect to the cradle, forcing the gear set to translate aft against the preloaded spring 116. The gear rack, which is connected to the hydraulic cylinder, also moves aft at the speed of the recoiling parts. This rack motion tends to rotate the gear set so as to produce forward motion of the ram 74. The net result of both the translation and rotation of the gear set is such that the ram moves aft and carries the tray aft with it by abutting an afi-projection on the tray. While moving rearward, the round 30 on the tray 102 is overtaken by the recoiling parts and is chambered at a relatively low velocity (the vector addition of the two velocities). As the recoiling parts begin counterrecoil. with the round in the chamber, the action of the preloaded spring 106 and the motion of the rack [12 result in the ram 74 moving forward to its neutral position. The gear housing 118 is stopped at its neutral position by a stop 124 which is fixed to the nonmoving center rod 32. The tray 102 is so constructed so that the ram 74 may move through it while ramming and also receive adequate lateral stability from the tray which is supported by two sway braces 126 which ride in slots 128 on the center rod 32. An ogive guide (not shown) is pivotally mounted to the tray. The ogive guide forces the projectile to move afi with the case and thus precludes the separation of the projectile from the case in semifixed ammunition.

B. Cradle Asembly The cradle assembly supports the recoiling parts assembly. This asembly consists of a cradle structure 202. a center rod 32, a recoil brake piston rod (not shown). a center pin 45. a magazine feeding mechanism 210. elevating trunnions 212 and fire control equipment 214.

The cradle 202 is a rectangular structure with ribbed sections across the bottom for increased strength and rigidity. The sides of the cradle have steel inserts which serve as ways 52 for the recoiling parts. The ways are centered on the gun tube axis and extend for nearly the total length of the cradle. The center rod 32, which fits through the center of the breech, is rigidly mounted both front and rear to the cradle assembly. Sections of this rod have keyways and teeth 70 to assist in the operation of the main cam 22 and the rammer tray mechanism 74. The keyway in the center rod 32 provides the cam 22 with a nonrotating ground" and stopping point as the cam-tube pawl 68 locks onto the teeth 70 cut into the center rod 32. The rammer and tray are also keyed to the center rod.

A single-shot indexing mechanism is also located at the front end of the cradle structure. For ease of operation, the handle 226 itself is located on the right side of the weapon to the rear of the breech. This mechanism is linked through a cam and gear assembly 227 for the rotation of a circular cam 236. for indexing a feeder pawl 238. The cam 236 is coupled to the feed shaft 239 which is located above the breech, and is coupled to the magazine indexing mechanism 210.

The magazine indexing mechanism 210. which is mounted directly on the front end of the magazine 240, contains two mechanisms and a standard set of bevel gears. One of the mechanisms is a torsional spring and ratchet to permit rotation of the magazine during a longer time interval than allowed from direct rotation by the breech during recoil. The second mechanism employs a slip clutch in the bevel gear set. In this manner a pin can be placed in position to limit the number of rounds to be fired. When the desired number of rounds has been fired, the pin becomes locked and the magazine ceases to rotate.

Ammunition for burst fire is contained in the magazine 240. The magazine is supported by four connecting ribs 254 to the cradle. The magazine contains three six-tooth sprockets 256, placed to give the rounds support and guidance. The magazine can be loaded from up to five rounds through a doorway 258 in the rear. The doorway is shaped to prevent the sixth space from being loaded since this space is required for the feeder pawl 238. A round-indexing link 260 is mounted on the feed shaft 239 forward of the magazine 240 and above the breech. and is provided to coordinate the motion of the magazine and the feeder pawl. The rotary earn 236 supported by the feeder shaft 239 engages a follower 266 on the breech to coordinate round feeding to the weapon cycle.

The elevating trunnions 212 are placed sufficiently rearward so that no recoil pit is required under any firing condition. The fire control equipment 214 mounted on these trunnions consists of a direct-fire telescope mounted on the right side and an indirect-fire telescope mounted on the left.

C. Top Carriage and Equilibrators The top carriage assembly is a structure that provides sup port for the tipping parts and contains the top carriage structure 370, elevating and traversing mechanism 372 and the equilibrators 374.

The top carriage structure 370 contains the upper support 376 for the main an'muth bearing 378. From this bearing two sides frames reach up to elevation trunnions. providing support for the tipping parts. The elevating mechanism is attached to each side of the top carriage and forward of the magazine. Two ball nuts are attached to both sides of the cradle while the ball screws and universal couplings are fixed to. and ride with. the top carriage. Pitch and gear reduction of the ball screw are provided to yield a convenient elevating rate per turn of the handwheel.

An elevation handwheel is mounted on the right side of the carriage and is convenient for use with fire control apparatus. The handloads required to elevate the weapon require a low maximum torque with five rounds in the magazine. The ball screw and nut combination in this mechanism serves as a locking device, a mechanical force amplifier, and a means of rigidizing the top carriage structure. The traversing mechanism employs a partial gear, cut for 40 on the bottom carriage around the main bearing, a worm wheel and a universal coupling. The handwheel on the left hand side of the weapon is also convenient for use with fire control equipment. Gear staging in the traversing mechanism yields a convenient traversing rate per turn of the handwheel. locking in this mechanism is provided by the use of a worm wheel and gear.

Equilibrators 374 are mounted between the top carriage and the cradle. They are coil-spring-loaded, of the pull type. These two equilibrators mount symmetrically from both sides of the top carriage. back to the sides of the cradle.

D. Bottom Carriage The bottom carriage consists of the bottom carriage structure 402. split trails 404. and spades 406. wheels 408, suspension and jacking assembly 410.

The bottom carriage provides a seat for the main azimuth bearing and connecting support for both the trails and wheel suspension. On the front of this structure is a ribbed pedestal 412 on which the front end of the weapon rests when in the firing position. This pedestal has a spherical seat to allow easier placement of the weapon in extended traverse. Similarly. the carriage structure also provides a pin joint connection for each of the trails. These open trails are of the box type construction. They are tapered in height, width, and material thickness with internal ribs for additional strength. The s ades have a large effective ground bearing area.

The wheels and the suspension and jacking assembly are supported from the front end of the bottom carriage. The wheel assembly is supported on two pivoting links, which also incorporate shock absorbers for improved roadability. Suspension is provided by two torsion bars, each one spanning the distance between the wheels. Lifting of the wheels to emplace the weapon on the pedestal is done by a ball screw and nut-coupled to a handcrank. The wheels can be raised off the ground to act as outriggers when the pedestal is lowered, which will prevent the weapon from overturning when the trails are lifted. This action lifts the wheels and suspension links by unwinding the suspension torsion bars, thus lowering the weapon onto the pedestal. For traveling, the wheels are lowered to provide ground clearance for road travel.

WEAPON FUNCTION To understand the operation of the weapon, it is important to know the cycle of events in the burst fire sequence. Since all of the mechanized events must occur within the time of the natural cycle," recoil and counterrecoil. the mechanical cycle is predicated on maximizing the time available for automatic firing function the natural cycle) and minimizing weapon complexity.

Determination of the automatic weapon sequence defines in large measure the single-shot procedure. as well as the basic weapon design itself.

A. Cycle Burst Fire Procedure 1. Five rounds (or less) are loaded in the magazine.

2. One round is placed in the exposed chamber, and the breech is rotated into firing position, also bringing one round from the now-loaded magazine to a position directly behind the top chamber.

3. The lanyard is pulled, the first round is fired. and recoil begins.

4. During recoil. the round that was placed behind the top breech is rammed into the breech.

5. Recoil ends between 20 and 68 inches from battery and. as the weapon begins counterrecoil. the breech engages a fixed cam and begins rotation.

6. As the breech rotates past the breech block. the fired case is extracted and ejected.

7. The breech continues rotation, indexing 180 in 19 inches, and continues forward. As it approaches battery position, a new round is fed behind the top breech. The centering pin aligns the tube with the loaded (bottom) breech.

8. The round in the bottom chamber is fired and the cycle begins anew.

This operation can be represented schematically. indicating the time duration for each phase of the cycle. Two conditions,

Zones

2 and 7, are represented as shown in FIGS. 10 and 9, respectively.

This cycle is similar for the single shot firing sequence except that the breech must be indexed to a secondary position for hand loading. Once this operation is performed the cycle is similar to that for burst fire.

The weapon function will be analyzed by the various elements that make up a cycle, i.e.. feeding, ramming, ejection.

B. Loading and Feeding The magazine. although it has six-tooth sprockets. can accept only five rounds or less. The hinged door at the rear of the magazine is shaped to expose only five spaces; the one space required for the feeder pawl remains empty. As the rounds are placed in their sprocketed positions. they become locked in axial position. This serves two purposes: first. should the weapon be elevated during the loading process, rounds will not fall backward out of the sprockets; and. second. the rounds need to be positioned accurately in the axial direction to insure proper feeding onto the tray and rammer. Since the energy for cycle operation is derived from recoil. one round must be initially placed in the firing chamber. This is accomplished by turning the indexing lever, which. through a gear train and linkage. causes the tapered centering pin to be withdrawn (approximately I inch) from the breech, and the breech to then be rotated in a clockwise direction (looking forward) The same indexing lever motion drives the feeder shaft 8 inches forward. This, through a cam and linkage, causes two actions to occur simultaneously: first, the feeder pawl moves through an arc of 60 from a position behind the breech into the space in the magazine allocated for it; second. the magazine sprockets index 60, placing a round in the feeder pawl. This feeder pawl has a spring-loaded finger that enables it to grasp the round circumferentially for 225. In this manner the round is secured during the feeding operation.

A round may now be loaded into the exposed chamber, and the indexing lever counterrotated. The same mechanisms as before cause the breech to rotate into firing position. lock the centering pin and cause the feeder pawl. now carrying a round, to rotate behind the top (empty) chamber. The magazine does not rotate at this time. The loading and feeding operations have now been completed. The firing mechanism, once the centering pin is in position. can be triggered by pulling the lanyard.

During the burst-firing sequence, these operations are carried out automatically. Initiation of this action is triggered by the cam follower (affixed to the forward side of the breech at its greatest diameter) and the feeder cam mounted on the feeder shaft. During the first 8 inches of recoil, the cam is actuated and rotation energy is stored in a spring in the magazine indexing mechanism. This energy can be then employed to index the magazine (and rounds contained therein) 60 over a longer period of time. Indeed, during the lowest cycle time, angular acceleration of the rounds can be held to 6 rad/sec. During the feed cycle, where the round is carried from the magazine to the tray the resultant maximum acceleration (again for zone 7, the worst case) can be shown to be less than rad/see.

C. Centering The centering device insures that the firing breech and tube are in line within 0.015 inch. The rifling in the tube can be undercut to minimize the effect of possible slight misalignment.

As the recoiling parts approach battery position, angular position is maintained indirectly through the center rod. One inch before battery position. a tapered pin on the cradle crigages a hole in the forward end of the breech. This action produces the necessary final alignment. When the breech is to rotate manually for single-shot firing, the pin is automatically withdrawn.

D. Ramming The function of the ramming mechanism is to chamber the rounds fed onto the tray by the feeding pawl. This section, by the design of the cycle, must be accomplished during recoil. Two important considerations will be stated prior to relating the functional operation. First, the length of recoil varies, depending on the zone fired and elevation angle, from a minimum of 20 inches to a maximum of 68 inches. Second, fuze sensitivity limits chambering velocity to a maximum of 20 feet per second. The rammer itself is dovetailed to the center rod and attached through a spring and hydraulic damper to the breech.

The required motion of the rammer (and tray) for all zones is obtained through the operation of a hydraulic damper and a constant force negator spring. The input signal to this system is the velocity and displacement of the recoiling parts. When the weapon is firing zone 2 at 5 elevation, recoil is 20 inches; thus the rammer must carry the case forward 20 inches (the rear of the magazine is located 40 inches from the rear face of the breech) to chamber the round. During this low velocity (maximum velocity is 55.9 f.p.s. and the force created by the action of the hydraulic damper overcomes the spring force and the rammer and round retreat back from the recoiling breech. The equation of operation is:

m=mass of tray, rammer and round, 2 slugs.

p=spring preload, 250 lb.

c=damping coeflicient, 0.55 lb.-sec.*/ft.

=angle of elevation, degrees.

k=spring gradient, 0.001 lb./ft.

g= gravitational constant, 32.2 fin/sec.

w 23,, :i.,= displacement, velocity and acceleration of the cartridge; ft., f.p.s., ftJsec.

a aE displacement, velocity of the recoiling mass, ft., f.p.s.

Intermediate zones of fire will result in recoiling velocities between these two extremes. In the zone 2 case, the relative chambering velocity is 15.04 f.p.s. For zone 7, the relative chambering velocity is 7.5 f.p.s. The round, during this sequence, is being accelerated rearward at l5l ftJsecF. The projectile is held by the yoke that grips the rotating band. This continues until the breech begins to overtake the rear of the projectile. In so doing it drives the spring-loaded yoke away from the rotating bands. The round. if the rammer stopped completely at this point, would have a chambering velocity of approximately 26 f.p.s. The mechanism can be made to produce constant velocity of the rammer from the time that the breech causes disengagement of the yoke and round. In this instance, the round continues rearward at 15.0 f.p.s. The round is chambered at 58.5 inches back of the battery position. At this time, the relative chambering velocity is only 7.5 f.p.s. Since there is no acceleration during this period, there is no possibility of case-projectile separation.

During this sequence the tray will move with the rammer. When the tray is below the magazine waiting to receive a round in the fully extended condition, its length is 26 inches. As the breech and rammer come together. and the nose of the projectile enters the breech, the tray begins to telescope. The tray is shaped to allow the round to be advanced over it and be chambered without shearing the rotating bands. When the round is fully chambered, the rammer and tray have an effective length of 15 inches. This eliminates the need for a recoil pit when firing at high zone and high elevations.

E. Breech Operation During recoil the breech translates rearward. engaging the main cam tube after 20 inches of recoil and thereafter carrying the cam tube with it. The breech does not rotate since. through a secondary straight line cam path. it is keyed to the center rod. The cam tube has a dog latch that skips over the teeth on the center rod. These teeth exist from 20 to 68 inches behind battery. When the weapon ceases recoiling (at a point between 20 and 68 inches. determined by weapon elevation and zone) and begins counterrecoil. the dog engages the tooth in that location on the center rod. This action locks the cam to the stationary center rod in both translation and rotation. and prevents it from moving forward with the recoiling mass. Two cam followers L5 in. diameter each). located diametrically apart on the breech inner diameter, are engaged by the cam and forced to rotate. thus rotating the complete breech assembly. The cam is a modified cycloid designed to impart 180 of rotation to the breech in the first 19 inches of recoil. (Since the minimum recoil distance is 20 inches, this leaves l inch for engaging the centering pin.) The cam design is such that only l of rotation occurs during the last 3 inches (from inch 15- l9) of travel. This allows time for damping the angular oscillation of the assembly. The cam has been designed to minimize the rotational and translational accelerations and thus keep the resultant forces down. Thus the highest angular acceleration occurs when the breech is just beginning to counterrecoil and the translational acceleration is low. The cam insures that, under what is potentially the most severe condition, zone 7, the resultant angular displacement plotted against time is a cycloid. During this rotational cycle, ejection takes place. As the breech comes to the end of the first 20 inches of counter recoil, the cam followers engage a latch on the dogs. lifting them out of the center rod teeth. The cam tube is then 0 carried back with the breech. A spring drives the cam tube back to the position it held at the initiationof the cycle.

F. Extraction and Ejection Extraction of the fired case is begun during counterrecoil when the breech has rotated 68. bringing it clear of the breechblock. At this point (the time of this occurrence changes with the zone) the ejector plate with its U-shaped fingers in front of the (just fired) case rim is struck by a finger on the cam tube, which has no forward velocity at this point. v

The extractor plate is constrained to pivot about one end and drive the case out of the breech, when struck by a protrusion on the cam wall. The geometry of the ejector is such that the velocity imparted to the case is three times the counterrecoil velocity at that time, and directed rearward.

' The minimum ejection velocity occurs at zone 2 and is 18.0

f.p.s.; the maximum is 42 f.p.s. at zone 7. The rotation of the breech during this time gives each ejected case a tangential velocity. perpendicular to the rearward ejection direction. This tangential velocity is approximately a third of the ejection velocity. Since the point of extraction and the direction of ejection are known for every zone an ejection guide can be added to the cradle to prevent fired cases from striking the weapon or crew. Since the ejection mechanism is positive (that is, no springs or pressure systems are employed) the case is certain to be ejected even if high breech sealing forces exist.

We claim:

1. An automatic. rapid firing. artillery piece. comprising:

support means having a first longitudinal axis;

a single tube. having a second longitudinal axis parallel to said first longitudinal axis, and mounted to said support means for reciprocation along said second longitudinal axis in recoil and counterrecoil;

a breech assembly. having a plurality of chambers disposed in an annular row about a third longitudinal axis which is parallel to said first longitudinal axis. and mounted to said support means aft of said tube for reciprocation along said third longitudinal axis in recoil and counterrecoil and for rotation about said third longitudinal axis whereby to sequentially align each of said plurality of chambers with the aft end of said tube on said first longitudinal axis; and

loading means. mounted to said support means. including transport means for transporting a round of ammunition in either of two opposite directions along a path parallel to said third longitudinal axis from an initial, fixed station. sensing means coupled to said breech assembly for providing a signal responsive to the recoil velocity of said breech assembly. first actuating means coupled to said transport means and said sensing means for moving said transport means in an appropriate one of said two opposite directions and at an appropriate variable velocity to a variable station along said path which will be functionally adjacent the aft end of one of said chambers at the nadir of recoil travel of said breech assembly. whereby the round will be chambered in said one chamber at low relative velocity between said transport means and said breech assembly 2. An artillery piece according to claim 1 wherein said breech assembly includes:

a breech containing said plurality of chamber; and

second actuating means operable during counterrecoil travel of said breech for indexing said breech about said third longitudinal axis to shift the next chamber in sequence into alignment with said tubev 3. An artillery piece according to claim 1 wherein said breech assembly includes:

a breech containing said plurality of chambers which are two in number and disposed diametrically about said third longitudinal axis;

extraction means. operable during the recoil travel of said breech, for extracting the case of the last fired round from the last fired chamber; and

second actuating means. operable during counterrecoil travel, for rotating said breech for shifting said last fired chamber out of alignment with said tube and the loaded chamber into alignment with said tube.

4. An artillery piece according to claim 3 wherein said support means includes:

a cradle having a plurality of ways extending parallel to said first longitudinal axis;

fore and aft plates and a main center rod fixed therebetween parallel to said first longitudinal axis:

said breech assembly includes a breech support assembly having runners mating with said cradle ways; and

fore and aft plates capturing said breech therebetween. said breech and fore and aft plates having respective longitudinal bores therethrough and passing said main center rod therethrough. whereby said breech is adapted to rotate about said main center rod.

5. An artillery piece according to claim 4 wherein:

said second actuating means includes a cylindrical cam means having a central longitudinal bore receiving said main center rod therethrough and an exterior surface having two cycloidal cam slots and two longitudinal return cam slots diametrically spaced apart therein with forward and rearward intersections respectively. said cylindrical carn means being keyed to said main center rod and free for relative longitudinal movement only, and having additional interlock means adapted to preclude forward longitudinal movement of said cylindrical cam means relative to said main center rod;

said breech being joumaled on said cylindrical cam means and having two diametrically spaced apart cam slot followers respectively engaging said cam slots in said cylindrical cam means and adapted to follow said longitudinal return cam slots during rearward movement relative to said cylindrical cam means and to follow said cycloidal cam slots during forward movement relative to said cylindrical cam means;

whereby. immediately prior to the firing of a round of ammunition. said breech and said cylindrical cam means are in their respective forwardmost positions with said cam followers in said forward intersections of the cycloidal and return slots; and

subsequent to firing. said breech recoils rearwardly with said cam followers riding in said return slots. and said cam means stationary. until said cam followers reach said rearward intersections of the cycloidal and return slots. causing said cam means to travel rearwardly with said breech until said breech reaches its nadir of recoil travel. and said additional interlock means becomes operable to preclude forward movement of said cam means; whereupon said breech counterrecoils forwardly with said cam followers riding in said cycloidal slots causing said breech to rotate with to respect to said stationary cam means until said cam followers reach said forward intersections of the cycloidal and return slots and deoperate said additional interlock 'means to permit forward movement of said cam means and causing said cam means to travel forwardly until said breech reaches its battery positron.

6. An artillery piece according to claim 5 wherein:

said additional interlock means comprises two diametrically spaced apart longitudinal series of rearwardly pointed teeth cut into said main center rod. and

two forwardly pivoted latching dogs respectively disposed in said forward intersections of said cam slots and extending centrifugally to normally engage with said respective series of teeth and adapted to be actuated. by said rollers when they are in said forward intersections. to disengage from said teeth.

7. An artillery piece according to claim I wherein:

said transport means includes a tray for receiving and sup porting a round of ammunition;

said first actuating means including a ram having a longitudinally extending rack;

a cylinder fixed to said breech and having a longitudinally extending rack;

a piston, disposed in said cylinder. having a longitudinally extending member fixed to a gear housing. and having a longitudinal orifice through said piston between the forward and aft sides thereof;

two gears fixed to a common shaft in said gear housing. one gear meshed with said rack of said ram. the other gear meshed with said rack of said cylinder;

said sensing means includes spring means normally biasing said gear housing and piston forwardly in the counterrecoil direction;

hydraulic fluid disposed in said cylinder and adapted to flow between said forward and aft sides of said piston through said orifice; and

whereby the direction and velocity of movement of said ram is responsive to the combined effects of the direction and which is responsive to the flow rate of through said position orifice.

said hydraulic fluid