IL28209A - Toothed rotor mechanisms for automatic guns feed from two cartridge belts - Google Patents

Description

PATENTS FORM No; 3 PATENTS AND DESIGNS ORDINANCE SPECIFICATION o*3Tion o»'t»»pioVK o'an "na? mmwa lio maiyaa o'^iVsw D'ins rinnn »nwa We, BREVETS AERO-MECANIQUES S.A., a Society organized and existing under the laws of the Confederation o Switzerland, with Office at 8, rue de 1"University GENEVE (Suisse), do hereby declare the nature of this Invention and in what manner the same is to be performed* to be particularly described and ascertained in and by the following statement. 3361-6† 7.6.1967-6 The present invention relates to feed mechanisms for automatic guns including two toothed rotors adapted to cooperate respectively with two cartridge "belts, means being provided for coupling one or the other of these rotors with 5 a common driving mechanism, advantageously operated by the recoil movements of a movable portion of the gun, whereby said gun can be fed from one or the other of said belts, which belts may be fitted with ammunitions of different kinds, for instance explosive shells for one of the belts and armor piercing projectiles for the other belt.

The chief object of our invention is to provide a feed mechanism which is better adapted to meet the requirements of practice than those existing at the present time, especialLy from the point of view of simplicity and safety of operation* Such a feed mechanism includes two tubular toothed rotors for conveying corresponding cartridge belts respectively toward two pulling systems from either of which the extracted cartridges are moved into a common feed passage loading to the gun, one or the other of said rotors being rotated from a common driving device actuated, on the firing of every cartridge, by the recoil movement of a heavy part of the gun, and possibly of the whole of said gun, with respect to a stationary cradle.

The chief feature of our invention consists in making use, for rotating one or the other of the rotors from tho common driving device, of two torsion rods housed respectively in said two rotors and coupled together in positive and permanent fashion at their onds located on one side of 0 tho device so as to form a transmission having a capacity of torsion greater than that of each torsion rod, coupling means "being provided for, on the one hand, angularly coupling with said common driving device either of the free ends of said transmission and, on the other hand, angularly coupling the other free end of said transmission with the rotor in which is housed the torsion rod to which belongs said last mentioned free end of the transmission, abutment means being advantageously provided for limiting the angular displacement of each rotor to a given pitch for every shot that is fired* Another feature of our invention consists in arranging the feed mechanism of the type in question in such manwv. ner that both of the cartridge belts enter the feed mechanism at the upper part thereof, that the elimination of the empty links takes place laterally on either side of the feed mechanism and preferably in the downward direction, and that the cartridges torn away from their links are pushed toward a middle delivery passage located at the lower part of the feed mechanism, A third feature of our invention, for use in a feed mechanism including two distinct systems each for detaching the cartridges from the corresponding cartridge belt and feeding them through a respective guideway to a common outlet passage through which they are led to the gun, consists in providing each of these guideways with at least one movable lever adapted to shift, against the action of resilient return means and under the thrust of a cartridge running through the guideway supposed to be in operation from a guideway closing position to a guideway clearing position, the movable lever located in the other guideway (not in operan ration) then remaining in its closing position where it ooming from the guideway in operation to penetrate, into tho delivery passage common to both of the guideways.

A preferred embodiment of the present invention will be hereinafter described with reference to the appended drawings given merely by way of example and in which, Fig.t is a side view, with portions in vertical section of a feed mechanism made according to the present inventionj Pig.2 is a cross-sectional view on the lino Ilfll of Pig.3; Pig.3 is a horizontal section on the line III-III of Pig.t in the position for which the gun is fed with cartridges from one of the cartridge belts; Pig.4 is a cross-sectional view on the line IV-I7 of Pig.3; Pig.5 is a view similar to Pig.3, but more diagrammatic, and in the position for which the gun is fed with cartridges from the other cartridge belt; Pig.6 is a cross-section on' the line VI-HI of Pig.3; Pig.7 is a cross-section on the line VII-VII of Pig.3; Pig.8 shows an enlargement of a detail of Pig.7> and Pig.9 is a cross-section on the line IX-IX of Pig.3.

In the embodiment of our invention illustrated by the drawings, the feed mechanism includes two toothed rotors for feeding cartridges supplied by means of two cartridge belts B.| and B2, the cartridges of each belt being connected together through links M. It will be supposed that the cartridges of belt B^ are explosive shell cartridges and that the cartridges of belt B2 are fitted with armor pleroing projectiles. The automatic gun comprises a relatively heavy portion recoiling, upon every shot, against the action of resilient return means. The gun proper may for instance constitute this reooillng portion moving with respect to a stationary support or cradle 8, with the interposition of a resilient element (not shown by the drawings) which absorbs the recoil of the gun and ensures its return into shootin position.

The barrel 1 and the breech case 2 fixed thereto con-stitute a movable portion of the gun having a reciprocating recoil and forward movement with respect to the fixed portion S in response to the firing of cartridges. Breech case 2 is slideably mounted beneath the cartridge feed mechanism housed in casing 3 connected to the support 3 by a holding member 4. 3?he casing 3 thus constitutes a fixed frame carried by the fixed portion of the gun; and the feed mechanism remains stationary during firing. The relative movement of the gun with respect to the feed mechanism is used, durin the recoil strokes of said gun, to actuate the feed mechanism through a cam 5 carried by casin 2 and acting upon a driving device belonging to the feed mechanism and which will be hereinafter fully described.

As shown by Figs. 1 to 6, the feed mechanism includes two tubular toothed rotors 6 and 7 journalled in the frame formed by casing 3 and having their axes parallel to the longitudinal plane of symmetry of the gun and disposed symmetrically to each other with respect to said longitudinal plane. Said rotors 6 and 7 comprises, respectively, three toothed reels 6a (for rotor 6) and 7a (for rotor 7).

The feed mechanism is arranged, as shown by Pig. 2, so that the two cartridge belts B^ and enter it at the upper h two inlet passages 8 separated from ector 9 and that the empty links mechanism, through evacuation passage 10. Furthermore the cartridges torn away from their links are pushed toward a delivery passage 11 located in the middle "bottom portion of the mechanism and the sidewalls of which project into breech*- case 2 so as to guide the cartridges detached from their c links into an introduction position where they lie upon the introduction edges 11a of passage 11· With a feed mechanism of this type it is advantageous to provide a resilient transmission between the mechanism driving device and rotors 6 and 7· Such a resilient transmission permits of storing" up the energy collected from tho recoil of the gun during its short recoil stroke. and of transmitting this energy to rotors 6 and 7 during a longer time interval.

For this purpose, according to this invention, the resilient transmission includes two torsion rods 12 and 13 (Fig,3) housed respectively in rotors 6 and 7 and extending substantially over the whole length of the feed mechanism.

These two torsion rods 12 and 13 are coupled together in a positive and permanent fashion through their respective ends 12a and 13a located at the rear of the mechanism, so as to constitute a resilient transmission having a total torsion capacity equal to twice that of each of the torsion rods 12 and 13; for instance on the ends 12a and 13a of torsion rods 12 and 13 we fix two identical pinions 1 and 1 connected together by an intermediate pinion 16, We provide means capable, on the one hand, of angularly coupling with the device froe which the feed mechanism is driven either of the free ends 12b and 13b of torsion rods 12 and 13 and, on the other hand, of an^uiGrly coupling the other free end (13b or 12b) of said torsion rods with the rotor (7 or 6) in which is housed the torsion rod (13 or 12) to which belongs said other free end (13b or 12b).

The device for driving the feed mechanism is to be operated by can 5 during the recoil movement of the gun.

This driving device actuates a rotary nenber 17 (Pigs.3 and 4) rotated, every tine a shot is fired, through an angle equal to, or just a little greater than one pitch, 2 J t that is to say — ■ ■ (n being the nunber of teeth of each of the wheels of rotors 6 and 7). For this purpose, as shown by Figs.1 and 4, this driving device essentially conprises the following elements: a roller 18 carried by the casing of the feed necha-nis and located across the recoil trajectory of can 5 and a roller 19 located opposite roller 18 and carried by a push-piece 20 slidable in said casing against the action of a return spring 21 , the rearward novenent of can 5 between said rollers 18 and 19 inparting an upward displacenent to push-piece 20 whereas the return of said cam toward the front permits a return downward movement of said push-piece 20 under the action of spring 21 , and an area 22 carrying two toothed sectors 23 and 24 one of which, 23, is in mesh with a rack 20a carried by push-piece 20 whereas the other one,24, imparts a reciprocating movement to rotary member 17, consisting of a pinion in mesh with said toothed sector 24.

Between oscillating pinion 17 and toothed rotors 6 and 7, we provide a transmission such that there is leftf between central pinion 17 and each of the toothed rotors 6 V- and I f an angular play X corresponding to a portion of a complete pitc of either of said rotors, torsion rods 12 and 13 tending to maintain this play. Thus, if during a motive impulsion imparted "by pinion 17, the toothed rotor that is active does not rotate sufficiently under the action of torsion rods 12 and 13, said pinion 17 absorbs this play X so as finally to ensure a positive drive of said toothed sector.

In order to constitute the transmission means which permit of coupling at will oscillating control pinion 17 with one or the other of toothed sectors 6 and 7, use is made of the arrangement illustrated by the drawings and in particular by Fig_.3.

There is provided, between each rotor 6 or 7 and the corresponding torsion rod 12 or 13, an intermediate tubular piece (25 for rotor 6 and 26 for rotor 7) on which the corresponding rotor is freely rotatable.

The end 12b of torsion rod 12 is angularly coupled by means of splines with the corresponding end of interme-diate piece 25 and the end 13b of torsion rod 13 is similarly coupled by means of splines with the corresponding end of intermediate piece 26. The other ends of said intermediate pieces 25 and 26 are respectively coupled with the hubs of the coupling pinions 1 and 1 of the torsion rods through the intermediate of abutment means 27 and 28, having with respect to the corresponding intermediate pieces 2 and 26^ the above mentioned angular play X intended to permit the desired operation for torsion rods 12 and 13 (play X visible inPig.6).

Oscillating control pinion 17 is freely rotatable and slidable wit respect to internediate piece 25 and it is provided, on its side, with teeth 29 adapted to cooperate in a non reversible manner with corresponding teeth provided on the side of a toothed wheel 30 freely rotatable with respect to said internediate piece 25» The whole of pinion 17 and teeth 29 is urged axially toward toothed wheel 30 by a spring 31. Thus, as long as pinion 17 is rotating in one direction ,its teeth 29 cooperate with the teeth carried "by toothed wheel 30 on the left hand side-thereof so as to cause rotation of said wheel 30. Bat when pinion 17 rotates in the opposed direction, its teeth 29 slide on the olflci teeth of wheel 30 and do not drive said wheel.

Toothed wheel 30 is constantly in mesh with a sinilar toothed wheel 32 freely rotatable on the internediate tubular piece 26 corresponding to toothed rotor 7.

This transnission system further comprises reversing coupling means as above mentioned, which must permit of driving through pinion 17 either rotor 6 or rotor 7» Said coupling means are shown by Pig.3.

On intermediate tubular piece 25 there is provided a sliding sleeve 33 adapted to rotate together with said intermediate piece by means of a sliding key. Said sleeve 33 carries at its ends two dog clutch sets of teeth 33a and 33b. Teeth 33a are adapted to cooperate with corresponding teeth provided on toothed wheel 30 and teeth 33b are adapted to cooperate with corresponding teeth provided on the corresponding edge of rotor 6.

. On intermediate tubular piece 26, there is provided a sliding sleeve 34 adapted to rotate together with said intermediate piece by neans of a sliding key. Said sleeve 34 carries, at the ends thereof, dog clutch sets of teeth 34a and 34b. Teeth 34a are adapted to cooperate with corresponding teeth carried by toothed wheel 32 and teeth 34b are adapted to cooperate with corresponding teeth provided for this purpose on the corresponding edge of rotor 7» A rocking bar 35 operable by a lever 36 is provided for imparting sliding displacements in opposed directions respectively to sleeves 33 and 34.. This permits of bringing.' into operation simultaneously, either the teeth 33a of sleeve 33 cooperating with toothed wheel 30 and the teeth 34b of sleeve 34 cooperating with rotor 7 (case of Pig,3) or the teeth 33b of sleeve 33 cooperating with rotor 6 and the teeth 34a of sleeve 34 cooperating with toothed wheel 32 (case of Fig, ).

In the first case (Fig.3), the transmission system drives toothed rotor 7 due to the fact that the rotation of pinion 17 is transmitted through toothed wheel 30 sleeve 33, intermediate tubular piece 25, torsion rod 12, pinions 14, 1 and 16, torsion rod 13, tubular piece 26 and sliding sleeve 34. Toothed rotor 7 is thus resiliently driven through both of the torsion rods 12 and 13 in tor-sional prestressed state, the drive becoming imperative in case of the angular play X being absorbed, as above stated.

In the second case (Fig.5), the transmission system drives toothed rotor 6 due to the fact that the rotation of pinion 17 is transmitted through toothed wheel 30, toothed wheel 32, sleeve 34, intermediate piece 26, torsion rod 13, pinions 16, 15 and 14, torsion rod 1 t intermediate piece 25 and sliding sleeve 33. Toothed rotor.-' 6 is thus driven, either resiliently or, on the contrary, imperatively if play X is absorbed.

Thus, in both cases, torsion rods 12 and 13 introduce the sum of their respective torsions in the drive of the toothed rotor which is to be operated.

Advantageously, as shown by Pigs.2 and 6> the feed mechanism comprises, in each of the guideways connecting the points where the cartridges are torn away from belts B^ and B2 to the common delivery passage 11, at least one movable lever 37a or 37b adapted to shift, against the action of a return spring 38a or 38b working in compression and under the thrust of a cartridge travelling through the guideway supposed to be in operation, from a guideway closing position to a guideway clearing position, the movable lever 37b or 37a located in the other guideway (not in operation) then remaining in its closing position, in which it compels the cartridges coming from the guide-way in operation to penetrate into delivery passage 11.

In Pig.2 we have shown levers 37a and 37b in their guideway closing position, the feed of cartridges taking place from the. left hand cartridge belt to which corresponds the guideway provided with lever 37a. 0 Cartridge , which has just been extracted from its linkj rests upon a fixed guide 3a rigid with the casing and when said cartridge is urged toward evacuation passage 11 by rotor 6 it compels lever 37a to lift against the action of spring 38a (position shown in dot-and-dash lines in Pig.2) and thus permit? displacement., of said cartridge B^ which cones into position B,j , above evacuation passage 11. For this position, cartridge B| is, on the one hand, pushed toward said evacuation passage 11 by lever 37a returned into its guideway closing (lower) position by spring 38a and, on the other hand, conpelled to penetrate into said evacuation passage 11 by lever 37b kept in guideway closing (lower) position by spring 38b.

Of course, when the gun is fed fron the right hand cartridge belt B^, it is lever 37a that remains in guide-way closing (lower) position, lever 37b reciprocating between its lower and its upper positions (Fig,6).

On the other hand, it is of interest to provide a feed nechanisn as above described with automatic stopping means which stop firing when one of the bilts, B^ or Bg, is exhausted and preferably in this case the operation of a single control member 39 (Figs.1 and 6) simultaneously permits of operating sliding sleeves 33 and 34 and of resetting said automatic means.

In the embodiment described, said automatic stopping means include, as shown by Fig,6, two feeler members 40a and 40b subjected to the action of a spring 41 urging them to pivot upwardly, said feeler members being prevented fron pivoting by the presence of the cartridges travelling toward the corresponding extraction position (case of the feeler lever 40a on the left hand side of Fig.6). Each feeler lever is adapted, when it pivots upwardly (case of feeler lever 40b in Fig.6) to canase, t through a rocker arm (42a or 42b) turning together with the corresponding feeler lever, the pivoting of a last shot stopping lever 43 which then permits the lever 44 of the trigger systen (Fig, I) to escape, thus naking the trigger systen inoperative The operator then ceases to act upon said trigger systen and lever 44 returns to its nornal position, as shown in solid lines in Fig,1, In these conditions, the single control nenber 39 consists of a handle actuating, on the one hand, through a spindle 45 and a fork 46, the lever 36 for controlling sliding sleeves 33 and 34, and, on the other hand, a can 47 capable of pushing back the rocker am 42a or 42b precedingly driven by the rotation of the feeler lever 40a or 40b corresponding to the exhausted cartridge belt, this novenent of rocker am 42a or 42b pernitting the return of the last shot stoppin lever 43 to its initial position under the action of a return spring 48.

Thus, control nenber 39 remits of both controlling sliding sleeves 33 and 34 and resetting the autonatic stopping neans i Advantageously, a feed nechanisn as above described further includes neans for liniting, on every shot that is fired, the rotation of the operating rotor to one pitch (that is to say to an angle equal to — 2^7—Γ n being the nunber of teeth of the wheels of the toothed rotor) . This in order to ensure that, after every shot that is fired, the cooperating teeth of the two dog clutch nechanisns^are in a position permitting their cooperation. In other words, the neans in question are intended to garantee the possibility, under all circumstances, of good operation of the coupling neans which are to pernit of bringing into action the rotor that was precedingly inoperative.

By way of example it will be supposed that the feed nechanisn is to be used with an open breech automatic gun of the type in which, when the breech is closed, the first •artridge to be introduced rests upon the upper edge of the breechblock 49 of the gun (case of Fig,7)> whereas, when the breech is open, that is to say in the rear position^ where it is held by the Bear when the gunner has stopped firing, the first cartridge to bo inserted rests upon the edges 11a of evacuation passage 11, breechblock 49 being then located at the rear of said evacuation passage and being ready, on its return stroke toward the front, to catch said first cartridge to introduce it into the car~ tridge chamber of the gun (case of Fig.9)» For a gun of this type it will be of interest to make the means for limiting the rotation of the rotors to one pitch for every shot such that said neans are operative both when breechblock 49 is in closing and when it is in opening position.

For this purpose it seems simpler to divide said neans into two groups of elementary means the first of which operates when breechblock 49 is in closing position (case of Fig.7) whereas the second one works whbnsaid breechblock is in opening position (case of Fig.9).

The first group of elementary means nay be nade as illustrated by Figs.7 and Q .

One of the wheels 6a, 7a of each rotor is associated with a retractable abutment 50a, 50b capable of shifting from an active position (wherein it forms an abutment for a tooth of said rotor toothed wheel which has just conple-* ted an angular novenent of one pitch) to a neutral position (for which it permits novenent of said tooth, that is to say a new angular displacement of the rotor) · Retractable abutnents 50a and 50b are subjected to the action of return neans, for instance a connon spring .' , 51 , constantly urging said, retractable abutnents toward their active positions.

Retractable abutnents 50a and 50b, respectivelyj are controlled by two levers 37c and 37d analogous to the above nentioned levers 37a and 37b and carrying each a control can (52a for lever 37c and 52b for lever 37d) adapted to cooperate with the corresponding retractable abutnent 50a or 50b to shift it fron its active position. to its neutral position against the action of a return spring 51 when the lever 37c or 37d that is considered shifts fron the position for which it pemits the passage of the cartridges through the corresponding guideway (position of lever 37c in Fig.7) to the position for which it closes said guideway (position of lever 37d in Fig.7).

Each retractable abutnent 50a, 50b consists of a pawl pivoting about a spindle 53a, 53b, respectively, and provided, near its end, with a lateral recess d pernitting the passage of the teeth of toothed wheel 6a or 7a, which teeth then cone into contact with the base of this lateral recess when the pawl is in active position (as clearly visible for pawl 50a in Fig.7 and on an enlarged scale in Fig,8) whereas the teeth in question can nove on in rotation when the pawl is in neutral position fcase of the pawl 50b in Fig.7).

The operation of such means is then as follows, ■breechblock 49 "being in the closing position.

When lever 37c has been turned upwardly by the passage of a cartridge II, bearing upon the next cart-ridge I resting upon the upper edge of breechblock 49, the control can 52a of this lever 37c releasesthe corresponding pawl 50a which, under the action of spring 51, cones into its active position for which it is located, across the path of travel of a tooth D of toothed wheel 6a thus temporarily preventing further rotation of said too-thed wheel, the forward displacement of which is thus limited to one pitch. As soon as said cartridge II has noved forward (due to the resetting of breechblock 49 and to the downward novenent of the first cartridge to be shot onto the edges 11a of passage 11) lever 37c rotates downwardly and its control cam 52 compels pawl 50a to cone, against the action of return spring 51, into its neutral position for which it permits a further rotation of toothed wheel 6a. This further rotation is also limited to one pitch due to the upward novenent of lever 37c produced by the passage of the cartridge noved forward by this further angular rotation, said cartridge being at the end of the pitch, temporarily blocked by breechblock 49 in closing position.

As for the seoond group of elementary means for Uniting to one pitch the rotation of the toothed rotors, said means being intended to operate when shooting has been stopped with breechblock 49 in opening position/ it nay be nade as illustrated by Figs.3 and 9.

The upper portion of the feed mechanism casing 3 carries, above evacuation passage 1 1 a push-piece 54 slidablo vertically in a guide frame 55 between ¾n upper position and a lower position determined, respectively, by two lateral abutments 56a, 56 disposed at the same level and with which cooperateseither of two external shoulders located respectively at the ends of said push-piece 54. The latter is subjected to the action of a return spring 57 urging it toward its lower position, shown in solid lines in Pig.9 · To the lower end of push-piece 54 are pivoted, respectively about axes 58a and 58b, two abutments 59a and 59b the free ends of which are located respectively opposite the outlets of the two guidewgp.s leading to the common evacuation passage 1 1 .

Pivoting abutments 59a and 59b are subjected to the aotion of return means urging them from an active position (illustrated in solid lines in Pig.9 ) for which said abutments stop, through their free ends, the outlets of the corresponding cartridge guideways, to a neutral position (illustrated in dot-and-dash lines in Pig.9 ) for which said abutments are partly retracted upwardly, thus forming marginal cams in the outlets of the two cartridge guideways. Said return means advantageously consist of a spring 60 (weaker than spring 57) housed in the central portion of push-piece 54 and bearing upon a push rod 61 adapted to cooperate with heels 62a and 62b carried by pivoting abutments 59a and 59b, respectively.

The operation is as follows, the gun breechblock 49 being supposed to be in the opening position as illustrated Cartridge which rests upon the edges 11a of delivery passage 11 is ready to be introduced into the gun on the next frontward stroke of breechblo*!-: 49.

Push-piece 54 is close to its lowermost position for which it would hear upon side abutments 56a and 56b and the pivoting abutments 59a and 59b are applied through their heels against cartridge B| which is located before 2 cartridge in delivery passage 11 by spring 57 actings through axes 58a and 58b, in opposition to return spring 60. Said pivoting abutments 59a, 59b are therefore compelled to remain temporarily in their active positions where they close the outlets of the two guideways leading to delivery passage 11. As soon as cartridge 2 has been caught by breechblock 49, cartridge B.j , under the action of spring 60, moves into delivery passage 11 toward the position shown in dot-and-dash lines in Fig,9, where it rests upon the upper face of breechblock 49. Siriulta--neously with this displacement of cartridge | , heels 62a and 62b are released from pivoting abutments 59a and 59b which, under the action of return spring 60, come into their retracted positions (shown in dot-and-dash lines in Pig.9) where they clear the outlets of the two guideways^ while forming side cams on the upper edges of these outlets. The first cartridge B^ , fed by the rotor that is in operation, bears against the oblique plane formed by the corresponding pivoting abutment 59a or 59b in retrao*:. ted position and, through a cam effect, said cartridge B^ compels push-piece 54 to move upwardly against the thrust of its return spring 57 until cartridge B^ (which rested upon the top face of breechblock 49) moves down into introduction position where it bears upon the edges 11a of delivery passage 11, This downward novenent of cartridge permits a corresponding and simultaneous downward movement of cartridge which thus releases the corresponding pivoting abutment 59a or 59b and permits push-piece 54 to come back into its lowermost position under the action of its return spring 57. The whole is again in its initial position illustrated in solid lines in Fig.9, pivoting abutments 59a and 59b closing the outlets of the two guideways and thus temporarily stopping the two rotors through the cartridges present in said guideways. Thus the angular stroke of the rotors Is United to one pitch for every shot that is fired.

It will be noted that these devices for limiting the rotation strokes will play their part not only during firing but also when the cartridge belts are being engaged^ which requires imparting rotation of the rotors, for instance by acting upon flat faces provided on the hubs of pinions 14 and 15 or acting upon intermediate tubular pieces 25 and 26.

Furthermore said limiting devices eliminate any risk of engagement of the delivery passage 11 · In a general manner while we have, in the above description, disclosed what we deem to be practical and efficient embodiments of our invention, it should be well understood that we do not wish to be limited thereto as there might be changes made in the arrangement, disposition and form of the parts without departing from the principle of our invention as comprehended within the scope of the appended claims.

Claims (1)

1. CLAIM9; 1· For use with an automatic gun including a fixed portion and a movable portion having a reoiprocating recoil and frontward movement with respect to said fixed portion, a feed mechanism which comprises, in combination, a fixed frame carried bji said gun fixed portion, two toothed rotors, a first one and a second one journalled in said frame about respective axes parallel to the gun axis, and located on opposite sides, respectively, of said gun axis, said rotors including each at least two toothed wheels for engaging cartridges belonging to two cartridge belts, respectively, a common feed passage carried by said frame between said two rotors for receiving cartridges from either of them and guiding said cartridges toward said gun, a driving part movable step.by step with a given pltoh in said frame in response to said gun movable portion reo^pil displacements, first transmission means for rotating said first rotor in response to every pitch of said driving part, second I transmission means for rotating said second rotor in response to every pitch of said drivin part, both of said transmission means including in common two torsion rods, a first one and a seoond one, respectively journalled in said rotors c^oaxially therewith and having corresponding respective first ends angularly coupled together, said first transmission means being adapted angularly to couple the second end of -'^- "' 28209/2 .. ; . ■ . -21- :·.' '·-·:·''. : .;· . \ said first torsion rod with said driving part and the-seoond end of said second torsion rod with said second rotor* said second transmission means being adapted . angularly to couple the second end of said second torsion rod with said driving part and the second end of said first torsion rod with said first rotor, clutch' eane-:for "-·· alternately making one of said transmission means operative and the other one inoperative, and means for operating sa^d clutch means. 2. , A feed mechanism according to -claim 1 herein r both of said torsion rods are of the ame length. '-■:' ■} J. A feed mechanism according to claim 1 including two pinions secured to the respective first ends of said torsion rods and a pinion journalled in said frame , interconnecting said two pinions together. 4· A feed mecha ism accordin to claim 3 wherein said driving part is a pinion Journalled in said frame, further including means operative b the reciprocating movement of said gun movable portion for imparting a rotation of one pitch to said pinion, in response to every reciprocation of said gun movable portion with respect to said gun fixed portion. . .- :\ . ; 5. 1 A feed mechanism according to claim 4 wherein s^aid transmission means are adapted to provide^ between said driving part and said rotors, an angula play : correspondin to a portion only of said pitch, this play 28209/2 -22- ending to be maintained by said torsion rods. 6. A feed mechanism according to claim 5 wherein said first transmission means comprise, coaxially Interposed between said first rotor and the corresponding torsion rod, a first tubular piece on whic the corresponding rotor is freely rotatable, and ΒΠid second transmission means comprise, coaxially interposed between said second rotor and the corresponding torsion rod, a second tubular piece on which the corresponding rotor is freely rotatable, said driving part being a pinion coaxial with said first tubular piece and freely rotatable and longitudinally slidable thereon, said pinion being provided, on one side thereof, with a set of non-reversible teeth, the feed mechanism comprising a first toothed wheel freely rotatable on said first tubular piece provided on its side with a set of nonreversible teeth adapted to cooperate with the above mentioned set of non-reversible teeth, resilient means for urging said pinion toward said first toothed wheel to tend to engage said two sets of non-reversible teeth with each other, a second toothed wheel in mesh with said first toothed wheel and freely rotatable on said second tubular piece, a first dog clutch sleeve slidable longitudinally on said first tubular piece but angularly fixed with respect thereto, Baid dog clutch sleeve being provided at its respective ends with two sets of teedJh, a first one adapted to cooperate : 28209/2 ·■■; . ■ -23- with a corresponding set of teeth provided on the opposite fide of said first toothed wheel and a secon one adapted to cooperate with a corresponding set of teeth provided on the opposite edge of the corresponding toothed rotor, a second dog clutch sleeve slidable on said second tubular piece, this last mentioned sleeve being slidable longitudinally on said second tubular piece but angularly fixed with respect thereto, said second dog clutch sleeve being provided at its respective ends with two sets o teeth, a first one adapted to cooperate with a corresponding set of teeth provided on the opposite side of said second toothed wheel and a second one adapted to cooperate with a corresponding set. of teeth provided on the opposite edge o the corresponding toothed rotor, and control means of a reversing type for imparting sliding displacements in opposite directions to said dog clutch sleeves, said control means being arranged in such manner as to make it possible simultaneously to engage either the first set of teeth of said first sleeve with said first toothed wheel and the second set of teeth of said second sleeve with the corresponding rotor, or the seoond set. of teeth of said first sleeve with the corresponding rotor and the first set of teeth of said second sleeve with said second toothed wheel. 7. A feed mechanism according to claim 1 comprising a commoh . (Je11very passage, two guideways extending between the points 'where the cartridges are detached from the respective cartridge belts and said common delivery passage, 28209/2 ·.. -24-· . a movable lever In each of sa^d guideways, resilient return means working in compression, adapted to act on said levers respectively, each of said levers being adap-ted to shift, under the effect of the thrust exerted thereon by the nex oartridge travelling through the guideway in operation* from a lowermost position, in which it closes said guideway to an uppermost position in which it permits passage of said, cartridge, the movable lever present in the other guideway then remaining in its lowermost position where it compels by abutment the cartridges travelling through the guideway in operation to penetrate into the common delivery passage. 8. A feed mechanism acco ding to claim 1 including an automatic stopping system to interrupt firing when one of the cartridge belts is exhausted, which further comprises a single control member for simultaneously operating said clutch means and rearming said automatic stopping system. 9. A feed mechanism according to claim 6 including an automatic stopping system to interrupt firing when one of the cartridge belts is exhausted, which further comprises a single control member for simultaneously operating said dog clutch sleeves and rearming said automatic stopping system, wherein the automatic stoppin system comprises two feeler levers and a spring tending to pivot upwardly, said feeler levers prevented from pivoting by the presence of the cartridges- arriving at the place where they are detached from the cartridge belt, a roclcer arm fixed on the axis of the corresponding feeler lever, respectively, to cause, from their links being located at the lower part of the mechanism* 11. A feed mechanism according to claim 1 which further comprises means for limiting, on every shot that is fired, the rotation of the rotor in operation to one pitch, that is to say to an angle equal to 27r/xit n being the number of teeth of each of the wheels of said rotor. 12. A feed device acoording to claim 1 intended for use on an open breech automatic gun of the kind of those where, when the breech is closed, the first cartridge to be introduced rests upon the upper face of the gun breechblock, this rotor toothed wheel, at the end of an angular 3troke of one pitch to a neutral position where it permits rotation of said tooth, to act on the retractable abutments corresponding to the two toothed rotors, resilient return means constantly urging said retractable abutments toward their active position, and to control said retractable abutments, two levers eaoh bearing a control oam adapted to cooperate with the corresponding retractable abutment to shift said abutment from its active position to its neutral position, against 15· A feed mechanism according to' claim 14, wherein each retractable abutment consists of a pivoting pawl provided near its end with a lateral recess permitting the paesage of the teefch of the corresponding rotor toothed wheel said teeth then coming into contact with the base of this lateral recess when the pawl is in active position, whereas said teeth can move forward in rotation when the pawl is in neutral position. 16, A feed mechanism according to claim 13 which comprises, to constitute said second group of means for limiting the rotation of the rotor to one pitch for every shot that is fired, carried by the upper portion of the frame of the mechanism, on the vertical of said common feed passage, a' push-piece slidable in said frame between an uppermost position and a lowermost position, a return spring for urging said push-piece towards its lowermost position, carried by the lower end of eaid push-piece, two axes on which are pivoted respectively two abutments the free ends of which are located r espectively opposite the outlets of the two guideways leading to said common feed passage, and acting on said pivoting abutments, return means urging them from an active position, where aaid abutments close by their free ends the outlets of the corresponding guideways, to a neutral posit n where said abutments are