Gun barrel recoil brake with throttled counterrecoil
BACKGROUND OF THE INVENTION 
     The present invention relates to a hydraulic gun barrel brake including a pneumatic gun barrel recuperator which is moved jointly with the recoil brake by way of a breech ring of a gun barrel. 
     It is known that in heavy weapons systems, for example in guns, the recoil velocity of the gun barrel is controlled by means of a throttling rod built into the recoil brake. Such a recoil brake is disclosed in German Patent No. 1,283,706. DE-AS No. 2,053,098 also discloses the throttling of the counterrecoil velocity of the gun barrel by means of a throttling device disposed in a separate recuperator. 
     Due to the respective arrangement of a recoil throttle in the recoil brake and a counterrecoil throttle in the recuperator, considerable manufacturing costs result in the production of both devices. For example, the throttling of the counterrecoil movement within the recuperator requires, in addition to the provision of a gas pressure chamber, also a complicated hollow recuperator cylinder filled with hydraulic fluid and an additional throttle valve. Due to the arrangement of the fluid throttle within the recuperator whose external dimensions are given, the internal gas volume is subjected to an increased pressure level and greater pressure fluctuations, thus possibly resulting in increased wear of the seals and thus also in increased maintenance costs. 
     The use of maintenance friendly seals is possible according to U.S. Pat. No. 4,587,882, but in this hollow cylinder no defined counterrecoil velocity can be set for greatly varying recoil lengths as they occur with weapons that fire at high angles. However, the realization of a uniform counterrecoil velocity is necessary for trouble-free operation of the weapon mechanism. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the present invention to improve the brake and recuperator system of a gun barrel composed of a separate brake cylinder and a separate recuperator cylinder so that the components in the recuperator are reduced and its readiness for use and reliability are increased, with a given counterrecoil velocity being realized even with varying recoil lengths. 
     This is accomplished by providing a hydraulic recoil brake to accompany a recuperator on the breech ring which provides damping of both recoil and counterrecoil of a gun barrel. The brake has a piston ring which is axially reciprocally displaceable on the break piston and is engaged by a spring which elastically urges the piston ring to a position after a recoil in which an axial bore in the piston ring damps the counterrecoil by resisting a flow of hydraulic fluid therethrough. Brake pressure from the hydraulic fluid urges the piston ring into an opposite position against the force of said spring during a recoil where a face of the brake piston abuts an end of the bore to render it ineffective for damping. The piston ring additionally serves to render damping by the control rod ineffective during counter-recoil by blocking connecting channels formed in the brake piston which connect a brake chamber formed between the inner surface of the brake cylinder and the brake piston rod, and an elongated throttle chamber between the brake piston rod and the control rod. 
     By placing the counterrecoil damping means into the recoil brake, the recuperator can be constructed much more simply and more economically. The recuperator is now composed of only a cylinder and a piston rod including a piston and the associated seals. With the same given total volume for the recuperator, a large gas volume is available with the advantages of a flat compression characteristic, particularly in view of the service life of the seals. 
     The arrangement according to the invention of an axially displaceable piston ring on the brake piston of the recoil brake makes it possible in a simple manner during recoil of the gun barrel that only the passage openings required to throttle the recoil are opened and they are closed immediately when the gun barrel switches to counterrecoil. At the same time that the gun barrel switches to counterrecoil, the means for damping the counterrecoil become effective in that at least one bore is opened which is arranged axially parallel within the piston ring and has a constant throttling cross section. Thus, additional throttling devices for the counterrecoil of the gun barrel are no longer needed in the recuperator. 
     Moreover, the constant throttling cross section ensures a uniform movement whose velocity can be predetermined as it is required for operational and mechanical functioning of the weapon. 
     The movements of the piston ring, which acts as a blocking slide, are limited on one side by a piston head releasably connected with a brake piston. The releasability of the piston head ensures easy installation of the piston ring on the brake piston. 
     For the process of closing the passage bores required, on the one hand, for the braking process and, on the other hand, for the counterrecoil movement, no additional seals are needed at the piston ring because the end and guide faces of the piston ring and the contacting faces of the brake piston are configured as sealing faces. 
     A further advantage of the gun barrel recoil and counterrecoil system according to the invention is that it is possible to effect positive throttling of the counterrecoil velocity even with different recoil lengths. For this purpose, a further feature of the invention provides that the control rod is equipped with throttling grooves of different lengths, with the piston ring only being able to block or release, respectively, throttling grooves of the same length. This possibility of making adjustments offers an advantageous possibility for installation in high-angle firing weapons which require different recoil lengths as a function of their fire height. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     These and other features and advantages of the invention will be more completely understood from the following detailed description of the preferred embodiments with reference to the accompanying drawings in which: 
     FIG. 1 is a longitudinal sectional view of a recoil brake and a recuperator connected to the breech ring of a gun barrel; 
     FIG. 2 is an enlarged view of a detail marked II in FIG. 1; 
     FIG. 3 shows the direction of movement of the recoil brake and of the recuperator during recoil; 
     FIG. 4 shows the direction of movement of the recoil brake and of the recuperator during counterrecoil; 
     FIG. 5 is a longitudinal sectional view of a recoil brake that can be set to different recoil lengths; and 
     FIG. 6 is a cross-sectional view along a line marked VI--VI in FIG. 5. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 illustrates on its right side the schematically illustrated breech ring 2 of a gun barrel in a gun (not shown). A recoil brake 1, on the one hand, and a recuperator 3, on the other hand, are fastened separately to breech ring 2. 
     Recoil brake 1 here has its brake piston rod 48 connected with breech ring 2 by way of a conventional fastening means 62 which are not here described. Recuperator 3 is fastened analogously to breech ring 2 by way of a piston rod 25 and a conventional fastening means 63 likewise not here described in detail. 
     The respective cylinders of recoil brake 1 and of recuperator 3 are disposed at a mantlet (not shown; see, for example, Handbook on Weaponry, Rheinmetall GmbH, 1982, particularly at p. 381 and FIG. 886), preferably so that the recoil brake and recuperator are diametrically opposite one another. 
     According to FIG. 1, recuperator 3 includes a cylinder 24 having a stepped diameter and being composed of prefabricated tubes which preferably have a smooth interior so that additional later treatment can substantially be omitted. In a manner not shown, cylinder 24 of recuperator 3 may also be composed of a single tube of unchanging diameter. At the end of piston rod 25 facing away from breech ring 2 within cylinder 24 of recuperator 3, a piston 26 is slidably arranged. Due to the relatively large pressure chamber 27 formed between piston rod 25 and the interior wall of the cylinder and preferably filled with nitrogen, the pressure gas is compressed only comparatively slightly during recoil of the gun barrel so that the increase in pressure is minimal compared to prior art recuperators and, for example, the load on sealing elements 28, 29 provided at piston 26 and at cylinder 24 is only slight. 
     Cylinder 24 is closed on both sides by known flanges 30, 31, with the flange associated with breech ring 2 including guides and further sealing members 32, 33 and the other flange 31 including a ventilation bore 34. 
     The recoil brake 1 shown in FIGS. 1 to 4 is closed off by flanges 36 and 37 respectively at opposite ends of the cylindrical jacket 35, with the flange 36 disposed on the side of the breech ring being equipped in a known manner with means for guiding and sealing the brake piston rod 48 which is connected with brake piston 4, while the flange 37 fastened to the other end of jacket 35 forms a support bearing for the spring 38 of an equilibrator (see Handbook on Weaponry, FIG. 927) piston 39 as disclosed in German Patent No. 1,283,706 and a guide for an indicator 40 which provides an exterior indication of the position of equilibrator piston 39. These components are essentially known and not relevant to the invention so that their detailed description is omitted for the sake of brevity. 
     Within brake piston 4 and brake piston rod 48, a fluid stream control rod 5 is provided which is rigidly fastened to cylinder jacket or wall 35 ahead of equilibrator piston 39. In the region where it is fastened, this control rod 5 is configured as a disc 41 so that the space formed between equilibrator piston 39 and flange 36 at the breech ring is divided into a heat compensation chamber 42 and a brake chamber 13. Both chambers 13 and 42 are connected with one another by means of at least one known compensation bore 43. 
     In order to fasten control rod 5, disc 41 is connected to cylindrical jacket 35, on its side facing heat equalization chamber 42, by way of a flange 45 which can be screwed on to the side of disc 41 by means of screws 44 and which, together with preferably three segments 47 distributed over the circumference and engaging form-lockingly in recesses 46 of cylinder jacket 35, form a solid attachment for control rod 5 to cylinder wall 35. The segments 47 here ensure simple installation and removal of control rod 5. 
     With part thereof projecting into brake piston 4 and into brake piston rod 48, control rod 5 forms a known throttling chamber 14 to throttle the recoil movement of the gun barrel. At its free end, control rod 5 includes, in a known manner, a counterrecoil restraining spear 49 which is provided with a longitudinal groove (not shown here) for return of the pressure fluid, with this groove opening into a counterrecoil restraining spear chamber 51. For further removal of the pressure fluid that has been pressed by counterrecoil restraining spear 49 out of bore 50 of brake piston rod 48 into counterrecoil restraining spear chamber 51, control rod 5 is provided with an axial bore 52 which, on the one hand, is connected by way of further bores 53 with counterrecoil restraining spear chamber 51 and, on the other hand, ahead of disc 41 and by way of radial bores 54, directly with a chamber 56. On the side where control rod 5 is fastened to cylinder wall 35, the outlet of axial bore 52 is, as shown in FIG. 2, closed off by a plug 55. 
     Brake piston 4 of recoil brake 1 includes, as medium for damping recoil and counterrecoil, a piston ring 7 which is axially displaceable against the force of a spring 6 and is configured as a blocking slide. On the one hand, during counterrecoil of the gun barrel, piston ring 7 blocks with the force of spring 6 the connecting channels 12 formed in brake piston 4 between brake chamber 13 which is formed by brake piston 4 or, more precisely, brake piston rod 48 and the interior face 10 of the brake cylinder wall 35, and a throttle chamber 14 formed jointly by brake piston 4 or, more precisely, brake piston rod 48 and control rod 5. On the other hand, piston ring 7 causes at least one bore 15 disposed within it to become effective as means for positive counterrecoil damping. 
     Bores 15 extend axially parallel within piston ring 7 and connect, during recoil, the brake chamber 13 lying behind the free outlets 16 of the bores with the chamber 56 which is formed between piston ring 7 and disc 41 of control rod 5. The diameter d and the length 1 of each bore 15 are here selected in such a manner that the counterrecoil velocity of the gun barrel fastened to breech ring 2 can be positively predetermined and remains approximately constant. 
     On its side facing away from outlets 16, piston ring 7 is provided with an end face 17 which is adapted to the preferably radially extending abutment face 18 of brake piston 4 and into which bores 15 open. 
     During recoil, under the effect of the brake pressure existing in brake chamber 13, the end face 17 of piston ring 7 is pressed against abutment face 18 of brake piston 4. This causes the passage of bore 15, which is open during recoil, to be interrupted at the time of braking. 
     FIG. 3 illustrates the position of the annular piston during recoil. Brake piston rod 48 is here pulled in the direction 57 through breech ring 2 out of recoil brake 1. This causes pressure fluid to flow as indicated by the arrows out of pressure chamber 13, through connecting channels 12 of brake piston 4 into pressure chamber 14 and from there into chamber 56, thus braking the recoil in a known manner corresponding with the throttling cross sections of control rod 5. 
     During recoil, piston rod 25 is likewise pulled through breech ring 2 out of the recuperator, likewise in direction 57, thus compressing by means of piston 26 the gas volume present in pressure chamber 27. 
     FIG. 4 shows the movement during counterrecoil when the expanding pressure gas pulls piston rod 25 through piston 26 into recuperator 3, thus also moving brake piston rod 48 into cylinder 35 of recoil brake 1 by way of the likewise moved breech ring 2. Before the onset of the counterrecoil movement, piston ring 7 has been displaced axially under the force of spring 6 into the position in which connecting channels 12 are closed, such position being delimited by a stop 59 provided at brake piston 4 (FIG. 2). Thus, during counterrecoil, pressure fluid flows in the direction of the arrows in FIG. 4, no longer through connecting channels 12 but, in order to realize a predetermined counterrecoil velocity, through the released bores 15 of piston ring 7 out of chamber 56 which is now under pressure and into brake chamber 13 which is pressure relieved during counterrecoil. 
     In order to provide a seal and realize a fast sliding movement, piston ring 7 is equipped, on its outer face 8 facing the interior face 10 of cylinder jacket 35, with low-friction and low-maintenance sealing elements 9, 9.1. On its interior, piston ring 7 has guide faces 11 in the form of a bore which slide on a cylindrical attachment(extension) 60 to brake piston 4. 
     For easy installation of piston ring 7, a head 19 which accommodates the abutment face 18 for brake piston 4, is releasable fastened by means of a thread 61 to the free end of brake piston 4. For this purpose, thread 61 has a smaller diameter than attachment 60. Spring 6 which is disposed between the end face 17 of piston ring 7 and the abutment face 18 of head 19 is a compression spring and is mounted in respective grooves 20, 21 oriented in the respective axial directions in piston head 19 and in piston ring 7. 
     In a further embodiment of the recoil brake 1.1 shown in FIGS. 5 and 6, the closable connecting channels 12 which are disposed in brake piston 4.1 inside piston ring 7 open into throttling grooves 22, 23 of control rod 5.1, with throttling grooves 22, 23 having different lengths and being rotationally adjustable, in a manner not shown in detail, from outside recoil brake 1. 
     Thus, the maximum recoil path of the gun barrel as indicated by an &#34;s&#34; in FIG. 1, can be realized by comparatively long throttling grooves 23 and a shortened recoil path can be realized by shorter throttling grooves 22. Throttling grooves 22, 23 are offset relative to connecting channels 12 in such a manner that only oppositely disposed throttling grooves 22 or 23 of the same length can be connected with connecting channels 12. The throttling rod is here fastened in a manner different from the embodiment shown in FIG. 2, namely outside of recoil brake 1. 
     It will be understood that the above description of the present invention is susceptible to various modifications, changes and adaptations, and the same are intended to be comprehended within the meaning and range of equivalents of the appended claims.