Abstract:
A method and device for cooling a gun barrel wherein coolant is provided to the gun barrel via a nozzle arranged at the downstream end of a pressure feed line arrangement. The coolant is originally conveyed from a reservoir into a pressure cylinder, while the pressure feed line between the pressure cylinder and the nozzle is closed. Thereafter, the coolant in the pressure cylinder is placed under a predefined operating pressure. Prior to firing a round, the pressure feed line is opened, so that the coolant flows to the gun barrel before firing. When firing a shot, the coolant in the gun barrel is compressed to a pressure above the predetermined operating pressure by the firing gases and pushed out of the gun barrel. In the process, the coolant is expanded into a buffer reservoir adjacent to the nozzle and is injected back into the gun barrel after the gas pressure built up has been reduced to the predetermined operating pressure.

Description:
The present invention is a continuation-in-part to U.S. application Ser. No. 09/352,469, filed Jul. 14, 1999 which issued as U.S. Pat. No. 6,311,602 on Nov. 6, 2001. 
    
    
     FIELD OF THE INVENTION 
     The invention relates to a method for cooling gun barrels of firearms, wherein a coolant is provided to the gun barrel via at least one feed line and at least one nozzle. The invention further relates to a device for executing the method. 
     BACKGROUND OF THE INVENTION 
     A prior cooling device for the gun barrels of firearms is known from German Letters Patent DE-PS 31 45 764, which is particularly suited for automatic firearms and heavy-duty automatic cannons. In connection with such heavy-duty firearms firing highly developed munitions, great wear of the gun barrels is a result of the fact that the surface heat cannot be dissipated with sufficient speed. The heat stress, which occurs in rapid sequence when firing a volley, causes surface tensions and changes in the material. The surface area can be heated up to temperatures where the material is in a plastic deformation phase. In addition, because of the outflowing powder gases, as well as the friction between the shell and the gun barrel, the gun barrel material is worn off. 
     To extend the service life of the gun barrels, the above mentioned German patent proposes to provide cooling conduits in the area of the end section of the gun barrel adjoining a drum, which are oriented radially outward between the individual cartridge seats and which are connected with a main conduit for coolant supply extending in the drum axis. The cooling conduits are connected with nozzles which extend parallel with respect to the longitudinal direction of the drum, terminating in the front face of the drum and are arranged at the same distance from the longitudinal axis of the drum as the center longitudinal axis of the cartridge seats. Blocking elements for the nozzles are provided in the cooling conduits which, in the case of firing, briefly release the respective nozzles located in the area of the barrel opening. The blocking elements are, for example, slides, which can be displaced by means of control elements sliding along a control cam during the rotating movement of the drum. The coolant reaches the interior wall of the gun barrel directly through the nozzles. In this case the nozzles are only opened for the period of time they slide by the rear of the gun barrel, and coolant is only provided if firing takes place. However, the length of sliding time can be too short in connection with gun barrel systems of higher cyclic rates, or respectively with more intense rhythmic firing, so that not enough coolant reaches the gun barrel and insufficient cooling is provided. 
     OBJECT AND SUMMARY OF THE INVENTION 
     The object of the invention is to provide a method and a device to sufficiently cool the gun barrels of weapons systems, especially so that high cyclic firing rates can be achieved. 
     This object is attained by means of the method and device in accordance with the invention. Here, a coolant is conveyed from a reservoir into a pressure cylinder by drawing up a hydraulic piston, in the course of which the feed line arrangement to the gun barrel is closed. Thereafter, the hydraulic piston is moved in the opposite direction by reversal of the pressure, and the coolant in the pressure cylinder is put under a defined operating pressure. Prior to triggering a volley, the feed line is opened so that the coolant can flow via the feed line through a nozzle to the gun barrel. The coolant is respectively pushed back by the gas pressure created when a shot is fired, and is re-injected into the gun barrel after the gas pressure has been reduced to the operating pressure. 
     The advantages which can be achieved by means of the invention reside in, among other things, the pre-firing lubrication of the gun barrel, the automatic re-lubrication of the gun barrel and the resulting increased service life of the barrel in connection with higher firing cycles. By using one or several nozzles, it is assured that a sufficiently large amount of coolant is injected into the gun barrel, wherein only little coolant can flow back after each round. 
     A further advantage can be seen to reside in that during the employment of the proposed cooling device, no mechanically actuated parts are required, with the exception of the piston, so that a high degree of dependability can be achieved. 
     The invention will be explained in what follows by means of an exemplary embodiment in connection with the drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows a partial longitudinal section of a cannon with a device in accordance with the invention, in a schematic representation; 
     FIG. 2 shows a nozzle of the device represented in FIG. 1 in an enlarged scale; and 
     FIG. 3 shows a partial longitudinal section of a cannon with a second embodiment in accordance with the invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     A gun barrel of an automatic cannon, for example a gun barrel known from the prospectus OC 2059 3 94 of the Oerlikon-Contraves company of Zürich, Switzerland, is identified by  1  in FIGS. 1 and 2, which has a muzzle brake  3  at its front  2  and on whose back end  4  a revolving housing  5  with a revolving drum, not shown in greater detail, is arranged. A reservoir  6 , which contains a coolant  7  being used as a lubricant for the gun barrel  1  at the same time, is connected via a line  8  and a flap valve  9  with a pressure cylinder  10 . A piston  11 , which is fixedly connected with a hydraulic piston  13  guided in a hydraulic cylinder  12 , is guided in the pressure cylinder  10 . The pressure cylinder  10  is connected via a feed line  14  and a valve  15  which, for example, can be electrically controlled, with the gun barrel  1 . A nozzle  16 , which has a sleeve  17  connected with the feed line  14  and is fixed in place on the gun barrel  1 , is provided at the termination of the feed line  14  located at the back end  4  of the gun barrel  1 . A labyrinth  18 , or respectively  18 ′, in the form of one or several insertion pieces is arranged in the sleeve  17 , in which a labyrinth- or meander-like conduit  19 , or respectively  19 ′, for example, is provided which, as will be explained later, causes a pressure reduction. Alternatively, instead of labyrinth insertion pieces, a similar effect can be obtained by arranging a diaphragm in the path of the coolant. A nozzle bore in the gun barrel  1  is identified by  20  which, in the present case, is arranged concentrically in respect to the sleeve  17  and whose diameter is less than that of the feed bores  21 ,  22  provided in the gun barrel  1 , or respectively in the sleeve  17 . 
     The above described device functions as follows: By drawing up the hydraulic piston  13 , the coolant  7  is conveyed from the reservoir  6  via the line  8  and the flap valve  9  into the pressure cylinder  10 , while the electrically actuated valve  15  in the feed line  14  is closed. Thereafter, the hydraulic piston  13 , and with it also the piston  11 , is moved in the opposite direction by a pressure reversal in the hydraulic cylinder  12 , and the coolant  7  in the pressure cylinder  10  is placed under a defined operating pressure of, for example, approximately 500 bar, so that the device is ready for use. Prior to triggering a volley, the valve  15  is opened, so that the coolant  7  can flow to the gun barrel  1  via the feed line  14  and the nozzle(s)  16 . The high gas pressure of, for example, approximately 5000 bar being created in the course of subsequent firing pushes the coolant back, wherein the gas pressure is reduced by friction in the nozzle  16  to the operating pressure of approximately 500 bar and only little coolant flows back. As soon as the gas pressure in the gun barrel  1  has been reduced, the coolant  7  is continuously injected into the gun barrel  1  by the operating pressure until a further shot is fired. The valve  15  is closed again at the end of a series of firings. 
     FIG. 3 is a schematic drawing which shows a gun barrel  101  with a barrel axis A. The end portion  104  of the barrel  101  is arranged in a housing  105 , not shown in greater detail. The firearm is, only as an example, a cannon as known from the prospectus OC 2059 3 94 of the Oerlikon-Contraves company of Zürich, Switzerland. 
     A reservoir  106  containing a coolant  107  is connected via a line  108  in which a flap valve  109  is arranged with a first chamber  110 A of a pressure cylinder  110  of a cylinder/piston device. A second chamber  110 B of the pressure cylinder  110  is separated from the first chamber  110 A by a piston  111  having different pressure surfaces in the first and second chambers. The cylinder/piston device comprising the pressure cylinder  110  and the piston  111  serves as a media exchanger of pressure fluids and as a pressure transducer. Chamber  110 A contains the coolant which fed to the gun barrel  101  under an operating pressure; chamber  110 B contains a pressure fluid and is connected via a line  112  with a pressure system  113  which generates a system pressure which may also be used for other purposes than for cooling the barrel  101 . 
     The coolant is a liquid with, preferably, a high cooling capacity which is heated up while cooling the barrel. A very high cooling capacity is obtained when using a coolant which evaporates during cooling the barrel  101 ; it is however important to chose a coolant which, when evaporating, does not deteriorate in a way which could harm the surface of the barrel. A preferred coolant is water, to which a lubricant like e.g. graphite powder, is added. 
     The pressure fluid is a liquid, preferably an oil, which is suitable to be used in a pressure system of the firearm; the pressure fluid may be a liquid which is not suitable to be used as a lubricant or as a coolant. The pressure fluid is brought to a system pressure which may be higher or lower than the operating pressure of the coolant. 
     By using as a cylinder/piston device a media exchanger and pressure transducer, it is possible to chose on the one hand the most appropriate coolant and operating pressure and on the other hand the most appropriate pressure fluid and system pressure. 
     Chamber  110 A of the pressure cylinder  110  is connected with the interior of the gun barrel  101 , whereto the coolant  107  has to be fed. The coolant  107  from chamber  110 A flows through a first feed line portion  114 A of a feed line arrangement  114 , a valve  115 , which, for example, can be electrically controlled, a second feed line portion  114 B of the feed line arrangement  114 , a distributor  114 D where the second feed line portion  114 B is split in at least two partial feed lines, in the present embodiment into four partial feed lines  114 C; the partial feed lines  114 C are connected to end portions  116 . Two partial feed lines  114 C end at the outer surface of the housing  105 , and the end portions  116  traverse the housing  105  and a rear portion  104  of the barrel  101 . Two further partial feed lines  114 C shown in dotted lines end directly at the barrel  101 , i.e. in a portion of the barrel  101  which is not situated in a housing. 
     Each partial feed line  114 C is connected with a diaphragm  116 A, which may simply be a smaller diameter boring, near the feed line end portion  116 . Each diaphragm  116 A ends in a buffer reservoir  116 B of the end portion  116 . A nozzle  116 C finally connects each buffer reservoir  116 B with the inside of the barrel  101 . 
     While the cross sections of the partial feed lines  114 C and of the feed line portions  114 A and  114 B are so large that variations of the pressure therein may be neglected, the cross section of the diaphragm  116 A and the cross section of the nozzle  116 C are considerably smaller than the cross section of the partial feed lines  114 C and of the feed line portions  114 A. 
     The embodiment of FIG. 3 has two partial feed lines  114 C with end portions  116  at a rearward section of the gun barrel  101  and two partial feed lines  114 C with end portions  116  at a frontward section of the gun barrel  101 . The coolant  107  therefore is fed to two gun barrel sections. In each of these sections of the barrel  101 , the nozzles  116 C are facing each other so that streams  107 A,  107 B are ejected from opposite nozzles  116 C and meet in a central area of the barrel  101  with the intention of creating a mist of small quantities of coolant and achieving the same cooling effect around the barrel  101 . This effect can be enhanced by arranging one or more additional end portions in mutual angular distances around the barrel in the same cross section, each of these end portions  116  being connected to a partial feed line  114 C. 
     In the embodiment of FIG. 3, the end portions  116  in cross section F being connected with the feed lines  114 C ending at the gun barrel are arranged with their axes at 90° with respect to the axis of the barrel  101 , so that the coolant is ejected in radial direction. The end portions  116  in cross section R connected with partial feed lines  114 C ending at the housing  105  are arranged with their axes at an angle of less than 90° with respect to the axis of the barrel  101 , such as the approximately 45 degree angle shown, so that the coolant is ejected in a forward direction. Although this non-perpendicular arrangement is more difficult to make, it is chosen in order to prevent the coolant from immersing the rear portions of the fire arm. End portions, especially when they are arranged at the foremost end of the gun barrel, may also be arranged to eject the coolant rearwardly. 
     The arrangement of the feed lines, pressure cylinder and branching may be different in detail than what has been described above, but the basic concept is that coolant under operating pressure is fed to the barrel chamber through an end portion, preferably with a diaphragm, a buffer reservoir and a nozzle prior to and during firing a round, and that the coolant is pushed back between the shots of a round. 
     The above described device as depicted in FIG. 3 functions as follows: Chamber  110 B is de-pressurized. The coolant  107  is conveyed from the reservoir  106  via the line  108  and the flap valve  109  into the chamber  110 A of the pressure cylinder  110 , while the electrically actuated valve  115  in the feed line portion  114 A is closed. Thereafter, the chamber  110 B is pressurized, and the coolant  107  in the chamber  110 A is placed under the defined operating pressure of, for example, approximately 500 bar, so that the device is ready for use. Prior to triggering a series of firings, the valve  115  is opened, so that the coolant  107  can flow to the gun barrel  101 . The high gas pressure in the barrel  101  of, for example, approximately 5000 bar is created in the course of subsequent firing which pushes the coolant back, wherein the gas pressure is reduced by friction to the operating pressure of approximately 500 bar and only little coolant  107  flows back. As soon as the gas pressure in the gun barrel  101  has been reduced, the coolant  107  is again continuously injected into the gun barrel  101  by the operating pressure until a further shot is fired. The valve  115  is closed only at the end of a firing.