Abstract:
The technical scope of the invention is that of devices to regulate the counter-recoil rate of an artillery cannon according to the temperature. 
     The regulation device according to the invention comprises a buffer co-operating with a ring, so as to ensure the gradual braking of the cannon at the end of the counter-recoil operation by rolling the brake oil through a leakage section located between the buffer and the ring. It is characterized in that it incorporates at least one modulation device comprising a heat-sensitive element made in a shape-memory alloy, such element ensuring, by its distortion, an increase in the leakage section when the temperature drops below a given threshold. 
     Application to recoil mechanisms of artillery cannons.

Description:
BACKGROUND OF THE INVENTION 
     The technical scope of the present invention is that of recoil mechanisms for artillery cannons. 
     In a known manner, an artillery cannon comprises: 
     a recoil mass, essentially formed by a barrel-breech assembly, 
     a recoil mechanism, generally hydraulic, placed between the recoil mass and a cannon top carriage. 
     The recoil mechanism is formed of a recoil brake and a recuperator. The recoil brake is intended to brake and limit the recoil of the recoil mass after firing. The role of the recuperator is to stock part of the recoil energy and thereafter to return it to the recoil mass to perform the counter-recoil, in preparation for further firing. 
     During the counter-recoil, the recoil mass is gradually braked at the end of its course, so as to avoid jolting the top carriage. This braking is generally ensured by a buffer that penetrates inside a ring rolling the oil located between the two parts. This braking device operating at the end of the counter-recoil is generally an integral part of the recoil brake. 
     According to the temperature, the brake oil of the recoil brake is of variable viscosity. At low temperatures, its viscosity is increased, causing the braking to slow down at the end of the counter-recoil, and thus increasing counter-recoil time. This causes the firing rates of the artillery cannon to be reduced, which is extremely disadvantageous for the weapon system. 
     SUMMARY OF THE INVENTION 
     The aim of the invention is to propose a device to regulate the counter-recoil of an artillery cannon, according to the temperature, thus enabling the afore-mentioned disadvantages to be overcome. 
     Thus, the subject of the invention is a device to regulate the counter-recoil rate for an artillery cannon according to the temperature, comprising a buffer co-operating with a ring, so as to ensure the gradual braking of the cannon at the end of the counter-recoil operation by rolling the brake oil through a leakage section located between the buffer and the ring, wherein said device incorporates at least one modulation device comprising a heat-sensitive element made in a shape-memory alloy, such element ensuring, by its distortion, an increase in the leakage section when the temperature drops below a given threshold. 
     The heat-sensitive element can, advantageously, be constituted by the ring and/or the buffer. 
     According to another embodiment, the heat-sensitive element can be integral with the buffer. 
     According to a first variant embodiment, the buffer can incorporate an additional passage for the oil whose section is modified by the modulation device displaced by the action of the heat-sensitive device. The additional oil passage can be constituted by at least one blind axial channel opening out to the fore of the buffer and by a blind radial channel made somewhere to the rear of the buffer, the two channels being inter-connected. The modulation device can comprise a tube placed inside the axial channel of the buffer, such tube being able to block the radial channel under the action of the heat-sensitive element when the temperature has reached the given threshold, such tube being displaced axially in one direction by the action of the heat-sensitive element and in the other by the action of a spring. 
     According to a second embodiment, the buffer can incorporate a second axial channel opening out at the end of the radial channel so as to provide the additional oil passage and the modulation device can comprise an axial rod placed inside the first axial channel, such rod being able to block the radial channel under the action of the heat-sensitive element when the temperature exceeds the given threshold. The rod can incorporate a groove for the passage of the oil and can be displaced axially in one direction by the action of the heat-sensitive element and in the other by the action of a spring so as to bring the groove opposite the radial channel of the buffer. 
     According to another embodiment, the rod can incorporate a radial opening for the passage of the oil located level with the radial channel of the buffer and it can be displaced angularly by the heat-sensitive element. The modulation device can comprise a flap able to block the front end of the axial channel of the buffer, such flap being displaced angularly by the heat-sensitive element. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be better understood after reading the following description of the different embodiments, such description being made with reference to the appended drawings, in which: 
     FIG. 1 is a section view of a recoil brake accommodating a braking device for the counter-recoil, in the starting position, 
     FIG. 2 is a section view of a device to regulate the counter-recoil rate of a cannon, according to a first embodiment, 
     FIG. 3 is a section view of a device to regulate the counter-recoil rate of a cannon, according to a second embodiment, shown at high temperature, 
     FIG. 4 shows the regulation device in FIG. 3, at low temperature, 
     FIG. 5 is a section view of a device to regulate the counter-recoil rate of a cannon, according to a third embodiment, shown at high temperature, 
     FIG. 6 show the regulation device in FIG. 5, at low temperature, 
     FIG. 7 is a section view of a device to regulate the counter-recoil rate of a cannon, according to a fourth embodiment, 
     FIG. 8 is a view along A of the front end of the buffer shown in FIG. 7, 
     FIG. 9 is a section view of a device to regulate the counter-recoil rate of a cannon, according to a fifth embodiment, 
     FIG. 10 is a view along B of the front end of the buffer shown in FIG. 9, shown at high temperature, 
     FIG. 11 is a view along B of the front end of the buffer shown in FIG. 9, shown at low temperature. 
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
     With reference to FIG. 1, a recoil brake  1  according to prior art, incorporates a piston  2  sliding inside a cylinder  3 . Said cylinder incorporates a cover  4  mounted integral with it, and contains a fluid, generally oil. 
     The piston  2  thus defines, inside the cylinder  3 , a first ring-shaped chamber  5  and a second chamber  6 . It incorporates openings  7  and  8 , a first axial cylindrical bore  9 , followed by a second axial cylindrical bore  10 , of a smaller diameter. The bore  10  receives a ring  14  integral with the piston  2 , whose purpose will be explained later. 
     The cylinder  3  can be integral with an immobile top carriage of the artillery materiel (not shown), and the piston  2  can be integral with the recoil mass (not shown), or vice-versa, according to the type of artillery materiel. 
     A conical counter-rod  11  is mounted integral with the cover  4  of the cylinder  3 . The largest diameter of the counter-rod, located towards its end  12 , is of a dimension less than that of the inner bore  9  of the piston  2 , such that the oil can freely circulate between the piston  2  and the counter-rod  11 , the smallest diameter being located level with the cover  4 . 
     A buffer  13  is mounted integral, for example by threading, to the end  12  of the counter-rod  11 . 
     The oil contained in the cylinder  3  is intended, first of all, to provide braking for the relative motion of the piston/cylinder during the recoil of the recoil mass. The braking intensity depends on the geometry of the means of communication between the two chambers  5  and  6 . In this case, the means of communication are constituted by the combination of openings  7  and  8  of constant geometry and the counter-rod  11  of variable diameter over its length. During the relative piston/cylinder motion, the counter-rod  11  reduces the section of the opening  7  of the piston  2 , thereby varying the section for the oil passage between the two chambers and thus the braking intensity. 
     Secondly, the oil is intended to ensure the braking of the recoil mass at the end of the counter-recoil operation. To do this, the buffer  13  penetrates inside the ring  14  of the piston  2  rolling the oil through a leakage section located between the two parts. In a known manner, so as to ensure gradual braking during the counter-recoil, the buffer can be made according to at least two concepts. The first concept consists in making the outer profile of the buffer slightly conical in shape, the base of the cone being located on the side of the counter-rod  11 . The second concept consists in making one or several longitudinal grooves on the outer diameter of the buffer. This groove, or grooves, has a depth that gradually reduces as it approaches the counter-rod  11 . 
     FIG. 2 shows a first embodiment of a device to regulate the counter-recoil rate of a cannon according to the invention. It is a partial view of a recoil brake level with the buffer  13 , of the type described previously in FIG.  1 . 
     In a known manner, a slight play or leakage section  15  remains between the outer diameter  35  of the buffer  13  and the inner diameter  16  of the ring  14 . The outer profile of the buffer being, for example, slightly conical in shape, according to a known concept in prior art and as explained earlier in the text, the leakage section  15  varies according to the relative position of the buffer  13  and the ring  14 . Thus, during the counter-recoil of the recoil mass, the oil is gradually rolled in the leakage section  15 , ensuring the gradual braking of the recoil mass. 
     According to the temperature, the recoil brake oil can have variable viscosity that increases when the temperature drops. 
     In this embodiment, the buffer is a heat-sensitive element made of a shape-memory alloy. 
     So-called shape-memory alloys allows the manufacture of mechanical parts that, after having been subjected to strain, can recover their starting shape as soon as the temperature has reached a certain level. This effect occurs only at a specific temperature that is selected when the mechanical element is being defined. 
     The heat-sensitive element, subject of the invention, is made of an alloy having two reversible shape-memory states, that is it is able to ensure two different positions. Thus, in this embodiment, the diameter of the buffer will be greater at low temperatures than at high temperatures, thereby enabling the leakage section to be increased when there is high oil viscosity. 
     The heat-sensitive element has firstly been subjected to a so-called forming process enabling it to occupy, according to the temperature at which it is subjected, both afore-mentioned memorized shape positions or states. The forming process relies on the passage of the alloy from its austenitic-type crystallographic phase to its martensitic-type phase. 
     The properties of these alloys and their forming process are well known to the expert and therefore will not be described here in any further detail. 
     The threshold temperature that corresponds to the phase transition temperature of the alloy will easily be defined by the expert, depending on the conditions of use of the artillery materiel, on the type of oil used and the type of alloy. 
     The buffer made of shape-memory ally can, for example, be constituted by an alloy of the nickel-titanium, nickel-titanium-iron, nickel-aluminum, copper-zinc-aluminum or copper-aluminum-nickel composite groups. 
     When the oil temperature reduces going from the so-called high temperature state to the so-called low temperature state and passing through the threshold temperature, the outer diameter  35  of the buffer reduces, thereby increasing the leakage section  15  of the buffer  13  and the ring  14 . 
     Thus, according to the temperature, the outer diameter of the buffer  13  varies from the high temperature state to the low temperature state (and vice-versa), causing an equivalent variation in the leakage section  15  allowing a counter-recoil rate to be obtained that is substantial constant whatever the temperature and thus whatever the oil viscosity. 
     The expert will easily define the necessary variation in the leakage section, thus of the outer diameter of the buffer, according to the type of materiel and the type of oil used, so as to obtain a counter-recoil rate that is substantially constant whatever the temperature. 
     According to a variant embodiment, the heat-sensitive element can be the ring  14 , or both the ring  14  and the buffer  13 . 
     The advantage of this embodiment lies in that it is not necessary to have additional parts, the use of a specific, shape-memory, alloy being all that is required. 
     FIGS. 3 and 4 show a device to regulate the counter-recoil rate of a cannon according to a second embodiment of the invention. 
     In this embodiment, the buffer  13  has an additional oil passage  30  whose section is modified by a modulation device  17 . 
     The modulation device  17  is composed of a tube  21  having an inner bore  22 , of a tubular heat-sensitive element  20 , of a spring  26  and a plug  23 . The tube  21  is positioned inside a blind axial channel  24  of the buffer  13 . The axial channel  24  has two supports  25  and  27  of different diameters and connected together by a should  19 . The tube  21  has a shoulder  28  pressing against the heat-sensitive element  20 .The spring  26 , pressing against the plug  23 , holds the heat-sensitive element  20  in place and holds the shoulder  28  of the tube  21  against the shoulder  19 . The plug  23 , mounted integral by threading with the front  18  of the buffer, has an axial bore  29  of a greater diameter than the inner bore  22  of the tube  21 , as well as an indentation  31 , for example of the hexagonal type, intended to ensure its assembly. 
     The rear part  32  of the buffer incorporates a radial channel  33  that opens into the inside of the axial channel  24 . 
     The additional oil passage  30  is thus provided by the radial channel  33 , the axial channel  24 , the inner bore  22  of the tube  21 , and then the inner bore  29  of the plug  23 . 
     The tubular heat-sensitive element  20  is made of a shape-memory material of the groups of composites such as defined in the previous embodiment. This element has been formed to lengthen or shorten when the temperature threshold is passed. 
     Thus, FIG. 3 corresponds to the operating situation at high temperature, thus at a low hydraulic viscosity. The heat-sensitive element  20  is consequently in its high temperature state, that is it has a small axial dimension. In this position, the spring  26  has compensated for the axial shortening of the element  20  by pushing one end  34  of the tube  21  in front of the radial channel  33 , so as to block it. The oil passage in this case occurs, in a traditional manner, via the leakage section between the buffer  13  and the ring  14 . 
     FIG. 4 represents a situation at low temperature, corresponding to a high oil viscosity. The heat-sensitive element  20  has reacted to the drop in temperature, moving from its high temperature state into its low temperature state as soon as the threshold temperature has been reached, by axially elongating. This elongation has caused the displacement of the tube  21  in a direction F, opening the additional oil passage  30  at the radial channel  33 . 
     The rolling of an oil that has a higher viscosity being more difficult, therefore slower, the passage  30  thus enables in the quantity of oil rolled to be increased and therefore the counter-recoil rate of the recoil mass to be modified, thereby making it substantially constant whatever the temperature. 
     This embodiment has the advantage of being able to use the definition of buffers known to prior art. 
     FIGS. 5 and 6 show a third embodiment of a device to regulate the counter-recoil rate of a cannon according to the invention. 
     In this embodiment, the modulation system  17  is composed of a spring  40 , a rod  41 , a cylindrical heat-sensitive element  42  and a threaded plug  43 . The rod  41  has a groove  44  whose purpose will be explained later. 
     The additional oil passage  30  is provided by a radial channel  45  and a blind axial channel  46 . The radial channel  45  opens into the axial channel  46  and passes through a second axial channel  47  in which the modulation device  17  is positioned. 
     The heat-sensitive element  42  is made of a shape-memory material of the group of composites such as defined in the first embodiment. This element has been formed so as to lengthen or shorten when the temperature threshold is reached. 
     FIG. 5 corresponds to the operating situation at high temperature, thus to a low hydraulic viscosity. The heat-sensitive element  42  is consequently in its high temperature state, that is it has a large axial dimension. In this position, the spring  40  is compressed and the radial channel  45  is blocked by the rod  41 . The oil passage in this case occurs, in a traditional manner, via the leakage section between the buffer  13  and the ring  14 . 
     FIG. 6 represent a low temperature situation, corresponding to a high oil viscosity, where the heat-sensitive element  42  has reacted to the drop in temperature by shortening axially, moving from its high temperature state into its low temperature state. This compression has caused the displacement of the rod  41  in direction F, under the action of the spring  40 , until groove  44  is located at the radial channel  45 , opening additional oil passage  30 . The oil passage in this case occurs via the combination of the leakage section between the buffer  13  and the ring  14  and the additional passage  30 . 
     The advantage of this embodiment, which is the preferred embodiment, lies in that the heat-sensitive element is not subjected to the pressure of the oil during operation. 
     FIG. 7 represents a fourth embodiment of a device to regulate the counter-recoil rate of a cannon according to the invention. 
     This embodiment differs from the previous one only in the design of the modulation system  17 . Said system is composed of a rod  50  and a heat-sensitive element  53 . The rod  50  incorporates a radial opening  51  and a shoulder  52 . 
     The front end of the buffer incorporates a cap  54  that holds the rod  50  in place axially. The cap is perforated by a bore  57  intended to enable the passage of the oil. 
     FIG. 8 is a view along A of the front end of the buffer  13 , without the cap  54 . 
     The heat-sensitive element  53  is constituted by a spiral spring integral firstly with the buffer  13  by one of its ends  55 , for example by means of screws, and secondly to the rod  50  by its other end  56 , which is, for example, introduced into a slot made in the end of the rod. 
     The spiral spring  53  is made of a shape-memory material of the group of composites such as defined in the first embodiment. This element has been formed so as to lengthen or shorten when the threshold temperature is reached. 
     When the temperature drops and after the threshold temperature has been reached, the spiral spring  53  moves from its high temperature state to its low temperature state. It reacts by shortening, thereby causing an angular displacement of the rod  50  that brings the opening  51  into alignment with the radial channel  45  such as to open the additional oil passage  30 . The oil passage occurs therefore by the combination of the leakage section between the buffer  13  and the ring  14  and the additional oil passage  30 . 
     On the contrary, when the temperature rises, the spiral spring  53  elongates after the temperature threshold has been reached, thereby causing an angular displacement in the opposite direction of the rod  50  so as to close the radial channel  45 . 
     The oil passage in this case occurs, in a traditional manner, via the leakage section between the buffer  13  and the ring  14 . 
     FIG. 9 shows a fifth embodiment of a device to regulate the counter-recoil rate of a cannon according to the invention. 
     This embodiment only differs from the previous one in the design of the modulation system  17 . Said system is composed of a flap  60  integral with a heat-sensitive element  61  in the shape of a bent blade. Said blade is integral with the buffer  13 , for example by means of screws. 
     The front end of the buffer also incorporates a cap  54 . 
     The heat-sensitive blade  61  is made of a shape-memory material of the group of composites such as defined in the first embodiment. This element has been formed to open or close when the threshold temperature has been reached. 
     FIG. 10 represents the front end of the buffer  13  along B, without cap  54 . 
     It represents a high temperature situation, corresponding to a low oil viscosity, where the heat-sensitive blade  61  is in its high temperature state. The flap  60  incorporates an opening  62  that is in an offset position with respect to the passage  30 . Said passage being closed, the oil passage in this case occurs, in a traditional manner, via the leakage section between the buffer  13  and the ring  14 . 
     FIG. 11 represents a low temperature situation, corresponding to a high oil viscosity, where the heat-sensitive blade  61  has reacted to the drop in temperature by unfolding, moving from its high temperature state to its low temperature state, thereby causing the angular displacement of the flap  60  in a direction G such as to bring the opening  62  opposite the passage  30 . The leakage section is thus increased by the passage  30 . 
     Naturally, these braking devices for the recoil mass at the end of the counter-recoil operation can be integrated into another type of recoil brake. In particular, they can be mounted onto a recoil brake fitted with a sheath or jacket incorporating a profiled opening instead of a counter-rod system.