METHOD AND ARRANGEMENT FOR ARTILLERY MISSILES

Abstract: The present invention relates to a method and an arrangement for shells (1a, 1b) fired from launch weaponry, using some of the barrel pressure built up in the barrel during the launch phase for an additional active function over and above that of giving the shell (1a, 1b) in question its trajectory velocity. According to the invention, during the launch phase, some of the propellant powder gas accelerating the shell is therefore introduced into a chamber (12, 38, 60) which is arranged in the same and which is delimited in at least one direction by an element (8, 31, 58, 52, 53) which is movable relative to the rest of the shell and on which the barrel pressure acting on the shell simultaneously acts to maintain the original direction as long as the shell is located inside the barrel during the launch phase. This technique can thus be used to remove protective casings covering the fins, in order to push out fin units and to deploy initially retracted fins.

Description: Method and arrangement for artillery missiles. The present invention relates to a method and an arrangement for producing a relative displacement of specific elements included in artillery missiles, this relative displacement being intended to be activated as soon as the missile has left the barrel from which it has been fired. The invention is in the first instance intended to be used in those artillery missiles which are fired without rotation or at a low inherent rotation about their longitudinal axis, and which, for stabilizing them in the continued trajectory towards the target, are assumed to be provided with stabilizing fins which are arranged at the rear end and are initially retracted until the missile has completely exited the launch arrangement from which it has been fired, and then are deployed once it has left the launch arrangement. To guide the missiles in their trajectories in pitch and yaw towards their intended targets, they can also be provided with guide members arranged for this purpose preferably at their front end and deployable more or less simultaneously. Airborne missiles can be rotation-stabilized in their trajectory or stabilized in another way, for example by means of fins. Rotation-stabilized missiles have steady trajectories and they can be made mechanically simple since the launch arrangement as a rule is responsible for ensuring that the missile acquires the necessary initial rotation. However, the high rotational velocity has at least hitherto made it impossible to provide this type of missile with a well-functioning guidance system. When work is undertaken today to develop effective guidable missiles, one has therefore concentrated efforts on missiles which do not rotate at all, or rotate only slowly, about their own longitudinal axis and which are aerodynamically stabilized by means of fins arranged in their rear part. In addition to stabilizing the missile flight, the stabilizing fins, in a fin-stabilized nonrotating missile, or in a missile rotating only slowly, can additionally, if they are arranged for this purpose, give rise to an active lifting force which acts on the missile and can be used to increase its range of fire. A current trend in the development of artillery technology is towards new long-range artillery missiles guided in their final phase, and interest has increased in different types of fin-stabilized shells intended for firing in conventional guns and howitzers. To make it possible to launch fin-stabilized shells with a low inherent rotation directly from grooved barrels, the shells need to be provided with a drive band as their only direct contact with the grooving of the barrel. The same gun or howitzer can thus be used, without special intermediate measures, to successively fire essentially nonrotating shells provided with drive bands and with stabilizing fins, which can be deployed in trajectory, and entirely conventional rotation- stabilized shells. In controlling the trajectory of fin-stabilized missiles such as shells, rockets and projectiles, it is necessary to know and be able to control the roll position of the missile. This in order to be able to control the missile in pitch and yaw. This control is achieved preferably with special control elements, for example in the form of movable nose fins, so-called canard fins, or jet nozzles. The roll control moment which such control members in the front part of the missile give rise to can however in many cases be counteracted or completely eliminated by the guide fins in the rear part of the missile, unless special measures are taken. This is due to the fact that the vortices caused by the control moment from the rudder or other control activity impact the fins and this in turn gives rise to a counteracting moment. A way of solving this problem which has already been tested to an at least limited extent is to let the part of the missile in which the fins are secured constitute a unit which can rotate freely in relation to the rest of the missile about an axis concentric with the longitudinal axis of the missile. In this way, the effect of the control moment on the fins cannot be transferred to the front part of the missile, as a result of which the missile is made easier to control. However, the design and function of the fins are of secondary importance in connection with the present invention to the extent that said invention does not concern the fins as such, although a preferred embodiment of this offers a method and arrangement for protecting the fins and keeping them retracted during the launch phase and releasing them as soon as the missile in question has left the barrel of the gun or howitzer from which it is fired. The invention can thus be applied both to those fin units which during the launch phase are protected by a special protective casing which has to be removed in order to release the fins, and in those fin units which during the launch phase are protected inside the missile and which, immediately after the latter has left the barrel, are pushed out behind the original rear plane of the missile. The basic concept of the invention is that it is possible during the actual launch phase, that is to say while the missile is being driven through the barrel of the gun, howitzer or the like from which it is being fired, to introduce some of the powder gases driving the missile from the space behind the missile into a partially closed chamber in the missile, this chamber being delimited in at least one direction by the object, element or the like which is displaceable relative to the rest of the missile and which is to be displaced after the missile has left the barrel, while the inlet through which the powder gases are introduced into the chamber in question is so dimensioned that the high powder gas pressure inside the chamber is not able to equalize as quickly as the pressure behind the missile is equalized in relation to the surrounding atmosphere as soon as the missile has left the barrel. If correctly dimensioned, the pressure inside the chamber then gives rise to the desired relative displacement as the powder gas pressure inside the chamber acts on the displaceable object which, when the missile has left the barrel, is no longer acted upon in the opposite direction by the rear barrel pressure. This basic idea can then be used to release and push aside a protective casing which during the launch phase covers the rear part of the missile and a fin unit included therein or in a corresponding manner to push out a fin unit which during the launch phase has been retracted in the rear part of the missile, or to force out radially displaceable fins, or for other areas of application which fall within the scope of this basic idea. The general concept of the invention is defined in the attached patent claims and it will now be described in more detail in connection with three different examples of how the invention can be used. Of these, the first describes a method of removing a protective casing which initially covers the rear part of a missile and which during the launch phase protects an axially fixed fin unit comprising blade fins incurved towards that part of the missile body situated inside the casing. In this variant, the barrel pressure is introduced during the launch phase into the casing via an opening provided and dimensioned for this purpose. As soon as the pressure behind the casing drops, that is to say as soon as the shell has left the barrel, the pressure inside the same forces the casing off from the missile body, whereupon the hitherto incurved fins are deployed. In the second use of the invention described below, the same internal barrel pressure is used to push rearwards in the direction of flight of the shell, an axially movable fin unit out from a first position retracted in the missile to a second position in which the fins, which can also be deployable, reach behind the original rear plane of the missile. In this variant of the invention, some of the barrel pressure during the launch phase is introduced into an inner chamber situated between the axially displaceable fin unit and the main part of the missile, and when the counterpressure behind the missile which also loads the fin unit ceases when the missile leaves the barrel, this internal pressure forces the axially movable fin unit out to its rear position in the longitudinal direction of the missile. The third example describes how the same barrel pressure is used to release a protective casing of approximately the same type as in the first example and additionally at the same time to force radially movable fins out from a first retracted position to a second deployed position. However, all these examples must be seen for what they are, namely a few possible variants of practical applications of the invention, which itself can be given other applications falling within the scope of the patent claims. Figure 1 shows a shell according to the abovementioned first variant, on its way towards its target, Figure 2 shows in longitudinal section the rear part of the same shell as in Figure 1, before being launched, Figure 3 shows the cross section along III-III in Figure 2, Figure 4 shows the same details as in Figure 2, but after launch, and with the fins deployed, Figure 5 shows a partial cross section of a missile according to the abovementioned alternative two, that is to say with a fin unit which is displaceable in the longitudinal direction, while Figure 6 shows the fin unit according to Figure 5 in the retracted position, and Figure 7 shows the cross section VII-VII from Figure 6, Figure 8 shows a sectional view of the rear part of a shell according to the abovementioned alternative three, Figure 9 shows a cross section along the line IX-IX in Figure 8, and Figure 10 shows the same view as Figure 8, but after the fins have been deployed. The missile shown in Figure 1, in this case the shell la, is provided with a band track 2 for a drive band (this is generally lost when the shell leaves the barrel) , a number of deployable fins 3 which are shown fully deployed in the figure and which are fixed on a body part 4 which rotates freely relative to the rest of the shell about an axis concentric with the longitudinal axis of the shell. The dividing plane between the shell 1 and the body part 4 has been labelled 5. In addition, the shell 1 has two pairs of controllable canard fins βa, βb and 7a, 7b arranged on a respective quadrant axis and with which the course and trajectory of the shell can be corrected in accordance with control commands received either from an internal target seeker or from the launch site, via satellite, radar or other means. The way in which the shell receives control commands has nothing to do with the invention. This question will not therefore be mentioned again below. Figures 2, 3 and 4 show in greater detail how the body part 4 is constructed. Also included here are reference labels 2 for the band and 5 for the dividing plane between the body part and the rest of the shell. As will be seen from the figures, the band of the shell in this variant is placed on the body part 4 of the fin unit. This is because it is advantageous to have the band placed far back on a shell. The fins 3 are shown in Figures 2 and 3 in the retracted position (see also Figures 1 and 4) in which they are covered by a removable casing 8. In the case shown in Figures 2 and 3, the casing covers the fins and also a base-bleed unit 10 which is arranged in the centre of the body part and whose charge of slow-burning powder here has the label 11 and its gas outlet has the label 12. As will be seen from Figure 3, the fins 3 in the retracted position are incurved towards the inside of the casing 8. In the casing 8 there is also a relatively narrow gas inlet 13 which upon launch of the shells gives the barrel pressure, i.e. the powder gases from the propellant powder charge, free access to that part of the inside 40 of the base-bleed unit which is not taken up by its powder charge 11. At the same time the inlet and outlet 13 in the casing 8 is so designed that when the shell leaves the barrel and the pressure surrounding the shell quickly drops to atmospheric pressure, the gas expansion reaches inside the casing by means of the fact that the inlet and outlet 13 is so designed that the gases do not get out quickly enough, resulting in the casing being removed and the fins being released and deployed. This position is shown in Figure 4. As will further be seen from the figures, the body part 4 is joined to the rest of the shell via a ball bearing 14 which means that the fin unit can rotate freely after the fins have been deployed. This does not in itself have anything to do with the present invention even though, as mentioned in the introduction, it does have some important advantages. The shell illustrated in Figures 5, 6 and 7 is thus of the second type described in more general terms earlier, with a fin unit which is axially displaceable in the longitudinal axis of the shell. Its main part has been labelled lb and it is provided in its rear part, here labelled 29, with a drive band 2. A cavity 30 is also arranged in the rear part 29 of the shell. A specially configured fin body 33 is arranged inside this cavity until the shell has left the artillery piece in which it is fired. The fin body with its retracted fins is shown in the retracted position in Figures 6 and 7. There are eight fins here and they are all labelled 32. Each one of them lies in its own track 37 in the body part 31 and they can be deployed outwards and rearwards about their axes 33, in the manner indicated by the arrows A in Figure 7. The special fin body 31 consists of a front part 34 and a rear part 35 which are rotatable relative to each other with a ball bearing 36 which means that this fin unit too spins freely in the deployed position. The special feature of the variant of the invention described here is that when the shell has left the artillery piece from which it is fired the whole of the fin body 31 is displaced from its fully retracted position in the space 30 to a position where only its front part 34 is left in its outlet, where it is blocked by means of a deformation joint of one type or another, while the whole of the rear part 35 of the fin body is located behind the original rear plane B of the shell and where the fins 32 are deployed in the manner indicated in Figure 6 and the rear part of the body in which they are secured is allowed to rotate freely relative to the main part of the shell about the bearing 36 concentric with the longitudinal axis of the shell. For moving the body part 31 to its rear position, propellant powder gases are used which during the launch phase are allowed to flow via the channel 39 into the inner chamber which is labelled 38. When the shell leaves the barrel from which it has been fired, the pressure behind the fin unit quickly drops to atmospheric pressure, while the pressure inside the chamber 38 becomes higher. As the counterpressure behind the fin unit drops, the gas quantity at a higher pressure inside the chamber 38 will expand. This gives the desired displacement of the fin unit to its outer position shown in Figure 5. However, the original pressure inside the chamber 38 should never be allowed to rise to the same level as the barrel pressure since this would result in excessively rapid fin deployment with associated risks of damage to the fin unit. The maximum pressure inside the chamber 38 is entirely dependent on what quantities of propellant gas leak into the chamber through the channel 39 as the missile passes through the barrel. The maximum pressure inside the chamber can thus be regulated by precise dimensioning of this channel. A particular advantage of the push-out fin unit is that its fins reach further away from the centre of gravity of the missile than when the fins are secured directly at the rear end of the missile. This in turn means that the fins of the push-out fin unit can be made smaller while retaining the stability of the missile. Figures 8 to 10 show the rear part of a shell which otherwise can correspond to the shell la in Fig. 1. In this variant, the rear part 41 of the shell la has a base-bleed unit which is generally labelled 42. Immediately in front of the base-bleed unit 42 there is a track in the shell body in which the plastic drive band 43 of the shell la is mounted. The base-bleed unit 42 comprises a number of powder chambers 44 which in cross section have a circular sector shape (see Figure 9) and each initially includes a slow-burning powder and a central gas outlet 45. Figures 8 and 10 show the position after the shell la (which is not shown in its entirety in the figures) has just left the barrel of the artillery piece. A number of deployable fins 46-51 are also arranged in said rear part 41 of the shell. These fins are shown in the retracted position in Figures 8 and 9 and in the deployed position in Figure 10. Each of the fins consists of an inner primary fin 52, which can be retracted into the shell body or more precisely into the base-bleed unit 42, and a secondary fin 53 which can be telescoped into the primary one. Each of the primary fins 52 is radially controlled and radially displaceable between supporting and protecting walls 54 and 55, respectively, arranged on either side of it (see Figure 9), and since the inner longitudinal edges 56 of the primary fins 52 additionally have free contact with the inside of the powder chamber 44, the primary fins 52 start to move, as soon as they are allowed to, after the shell has left the barrel and the casing 58 has been removed, forced out by the remaining barrel pressure through respective slits 57 in the shell body by the remaining pressure from the barrel phase, possibly supplemented by the pressure from the ignited base-bleed powder. The secondary fins 53 are correspondingly mounted and are displaceable in the primary fins 52 and thus are also dependent on the powder gas pressure in the powder chamber 44 for their deployment . Until the moment when the shell la has left the barrel of the artillery piece in connection with the launch phase, allowing for a slight margin, both the base-bleed unit 42 and the retracted fins are covered by a protective casing 58. Figure 8 shows a position in which the protective casing 58 has begun to be pushed away from its original position. In the original position, the protective casing 58 covers the whole of the base-bleed unit 42. The pushing-off of the casing and the deployment of the fins are activated in the previously described manner by that part of the propellant gas pressure which has been allowed during the launch phase to leak into the inside of the casing and the base-bleed unit 42 via the opening 61. At the same time as or immediately after the protective casing 58 is removed, the powder charge of the base- bleed unit is initiated, and at the same time the remaining pressure from the barrel phase is used to force out the fin parts. When the primary fins 52 reach their respective outer positions, their respective inner longitudinal edges 56 seal the gap in the base- bleed unit wall through which they are deployed and at the same time the gas pressure also forces out the secondary fins 53 to a correspondingly sealed and blocked outer position. As can be seen principally from Figure 9, the inner primary fins 52 in the retracted position are surrounded on each side by the previously mentioned protective walls 54, 55 which form part of a temperature-resistant lining 59 of the powder chamber 44 of the base-bleed unit and which thus in pairs of two adjoining fins divide up the powder chamber into a number of sectors or fissures which each originally contain a suitable quantity of powder or powder body. Also arranged at the centre of the unit there is a central powder gas and ignition channel 60 which is common to all the powder chamber sectors to the extent that these open into the latter. As has already been mentioned, the inlet of the casing 58 has been labelled 61. Since each of the powder sectors has in this way been able to be given a limited size and a good lateral support between the protective walls 54, 55 of the adjoining primary fins 52, it has been possible to eliminate the risks of the powder charge in the base- bleed unit being damaged during actual firing, that is to say before it is brought into operation, and at the same time the division gives the powder bodies a high level of strength right up to the time they burn out.

Claims: PATENT CLAIMS 1. Method applied to missiles fired from launch weaponry, for example shells (la, lb) etc., and using some of the powder gases generated in the barrel during the launch phase for an additional active function over and above that of giving the shell (la, lb) in question its trajectory velocity, characterized in that, during the launch phase, some of the propellant powder gas accelerating the shell is introduced into a chamber (12, 38, 60) which is arranged in the same and which is delimited in at least one direction by an element (8, 31, 58, 52, 53) which is movable relative to the rest of the shell and on which the barrel pressure acting on the shell simultaneously acts to maintain the original direction as long as the shell is located inside the barrel during the launch phase, after which the propellant gases in the chamber are used, as soon as the external counterpressure ceases, to activate an active displacement between two components included initially in the missile. 2. Method according to Claim 1, characterized in that the propellant powder gases introduced into said chamber inside the shell (la, lb) are used to activate and force through a relative displacement between the main part of the shell (la, lb) and said movable elements (8, 31, 58, 52, 53) immediately after the shell has left the barrel and the counterpressure of the propellant powder gases has begun to be equalized in relation to the atmospheric pressure. 3. Method according to Claim 1 or 2, characterized in that the propellant powder gases are introduced into said chamber (12, 38, 60) via an inlet (13, 39, 61) which is dimensioned in such a way that, when the counterpressure drops to normal atmospheric pressure outside the barrel, the propellant powder gases introduced at high pressure into said chamber do not have time to be equalized at the same rate but instead give rise to the desired relative displacement. 4. Method according to any of Claims 1-3 in which, after said shell (la, lb) has been fired from the barrel provided for this purpose, a protective casing (8, 58) is removed which during the launch phase covers at least part of the rear part of the shell (la, lb) situated behind the drive band (2, 43) of the shell, characterized in that some of the powder gases driving the shell through the barrel in the launch phase are allowed to leak into a space (12, 60) provided for this purpose inside the protective casing (8, 58) . 5. Method according to any of Claims 1-3 in which, after a shell (la, lb) has been launched from a barrel provided for this purpose, it is possible for a fin unit (31), initially located inside the shell, to be pushed rearwards relative to the direction of flight of the shell to the trajectory position of the fin unit, with the fins (32) behind the rear plane of the shell (lb) during the launch phase, characterized in that some of the propellant powder gases driving the shell (lb) through the barrel are introduced during the launch phase into a chamber (38) which is arranged inside the shell and whose boundary wall forms part of the fin unit (31) which is axially movable within the shell and on whose opposite side the barrel pressure acts for as long as the shell (lb) is located inside the barrel during the launch phase. 6. Method according to any of Claims 1-3 in which, after a shell (la) has been launched from a barrel provided for this purpose, it is possible to deploy a plurality of fins (52, 53) which are arranged in the rear part of the shell and which, from a retracted position, can be forced out transverse to the direction of flight of the shell, characterized in that during the launch phase the fins (52, 53) are kept retracted by a casing (58) covering the rear part of the shell, in that this casing is removed by means of some of the powder gases driving the shell being introduced into the casing (58) during the launch phase, and in that after the casing has been removed the remaining powder gas pressure is used to force out the fins (52, 53) . 7. Arrangement which can be used, in conjunction with the method according to any of Claims 1-6, in shells (la, lb) fired from launch weaponry, using the barrel pressure built up in the barrel during the launch phase to implement an active function over and above that of giving the shell the necessary trajectory velocity, characterized in that it comprises a chamber (12, 38, 60) which is arranged inside the shell and which is delimited in at least one direction by a movable object (8, 58, 31, 52, 53) which, in the original position during the launch phase of the shell from the barrel, is acted upon from outside by the propellant powder pressure in the barrel, and an inlet (61) which leads to said chamber from that part of the shell which, viewed in the direction of flight, is situated behind its drive band (43) , and through which inlet (61) some of the barrel pressure during the launch phase gains access to the chamber (60) . Arrangement according to Claim 7, characterized in that said inlet (61) is so dimensioned that the pressure which is able to build up inside the chamber (60) during the launch phase of the shell (la) , by means of propellant gases leaking into the chamber after the shell has left the barrel and the barrel pressure behind the shell is equalized in relation to the atmospheric pressure, cannot be regulated in the same way before said movable object (52, 53) has been displaced by the same pressure to the desired final position.

Inventors: HELLMAN ULF, HOLMQVIST ULF, JOHNSSON STIG, HELLMAN, ULF, HOLMQVIST, ULF, JOHNSSON, STIG
Applicants: BOFORS DEFENCE AB, HELLMAN ULF, HOLMQVIST ULF, JOHNSSON STIG, HELLMAN, ULF, HOLMQVIST, ULF, JOHNSSON, STIG
Application year: 2001
Main classification: F42B10
IPC codes: F42B10