Method and apparatus for angle coding
BACKGROUND OF THE INVENTION 
     The present invention relates to a method and apparatus for angle coding in a projectile which can be guided by means of a data transmission device, can be launched from a smooth-walled tube and begins to rotate immediately after leaving the launching tube. 
     Such trackable projectiles which begin to rotate only after leaving the launching tube, require exact information as to their instantaneous roll position for carrying out guidance maneuvers. For guiding the projectiles, for instance, guide beams with polarized light are used which allow detection of the roll position. This method, however, has the disadvantage that in the position information obtainable from the light beams, an ambiguity is always still present as to whether the projectile is, relatively in the 0° or the 180° position. For this reason, a fixed precoding of the roll position in the projectile is necessary. This, however, requires a large amount of technical means for the signal processing in the projectile if additional information regarding the roll position must further be processed. Practically, this could be accomplished by evaluating guide beam information by a stern receiver of the projectile, but this is hardly possible due to the heavy smoke development at the start. Otherwise, it is necessary to insert the projectile into the launching tube with a given roll orientation prior to the launching. This is not feasible in practice, however. The above mentioned disadvantages are to be avoided by means of the present invention. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the present invention to code in trackable smooth-tube projectiles the roll position present at the launching in such a manner that this can be accomplished on the one hand for any insertion position of the projectile in the launching tube and that, on the other hand, the thus achieved roll position coding is preserved during the flight. 
     The above and other objects of the present invention are achieved in a method for angle coding in a projectile by the provision that the launching tube comprises a coding device for attaching a marking serving as a position reference for guiding the projectile, and that the projectile contains a device which is arranged at the circumference of the projectile jacket, corresponds to the location of the coding device of the launching tube and can be coded by the coding device irreversibly. 
     The apparatus for carrying out the method for angle-coding a guided projectile according to the invention is characterized by the features that the launching tube has at a given location with known position relative to the tube axis, a firing pin with a radial direction of action aimed at the tube axis, and that the projectile comprises a codable device which circles the projectile jacket at the circumference and corresponds, in the launching position of the projectile, effectively to the firing pin. The codable device comprises a multiplicity of bolts which are aligned radially to the roll axis and which are surrounded by a ring-shaped deformable subarea of the projectile jacket. The bolts surround, in insulated fashion, a ring-shaped conductor run and a ring-shaped resistance path arranged concentrically with a small spacing from each other and both with a spacing from the bolts. When the firing pin fires, it forces one of the bolts into conductive engagement with the conductor run and the resistance path, thus generating a resistance signal which identifies the angle of the projectile, in the manner of a potentiometer. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The invention will be described in greater detail in the following detailed description, with reference to the drawings, in which 
     FIG. 1 shows a schematically simplified section through a launching tube with a projectile; and 
     FIG. 2 shows a section through a roll angle coding device according to the invention. 
    
    
     DETAILED DESCRIPTION 
     With reference now to the drawings, FIG. 1 shows, in simplified form, a smooth-walled launching tube 1 which contains a closure 14 which is reinforced in the region of its end 1&#39;. In the launching tube 1 is shown a steerable projectile 3. 
     The launching tube 1 has at a location, the position of which is accurately fixed, a device 2 for the purpose of transmitting the position T to an irreversibly codable device 5 in the projectile 3. The position of the coding device 2 is fixed relative to the launching tube on the one hand by the dimension L which is given by the location of the device 5 to be coded in the projectile 3 inserted ready for starting. On the other hand, the angular dimension φ relative to the tube axis 6 is arbitrarily chosen as the reference dimension. In the embodiment, φ=0°=T was fixed for this purpose. The reference systems are defined here in such a manner that the roll axis 7 of the projectile 3 coincides with the tube axis 6 of the launching tube 1. 
     In FIG. 2, a functional embodiment of a decoding device according to the invention is shown in a simplified manner. The coding device comprises a spring-loaded firing pin 2 positioned in the launching tube 1 in accordance with the description of FIG. 1. With the projectile inserted ready to start, the device 5 to be coded corresponds therewith as far as its position is concerned. This device 5 has, first, an easily deformable covering 8 which forms a circular subarea of the projectile jacket 4. This part can be made as a plastic or soft metal ring. Within the subarea 8, a multiplicity of short pins 9a, . . . 9n of conductive material is arranged, all of which are aligned radially to the roll axis 7 of the projectile 3. The number of pins depends on the desired angular resolution of the coding device. The quantizing of the angle is obtained as φ=360°/n, n representing the number of pins. Concentrically within the pins 9a, . . . 9n, two concentric annular tracks, a conductor track 10 and a resistance track 11, are arranged. The latter are arranged insulated from each other as well as from the pins 9a, . . . 9n. The tracks have contacts 12 and 13a, 13b. The tracks 10 and 11 are arranged relative to the pins in such a manner that upon actuation of the firing pin 2, at least one pin 9 is hit and in the process is shifted toward the roll axis 7 in such a manner that an electrically conducting connection between the conductor run 10 and the resistance path 11 is provided. Thereby, a tap of a resistance value defined by the position of the hit pin 9 relative to the resistance path 11 is obtained between the contacts 12 on the one hand and 13a, 13b on the other hand, in the manner of a potentiometer. This once-fixed resistance value remains irreversibly preserved due to the fixation of the hit pin with respect to tracks 10,11. During the flight of the projectile it serves as an unequivocal position reference of the roll position for the control of the projectile. The resistance value characterizes the roll position at the launching. Since, due to the setting of its control wings, the projectile begins to rotate only slowly and in accordance with a reproducible time relationship, it is sufficient for steering maneuvers during flight that make sense, to know the roll position at the launching and to then calculate it via the time relationship stored in the control device until the guiding beam is received and thereby, counting of the roll revolutions becomes possible. 
     The special advantage of the invention is seen in the fact that an unequivocal irreversible roll-position coding in a tracking smooth-tube projectile is obtainable which is independent of the insertion position of the projectile in the smooth-walled launching tube. 
     In the foregoing specification, the invention has been described with reference to a specific exemplary embodiment thereof. It will, however, be evident that various modifications and changes may be made thereunto without departing from the broader spirit and scope of the invention as set forth in the appended claims. The specification and drawings are, accordingly, to be regarded in an illustrative rather than in a restrictive sense.