US2564981A - Sighting device for firing at moving targets - Google Patents

Description

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S'IGHTING DEVICE FOR FIRING AT MOVING TARGETS Fred M. Knecht, Mar del Plata, Argentina, as-

signor to Contraves A.G., Zurich, Switzerland Application February 28, 1949, Serial No. 78,795 In Switzerland January 19, 1948 3 Claims.

In connection with guns intended for ring at moving targets such as aircraft, it is customary to reproduce in the sighting device the aimingolf triangle in space formed by the gun-site, the momentary location of the target and the subsequent point of impact and to point the gun-barrel in accordance with the side of the triangle joining the gun-site to point of impact which is yielded by the aiming-off triangle due allowance being made for the angle of superelevation. There are several ways of reproducing the spatial aiming-off triangle. may be selected for the reproduced triangle that the length of the side corresponding to the distance to the point of impact is invariable. It is, however, equally practicable to employ a scale in which this length varies uniformly according to the distance to the point of impact. The present invention relates to a sighting device in which the latter method is employed. The aiming-oir triangle is expediently reproduced in such manner that the sides of same correspond to velocities. In this case the side corresponding to the vector momentary location of the target to point of impact is proportional to the speed of the target and the side corresponding to the distance to the point of impact is proportional to the mean velocity of the projectile.

In order to set the angle of super-elevation i. e. the angle between the axis of the gun-barrel and the side of the reproduced aiming-01T triange corresponding to the distance to the point of impact, the method is known of employing cams which are adjusted in accordance with two different vectors, viz. the angle of elevation and the distance of the point of impact from the gun. The cost of producing such cams and the feelers which cooperate with these latter constitutes in the case of many sighting devices, and especially in the case of such for small-calibre guns, a disproportionately large proportion of the total cost. The purpose of the present invention is, therefore, to provide a sighting device in which simpler and therefore less expensive means can be used for setting the angles of superelevation.

The sighting device in accordance with the invention is, to this end, designed in the following marmer: For modifying the length of the side of the reproduced aiming-off triangle corresponding to the distance from gun to point of irnpact, the point on the same corresponding to the gun-site is formed by a point which is xed in relation to a carriage; the carriage is slidable along a straight guideway and the guideway lies For example, such a scale in a vertical plane parallel to the barrel axis and is swivelable in said plane on a horizontal axis: furthermore, means are provided which serve to set the inclination of the guideway in relation to the barrel axis in accordance with the angle of elevation of the target to be red at.

One typical embodiment of the invention is described below with reference to the drawing. In the latter Fig. 1 shows a representation in perspective of the sighting device with parts broken away for greater clarity,

Fig. 2 is a graph illustrating the dependance of the angle of elevation upon the mean velocity of the projectile, and

Fig. 3 is an elevation of a part of the sighting device.

The sighting device in accordance with Fig. 1 possesses an elongated housing 5 which is pivotally mounted on the horizontal shaft 6. The latter is located approximately at one end of the housing 5, lies perpendicular on the vertical plane through the gun-barrel and is non-pivotally secured in a cylindrical part 8 which forms the end of the rod '1. The latter in turn is secured to the upper carriage of the gun, which can be swung in traverse and in which the horizontal trunnions of the cradle of the gun are pivoted, so that it participates in the movements of the gunbarrel about said axis, i. e. any variations in the training angle. At the opposite end of the housing 5 the shaft 9 is pivotally mounted therein, a bar II being pivotally secured at its end remotestfrom the viewer. The other end of said bar II is articulated in a manner not shown in the drawing to the cradle of the gun, which participates in the pivotal movements of the gunbarrel about its horizontal axis, i. e. the variations in the angle of elevation. This point of articulation of the bar I I to the gun on the one hand, and the length of the bar I I on the other, are so chosen that the latter always lies parallel to the line connecting the shaft 6 and the horizontal axis of rotation of the gun-barrel; consequently the housing 5 always rotates through the same angle as the gun-barrel.

At the end of the shaft 9 nearest to the viewer the part I2 is secured to said shaft, which part carries the annular plate I3 which remains constantly parallel to the shaft 9. On this plate a further plate I4 is rotatably mounted on which the housing I5 is xed. This latter serves to set that side of the aiming-off triangle reproduced in the sighting device which is parallel to the target path. To this end the housing I5 is provided with a guide-rod |1 passing through the slot I6 in the plate I4, which rod carries at its extremity a ball |6 which forms, together with the fork I9, a universal joint. The guiderod I1 is so secured in the housing |5 that it remains constantly perpendicular to the plate 4, participates in the rotation of the housing I5 about the vertical axis of rotation a--a of the latter, and can be radially displaced in the slot I6; moreover, the guide-rod |1 can also be displaced vertically along its own axis. The arrangement of rod I1 in the described manner is shown in Patent No. 1,651,093 to Y. P. G. Le Prieur. These three movements of the guiderod I1 are effected by rotation of the housing l5 by hand, by turning the bar 2| upward or downward from the horizontal through an angle corresponding to the inclination of the target path, and by setting the knob 22 to the estimated or measured velocity of the plane on the scale 23. If the knob 22 is at the position 11:0, this means that the target to be red at is stationary and tvhatJ foi-this.reaglillaimingeoi allowance isecessarynstheenter M of the ball I8 is in his' case located at the point of intersection S of the axis a-a and the axis of the shaft 9. If the target velocity is other than zero and if the bar 2| has been set parallel to the target path, the direction of the line connecting the points S and M likewise coincides with the direction of the target path, whilst its length is proportional to the target velocity providing the knob 22 has been set to the value corresponding to that velocity.

The line SM forms one side of the reproduced aiming-off triangle. The third corner of said triangle is formed by point T, which lies at the point of intersection of the axis of a bolt 24 with the axis of a further bolt 25. This latter is pivotally mounted in a beam 26 projecting from the housing 5 through a slot not shown in the drawing and is held against axial displacement by means likewise not shown. At its lower end the bolt 25 carries a device which serves for setting the optical axis of the reflector sight 21 in a direction parallel to the line MT. This device comprises the U-shaped part 28 in which the flat-shaped guide-piece 29 is pivotally mounted by means of two bolts whose axes lie perpendicular to the axis of the bolt 25. Of these two bolts, one 24) is mounted in the front end-wall of the part 28 as seen in Fig. 1, Whereas the other, which is not visible, is mounted in the rear end-wall of said part. The guide-piece 29 is provided with a bore in which one end of the rod 3| is slidably guided, whilst the other end of said rod is secured to the fork I9.

On the upper end of the bolt 25 the arm 32, which is rectangular in cross-section, is attached, the free end thereof being shaped like a cylindrical bolt, on which the reflecting sight 21 is placed pivotally. This latter furthermore has a lug 33 to which the link 34 is pivotally xed. The lower end of this latter is articulated to an overhanging arm 35 provided on the guide-piece 29, the distance between the lower fulcrum of the link 34 and the axis of the bolt 24 is equal to the distance between the axis of the arm 32 and the upper point of articulation of the link 34. This link 34 serves on the one hand to transfer the pivotal movement of arm 35 around shaft 24 to the reflecting sight 21 and on the other hand to secure the latter on arm 32 against axial displacement. The reector sight 21, which is not represented in detail, is provided in the known manner with a glass plate 36, silvered so as to be semi-translucent, which is inclined in relation to the upper limiting surface of the sight, upon which plate a beam of parallel light rays is projected through a set of lenses arranged inside the sight. Said beam casts on the glass plate 36 the image of a mark by means of which the gunner can aim at the aircraft to be taken under lire. The optical axis 0f the sight is determined by the direction of this beam of rays reflected by the glass-plate 36 into the gunners eye. If the rod 3| is swivelled about the axis of the bolt 24, the sight 21 participates in this movement, rotating about the axis of the arm 32 through the same angle. In the same manner the swivelling of the rod 3| about the axis of the bolt 25 produces an equal swivelling motion of the sight about said axis. Once the optical axis of the sight has been set parallel to the rod 3|, it remains so throughout any swivelling motions said rod may perform. The distance of the bolt 25 from the housing 5 is, moreover, so selected that the line ST lies parallel to the vertical plane through the gun-barrel.

The fact that, as already mentioned, the side MS of the reproduced aiming-0E triangle is set solely in accordance with the velocity v of the target, whilst the length of the aiming-off vector formed by the target path is determined by the product of said velocity and the duration of ight t of the projectile to the point of impact, signifies for all three sides of the reproduced aiming-olf triangle a change of scale by the factor l/t.

The vector ST of the reproduced triangle corresponds to the distance of the point of impact from the gun. Said distance can also be expressed by the product of the mean velocity of the projectile and its duration of iight. The above-mentioned change in scale signifies in this case that the length of the vector ST is dependent solely upon said mean velocity of the projectile. As, from the outset, only the distance from the target to the gun at the moment of departure of the projectile (distance to measuring point) is known but not the distance from the target to the gun at the moment of impact of the target and the projectile (distance from gun to point of impact), an approximation value is employed for the vector ST, this value being yielded by the mean velocity of a projectile in ight from the gun to the measuring point. The error arising from this approximation value is negligible, as the mean velocity of the projectile varies only very slightly with changes in the intervening distance. For setting the vector ST, the device described below is Provided.

The beam 26, in the end of which the sight 21 is pivotally mounted, is secured to the plate 31, which latter is carried by the guideway 38 and is slidable along same. Moreover, the plate 31 carries by means of a supporting web 39 a tubular section 4| threaded on the inside, in which the threaded spindle 42 engages. Said spindle is furthermore rotatably mounted in the tubular section 43 fixed t0 the plate 44 and is vsecured against axial displacement; it also carries at its right extremity (as viewed in Fig. 1) the bevel gearwheel 46, which engages with the bevel gearwheel 41. The latter is rigidly mounted on a shaft 48 which in turn is rotatably mounted at one end in the tubular section 49 xed to the plate 44 and at the other end in the end wall 5| of the housing 5 and rcarries at its left extremity (as Vani n sv- I viewed in Fig. 1) the crank 52. The plate M is secured to the guideway 33 at such a distance from the left end (as viewed in Fig. 1) of the latter that the plate 31 can be set at any value of mean velocity of the projectile which may arise for the gun in question. The shaft 48 is threaded along part of its length and carries at its threaded section the nut 53 to which the pointer 513 is attached. This projects through a slot 56 in the housing 5 and is slidable along a scale 51. The latter is calibrated in meters and serves for setting the pointer according to the distance from target to gun, which distance may, for example, have been obtained by measurement. The scale is moreover designed in such a Way that at any position whatsoever of the pointer, the distance TS is set t the vector value of the mean velocity of the projectile. If, for example, the sighting device is used on a smallcalibre gun, it is permissible to provide the scale 51 with a linear graduation, seeing that for the projectiles of such guns the graphical curve of the mean velocity of the projectile as a function of the intervening distance to the point to be red at is very fiat.

It is clear from the foregoing description in what manner the reproduced aiming-off triangle STM is set at any given moment. Once the range of the target at such moment has been set on the scale 51, the vector TS represents the vector value of the mean velocity of the projectile. If, in addition, the bar 2l has been set parallel to the target path and the knob 22 to the value corresponding to the speed of the aircraft, the vectors ST and MT form the desired aiming-o angle. In other words, providing the optical axis of the sight 21 or, and this comes to the same thing, the vector MT is directed towards the momentary location of the target, the vector ST points towards the point of impact. As, when following an aircraft with the sighting device, both the angle of elevation and the training angle of the gun and consequently of the sighting device constantly vary, it would be necessary according to the embodiment hitherto described continuously7 to reset the direction of the vector SM. In order to avoid this, the following measures have been taken, whereby on the one hand the axis a--a of the housing l5 is constantly maintained vertical and said housing is, on the other hand, turned back, upon any modication of the training angle, through the same angle about the axis @L -a. On the pivot 6 within the housing 5, a sleeve 58 is non-rotatably secured, carrying at one of its ends the arm 59. A similar arm 6l is rigidly mounted on the shaft 9. The two arms 59 and 6i are connected by the rod 62, the ends of the latter being pivotally secured to said arms at equal distances from the axes of the shafts 6 and 9 respectively.

The parallelogram thus formed serves, upon any rotation of housing 5 about the shaft 6, to transmit said rotation to the shaft 9, thus maintaining the axis a-a of the housing l5 in the vertical position at all times.

For the purpose of turning the housing i5 about the axis a-a the ring 63 is provided. It carries on its outer circumference a toothed rim and forms in conjunction with the plate l 5 a slipping clutch in such a way that upon rotation of the ring 63 the plate ll participates in this movement, although said plate can beturned easily in relation to the ring by turning the housing I5 by hand, thus overcoming the friction of the clutch. The worm 64 engages with the toothed rim of the ring 63, being connected, in a manner not shown in greater detail in the drawing, via the flexible shaft `66 to the training drive of the gun. If this drive is operated the gun turns, together with the sighting device, about its vertical axis and at the same time the housing I5 turns in the opposite direction through the same angle.

The sighting device is provided with a further device for setting the angle of super-elevation a, which device is described in detail below. As already mentioned, the vector TS is directed towards the point of impact when the sighting device is correctly set. To ensure that the gun shall re at said point, the gun-barrel must exhibit an angle of inclination to the horizontal greater by the angle of super-elevation than the angle of said vector. As already described, the housing 5 participates in all rotation of the gunbarrel about its horizontal axis through the same angles and is moreover from the outset set in such a way that the line RP lies parallel to the gunbarrel, said line connecting the axes of the two shafts 9 and 61 rotatably mounted in the housing 5. In this connection the shaft 61 serves to carry the guideway 38, on which the plate 31 is slidably arranged and the right end of which, as viewed in Fig. 1, is fork-shaped. Between the two arms 63 of this forked end the disc 69 is inserted, being rigidly and eccentrically mounted on the shaft 9. Consequently the disc 69 turns between the mutually parallel arms 68 in response to any change in the angle of elevation of the gun-barrel and thus changes the inclination of the longitudinal axis RQ of the guideway 38 which axis passes through the point R and the center Q of the disc 69 (see Fig. 3). The arrangement is such that if the vector TS is set horizontally, i. e. if the gun is adjusted to a target lying in a horizontal plane passing through the gun, the greatest angle of inclination of the longitudinal axis RQ in respect of the line RP is produced. On the other hand these two vectors coincide when the vector TS is vertical, that is to say when the sighting device is pointed at a target located vertically above it. As, on the one hand, the length of the bolt 25 is such that the point T lies on a horizontal passing through the point L, which lies on the line RQ and is displaceable along the same together with the plate 31, and as, on the other hand, the point S lies on a horizontal passing through the point P, the distance between the points L and T being made equal to the distance between the points P and S, the lines LP and TS are at all times mutually parallel and of equal length. The vector TS corresponding to the distance from gun to point of impact is therefore generally inclined in relation to the axis of the gun-barrel, this inclination representing the angle of super-elevation fr.

In Fig. 2 the curve of this angle (in ordnance per mil units) is represented as a function of the mean velocity of the projectile v (in meters per sec.) for two different small-calibre projectiles and for firing at a target lying in a horizontal plane passing through the gun; in order to draw attention to the fact that the angle of elevation in question is )\=0, the angle of super-elevation is here designated by ao. It is clear that this angle an increases steeply as the mean velocity E of the projectile decreases, i. e. as the range increases. Comparison with the embodiment exemplified in Fig. l reveals that such an increase in the angle of super-elevation also occurs in the case of this embodiment, in that the point L approaches the point Q as the mean velocity of the projectile diminishes, the angle between the vectors RP and LP increasing. By appropriate selection of the length of the vector RP and of the degree of eccentricity of the disc 69, the characteristic curve of the angle of super-elevation formed in the sighting devices as a function of the mean velocity of the projectile can, for any given projectile in respect to which the mean velocity of the projectile and the angle of superelevation for any target range are known, be so adapted to these data that to all practical purposes complete coincidence is achieved.

When firing at a target which does not lie in a horizontal plane passing through the gun, the angle of super-elevation must be correspondingly reduced. As is known, the angle of super-elevation can in this case be computed with a fair degree of accuracy from the angle of super-elevation im for the angle of elevation from the equation The eccentric disc 69 is provided for this purpose. With an assumed angle of elevation A said disc occupies the position shown in Fig. 3. In the triangle PQD the distance PQ represents the constant degree of eccentricity of the disc 69. The distance PD is, therefore, proportional to cos A and, owing to the similarity of the triangles RLE and RDP, the distances PD and EL are also mutually proportional. As, moreover, the angle of super-elevation a can only assume small values, proportionality exists between this angle and the distance EL and consequently also between this angle and cos i. If the point L on the guideway 38 is held xed whilst the shaft 9 is turned, the angle of super-elevation a changes proportionally to cos A, as should be the case in accordance with the above equation.

The manipulation of the described sighting device in ring at a flying target, such as an aircraft, is in accordance with the usual procedure. The gunner controls the movement of the 'gun in train and elevation in such a way that he always sees the aircraft in the center of the mirror 36. At the same time his mate adjusts the housing I by turning the latter about its vertical axis a-a. and the bar 2| about the horizontal axis of said housing I5 in such a way that the arrow provided on the bar 2l lies parallel to the target path. Providing the aircraft does not change its course, the direction of the arrow continues to coincide with the target path. The gunners mate furthermore operates the crank 52 and constantly adjusts the pointer 54 to the momentary range of the aircraft. Once all these settings have been carried out true to the actual values, the vector TS is directed on the point of impact at any given moment; the gun-barrel has at the same time automatically received the necessary adjustment for firing at this point.

The described device for setting the angle of super-elevation r may, of course, also be used in conjunction with a sighting device intended only for firing at stationary targets. In this case the point M is fixed at the point S, and no rotation of the sight 21 about the axis of the bolt 25 takes place. Furthermore, this device can also be used in conjunction with other sighting devices, provided that in these devices also the aiming-01T triangle is reproduced in such a way that the length of the vector corresponding to the distance from gun to point of impact likewise varies in accordance with variations in the target range.

It is thought that the invention and its advantages will be understood from the foregoing description and it is apparent that various changes may be made in the form, construction and arrangement of the parts without departing from the spirit and scope of the invention or sacrificing its material advantages, the form hereinbefore described and illustrated in the drawings being merely a preferred embodiment thereof.

I claim:

1. In a sight arrangement on a gun capable of being displaced as to azimuth and elevation, with a sight for tracking a movable target, in combination a frame, a rst shaft which is parallel to the horizontal swinging shaft of the gun barrel on which said frame is pivotally journalled, means for determining the target-velocity-allowance vector corresponding to the speed of the target including, a carrier pivotally journalled on said frame to pivot around a first axis parallel to said first shaft and to be turned during a swinging motion of the frame in an opposite sense to said motion and to the same degree, a housing journalled pivotally on said carrier about a second axis which is always maintained vertical by the pivotal movement of said carrier, and a guide rod, mounted in said housing in a vertical plane extending through said second axis and determined by the rotation of said housing for setting the same parallel to the course of the target, said guide rod being mounted in said housing to be displaceable in two directions for the setting of the length of said vector and the inclination thereof to the horizontal, a straight guideway which is pivotally fixed to said frame to be swung in the same plane as the latter, a cam attached to said carrier and connected to said guideway to swing said guideway upon the turning of said carrier with respect to said frame, a slide displaceable on said guideway dependent on the distance of the target to which the sight is pivotally connected, and means connecting said guide-rod to the sight to position the latter according to the target distance and size and direction of said vector, whereby the setting of the super elevation angle is determined by the position of said guideway with respect to said frame.

2. In a sight arrangement on a gun capable of being displaced with respect to the azimuth and elevation, with a sight for tracking a movable target, in combination a rst housing, a first shaft Lhilgaalfellslio the horizontalsifirgnfi of the gunhbarrueipnllhsaid rst homi'lsing j spiyptallywmouted, saidmistnshaft being mounted nonpivotally and traversing said housing, a second shaft mounted pivotally in said housing and parallel to said first shaft, a parallelogram mechanism which is located in said housing and which connects said rst shaft to said second shaft, in order to turn the latter during a swinging motion of said housing in an opposite sense to said motion and to the same degree, means for determining a vector which corresponds to the speed of the target having a carrier which is secured outside said housing to said second shaft, a second housing pivotally mounted on said carrier for rotation about an axis, which is always maintained vertical by the turning motion of said second shaft, and a guide rod mounted in said second housing in a vertical plane which runs through said axis, and which is determined by the turning of said second housing for the setting parallel to the course of the target, said guide rod being arranged in said housing so as to be displaceable in two directions for the setting of the length of said vector and its inclination to the horizontal, a guideway mounted pivotally in said first housing to be swung in the same plane as the latter, a cam within said rst housing attached to said second shaft cooperating with said guideway to swing said guideway upon an elevational movement of said rst housing with respect to the latter, a slide displaceable on the said guideway dependent upon the distance of the target, an extension on said slide extending from said rst housing, a universal joint on said extension to which the sight is attached, a rod connecting said guide rod operatively with said sight to position it corresponding to the target distance and size and direction of said vector, whereby the setting of the elevation angle is determined by the position of said guideway in said first housing.

3. The combination according to claim 2 wherein there is provided a screw spindle means held non-displaceably to said guideway and in which the screw spindle is journalled pivotally, a nut attached to said slide and cooperating with said screw spindle, a scale on said first housing, which for indicating the target distance is linearly subdivided and a pointer cooperating with said scale connected to said screw spindle,

l said spindle adapted to displace said slide in coriformity with the average projectile speed corresponding to the set target distance.

FRED M. KNECHT.

REFERENCES CITED The following references are of record in the le of this patent: s

UNITED STATES PATENTS Number Name Date 1,651,093 Le Prieur Nov. 29,.;'1927 1,962,590 Haubroe June 12, 1934 2,237,613 Petschenig Apr. 8, 1941 2,372,613 Svoboda Mar. 27, 1945 2,471,204 Elliott May 24, 1949 2,476,342 Weiss July 19,1949 2,479,717 Bernart et al. Aug. 23,1949

FOREIGN PATENTS Number Country Date 635,895 Germany Sept. 30, 1936 693,295 France Aug. 19, 1930 OTHER REFERENCES Ser. No. 374,007, Allec (A. P. C.), published Apr. 27, 1943.

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