US2476342A - Gun sight - Google Patents

Description

$bRRUH R09! H. K. WEISS July 19, 1949.

GUN S IGHT 4 Sheets-Sheet 1 Filed Oct. 28, 1944 gwucwhw Herberi K. Webs-5 SLHRUH HUGH July 19, 1949. wg ss 2,476,342

GUN SIGHT Filed Oct. 28, 1944 4 Sheets-Sheet 2 fl I /renear PATH;

FICTITIOUS LEAD sar INTO 556m fi 4 a;

5 I 2% In TRUE TARGET Zn PATH a HUH KUUN H. K. WEISS July 19, 1949.

GUN S IGHT 4 Sheets-Sheet 3 Filed 001;. 28, 1944 WI y Q gwuentoi Hex her c K- Weiss saw:

H. K. WEISS GUN SIGHT July 19, 1949.

4 Sheets-Sheet 4 Filed Oct. 28, 1944 ml m 3r vucn'vfw; Herbert K WE'155 agyammw mmw Patented July 19, 1949 UNITED SEARCH ROOM STATES PATENT OFFICE GUN SIGHT Herbert K. Weiss, Fort Bliss, Tex., assignor to the United States of America as represented by the Secretary of War (Granted under the act of March 3, 1883, as amended April 30, 1928; 370 O. G. 757) 2 Claims.

The invention described herein may be manufactured and used by or for the Government for governmental purposes without the payment to me of any royalty thereon.

The invention relates to the general class of sights the general purpose of which is to enable the rapid introduction of computation factors into the relation betweena gun "bore and the gun sight trained on a moving target, whereby a projectile may be fired with coordinated propulsion and angular relation of its trajectory to the line of sight so as to reach an advanced point in space on the course of the target when the target reaches the same point.

The invention has as its principal object to enable the attainment of the necessary functions without requiring actual detailed mathematical computations or use of range finders or data transmission, but-by mere reckoning of one or two factors which are capable of close estimation by practiced personnel-obtaining immediate close approximation of the correct gun pointing so as to either produce a hit or such slight deviation that the necessary further required correction will be at once apparent and instantly imposable. This is of paramount value in antiaircraft encounters, the invention enabling, ordinarily the preliminary setting and correction well within the short interval of time available between the observation of a target entering the practical zone of fire of a weapon and its movement through the most advantageous range area of that zone. The apparatus will also so function that an initial setting may be obtained in time to be effective in exceptionally short encounters, so that the extent of error may be so reduced that the gunner or a correction setter has a reasonable chance to correct the setting by estimate and manipulation based on observation of error in the flight of tracers. The sight in this last particular may be found particularly useful in flexible gun mounts where the gun is free to be swung without the use of tracking gearing as well as in such guns as the 40 mm. anti-aircraft weapon where two trackers operate respectively the elevating gearing and the traverse gears, or guns utilizing other traverse and elevation gear.

It is an aim to enable the interpolation into sight functions of lead and elevation factors determined by simple visual judgement or knowledge of speed and direction observed in targets or speed specifically known to be an attribute of the particular target,

Particularly it is an object to enable the use of personnel without extended mathematical training, but capable of judging direction by simple observation, and with knowledge of speeds to be expected in specific models of airplanes, to operate manually devices by which such data may, at the instant of encounter, or very shortly before, be interpolated, so that the gunner in the case of the flexible gun need only keep the sight on the target and operate the trigger, or, in the case of the tracking mechanism the trackers need only keep the target centered in the sights, to insure the coincidence of the projectile and the target in space and time. The invention is applicable to direct laying using either case I or case II pointing.

As applied to guns having tracking gearing, such as in the current thirty-seven millimeter or forty millimeter anti-aircraft guns, my invention enables use of much of the structure of the tracking and sight mounting already in use. But in the prior sight procedure it was the function of the azimuth and elevation trackers to sight the plane target within particular parts of respective grill sights by judgbment, or by instruction from an observer or data transmitter, depending on the one hand upon an approximation of a proper relation between speed and direction of the plane and the offset of the target from a vertical center line of the grill with element of lead, and on the other hand depending on proper relation of range and the offset of the :target from a horizontal center line in the grill. In the operation of my invention, on the contrary, the trackers are required only to keep the target centered in the lines of sight, without estimation of any kind, and without deviation allowance by the trackers, or offset of any kind carried out by them; but a third person (who has been schooled in identifying planes and in a knowledge of the speed characteristics of the various planes which may be encountered; and also trained to judge well the direction of the course being followed by the target), who will be termed the setter, will turn a pointer in the target course direction ascertained, and will also set a pointer to indicate a specific target speed on a dial. He may also set in a range factor for super-elevation. This reduces the number of persons operating at one time each with complicated or diversified functions and assures greater accuracy in the execution of the single detail required of the tracker. It enables the setter to exercise judgement with a minimum of distraction and to apply the result in the function of the machine with a minimum of effort and without being required to attend any other function of the piece or crew.

With a flexible gun the gunner may effect the laying of the piece and firing while another preferably operates the means by which corrections are imposed, although the gunner may in some cases operate the correction device as well as fire the gun. As will be understood from the disclosure, the setter need not be located immediately at the gun, so that sights may be set and corrected by a setter oif-carriage.

Incident to the objects named it is a purpose to enable the interpolation of certain lead factors by more or less exact computation or from data, or by (a), judgement of one of the simplest details of the course of a targetviz, its directionand the manual setting of a free rectilinear element to coincide with the reckoned direction, and (b), to utilize usually definite knowledge of target speed to set in another principal factor of lead by operating a simple pointer to indicate on a dial the speed of the target. The further vector of range may also be incorporated, as will be shown, although this is not important and in practice range or superelevation adjustments are omitted.

It will be apparent that the computing apparatus constitutes a vector system in which values may be represented for (1) ammunition ballistics, (2) target speed, (3) target direction, and optionally (4) target range; and these values converted into a mechanical function of the apparatus by which the bore axis of the gun is disposed at the necessary angle to the line of sight to apply the factors in eifecting placement of the fired projectile at an intersection of the trajectory and projected target course coincidently with arrival of the target thereat.

Further purposes and objects as well as features of invention will be found from the following description and accompanying drawings wherein:

Figure 1 is a perspective view of my sight system in one form associated with a gun mounted for movement in elevation and train;

' Figures 2, 3 and 4 are diagrammatic illustrations of the theory of the function of the apparatus.

Figure 5 is a detail section of the floating frame mounting and lead screw connections.

Figure 6 is a detail section of the superelevation element.

Figure 7 is an elevation from the right of Fig. 6.

Figure 8 is a sectional detail of the manual directional setting means.

Figure 9 is a detail of the clutch gear.

Figure 10 is a formal detail of the speed setting device.

Figure 11 is a diagrammatic representation of the sight functioning with a directly approaching target, in side elevation.

Figure 12 is a similar view involving a departing target.

Referring to the drawing, I0 indicates the cradle of a gun and II the upper carriage, traversable on a base carriage of any approved construction the details of which require no illustration for an understanding of the invention. The base carriage includes a stationary azimuth gear I2 on the vertical axis of which the upper carriage turns. The cradle has horizontal trunnions l3 pivoted in the upper carriage and may be assumed to be balanced and constructed'so as to be swung vertically as required for elevation and retained at elevation, with or without tracking gearing, according to the type of gun. The gun may also be swung in traverse with or without tracking gearing, although there is indicated a driving pinion I4 carried by the traversable carriage II meshed with the gear l2 and operated through a shaft I5 journalled on the carriage II and operated by trackers crank shaft I6 through bevelled gears I? and I8, which may conform to trains in the current 40 mm. anti-aircraft guns and others. The 40 mm. gun last mentioned is trained by two tracker crewmen operating respectively the azimuth gearing and the elevation gearing, using respective telescopes connected in angularly adjustable relation to the gun. There would still be some conventional connection of the azimuth telescope to the elevation trackers telescope when my invention is applied thereto. In a flexible gun, the gears I2 and I I would be retained, but the crank I6 omitted.

A rear horizontal arm I9 is rigidly connected to and extends from the right side of cradle III. A forward bracket 20 is also attached to cradle Iii. A rod 2| is journaled in bracket 20 and a bifurcated yoke 22 is journaled on the end of bracket E9. The axes of rod 2| and yoke 22 are parallel with the axis of trunnions l3.

An arm 23 is fixed on the extension 2| and from the lower end of the arm a link 24 is extended rearwardly and pivoted to the upper carriage II. The distance between the axis of trunnion I3 and the axis of rod 2 I, is equal to the efie'ctive length, that is, the distance between pivots, of rod 24. Likewise the effective length of arm 23 is equal to the distance between the axis of trunnion I3 and the pivotal connection of rod 24 to carriage II. The parts thus form a deformable parallelogram which acts to maintain arm 23 and rod 2| in fixed angular relation with the horizontal plane for all angles of gun elevation. The connections are such that axis 9, subsequently described, is maintained vertical.

At the extremity of the rod 2| a frame 24 is pivoted on a normally vertical axis 9, and has a gear 25 fixed therewith concentric of axis 9. The frame is provided with a horizontal arm 26 in which a horizontal worm or lead screw 21 is journaled on an axis radial to axis 9 below gear 25. A small bevel gear 28 is fixed to the inner end of the worm 21, meshed with which there is a like bevel pinion 29, below and coaxial with the gear 25 but independently revoluble, and connected for operation by a flexible shaft 70. The shaft :9 is extended from a speed-setting operating hand wheel and pointer, with dial, conveniently mounted on the bracket I9.

The direction of the arm 26 and lead screw 21 is determined at the will of the operator or setter and maintained at the setting automatically by connection with the azimuth gearing I2 and I4. This is utilized to give proper angular value to speed vector components introduced separately into the setting of the instrument, so that in azimuth the gun will have the proper lead angle to the line of sight, throughout a reasonable length of flight of the target, and also include the elevation component of lead.

In the present instance the position of the float ing frame is set by means of a hand Wheel 33 located conveniently to the gunner on the bracket E9 or elsewhere for use by a setter and connected by a flexible shaft 36 to a small driving pinion 35 mounted on the rocking bracket 2| and meshed with the turntable gear 25. The shaft 36 is anchored to the forward side of the bracket I9. The flexible shaft is connected to a coaxial tubular shaft 37 journalled in the bracket I9 parallel to the gun and having a collar 38 thereon to hold Shh-UH KUUN it against reciprocation. The sheath 36 has a flanged terminal piece 39 held in a split bearing cap 40 secured to the bracket l9 at the forward side, the cap also inclosing the collar 38 and forward end of the shaft 31, holding the collar revolubly against the side of the bracket 9. The shaft 31 projects from the rear side of the bracket l9 and has a bevelled gear 4| revoluble thereon, meshed with a gear 46 mounted on the under side of the bracket 9 and rotated by flexible shaft 42 from the shaft I5.

The gear 4| is in abutment with an annular bearing 4| on the bracket I9 and engaging just Within the teeth of the gear. Within this bearing a circular recess 43 is formed in the bracket and on the gear opposed to the recess a rosette 44 of serrations is formed. The tubular shaft 31 has diametrically opposite longitudinal slots formed therethrough between the gear 4| and the inner face of the recess. A solid shaft plunger 45 is reciprocable in the tubular shaft 31, extending from adjacent the recess to a distance longitudinally rearward of the shaft 31, and has fixed thereon an operating knob or wheel 33. A transverse knife-edge key 41 is set fixedly through the inner end of the shaft 45, its ends extending radially from the shaft and reciprocable with the shaft from engagement with the rosette 44, to an inner cleared position in the recess. The knifeedge key is held normally engaged with the rosette as a clutch by means of a helical compression spring 48, confined between the outer side of the gear 4| and the knob 33. The rosette and key 41 may be alternatively a friction clutch means permitting at will manual rotation of the shaft 34 independently of the gears, without clutch release.

A traveler nut 49 is engaged on the lead screw 21, having a dependent stud pin on which there is pivoted for oscillation in or near a plane with the screw the forward end of a square tube arm 50 having a telescoping rear arm slidably fitted therein, and having its rear extremity cylindrically tenoned and revolubly mounted in a bearing 52 at the yoke 22 before mentioned. The arms 5|l5l constitute a telescoping linkage between the nut and sight, proper, as will appear. The bearing 52 is carried at the lower end of a vertical screw 53 slidably engaged through the top and bottom arms 54-55 of the yoke 22, a bevel gear nut 56 between these yoke arms being engaged on the screw tormove the screw up or down and to hold it in vertically adjusted positions.

At the upper end of the screw there is fixedly mounted a sight 51, which may be of any conventional form suited to the use involved. In a flexible gun installation it may be what is known as a direct or other infinity sight with or without a reflector-reticle unit, such as the N-2 sight used in the military services of the United States, but may comprise a telescope as here shown, especially Where a tracker forms part of the gun crew to operate the pointing mechanism, these various forms of sight being well known and understood, specific details are not required here and are not illustrated. It is important however, that the sight device be so mounted in this embodiment of the invention as to establish a line of sight parallel to the telescoping linkage 50-5], or in some fixed relation thereto. The engagement of the rear cylindrical end of the arm 5| in the bearing 52 in this instance insures a permanent angular relation of the telescope 51 to the axes of the arms 50-5|. In the present instance the screw axis is normal to the plane of the arms 50--5| and head screw, and the sight is fixed across the top of the screw 53 with its optical axis at right angles to the screw axis and in a vertical plane with the arms 5ll5|. The floating frame extension 26 may be utilized as a pointer to be set parallel to the direction in which a target is moving, or connections extend therefrom to a more conveniently located pointer or direction indicating device if desired. The extension 26 is left exposed and this operates as a straight edge device, which may be utilized in adjusting the sight apparatus in relation to the target course, as will be explained.

The nut gear 56 is preferably small, and may be operated by a much larger bevel gear 60 fixed on the shaft of a knob 6| revolubly mounted in a depending dial plate extension 62 from the upper arm 54. The knob 5| may carry a pointer 63 movable over a scale 64 formed on the face of the plate 62, which may be calibrated in yards range, or yard units without specific total range indicated so that several turns of the knob may be used, if desired.

The speed-setting hand Wheel 32 is mounted coaxially with a speed dial plate 66 on which a scale 67 is calibrated in units of speed in miles per hour input values, the wheel 32 carrying a pointer 68' movable on the scale 64. In order to enable adequate rotation of the lead screw 21 an increase gearing 58 may be included between the wheel 32 and shaft 3|.

Use of the invention Upon discovery of a target which is to be attacked, a gun crewman or ofiicer detailed as the setter, pre-sets in the device the factors of lead and direction. The requirements of lead components are met by pressing and turning the knob 33 so as to set the arm 26 and-consequently the lead screw 2'|-paralle1 to the path which the setter estimates the target is following, and by turning the hand wheel 32 so as to indicate by the number of turns or by the pointer 63 on the scale 64, the known or estimated speed at which the target is moving. These adjustments will turn the telescope to such angle to the bore of the gun that when the target is brought into the line of sight by traverse of the gun, the necessary lead will be approximated, and errors may be compensated for by further adjustment after observing the trace in trial fire.

The factor of range, estimated or known, may be omitted as before stated but if required is preset by moving the knob 6| so that the range is indicated by pointer 63 on the scale 64. It is possible to ignore modifications involved by the slant plane at moderate ranges and to effect corrections in that respect by adjustment to tracer paths. The lead eifect from the screw 21 and traveller will introduce elevation more as the gun is elevated and will consist entirely of elevation on a. directly approaching target as in Fig. 11, or with a departing target the course of which is alined with the gun, as in Fig. 12.

It is clear that the rotation of lead screw 21 will cause nut 49 to move along the lead screw, and that the axial movement of the nut 49 will cause the telescope to be turned on the vertical screw 53, the telescope remaining in parallelism with the linkage 5ll5|. Such angular turning of the telescope is effected to alter the angular relation between the line of sight and the bore axis of the gun, and in this manner to introduce the required lead. The extent and direction of turning of the telescope will depend upon both the axial adjustment of the nut on the lead screw and the angular orientation of the lead screw 21 around the axis 9. As described above, the axial adjustment of the nut is made by manipulation of speed handwheel 32; and adjustment of the lead screw in parallel relation to the target path is achieved by manual operation of the handwheel or knob 33. Additional or alternative other means geared or otherwise may be provided as required.

The speed hand wheel 32 and the orientin handwheel 33 are (repeatedly or continuously, if necessary) manipulated by the setter who watches the plane target and endeavors by adjustment or orientation through the handwheel 33 to keep the lead screw in parallelism with the path of the target. The gunner or an azimuth tracker sights the target through telescope 51 and swings the gun or operates the azimuth crank I6 to turn the gun so as to maintain the target centered in the field of the telescope.

As the gun is trained in azimuth to maintain telescope 51 trained on the moving target, the lead screw 21, being mounted on the gun cradle, tends to be moved out of parallelism with the target path. However, the gearing between the base carriage and the flexible shaft 34 and pinion 35, by this very same azimuth turning of the gun, operates to turn the lead screw with its turntable gear in a direction opposite to the direction of the azimuth turning of the gun. Operation of crank I6 is thus effective to turn the gun in azimuth and also maintain the lead screw parallel to the course of the target after an initial setting, provided the target continues on its early course. Or, in a flexible gun, when the crank I6 is omitted the remainder of the gearing will be similarly effective when the gun is traversed by manually pushing a part thereof in the proper direction.

The device may be used without compensatory connection between the turntable gear 25 and dial 66, as for instance in Fig. 5, where the sheath is fixed on the floating bracket 2|. In such event, if the floatin frame 26 is swung through 180 degrees, the gear 28 may travel on gear 29, in which event rotation of the screw will displace the nut 49 from the setting value indicated by the pointer 68; or the gear 28 may cause the gear 29 to turn, while the nut remains at its previous setting, and in this event the pointer will move on the dial 69 indicating a changed value although none has occurred. These variances are slight and are believed immaterial and well within even strict limits of error for speed settings in such a device since the half turn of the screw 21 or its equivalent variation will represent less than five miles in rate of speed using normal pitch in the screw threads for ready movement of the nut. Precaution would be taken to avoid repeated horizontal rotation of the frame 26 in one direction with accumulated error resulting.

The geometrical relations upon which the computing sight of this invention is based are shown in Figs. 2, 3 and 4, in conjunction with a plane target in level flight along the target path from To (present position of target) to Tp (future of predicted position). The lead screw 2'! and lead nut or traveler G9 are shown diagrammatically in Fig. 2, the lead screw rotatable about the vertical axis 9. As outlined in the foregoing description of the mechanism of Fig. 1, the lead screw is aligned parallel to the target path and at that side of axis 9 in the direction of the target approach (which is from right to left in Fig. 2). The nut on the lead screw is displaced a distance along the lead screw so that when a line of sight is passed through the point G on the gun over the nut so as to intersect the target path at present target position To, the axis of the bore of the gun is directed at the correct predicted target position Tp. That is, the line of sight is the line GT0 in Fig. 2; the nut is on the line of sight, which may be defined as G-49-T0. The axis of the bore of the gun is the line GT the axis 9 of rotation of the lead screw is assumed to be on the axis of bore, which may be defined as G-9-T The distance on the target path from To to Tp is SXtp where s is the speed of the target in miles per hour and tp is the time of flight of the projectile from G to Tp, i. e., for the slant range Dp. The distance d is a fixed length on the gun from G to the axis of rotation ll of the lead screw and arrow. The distance x, which is the distance the nut is required to be moved from the vertical axis 9 to rotation of the floating frame or zero position, may be determined from similar triangles, as follows:

dXs (DD) s) Since D /t is merely the average shell speed along the slant range Dp for the time i and does not change appreciably over the average course, an average value may be assumed to hold over the entire range of use of the sight. The dimension d, which determines the physical size of the sight, may be chosen any convenient length. Hence the position of the rider along the lead screw may be graduated directly in s, the target speed in miles per hour. As a matter of fact, the indicator 66, Fig. 1, is graduated in miles per hour target speed.

The application of the sight to a diving target (Fig. 3) differs somewhat. As mentioned above, the axis of rotation of the floating frame and lead screw is maintained vertical. Hence, it is not possible on a dive course to align the lead screw parallel with the target path. Instead, the lead screw is rotated about its vertical axis 9 until it is parallel to a line TpT0' (more fully described below) and in this position of the lead screw the nut 49 lies in the same slant plane containing the gun (G) and the target path (T0-Tp), as in Fig. 3. When the lead screw is rotated in this manner until its nut 49 lies in the slant plane, it will be oriented parallel to a fictitious target flying level (in the slant plane) from a fictitious present target position To to the predicted position Tp. That is, the lead screw when properly adjusted for a diving target on target path ToT will be parallel to a fictitious level target path T0'-Tp. Hence if the nut is adjusted to the proper lead (at) for the fictitious level target path T0'T that setting of the nut will be the proper one for the diving target T0-Tp. Accordingly, the nut is adjusted on its lead screw, not according to the speed of the diving target T0-Tp, but according to the fictitious speed of the level target T0'-Tp. The fictitious speed of the level target to traverse the distance T0'-Tp is evidently less than the speed of the diving target in traversing the greater distance To- Tp during the same interval of time (which is t time of SEARCH R projectile flight). The greater travel of the diving target is s t where s is the actual target speed, while the shorter travel of the fictitious level target is sr tp where Sf is the fictitious speed (less than 8).

The fictitious speed is less than the target speed of a diving target along its path up to about the midpoint of the course, i. e., along the incoming leg of the course (which is the condition shown in Fig. 3), but is greater than actual target speed after midpoint, i. e., along the outgoing leg of the course. This relationship is best seen in Fig. 4 which shows a diving target moving from right to left with two target positions T01 and T02 in the incoming leg and two target positions T04 and T in the outgoing leg. When the target is at point T01, the gun must be fired at the future or predicted position T 11, the distance T01-Tp1 being required for lead. However, lead screw 21 (see Fig. 3) must remain horizontal and when it is parallel with the apparent or fictitious target path, the lead screw will have a position parallel to T0l'--Tp1, Fig. 4. As seen in Figure 4 the gun must be aimed at the true predicted position Tpl, but the telescope points at a fictitious present position T01 which is, nevertheless, on the line of sight to the true present position T01. If T01Tp1 is called the true lead, then Ton-Tm is the fictitious lead which must be applied to the gun. When the target is at T01, the fictitious lead Tor-Tm is less than the true lead T0lTp1. This is likewise the case when the target is at T02. Both T01 and T02 are on the incoming leg of the course, T02 being nearer midpoint of the course. It will be observed from Figure 4 that the ratio of fictitious lead to true lead, which is of least value when the target is farthest from midpoint (as it is in position T01), becomes larger as the target approaches midpoint (as can readily be seen by comparing the relationship at T02 with that at T01). The target has passed midpoint at T04, this point as well as T05 being on the outgoing leg of the course. The relative values of fictitious lead and true leads have become reversed at outgoing point T04, the fictitious lead 04'--Tp4 now being greater than the true lead Tor-T 14 (the ratio of fictitious to true now being greater than unity). It will further be observed from Fig. 4 that the ratio of fictitious to true lead becomes greater as the target progresses from midpoint (as can readily be seen by comparing the relationship at T05 with that at T04) The sight setter sets his estimation or approximation of the fictitious speed on speed dial' 61, Fig. 1 (by adjustment of handwheel 32, as already described). He sets this speed lower than the target speed-or his estimation or approximation thereofon the incoming leg, and higher than target speed on the outgoing leg of the course. Moreover, the sight setter must continually change the speed (fictitious) set into the instrument during the course of the diving target. This is a result of the fact that the fictitious lead changes in the manner described above in conjunction with Fig. 4.

It will be apparent from the foregoing that the improved sight of this invention is not an automatic sight, but is based upon initial reckoning of the course of the target and knowled e or estimate of its speed (and also of fictitious speed in the case of diving targets). It is understood that the sight is designed for use in conjunction with the observation of a tracer stream. By observing such tracer stream the initial estimate of course and speed can be corrected to the degree required to obtain hits. Briefly, the method consists of initially estimating and setting the target speed (the fictitious speed in the case of a diving target), aligning the lead screw with the axis of the aircraft, and firing. If the tracers do not cross the line of sight to the target, the setting of the lead screw is adjusted until they do; the tracers will move in the direction sense in which the base (inner end) of the arm 26 is pointed. After the tracers are caused to cross the line of sight to the target, the speed setting is adjusted as follows: if the tracer stream passes between the sight and the target, the speed setting is increased, but if the tracer stream passes on the far side of the target, the speed setting is decreased. The last two adjustments are all that are required to produce a hit.

In the calibration of the speed dial, it should be noted that the vector relation requires that, since the base line distance between the axes of members 2i and 22 (corresponding to din Fig. 2) is held invariant, when the wheel 32 is turned the rider or traveler nut 49 on the lead screw 21 should be moved from its zero position a distance in relation to this base line which is proportionate to the target speed indicated on the dial divided by average shell speed of the ammunition in use.

Thus the setter can instantly estimate and set the wheel 32 and pointer 68 to a target speed reading on the dial 61, there being a widespread knowledge of speeds of air craft especially, and such knowledge is easily acquired. As well, a high degree of accuracy may be readily acquired in estimating speed by observation of the target. The sight, by its described functions, then inherently computes and imports the lead into the relation between the sight 5'! and gun, as represent-ed by its axis in Figures 2, 3, 4, 11 and 12, without requiring any further mental process by the setter.

Super-elevation corrections for range are relatively unimportant in this device as compared to other computing sights, because this sight in its lead computing function converts the lead into elevation as required, and because super-elevation is such a small factor at the ranges involved in the encounters involved usually that its inclusion or omission would not materially affect the accuracy of fire.

In these encounters the action is so fast that observation of dial settings is not practiced after opening fire, and corrections are made by observation of tracers and almost if not actually, instinctive adjustments of lead screw and speed settings.

The dial 6'! is useful in the making of the first speed setting which gives the fictitious lead set into the sight as referred to in Figure 4, which is made after observation of the target and determination to engage it, and before opening fire. This insures a quick approximation of proper lead as the target is brought into the sight, and a close placement of initial shots, if not hits, and thereafter the tracers indicate the necessary corrections.

It will be appreciated that in all encounters, except in the case of a crossing target there will be components of elevation introduced into the lead developed by my sight and this will be the greater in proportion to the lateral component as the direction of movement of the target more nearly approaches coincidence with a vertical plane through the gun position, until, on a direct approach, or a direct departure of the target 11 (movement along a vertical plane through the gun), no lateral or azimuth lead is required or set in by my sight, but only lead in elevation (or depression) effected.

This may be'seen in Fig. 11, where the angular relation of the line of sight or slant plane, and the bore axis of the gun are represented in the two cases last named, together with thev positions of the lead screw 21, traveller of nut 49 linkage Ell-5| and telescope 51.

The axis 9 of horizontal rotation of the frame 24 and extension 26 is indicated and in these two views the axes of the rear bracket 19 and trunnions I3 are for ready illustration and understanding represented as coincident, which may be actually the case in embodiment of the invention, although not essential (as may be understood from Figure 1) While the angular relation between the bore axis and line of sight is not mathematically exact in these views the nature of the difference is su gested and it will be appreciated that on the approaching target at an elevation of forty-five degrees, the lead effected by turning the member 26 so as to extend at its distal end toward the target (as in Fig. 11) is less than that imparted by adjusting the member 26 in the opposite direction, as would be the case with a departing target (as shown in Fig. 12), at the same elevation as in Fig. 11 and the reverse course. This gives a value equivalent to the greater speed of the shell as range'decreases with the approachin target, and its opposite deceleration factor on departing targets.

While I have disclosed the invention in the best form in which I have conceived it and approximating a form in which it may be operatively embodied, the actual measurement and operative proportions are not represented in the drawings and would conform to conventional ballistic computations well understood, and the proportions would vary according to the nature of the ammunition if different kinds having different traiectoral characteristics are used. There would also be a variance for different guns usually. It is thought these differences can be met for practical use if necessary by use of respective speed dials with calibrations appropriate to each case.

12 I claim: 1. In combination with a gun having a cradle mounted for angular movement in elevation on a carriage trainable in azimuth, forward and rear 5 brackets carried by said cradle and spacing along the axis of said gun, means journaling said forward bracket on said cradle for pivotal movement about a first axis parallel to the elevation axis of said gun, a speed arm pivoted on said forward 10 bracket on a second axis normal to and concurrent with said first axis, a part translatable along said arm radially of said second axis, ateles coping sight-armmpivoted at one end on said rear bracket and at its forward end on said part, sight 5 means connected for angular movement with said sight arm with its line of sight in parallelism with said sight arm, means maintaining said second axis vertical for all angles of elevation of said gun, said part comprising a nut, a

20 lead screw journaled on said speed arm radially of said second axis, said nut being threaded on said screw, and manually operable means to rotate said screw and correspondingly adjust the position of said nut radially'of said second axis.

2. The combination recited in claim 1, and drive means rotating said arm and screw about said second axis equally and oppositely to train ing movements of said gun to maintain said arm .in set position in azimuth for all angles of train 30 of said gun, a handwheel, and clutch means operable to alternatively connect and disconnect said handwheel with said drive means.

HERBERT K. WEISS.

REFERENCES CITED The following referenlces are of record in the file of this patent:

UNITED STATES PATENTS

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