US2363523A

US2363523A - Automatically compensating gun

Info

Publication number: US2363523A
Authority: US
Priority date: 1928-04-30
Filing date: 1941-09-05
Publication date: 1944-11-28
Anticipated expiration: 1961-11-28

Description

Nov. 28, 1944. L. w. GREENBLATT, JR., EI'AL 2,353,523

AUTOMATICALLY COMPENSATING GUN SIGHT Filed Sept. 5, 1941 2 Sheets-Shet l 50 4k 43 ww 46 42 ,47-7- RNEYS Patented Nov. 28, 1944 UNITED STATES PATENT OFFICE- Louis W. Greenblatt, Jr., and Guy '1. Bixby,

. Dayton, Ohio Application September 5, 1941, Serial No. 409,704 7 Claims. 11. 33-49) (Granted under the act of March 3, 1883, as

amended April 30, 1928; 370 O. G. 757) K platform and the target, and apparatus associated therewith and operated thereby for maintaining the gun in an alignment'which allows for the factor of time of flight of the projectile and for other factors affecting the flight of the projectile, such as ballistic and wind effects.

It is a further object of this invention to provide a sighting apparatus which, by maintaining the sight on the target, will enable training of the gun toward the predicted position of the target or, in other words, where the target will be when the bullet strikes it.

It is another. object of this invention to provide a tachometer device for measuring relative speed between the target and the gun platform and sight-operating means associated therewith, which responds directly and proportionately to the measured speed of the tachometer device.

It is still another object of this invention to provide in connection with lead-compensating mechanism, a reversing mechanism to maintain the lead compensation ahead of the target irrespective of the direction of movement of the target.

It is a further object of this invention to provide a mechanism which will also compensate for the ballistic deviations of the projectile and for deviations of the projectile caused by wind effects resulting from the position of the gun with res ect to the flight path of the airplane.

Other objects of invention will become apparent from the following description taken in connection with the accompanying drawings in which:

Fig. 1 is a perspective view. partly in section, of a machine gun flexibly mounted in an airplane and incorporating the present invention; 1

Fig: 2 is an exploded perspective view of the mechanism constituting the invention; and

Fig. 3 is a cross-sectional view through the sight-changing mechanism.

Referring to the drawings, and particularly to Fig. 1, there is shown a machine gun I mounted to pivot about a horizontal axis 2 and carried by a yoke 3 which in turn is fixedly mounted on a carriage member 4 rotatably slidably mounted on a guideway 5. The guideway 5 is integral with a body member 6 which, in the preferred embodiment of the invention, is an airplane. The guideway 5 and other stationary parts may be said to constitute a gun platform.

Coming now to the apparatus for maintaining the gun pointed with the desired lead, there is provided: (1) an apparatus for measuring the vertical component of the relative speed between the target and the gun platform and for correspondingly positioning the sight; (2) a device for mechanically measuring the horizontal component of the relative speed between the gun platform and the target and for correspondingly positioning the sight; (3) an apparatus for compensating for the ballistic deviations of the projectile; (4) apparatus for compensating for the deviation of the projectile resulting from the orientation of the gun with respect to the flight path of the airplane; and (5) reversing mechanism to maintain the lead compensation correction ahead of the target irrespective of the direction of movement of the target.-

Still referring to Fig. 1, the apparatus for measuring the vertical component of relative speed between the gun platform and the target is contained in box I54 fastened to yoke 3 by means of bracket I55; the apparatus for measuring the horizontal component of relative speed between the gun platform and the target is contained in box I56 fastened to member 4 by bracket I51, and the sight-positioning mechanism is contained in box I58 suitably fastened to the gun. It is to be understood that all members are suitably supported and that bearings and thrust bearings are provided wherever necessary.

Mounted'on the body of the gun I for universal movement with respect thereto is a sight I adapted to be positioned by the lead-predictingand-compensating mechanism which will now be described in detail:

Referring to Fig. 2, there is shown integral with the gun I, a curved rack 8 the axial center of which should coincide with, the pivotal center 2 of the gun and with which a pinion 9 disposed on an operating shaft I0 projecting upwardly from the box I54 is adapted to mesh, to be driven thereby upon rotatio of gun I about its horizontal axis 2. The driving of pinion gear 9 causes rotation of shaft I0 and gear II integral therewith. and enclosed in the box I54. Gear I I.

in turn, meshes with gearl2 to drive the same along withshaft l3 and gear l4, gears l2 and I4 being integral with shaft l3. Gear |4 drivingly meshes with gear IS, the motion of which is imparted to shaft I6 and gear l'l integral therewith. 4 Gear II meshes with gear )8, integral with shaft l9, which in turn is carried by block 20 to which is pivotally attached at the opposite ends thereof, arms '23 and-24 having weights 25 and 26 integral therewith, respectively, 'to constitute a tachometer. Attached to the arms 23 and 24 of the tachometer are a pair of

cam elements

29 and 39 having predetermined cam slope, characteristics. Riding on' the cam surfaces of

arms

29 and 30 is a saddle member 3| carrying a thrust member 32 freely rotatable with respect thereto as a result of the provisio of antifriction bearings 33. Between the saddle'member 3| and the cam surfaces of the

arms

29 and 30 there are also provided antifriction bearings 34. Since the relative vertical position of the weight members 25 and 26 with respect to their respective pivot points is a measure of the speed of rotation of the tachometer, it follows that the tachometer may be used to measure the vertical component of the relative speed between the gun platform and the target when the gun is trained to follow the movement of the target, and that by the provi sion of suitable connecting mechanism, to be presently described, the sight may be so positioned as to compensate for the necessary lead. The cam surfaces on

arms

29 and 30 must be so constructed as to result in given constant increments of movement of the saddle member in a vertical directio for given increments of measured rate resulting from changes in angularity of the arms 23 and 24 caused by operation of the tachometer.

Coming now to the mechanism responsive to the tachometer for changing the sight vertically to compensate for the vertical component of lead, thrust member 32 has integral therewith a shaft 35 slidably mounted in bearing member 36,

, suitably attached to box I54, and having integral therewith a flexible force-transmitting member 31. This member 3! extends into the box I56 and is connected to a slidably mounted frame member 38 having gear teeth 39 and 40 thereon. Tension spring 4| urges member 38 toward the right, as shown in Fig. 2 of the drawings, against the action of the tachometer. Meshingly engaged with gear teeth 30 is a spur gear 43 integrll with shaft 44, which in turn is suitably rotatably mounted in frame member 45. Also integral with shaft 44 is a bevel gear 46 adapted to mesh with bevel gear 41 rotatably mounted on shaft 48. Suitable thrust means (not shown) carried by box I58, prevent longitudinal 'movement of bevel gear 41. Also carried by frame 45 is .a spur gear 42 integral with shaft 49. Shaft 49 is, like shaft 44, suitably rotatably mounted in frame member 45 and has integral therewith a bevel gear 59. The frame member 45 is adapted to be shifted laterally, for a purpose to be more fully hereinafter explained, so.that either

gear

46 or 50 will be in driving engagement with gear 41 to rotate it in one direction or the other in response to reciprocation of member 38 under the action of the tachometer and spring 4| .7 Carried by the sleeve part .of bevel gear 41 is a cam follower 52 (Fig. 3) received in a cam-groove 53 in sleeve member 54. Sleeve member 54 is in turn slidably mounted on the part 5| of bevel gear 41 so that rotation of the bevel gear will result in a vertical displacement of sleeve member 54 in accordance with the characteristics of the j cam slot 53. Sleeve member 54 is provided with a shoulder part 55 adapted to be received in a correspondingly cut-away part in gear nut 56. Gear nut 56 is in turn slidably and rotatably mounted with respect to shaft 48 and is provided with a cam followerfl received in cam slot 58 in cylindrical plug member 5.9 slidably but nonrotatably, carried by shaft 48. The purpose of the cam follower 51 and cam surface 58 will be more fully explained hereinafter. Suitably connected to the upper end of cylindrical member 59 to be integral therewith and operated thereby isa member 60 having forked portions 6| received in a circumferential recess 48a in shaft 48. .To prevent rotation of member 66 and, consequently,v cylindrical member 59, there is provided a pair of pins 21 and 28 Vertical movement of member vertical movement of cam box member 60 as well as shaft 48 by reason of engagement of member 59 with recess 48a' of shaft 48. Member 66 is provided with a horizontally curved slot 6| a and a horizontal slot 62. Received in the vertical slot 6|a is a rod member 63 provided with ear members 64 having a pin 65 therethrough, which in turn is received in slot 66 of clamping member 61 attached to one end of telescope I. The

other end of the telescope I is provided with a clamping member 68 having a pivotal connection 69 operatively received by yoke memberJO, which, in turn, is mounted to rotate about a vertical axis in bearing member 1|.

Referring now to the other end of the telescope, and particularly to Fig. 3 taken in conjunction with Fig. 2, shaft 63 is provided with a pair of washers 12 suitably connected thereto. Vertical movement of member60 is transmitted to shaft 63. through the intermediary of these Washers, while horizontal movement of shaft 63 is accomplished by means of portion |3 6a of pitman I36 fixedly connected to the upper end of the vertical shaft 48.

Having described the mechanism for changing the sight vertically to compensate for the vertical component of the lead, there will now be described the mechanism for compensating for the ballistic deviation of the projectile in a vertical direction.

Cam slot 8| (on gun l in Fig. 2) and formed in the segmental rack 8 has incorporated therein predetermined slope characteristics such as to compensate for the deflection of the projectile in a vertical plane due to the wind effect caused in part or entirely by movement of the airplane through the air.

Cam 9|, located on the under side of, member 5, has incorporated therein slope characteristics such as to compensate for the vertical deflection of the projectile due to the above-mentioned wind effect in any horizontal or azimuth position of the gun. These additional compensations aretransmitted (as shown in Fig. 2) to the sight I by means of cam box member 60, member 59, gear nut 56, and cam follower 51 integral therewith and operatively received in cam slot 58 in member 59. Gear nut 56 is operated by rack 12 which combines the eifect of cams 8| and 9|, and may be referred to as a resultant rack, since there is transmitted thereto the algebraic sum of twice the linear movement of gear 13 plus the linear motion of rack 16.

Reciprocation of rack 12 to cause rotation of gear nut 56, and a consequent vertical movement of sight 1, is caused by a differential gear 13 59 results in a corresponding carried by a yoke 14 and rotatable upon a bearing pin 15. Yoke 14 and differential gear 13, meshing with racks 12 and 16, is caused to move by two separate mechanisms now to be described. The first of these is a direct movement through flexible connection 11, operatively connected to follower bar 19, guided forreciprocal movement in bearing member 19 which is carried stationary with respect to the gun supporting bracket 3 and has a suitable bearing or operating projection 80 received in the cam slot 8I in rack 8 fixed to move with the gun. Rotation of the gun about its horizontal-pivot 2 results in longitudinal movement of yoke member 14 under or against the action of spring 82 to cause reciprocation of rack 12. V nism for actuating rack 12. for the purpose of compensating for the vertical deflection of the projectile due to the azimuth position of the gun. This compensation is transmitted to rack 12 through differential gear 13 by rack 16, this rack having at one end thereof a roller 93 suitably mounted thereon and adapted to engage cam surface 84 of cam 85. A tension spring 86 urges the cam towards the right, as shown in Fig. 2, to its return position. The cam is urged towards the left through flexible connection 81 operatively connected to follower bar 88 suitably guided in bearing 89 carried by member 4 for reciprocatory movement. The follower bar 88 carries at the lower end thereof a follower 90 adapted to operatively engage cam surface 9| on member 5, the cam having, as previously stated, predetermined correction characteristics incorporated therein to compensate for the vertical deflection of the projectile due to the azimuth position of the gun.

While the characteristics of the compensating mechanism for vertical deflection due to the vertical position of the gun and the azimuth position of the gun are dependent upon the position of the gun, it is readily apparent that in order to properly compensate for lead in the proper direction to maintain the lead compensation ahead of the target irrespective of the direction of movement of the target, it is necessary to provide a reversing mechanism to obtain the desired results. This reversing mechanism will now be described. Referring again to Fig. 2, as previously described, frame member 45 is adapted to be shifted laterally to bring either

gear

46 or 50 into driving engagement with gear 41 to rotate it in one direction or the other in response to reciprocation of member 38 under the action of the flyball governor and spring 4I. Whether gear 46 or gear 50 is desired to be in engagement depends upon the desired direction of lead compensation. In order to suitably reciprocate frame 45 to bring the desired gear into engagement with gear 41, there is provided a flexible connection 93 operatively connected otally mounted upon pin portion 95 adapted to suitably engage with the teeth of gear I4. Operatively connected to the extreme right end of frame 45 is a spring 91 adapted to urge the frame toward the right. Lever 94 therefore moves to the right or the left. depending upon the direction of rotation of gear I4, and moves frame member 45 toward the left to bring gear 45 into engagement with gear 41 in one position of the lever, or gear 50 into operative engagement with gear 41 in accordance with the other position of the lever. Lever 94 has operatively associated therewith springs 98 and The second of these relates to mechato lever 94 suitably piv- 95 and having a pointed 99 for the purp se of equalizing the movement thereof.

Apparatus will now be described for mechanically measuring the horizontal component of the relative speed between the gun and the target and for correspondingly positioning the sight. In the normal installation of a flexible gun in an airplane, the gun is mounted on a suitable rotatins turret which permits the gun to be positioned at any azimuth angle. As shown in Fig. 1, the machine gun is carried by yoke 3 mounted on carriage member 4, which in turn is slidably mounted on guideway 5. The guideway 5 is suitably fastened to the body of the airplane 6 and has fastened thereto a large annular gear member I00 and a trackway IOI. Spur gear I02 is adapted to mesh with gear I00 and, upon movement of the gun about a vertical axis, causes rotation of gear I03, shaft I04, gears I05 and I06, and shaft I01. This train of gears constitutes a suitable mechanism for stepping up the speed of rotation of the gun to a speed that will reduce the necessary size of the rate-measuring device. Integral with shaft I01 is a block I08 having pivotally attached thereto at the ends thereof a pair of governor arms I09 and II 0 provided with suitable governor weights at the ends thereof. Governor weight III is ShlOWIl. at the end of governor arm H0, and it is to be understood that a similar weight is intended at the end of arm I09, it being omitted to avoid obscuring other details in the drawings. The governor arms are provided with cam members H2 and H3 respectively, having predetermined characteristics. Operatively engaging these cam members is a saddle member I I4 carrying a shaft I I5. Between the saddle member and the cam members there are provided suitable antifriction bearing members H6. The upper end of shaft H5 is rotatably mounted in the saddle member H4 and is provided with a thrust bearing II1. Between the thrust bearing and the saddle member there are provided suitable antifriction bearings II8. Shaft H5 is suitably slidably supported in a bearing member H9, and has operatively connected thereto a flexible member I20 suitably connected to a double rack member I2I. This double rack member is urged toward the left by means of spring I22 and is operatively positioned by reciprocation of shaft member H5 in response to the action of the flyball governor, which in turn serves as a means for measuring the rate of movement of the gun about a vertical axis. operatively associated with vdouble rack member I2I is a frame member I23 carrying a pair of spur gears I24 and I25 adapted to mesh with the teeth of rack I2 I. Integrally united with spur gear I24 to rotate therewith is a bevel gear I26, while a bevel gear I28a is integrally united with spur gear I25 to rotate therewith.

As will be more fully described hereinafter, frame I23 is adapted to reciprocate so that either gear I26 or I26a will be in operative engagement with bevel gear I21. Gear I21 is integral with one end of shaft I28, at the other end of which is provided a spur gear I29 adapted to mesh with rack I30. Rack I30 is provided at one end thereof with a yoke member I3I for ro-tatably supporting a differential gear I32. Differential gear I32 is adapted to mesh with racks I33 and I34. Rack I33 is in meshing'engagement with gear I35 integral with and carried by shaft 48. Gear I35 is of substantial width so that it will remain in mesh with rack I33 irrespective of vertical movement of gear I35 with shaft 48. The upper end of shaft 48 is provided with a pitman I36 having a slot I31 for receiving shaft 63. It is readily apparent that movement of the gun about a vertical axis will be measured, with respect to the speed of movement, by the fiyball governor, and that the sight 'I will be moved by an amount corresponding to the measured speed through the mechanism just described.

A reversing mechanism similar to the reversing mechanism previously described and used in connection with the means for compensating for the vertical component of the lead will now be described. As previously stated, either gear I26 or I26a is adapted to mesh with bevel gear I21, depending upon the position of frame I23. This frame is urged toward the left by spring I38 operatively associated with one end thereof. The

other end 10f the frame has operatively connected thereto a flexible member. I39, which in turn is connected to lever I40. This lever is pivotally mounted upon pin MI and is provided with a pointed portion I42 adapted to suitably engage the teeth of the annular gear member I (III. Lever I40 is pivoted to the right or to the left, depending on the movement of the gun with respect'to the trackway, frame member I23 being moved accordingly. Springs I43 and I 44 are provided to equalize the movement of the levers.

. To compensate for horizontal deflection due to horizontal or azimuth positions of the gun, there is incorporated in cams 9| and I49 horizontaldeflection-compensating characteristics. Cam 9| is carried by trackway and has associated therewith a cam follower I45 rotatably mounted on one end of follower bar I 46 which, in turn, is suitably supported for reciprocatory motion in bearing I 41 carried by member 4. Cam follower I45 engages cam 9i and responds to variations therein. Attached to the other end of follower bar I46 is a flexible cable I48 which, in turn, is attached to the cam member I49. Associated with cam member I49 to be operated thereby is a rack I34 carrying a roller I5I in operative engagement with the cam. Rack I34 is in operative engagement with gear I 32 and transmits the compensat' ing correction to this gear and, consequently, to the resultant rack I 33. The resultant rack therefore transmits to the sight the algebraic result of the linear displacement due to the ballistic cams plus twice the linear displacement of gear I26. This two-fold displacement oflead is compensated for by the selection of a suitable gear train which halves the distance moved by rack From the above description it is readily apparent that, from the'mechanism shown and described, the gun will be maintained in alignment with the predicted position of a target by merely training the gun so that the target is maintained in the gun sights.

In this respect, it has been shown that the gun sight is adjusted by the tachometer rate-meas uring devices and the reversing mechanisms and connecting mechanism for horizontal and vertical components of lead in the proper direction.

It has also been shown that deflection corrections for ballistics have been applied to the sights, these corrections being necessary because of ballistic deviationsdepending upon the position of P the gun with respect to the flight path of the airplane-resulting from gravity, drift due to airpressure, and the motion of the projectile due to its gyroscopic effect which is called windage jump. The vertical components of the deflection for azimuth position of the gun have been compensated for by cams and ill; the vertical component of deflection for the vertical position of the gun has been compensated for by-cam 8|; and the horizontal component of deflection due to azimuth position of the gun, by cams 92 and I49.

Although a single preferred embodiment of the invention is shown, it is to be understood that the invention may take various forms, it being intended to be limited y y the ap nded claims.

We claim:

1. In combination with a gun mount and a universally mounted gun thereon, adjustable sighting means therefor, and means operatively associated with said gun, mount, and sighting means,

for constantly predicting the future position of a moving target, means angularly adjusting the v sighting means relatively to the gun to maintain carrying a gunfor angular movement in elevation and in azimuth, relatively adjustable sighting means for said gun connected for movement thereby, and means between the gun and its mount responsive to angular movements of said gun with respect to its mount for adjusting said sighting means so that by maintaining the sight 'ing means in alignment with a relatively moving target the gun will be aligned with the point of coincidence of said target and the projectile fired from said gun, said last named means comprising centrifugal tachometer means operatively connected between the gun and its mount, and arranged to be actuated by angular movement of said gun with respect to its mount, for measuring the rate of said movement therebetween, operating means between the centrifugal tachometer means and the gun sighting means, responsive to movement of said centrifugal tachometer means for adjusting said sighting means relatively to the gun, and separate compensating sight adjusting means operatively positioned between the gun and its mount, and responsive to adjustment of the angular position of said sighting means with respect to said mount for adjusting the sighting means to compensate for horizontal deflection of the projectil due to azimuth position of the gun and the ballistic deviation of the projectile.

3. In combination with a universal gun mount adjustably carrying a. gun for angular movement in elevation and in azimuth, universally mounted adjustable sighting means on the gun, and oper ating means between said gun and its mount responsive to adjustment of said gun with respect to the mount for relatively adjusting the sighting means incident to relative movement of the gun on its mount, so that by maintaining the sighting means in alignment with a relatively moving target, the gun will be aligned with the projected point of the coincidence of said target and a projectile fired from said gun, said last named means comprising centrifugal tachometer means operatively connected between the gun and aseaeas mount responsive to elevational movement of said gun with respect to said mount for calculating the rate of elevational movement thereof, a rack operated by said centrifugal tachometer means, means operated by said rack and operatively connected to the sighting means for angularly moving said sighting means in elevation with respect to said gun, a second centrifugal tachometer means operatively connected between the gun and its mount, operated by azimuth movement of said gun with respect to said mount for calculating the rate of movement thereof in azimuth, a second rack operated by said second centrifugal tachometer means, and means between said second rack and sighting means op erated by said second rack for relatively moving said sighting means in azimuth relatively to the gun in proportion to the angular movement of the gun in azimuth with respect to said mount.

4. In combination with a universal gun mount carrying a gun for angular movements in elevation and in azimuth, adjustable sighting means on said gun, means responsive to movement of said gun for adjusting said sighting means so that, by maintaining said line of sight in alignment with a relatively moving target, the gun will be aligned with the predicted point of coincidence of said target and the projectile fired from said gun, said last named means comprising a plurality of centrifugal tachometer means driven by and responsive to horizontal and vertical angular movements respectively of said gun with respect to said mount for measuring the rates of movements thereof, cam arms carried by said centrifugal tachometer means, rack means connected to said cam arms to be reciprocated by said cam arms proportionate to the angular rate of movement of the gun as measured by said tachometer means, frame means, first and second gears carried by the frame means, each gear meshing with the rack, a third deal, said frame means being shiftable to selectively engage one or the other of said first and second gears with said third gear, a reciprocatory sleeve, cam means through which rotation of said third gear reciprocates said sleeve, a connection between said sleeve and said sighting means whereby re ciprocation of said sleeve operates said sighting means, and cooperating means controlled by angular movement of the gun in one plane and responsive to the direction of movement for shifting said frame means to bring a selected gear of one of said first and second gears into mesh with said third gear.

5. In combination with a universal gun mount carrying a gun mounted for relative angular movements in elevation and in azimuth, an adjustable sight on said gun, and means responsive to angular movements of said sun for adjusting the sight with respect to the sun so that, by

, maintaining said sisht in alignment with a movin; target, them will be aligned with the predictinz point of coincidence of the target and the projectile fired from the gun, said last named means comprising centrifugal tachometer means connected between the sun and its mount and operable by relative movement betwwn the gun and its mount for measuring the rate of angular movement of the gun about a horizontal axis; cooperating rack, gear and cam means operative- Lv connecting said centrifugal tachometer means and said Siliht, for adjusting the sight with re-. specttotbeguninreeponsetooperationoftbc centnfusal tachometer means, a second centrifugal tachometer means connected between the gun and its mount, operable by relative movement between the gun and its mount for measuring the rate of horizontal angular movement of the gun about a vertical axis; cooperating rack, gear and cam means operatively connecting said second centrifugal tachometer means with said sight for operatively positioning the sight with respect to the gun in response to operation of said second centrifugal tachometer means, supplemental sight adjusting means between the sight, the gun, and its mount, for D0- sitioning the sight with respect to the gun to compensate for ballistic corrections, said supplemental means including means operatively asso. ciated with the second tachometer means for compensating for a vertical deflection of the projectne due to azimuth position of the gun, means operatively associated with the first tachometer means compensating for vertical deflection of the projectile due to vertically adjusted positions of the gun, and means operatively associated with the second tachometer means for adjusting the sight with respect to the gun to compensate for horizontal deflections of the projectile, due to azimuth position of the sun.

6. In combination with a universal gun mount carrying a gun for angular s movements in elevation and in azimuth, an adjustable sight on said gun, and means responsive to swinging movements of the sun for adlusting'said sight with respect to the gun, so that by maintaining said sight in alignment with a relatively moving target, the gun will be aligned with a predicted point of coincidence with the target and the proectile fired from the gun, said last named means comprising a first centrifugal tachometer means connected between the gun and its mount, responsive to swinging movement of the about a horizontal axis for measuring the relative rate of movement thereof with respect to a fixed portion of the gun mount, a rack operatively connected with said first centrifugal tachometer means to be moved thereby in response to the operation thereof, a shiftable frame member including two pairs of opposed gears carried by said frame members, one gear of each pair .v 1- in operative engagement with said a third sight adjusting gear means, each of the other gears of each of said pairs of gears'being constructed and arranged to be selectively brought 'into' operative engagement with said third sight porated therein and arranged in cooperative relatlon with said adjustable sight, including means between the gun, its mount, and the sighting 4 means, responsive to angular positions of said gun on its mount for adjusting the sighting means in response to the said cam corrections. LOUIS W. GREENBIATI, JR. GUY T. BIZBY.