US 1708389 A
Description (OCR text may contain errors)
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SIGHTING APPARATUS FOR GUNS Filed April 1925 I50 ISOIZOIOSO gwmmtoc James I: Kar'nes FHJAL. l1" STFQLHWQN I s.
Patented Apr. 9, 1929.
UNITED STATES JAMES C. KARNES, OF BUFFALO, NEW YORK.
SIGHTING APPARATUS FOR GUNS.
Application filed April 8, 1925.
Serial No. 20,538.
(GRANTED UNDER THE ACT OF MARCH 3, 1883, AS AMENDED APRIL 30, 1928; 370 0. G. 757.)
The invention described herein, if pat ented, may be manufactured and used by or for the Government for governmental purposes without the payment to me of any royalty thereon.
This invention relates to a sighting apparatus for guns.
In aiming a gun upon a moving target, such as an aeroplane, it is necessary to so point the gun that the projectile will strike or burst at the predicted future position of the target. The factors entering into the determination of this future position include primarily, speed of the target, angle of approach, altitude, range, and time of flight of the shell. Since the aeroplane is free to alter its course in three directions during the interval between observation of its present position and the predicted future position the data as to present position even when ascertained by the most precise instrument form but a basis on which to calculate the future position, the estimate of which presumes constant values of speed, direction, and altitude. The more precise apparatus is capable of including secondary lateral and vertical deflection corrections and is usually employed with guns of the larger calibers Where rapidity of fire is not obtainable and a free expenditure of ammunition is too costly or not to be desired.
The sighting apparatus forming the subject of the present invention is designed primarily for use with automatic guns of all calibers but may likewise be used with heavy ordnance. Its purpose and effect lies not so much in the accuracy of its prediction as to the future position of the target as it does to the probability of obtaining a hit when a stream of bullets or cone of trajectories is placed in the probable path of the plane.
Appreciating the difficulty of following a rapidly moving target when it is necessary to aline two or more sights on the target, it is contemplated in the present invention to provide in the focus of an optical instrument fixed to the gun, a reticule in which the cross lines form the axes of coordinates representing speed and range as interpreting values of lead and superelevation which must be given the gun.
To these and other ends, the invention consists in the construction, arrangement, and combination of elements, described hereinafter and pointed out in the claims forming a part of this specification.
A practical embodiment of the invention is illustrated in the accompanying drawings, wherein Fig. 1 is an enlarged plan view of a reticule glass constructed in accordance with the invention; and
Fig. 2 is a more or less diagrammatic View showing the application of the reticule.
Referring to the drawings by characters of reference:
The sighting apparatus comprises a reticule glass A preferably placed in a telescope fixed to the gun so that the optical center B of the instrument is always parallel to the axis of bore of the gun. By virtue of being fixed to the gun, a gun server who operates both the gun and sight has merely to maintain the proper point of the reticule on the target to automatically lay the gun to the predicted future position of the target. The center B is established by the intersection of the horizontal and vertical cross lines, respectively C and D, which form the axes of coordinates representing ranges and speeds of the target. Two such systems of coordinates are employed, one in each of the lower quadrants so that the direction of travel of the plane may be taken into consideration.
The horizontal scale comprises lines E indicating ranges and representing by their distance from the axis of abscissas G, the superelevation corresponding to range which must be given to the gun to compensate for the curved trajectory of the projectiles.
The vertical scale comprises lines F indicating speeds of the target in miles per hour and represent by their distance from the axis of ordinates D, the lead corresponding to the speed of a target which must be given the gun to compensate for the travel of the target during the time of flight of a projectile. Since the lead varies proportionate to range the speed lines F are curved, being plotted as a function of apparent speed of a target and time of flight of the projectile. The speed curves are graduated on the assumption of the plane traveling at right angles to the normal plane of fire of the gun so that in selecting a speed line the apparent speed of the target as resulting from the angle of approach is the value employed. This value may be estimated by the gun server according to the known type of plane or may be announced by a second member of the crew who may obtain the data through special instruments or through a telescope having a reticule identical with that of the gun servers instrument. Similarly, the range to the target may be directly estimated by the gun server or more accurately obtained by a special apparatus.
As an example of the operation of the sight it may be assumed that a plane is approaching from the right at an apparent speed of 120 miles per hour at a range of 2,000 yards, these values being estimated by the gun server or determined through auxiliary apparatus and, announced to him. The target is then sighted on the intersection of the corresponding speed and range lines as shown in Figure 2, and this intersection represents in rectangular coordinates the lead and superelevation of the gun whose axis of bore corresponds to the optical center 13 of the sighting instrument.
The intersection of the range line E and the axes ol ordinates D represents at the instant of firing the expected point in the field at which the target and the projectile should meet.
For the purpose of securing a check on the data used, a duplicate sight, operated by a second server picks up the target at the given readings. At the instant of firing (tracer shells being used), he ceases to follow the target with his instrmnent and watches the expected point of hit on the axes of ordinates D. The observations made form the basis for announcing corrections to the gun server who from experience can estimate the proper change from the previous sighting point on the coordinates.
After the preliminary burst, the gun server while following the target with his instrument may himself view the striking point or burst of the shell with respect to the target and may adjust his line of sight accordingly.
The same result may be obtained without the use of a fired shell by having the time of flight corresponding to range counted off. At the expiration of the time of flight the position of the target with respect to the vertical axis D affords a basis for calculating the error of the given reading. This procedure can be adopted when using the sight to initially estimate the range or speed.
Although it is preferred to form the sighting apparatus on the retieule glass of a sighting instrument it can be made of metal and mounted on the gun in the same mannor as a front sight.
TVhile in the foregoing there has been illustrated and described such combination and :LIliLIlg'GIDQIIli of elements as constitute the preferred embodiment of my invention, it is nevertheless desired to emphasize the fact that interpretation of the invention should only be conclusive when made in the light of the subjoined claims.
1. In a sighting instrument, a reticule glass having inscribed thereon diametric axes of coordinates, and bearing intersecting lines forming coordinates in the lower quadrants, the ordinates indicating ranges and representing by their distance from the axis the superelevation corresponding to range and the abscissas indicating speeds and similarl represent-ing lead corresponding to speed, said ordinates being curves plotted as a function of speed of target and time of flight of projectile.
2. A sight for guns including a transparent body having inscribed thereon diametric axes of coordinates, and bearing intersecting lines forming coordinates in the lower (piadrants, the ordinates iniilicating ranges and representing by their distance from the axis the superelevation corresponding to range and the abscissas indicating sneeds and similarly representing lead correspondng to speed.
A siglit for guns including a body, having means forming axes of coordimrtes, and lines defining coordinates in adjacent quadrants, the ordinates indicating ranges representing by their distance from the axis the superelevation corresjmnding to range and the abscissas indicating speeds and similarly representing lead corresponding to speed.
'4. A sight for guns including a body having horizontal and vertical divisions, a scale of horizontal range lines representing by their distance from the axis the superelevation corresponding to range, and an intersecting scale of substantially vertical speed curves similarly representing the lead corresponding to speed.
JAMES C. KARNES.