US2562981A - Gunfire control mechanism - Google Patents

Description

Aug. 7, 1951 Filed July 29, 1947 C. D. BOCK GUN FIRE CONTROL MECHANISM 2 Sheets-Sheet 1 CHAiZLES D, BOCK Filed July 29, 1947 Aug. 7, 1951 BOCK 2,562,981

GUN FIRE CONTROL MECHANISM 2 Sheets-Sheet 2 31/ 3 SIGHT UNIT RATE PEEDICTOR. COMPUTER 'INVENTOR:

CHARLES D. BO CK av W v m3) HIS ATTORN YS.

iatentecl Aug. 7, 195T UNITED GUNFIR'E. CONTROL MECHANISM Charles D. Bock, New York, N. Y., assignor to Arma Corporation, Brooklyn, N. Y., a corporation of New York Application July 29, 1947, Serial No. 764,460 11 Claims. (01. 235-615) This invention relates to gun fire control mechanism, and has particular reference to mechanism for controlling anti-aircraft guns in defense against direct aircraft attack, including dive attack and torpedo attack. This application is a continuation-impart of copending application Serial No. 566,749, filed December 5, 1944, by applicant, now abandoned.

A dive attack may be defined as one in which the actual bomb discharging flight is down the line of sight of the attacking airplane, whereas the torpedo attack may be defined as one in which the torpedo launching flight is substantially horizontal. In either case, however, practically all of the action occurs in a single plane. There are usually three distinct phases to such attacks, first, the approach, which is generally along a horizontal straight line, second, the fast curve into the direct .attack line, and third, .the dive or torpedo attack, generally also straight.

Direct aircraft attacks are difiicult to combat, and many methods have been advanced to meet them without satisfactory results. The two recognized methods of defense against such attacks include shooting atthe target in its horizontal straight line approach, which is in practical, freasonably eflicient use, and shooting on the down curve portion of the approach, where the curving flight is considered as though composed of a series of short flights on chordal lines, a method which has been proposed and which is the method to which this invention is directed.

In accordance with the present invention, mechanism is provided for laying anti-aircraft guns so as to place shell bursts along the path of an attacking plane while it is swinging into, or

immediately after it has swung into, dive bomb or torpedo discharge position in its course, by predicting the dive angle from an observation of its flight in aproaching the dive and quickly shifting from curved fiight or chordal .shooting to straight line or dive shooting.

The invention is based on the following theory: If an aircraft target is coming in on a straight line towards a gun, substantially all that is needed to know to fire at it, is the range and the range-rate in order to compute values of advance range for each shot placed at intervals down the line of sight, which in this case is the line of flight and the line of fire. Any airplane flying in the horizontal may'suddenly swing into a curve and essay such a direct attack, and in-that-case, without the present invention, several wasted bursts will be placed along the expected line of flight before the control ofiicer will have noted 2 the curve and by the time the firing orders are changed, the bomb will have been launched and the target plane will no longer be worth destroying. In order to plan a defense for such attack 5 it is necessary for the control officer to know, as

early as possible, that (1') a direct attack is beginning, and (2) the radius of curvature of the target swing towards the same. Co-target angle rate is known from the rate-.computer'of the tracking 10 director and rate of change of the rate is known,

also. Furthermore, it is known that at. the com,- pletion of the target swing into the line of sight the co-target angle rate will be zero. This value is available from the rate computer. As a rule 1. the ,bombis released immediately the attacker enters the line of sight tangent to his swing. At this point, then, it is imperative that a shell be placed to meet him before he .can release the bomb, and such a shell must obviously leave the gun while the attacker is backon the curve adistance corresponding to the time .of fli ht of the shell. To know this point is to know when to shift to direct line-of-sight firing in order to lose no shots, and this is the crux of the inven- 2 tion. The point may be known by its co-target angle approaching the critical val-ueof .90 (the co-target.angl-e t being negative for approaching targets, and positive for outgoing targets), and the instant when the target is at this point is ,39 shown by the invention, automatically switchin the gun to .direct fire, since at this instant the gun has taken the line of sight as its line of fire.

Thereafter the fire is head-on into the target.

It will be seen that this provision ,for rapid 5 transition of gun control fromchordal shooting,

which assumes that the curved path is a portion of a circle and that the flight is a seriesotchords of that circlefito substantially straight dive shooting during the .dive, not onlz reduces the misses 4g ,but alsoisaves the valuable time heretofore egg pended in the attempt to recover the target in the line of sight from which it departed whenit changed its course.

For a more complete understanding of the in- 5 vention, reference'may be had to the accompanyingdrawings, in which: 7

Figure .1 is a diagram of a. typical dive attack; Figure ;.2 is an enlarged diagram of thecuryed flight portion ofthe diagram ofFig. 1;.and,

59 Fig. 3 illustrates a schematic drawing of vthe apparatus for solving the mathematicalequations inv d.-

Inasmuch astorpedoplane attack hasthe same mathematical elements of ,direattack, a-oescription of the .latterwill suffice for both. In a highly the diagrams of Figs. 1 and 2.

satisfactory type of apparatus for straight line tracking of targets, the operator trains his telescope on the target by means of control mechanism actuated by a control lever until the rate computer, actuated in accordance with the movements of the control lever assumes control of the telescope, which thereafter automatically follows the target as long as the latter maintains the same course and speed. Corrective motions with the control lever are thereafter necessary only to compensate for changes in course or speed of the target. The gun or guns are automatically controlled or otherwise actuated in accordance with the automatic calculations of the rate computer, and firing proceeds in the usual way. An example of this type of apparatus is disclosed in pending application No. 531,562, filed April 18, 1944, jointly by applicant and George Agins and Richard Y. Miner.

In using this apparatus for tracking a dive bomb or torpedo-carrying aerial target, the

operator moves the control lever to make the necessary correction when the target leaves the straight path and enters upon a curved path preparatory to diving. This correction is a measure of the radius of curvature of the target path and causes the gun or guns to be adjusted accordingly so as to place bursts upon the curve path of the target. Meanwhile, the computer, owing to these corrective changes in input automatically prepares for subsequent straight line dive shooting so that when the target straightens out in a dive and the shifting mechanism of this invention assumes control, the firing changes smoothly and automatically from chordal shooting to dive shooting.

The theory of this operation is illustrated by Referring to Fig. 1, numeral Iii designates thegun director, which may be mounted on a ship or other mount. The target, shown as an airplane at II, has progressed along the straight horizontal line I2 to point I3, from which it has digressed to begin the curve to point II. When the target was at point I3, its last point on the straight line I2, -the co-target angle was 5, being the angle between line I! from the director II) to point I3 and a line H perpendicular to the original straight target course I2. It will be understood that in its course along line I2 up to point I3, ordinary straight flight anti-aircraft fire is conducted, but beyond this point the aforementioned chordal type of shooting is employed, further details of which may be had upon reference to 'copending application Serial No. 677,870, filed 'June 19, 1946, by applicant, now abandoned.

Referring to Fig. 2, it will be observed that the continuation of the curve beyond point II becomes tangent at point I5 to a line I8 extended from director III into which the target moves and which it follows after it straightens out from the curve I3, II, I5. In order to hit the target in the region of point I5, the last instant at which the projectile may be fired is when the target is still at point II. A projectile fired when the target has progressed to point I9, for example, will burst at some point 20 on the downwardly projected curve, after the target has left the curve and is travelling along straight line I8. It is for this reason that when the target has reached the critical point II, chordal shooting must be quickly abandoned and dive attack technique instantly substituted. Thus if the shift to dive shooting is delay until the target has straightened out at I5, a wide miss, to the of hit for two distinct positions of the target,

one at point II on the curve and the other at a fictitious position 28 on the projected line of dive IB, because a target at point 28 reaches point I5 at the same instant in time that the target at point II reaches the point I5. Thus, when the target reaches point II it may be considered as being at point 28, insofar as firing is concerned.

The only known factors when the target is at point II are the co-target angle 22, being the angle between the line of sight I6 to the target and a line I6 from director I0 perpendicular to a tangent to the target course; present is being reduced as the target travels around the curve, from its value at point I I to the zero value at the tangent point I5, since the target, when moving down the line of sight, has fixed cotarget angle and hence no co-target angle rate. But the distance from point II to point I5 is the distance through which the target will travel while the projectile is travelling to meet it. Therefore, the time interval of target travel from point II to point I5 is the same time interval called time of flight of the projectile from 10 to 15, TI. The rate computer generates a value of which matches the value of the first time rate of change of observed co-target angle, when the target is flying on a straight course.

The difference,

iirtfi dt dt" dt is the first time rate of change of target course, where is the generated co-target angle rate for linear flight, and

gig

is the observed co-target angle rate for all types of observed flights.

From this value of d C dt a correction to 4: for prediction is obtained from h sn ox me e e a ion f dC Awe- X (l) an th DEQRQI val e of p for p di tion is;

T dC I2T=+TZZX- which with reference to Equation 1, may be. ex- Q ZQSQ Q 3 Q=.+ (2) In'the caseot a dive attack down the line ofsight, the final value ofis --90", hence a simpleswitch mechanism on the 45p output shaft can detect the targets approach to this attack line and reduce the curvature correction A to keep the predictions near'the attack line without losing any time. Therefore, at this pointthe aceaesl shift to dive firing technique should be made,

the line l8 being fixed as the line of fire from this point on. By this arrangement, the dive line of the target will be set up in the computer of director 10 a sufliciently long period of time before the dive begins, to maintain constant bursts over the entire target path.

Referring to Fig. 3, a, semi-diagrammatic illustration ofthe director I0 and the appurtenant parts of the mechanism of this invention, numeral 3D designates the usual stabilized telescope in thefield ofview of whose prism 3| the aerial targetisobserved; The control lever 32, pivoted for universal movement, introduces the rates to follow-up mechanism which causes the telescope to follow the target. The rate computer 33 cooperates with lever 32; and telescope to compute and feed to the predictor 34 for the gun or; guns the electrical quantities equal to present-range, R; target speed, S; the first time rate of changeof target course (it and'also the mechanical quantities of generated co-target-angle, and target plane tilt angle a. An example of such mechanism including the control lever 32 and the rate computer 33 for developing and delivering the aforementioned mechanical and electrical quantities to predictor 34: is disclosed in said copending application Serial No. 531,562, and is not claimed herein. Likewise the predictor 34, which feeds to the gun 35 or guns the results of the calculations and which also develops from R, S, and a the electrical quantity Tf the reciprocal of; time of flight-of projectile, is well understood and in accordance with standard practice. The predictor 34 may be constructed in the manner disclosed in copending application SerialNo. 446,886, filed June .13, 1942, jointly by ep l entan s.

Referring'now to the mechanism for switching the, rate, computer 33 and guns from a curve chordal firing to dive firing operation in accordance: with this invention, this mechanism is generallydesignated36 and includes parts 31 to 68, inclusive. A conventional electronic power amplifier 31, such as that illustrated in diagram 15-10, page 222 of RCA Technical Series RG15 (i947) Receiving, Tube Manual, is connected to computer-33, bywires 38 and receives therefrom and amplifies the, electrical quantity equal to the first time rate of change of target course, and is connected to a reversible type motor 33 by wires 40, for driving the same. Conventional damping means, not shown, are provided to stabilize the system.

The motor-39. drives brush 45 of potentiometermultiplier 43 by meansof the shaft 44, gears 49, the pinion 50 and the rack 5i carrying the brush 45. The potentiometer 43 is connected, as shown, with its brush 45 in series opposition with the 1 a p dt wirest38. The input to potentiometer 43 is connected to secondary winding 46 of scaling transformer 50, whose primary winding 48 is supplied by wires 41 with the aforementioned value Tf. from the predictor 34. Byreason of the Winding ratio of transformer 50, a voltage proportional to i is supplied to the end taps of potentiometer 43. The output, voltage of potentiometer 43 is the voltage across movable brush 45 and the center tap 52 of' secondary winding 46 of transformer 50. It will be observedthat because of the connections shown, the voltage proportional to is supplied by wires 38 from the rate computer 33in series opposition to the output voltage of potentiometer 43, and in series with the input terminals of amplifier 31.

The shaft of motor 39 is extended at 44' and connected to one side of mechanical differential 53, whose other input is supplied by shaft 54 from the rate computer 33 and is the mechanical value e. The output shaft 51 of the differential 53 is connected to the roller contact 59 of a simple rotary switch 58 arranged to engage relatively stationary segmental contact 60 carried by, disc 56. The initial spacing between contacts 59 and60f may be adjusted by rotating disc 56 of switch 58, this adjustment being effected by a worm and wheel connection 56' from hand crank 55. This adjustment is made in order to preset switch mechanism 58 manually to operate when thevalue of p reaches the predetermined value as read on dial 55'. Thus, when switch mechanism 58 is preset for dive-attack, its contact roller 59 is automatically brought into engagementwith contact so when the value. of p reaches Shaft 51 is extended'at 53'" to predictor 34 to continue to supply changing values of to the predictor 34 to modify the target deflection rate to gun 35. It will be understoodherein and in the claims that the general term .target deflection rate has the same meaning in the, art as the more common term gun orders.

Switch mechanism 58 is connected by wires 6| .in serieswith manual switch 62 at the director 10, which is closed by the observer, when he issatisfied that a dive attack is intended, and the second break in the circuit energized .from battery.63, is .closed by switch mechanism, 58,1as described. Also in 'serieslwith switches 58. and 62jis ,arelay, 64 havingits armature 65 normally held by spring 66 in engagement with stationary contact 61 to maintain the aforementioned dt circuit to amplifier 31. Upon energization of relay 64 the armature 65 engages contact 66 and disengages contact 61 to open the circuit which has the effect of reducing that braic difference between the magnitudes of the @Q dt and the 2 A ff voltages, and this difierence voltage is amplified by amplifier 31, and applied to motor 39, which drives movable contact 45 of potentiometer 43 to the position where the 2 TEX A output voltage of the potentiometer 43 is equal in magnitude to the voltage, and as the input voltage applied to amplifier 31 is then zero, motor 39 is deenergized, and Equation 1 is solved;

V Solving Equation 3 for A, results in Equation 1 Tf dC' A X7 Equation 2, p=+A, is solved in the following manner by mechanical differential 53: The quantity A is supplied by shafting 44, 44 as an input value ,to mechanical differential 53, while the quantity is supplied by the rate computer 33 by means of shafting 54, as another inputvalue to the mechanical differential 53. The output quantity 151: of mechanical differential 53. is the sum of the input quantities A and 1), and Equation 2 is solved.

As stated, hand crank 55 supplies the input quantity the selected attack line con-target angle, and, with the dial 55', is provided in order that switch mechanism 58 may be preset manually to operate when the value of p reaches the predetermined value as read on dial 55'. Value is approximately -90 for a dive attack and if the curvature correction A4) reaches a value which would make 451) algebraically less than 11 then contacts 59 and 60 of switch 58 close and reduc the value of qi until The resulting intermittent opening and closing of contacts 59 and 60 of switch 58 reduce the value of A just enough to keep (in: approximately equal to M.

In operation of the gun fire control mechanism of this invention, the observer or gun control officer operates control lever 32 and consequently rate computer 33 by keeping the target in view on the cross-hairs of the sighting unit 30, 3| to control the gun or guns 35 to place projectile bursts along thestraight path l2 of the target, in accordance with known practice. If the observer perceives that the target may go into a dive, he closes manual switch 62 and gives the necessary orders for dive attack defense. Mechanism 36 continuously solves Equations 1 and 2, and when the value of (Pp reaches switch 58 closes and energizes relay 64 to break the dC' dt circuit to mechanism 36.

Solution of Equation 2 by mechanism 36 determines the last instant that a curve or chordal shot can be made to hit the target, i. e., when the target is at point ll. Inasmuch as the distance from point I l to point I5 is the distance through which the target travels while the projectile is traveling to meet it and when the shift is made at that instant, the dive attack firing along line l8 requires no further change in the value. Hence, it is appropriate to cancel that value for corresponding unchanged supply to the guns, by breaking the circuits supplying it to the mechanism 36, which is accomplished by relay 64 in the manner described. It will be observed that the supply of the values of range, R, target speed, S, and target plane tilt, a, to predictor 34 is not affected by operation of mechanism 36, and these changing values are continued to be effectively supplied by rate computer 33 to predictor 34 during the dive attack.

When the dive attack defense is completed, the observer returns manual switch 62 to normally open position, which deenergizes relay 64 whose spring 66 causes armature 65 to restore the corresponding break in the Q dt value supply to mechanism 36, for resumption of normal firing. It will be observed that even if there are changing values of T or the corresponding mechanisms remain operative until the dive attack defense is completed as determined by opening of manual switch 62.

In the foregoing discussion, it is obvious that a dive line for the attacking airplane has been chosen which passes through the director ID or, in otherwords, the dive is shown as being down the line of sight. It is of course realized that this type of dive is purely academic and was chosen merely because the discussion is thereby rendered more clear. In most dive attacks, a line is chosen, because of the ballistics of the bomb release, which passes over the director, rather than "9 through it. Such a dive line therefore leaves the curve lll9,l5 at a point above the point I5. However, the device operates similarly and the rates fixed in the predictor cause the guns independentlyof the directorto follow the airplane in its dive, whatever straight line is chosen. A more accurate result can be obtained by using '.p=+lcA, for operation of the switch 58, where k=about 1.3, to more accurately blend the bursts into line [8.

An important feature of the system of this invention is "that an error in the assumption of dive attack, when none is going to take place, wastes no shots unless the target actually enters the turn into its dive, since the linear predictions are unaffected by the device. If targets turn leads to a dive attack on another ship, no shots are Wasted if the other ship is beyond own ship, and a minimum of shooting time is Wasted if other ship is between own ship and the attacking plane, since linear prediction is resumed as soon as A reaches zero.

The system of this invention is possible because of the appropriate choice of coordinates used in the analysis of the problem. A dive attack, down the line of sight, is simply 90. A torpedo attack is 90+L, where L is the lead angle for the torpedo. In an overhead level bombing approach, E, where E is the elevation angle. The device can also be applied to the angle a, which is unimportant in a line of sight attack, but which approaches 90 for an overhead attack.

Other forms of attack on own ship may be described and coped with, with like simplicity, because of the polar nature of the coordinates used in the solution of the problem.

The anticipated method of attack of the target is coped with by manually presetting the value of by means of hand crank 55, for the value of of the expected attack.

Although a preferred embodiment of the invention has been illustrated and described herein, it is to be understood that the invention is not limited thereby, but is susceptible of changes in :form and detail within the scope of the appended claims.

Iclaim:

1, In an anti-aircraft gun fire control apparatus, including calculating mechanism for continuously developing quantities corresponding to the co-target angle between the line of sight to the target and a relatively fixed base line, first time rate of change of target course, time of flight of projectile and target deflection rate, and for supplying said target deflection rate quantity to the gun, the combination of means for multiplying the said first time rate of change of the target course and one-half the projectile time of flight quantities to produce the product thereof, motive means driven in accordance with said product, and means jointly driven by said motive means and in accordance with said c'o-target angle for modifying said target deflection rate quantity supplied to the gun.

2. In anti-aircraft gun fire control apparatus, including calculating mechanism for continuously developing a mechanical quantity corresponding to the co-ta'rget angle between the line of sight to the target and a relatively fiXed base line and electrical quantities corresponding to the first time rate of change of target course time .of flight of projectile and target deflection rate, and .for supplying said target deflection rate quantity to the gun, the combination of means for multiplying the said first time rate of change of the target course and one-half the projectile time of flight quantities to produce the product thereof, electrical motive means driven in accordance with said product, and means jointly driven by said motive means and in accordance with said mechanical quantity for modifying said target deflection rate quantity supplied to the gun.

3. In anti-aircraft gun fire contral apparatus, including calculating mechanism for continuously developing quantities corresponding to the co-target angle between the line of, sight to the target and a relatively fixed base line, first time rate of change of the target course, time of flight of projectile and target deflection rate, and for supplying said target deflection rate quantity to the gun, the combination of means for multiplying the said first time rate of change of the target course and one-half the projectile time of flight quantities to produce the product thereof, motive means driven in accordance with said product, a normally closed switch interposed in said first time rate of change of target course quantity supply, means jointly driven by said motive means and in accordance with said co-target angle and operative to open said switch when said motive means stops, and operative connections between said last-named means and said mechanism for modifying the target deflection rate quantity supplied to the gun.

4. In anti-aircraft gun fire control apparatus, including calculating mechanism for continuously developing quantities corresponding to the co-target angle between the line of sight to the target and a relatively fixed base line, first time rate of change of target course, time of flight of projectile and target deflection rate, and for supplying said target deflection rate quantity to the gun, the combination of means for multiplying the said first time rate of change of the target course and one-half the projectile time of flight quantities to produce the product thereof, motive means driven in accordance with said product, means jointly driven by said motive means and in accordance with said co-target angle, and connections between said last-named means and said mechanism for modifying said target deflection rate quantity supplied to the gun.

5. In an anti-aircraft gun flre control apparatus, including calculating mechanism for continuously developing and supplying quantities corresponding to the co-target angle between the line of sight to the target and a relatively fixed base line, first time rate of change of the target course and time of flight of projectile, the combination of means for multiplying the said first time rate of change of the target course and onehalf the projectile time of flight quantities to produce the product thereof, motive means driven in accordance with said product,' and operative connections between said motive means and said co-target angle supply for modifying the same.

6. In an anti-aircraft gun fire control apparatus, including calculating mechanism for continuously developing and supplying 'quantities corresponding to the co-target angle between the line of sight to the target and a relatively fixed base line, first time rate of change of the target course and time of flight of projectile, the combination of means for multiplying the said first time rate of change of the target course and onehalf the projectile time of flight quantities, to produce the product thereof, motive means driven in accordance with said product, a normally closed switch interposed between said first time rate of change of target course supply and said motive means, and means responsive to a predetermined movement of said motive means for opening said switch.

'1. In anti-aircraft gun fire control apparatus, including calculating mechanism for continuously developing a mechanical quantity corresponding to the co-target angle between the line of sight to the target and a relatively fixed base line, and electrical quantities corresponding to the first time rate of change of the target course, time of flight of projectile and target deflection rate, and for supplying said target deflection rate quantity to the gun, the Combination of means for multiplying the said first time rate of change,

of target course and one-half the projectile time of flight quantities to produce the product thereof, electrical motive means driven in accordance with said product, means jointly driven by said motive means and in accordance with said mechanical quantity, operative connections between said last-named means and said target deflection rate supply for modifying the same, a normally closed switch interposed in said first time rate of change of target course quantity supply, and means driven by said last-named means for opening said switch.

8. Inan anti-aircraft gun fire control apparatus, including calculating mechanism for continuously developing a mechanical quantity corresponding to the co-target angle between the line of sight to the target and a relatively fixed base line, and electrical quantities corresponding to first time rate of change of target course, time of flight of projectile and target deflection rates, and for supplying said target deflection rate quantity to the gun, the combination of means energized by said electrical quantity corresponding to the first time rate of change of target course and responsive thereto, means energized by said electrical quantity equal to the projectile time of flight and responsive to onehalf said value, means for multiplying the output electrical quantities of said two means to produce the product thereof including series opposition connections between the output of said multiplying means and said time rate of change of target course output of said calculating mechanism, a normally-closed switch interposed in said time rate of change of target course quantity supply, operative connections between said mechanical quantity supply and said target deflection rate supply for modifying the same, and means responsive to an algebraic sum of the output of said last-named means and said mechanical quantity for opening said switch.

9. In anti-aircraft gun fire control apparatus, including calculating mechanism for continuously developing a mechanical quantity corresponding to the co-target angle between the line of sight to the target and a relatively fixed base line, and electrical quantities corresponding to first time rate of change of target course, time of flight of projectile and target deflection rate, the combination of means supplying said target course quantity, a normally-closed switch interposed in said means, normally deenergized electromagnetic means operatively connected to said switch, electrical means for multiplying the said first time rate of change of the target course and one-half the projectile time of flight quantities to produce the product thereof, electrical motive means driven in accordance with said product, means jointly responsive to said motive means and said mechanical quantity for combining the same, operative connections between said lastnamed means and said target rate supply for modifying the same, and operative connections between said last-named means and a normally open switch in circuit with said electromagnetic means for energizing said electromagnetic means to open said normally-closed switch.

10. In anti-aircraft gun fire control apparatus, including calculating mechanism for continuously developing a mechanical quantity corre-- sponding to the co-target angle between the line of sight to the target and a relatively fixed base line, and electrical quantities corresponding to first time rate of change of target course, time of flight of projectile and target deflection rate, the combination of means supplying said target course quantity, a normally-closed switch interposed in said means, normally deenergized electromagnetic means operatively connected to said switch, electrical means for multiplying the said first time rate of change of the target course and one-half the projectile time of flight quantities to produce the product thereof, electrical motive means driven in accordance with said product, means jointly responsive to said motive means and said mechanical quantity for combining the same, operative connections between said lastnamed means and said target rate supply for modifying the same, operative connections between said last-named means and a normally open switch in circuit with said electromagnetic means for energizing said electromagnetic means to open said normally-closed switch, and means for adjusting the spacing between the contacts of said normally open switch.

11. In anti-aircraft gun fire control apparatus, including calculating mechanism for continuously developing a mechanical quantity corresponding to the co-target angle between the line of sight to the target and a relatively fixed base line, and electrical quantities corresponding to first time rate of change of target course, time of flight-of projectile and target deflection rate, the combination of means supplying said target course quantity, a normally-closed switch interposed in said means, normally deenergized electromagnetic means operatively connected to said switch, electrical means for multiplying the said first time rate of change of the target course and one-half the projectile time of flight quantities to produce the product thereof, electrical motive means driven in accordance with said product, means jointly responsive to said motive means and said mechanical quantity for combining the same, operative connections between said lastnamed means and said target rate supply for modifying the same, operative connections between said last-named means and a normally open switch in circuit with said electromagnetic means for energizing said electromagnetic means to open said normally-closed switch, and a second normally open switch in the circuit of said first normally open switch and said electromag netic means for rendering the first normally open switch effective to energize said electromagnetic means.

CHARLES D. BOOK.

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

UNITED STATES PATENTS

Images