Eye bias device for homing bomb
US 2704513 A
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March 1955 E. B. DANE, JR
EYE BIAS DEVICE FOR HOMING BOMB 3 Sheets-Sheet 1 Filed May 5, 1947 March 22, 1955 E. B. DANE, JR
EYE BIAS DEVICE FOR HOMING BOMB 3 Sheets-Sheet 2 Filed May 5, 1947 INVENTOR. [FA/57 5 fli/VfJ. BY w March 22, 1955 B. DANE, JR
EYE BIAS DEVICE FOR HOMING BOMB 3 Sheets-Sheet 3 Filed May 5, 1947 nited States Patent EYE BIAS DEVICE FOR HOMING BOMB Ernest B. Dane, Jr., Belmont, Mass., assignor to the United States of America as represented by the Secretary of the Air Force Application May 5, 1947, Serial No. 746,025
7 Claims. (31. 102-4 This invention relates to the control system of a maneuverable bomb of the type designed to home on a source of infrared radiation, and particularly to an eye-biasing device for use in the control system of such a bomb. Bombs of this type have limited maneuverability and are dropped in the conventional manner with the aid of a bombsight. The control system is operative during the last thirteen seconds or so of the bombs fall and serves to steer the bomb to the target as represented by the strongest source of infrared radiation in the field of view of the bombs eye. The real function of the control system therefore is to correct for initial errors in the aiming of the bomb by the bombsight.
The flight of the bomb is controlled by rudder, elevator and aileron surfaces located in the tail. The ailerons are gyroscopically controlled and serve to stabilize the bomb as to roll. The rudder and elevator surfaces are controlled by servomotors operating in response to signals received from the infrared sensitive eye and an associated electronic circuit, and serve to control the direction of travel of the bomb by means of a yawing or skidding action.
A main timing device is provided in connection with the control circuit and is set in accordance with the altitude of release to turn on the control system when the bomb has reached an altitude of about 10,000 feet, or about thirteen seconds before the time of impact. Prior to the time at which the control system becomes operative, the bomb falls with its eye and controls in the new tral position. It is desirable that the target be in the center of the field of view of the eye at the time that the control system becomes operative, however, when the eye is in the neutral position, its field of view is centered about the axis of the bomb, and the attitude of the bomb at this point is such that the field of view falls beyond the target area. ance with the invention by providing an initial downward bias to the eye which is gradually decreased to zero as the bomb nears the target.
It is therefore the object of this invention to increase the accuracy of control of bombs of the described type by providing means to enable the eye to see the target during the entire period of operation of the control system.
The means for accomplishing this purpose are described in detail in connection with the accompanying drawings in which:
Fig. 1a shows a cut away view of the nose section of a homing bomb;
Fig. 1b shows a cut away view of the tail section of a homing bomb;
Fig. 2 is an end view of Fig. 1a with the shroud removed;
Fig. 3 is a diagram showing the relationship between the bomb, its field of view, the target and the free fall impact point; and
Fig. 4 shows the details of the eye biasing device.
As shown in Figs. la and 1b, the control system of the bomb comprises a nose section and a tail section which may be attached to a standard 1,000 pound bomb 1. Referring to Figs. 1a and 2, the plate 3 is fastened to the nose of the bomb and carries two supports 4 and 5 between which are mounted a gimbal ring 6 pivoted by pins 7 and 8 to rotate about a horizontal axis. The housing 9 contains the infrared sensitive eye of the bomb and is mounted in the ring 6 by pins 10 and 11 which permit the eye to rotate about an axis in the vertical plane. The principal elements of the eye contained in housing 9 are This difiiculty is corrected in accorda parabolic mirror rotated at constant speed, a bolometer located at the focus of the mirror and a commutating device. The mirror is mounted so that its optical axis makes an angle of about 5 with its axis of rotation and so that the principal focus falls at the intersection of the two axes. The bolometer is placed at this intersection and is of such size as to subtend an angle at the center of the mirror equal to twice the angle between the two axes, or about 10. With this arrangement, the eye scans a circular area 10 in diameter centered on the axis of the eye. The bolometer is a resistance element having a high temperature coefficient and coated with a black substance so as to convert the infrared radiations incident thereon into heat. The resistance of the bolometer is therefore a function of the infrared radiation striking it. The signal from the bolometer is applied to an electronic circuit which controls the servomotors actuating the rudder and elevator surfaces in the tail. The commutator is mounted on the same shaft as the mirror and rotates therewith and cooperates with the electronic circuit to distinguish between signals received from the four quadrants of the scanned area. Infrared radiations are admitted to the mirror through the conical window 12 which is made of material having a high transparency to this radiation such as fused silver chloride.
The eye housing 9 is biased upward by the coil spring 13 and to the right by coil spring 14. The housing is restrained from rotating upward by arm 15, attached to gimbal ring 6, and cable 16 which is fastened to arm 15 by adjusting screw 17. Housing 9 is also restrained from rotating to the right by arm 18, which is fastened to the housing near its bottom pivot point, and cable 19 which is fastened to arm 18 by adjusting screw 20. Cable 16 passes over pulleys 21, 22 and 23 and cable 19 passes over pulleys 24 and 25 and thence through holes in plate 3 and through cable 26 to the tail structure of the bomb. The cables 16 and 19 are provided with armored sheaths for passage through cable 26. Cable 26 also carries all electrical connections between the nose and tail structures. The electronic unit is contained in the nose structure and batteries for supplying power to the control system are located partly in the nose structure and partly in the tail structure, however, these elements have been eliminated from the drawings for the sake of simplicity. Increasing the tension in cable 16 causes the eye to turn downward,
and increasing the tension in cable 19 causes the eye to turn to the left. Decreasing the tension in cable 16 allows the eye to be rotated upward by spring 13 and decreasing the tension in cable 19 allows the eye to be rotated to the right by spring 14.
The tail structure of the bomb comprises an octagonal member 27, in the upper and lower surfaces of which are mounted elevator surfaces 28 and 29, and in the left and right surfaces of which are mounted left rudder surface 30 and a corresponding right rudder surface not shown. Also mounted within the octagonal member 27 are two ailerons 31 and 32 which are gyroscopically controlled and operate from the time the bomb is released to stabilize it in roll. Elevator servomotor 33 is arranged to actuate elevator surfaces 28 and 29 through shaft 34 and suitable linkages as shown, and, similarly, rudder servomotor 35 is arranged to actuate the rudder surfaces through shaft 36 and suitable linkages as shown. The cable 16 is attached to crank arm 37 on shaft 34 and cable 19 is attached to crank arm 38 on shaft 36. Thus when the elevator surfaces 28 and 29 are actuated upward by servomotor 33, the tension in cable 16 is increased and the eye is rotated downward against the action of spring 13. When the elevator surfaces are rotated downward, the tension in cable 16 is decreased and the eye rotates upward due to the torque exerted by spring 14. Likewise the left rotation of the rudders causes a right rotation of the eye and vice versa due to the action of cable 19 and spring 14. Thus the eye is caused to rotate through an angle opposite in direction to the angle through which the bombs axis is caused to rotate by the aerodynamic action of the control surfaces. In order to provide a slight anticipation in the control and thus avoid overshooting, the coupling between the tail surfaces and the eye is made such that the angle through which the eye rotates is equal to a constant less than unity times the angle through which the bombs axis is rotated. Thus the line of sighting of the eye is always on the target side of the velocity vector, or the direction in which the bomb is travelling, resulting in the eye removing the correction slightly before the velocity vector is pointed in the direction of the target. The above described coupling between the eye and the tail surfaces is necessary in order to keep the eye always looking along the velocity vector. Without this coupling changes in the attitude of the bomb brought about by the control system for the purpose of correcting the bombs course would throw the eye off the target or else cause the eye to initiate a false correction.
The bomb is provided with a main timing device 60 shown in Fig. 1b. This may be any suitable device, usually a mechanical timer, for measuring a definite time interval, the length of which may be set by adjustment 61, and for closing a set of contacts at the end of the time interval. The timer begins to operate at the time the bomb is released and measures the interval of time required for the bomb to reach an elevation of about 10,000 feet. The initial setting of the timing device is therefore determined by the altitude of release. At the end of the measured interval, the timing device renders the control system of the bomb operative, by applying a voltage through indicated connection 63 to control system energizing switch 62 for closing this switch and energizing the various components of the control system. so that the last 10,000 feet of the bombs fall is controlled. The bomb is released from the airplane in a horizontal position and its longitudinal axis gradually tends toward a vertical position as the bomb falls. That part of the bombs fall above 10,000 feet is made with the control system inoperative and with the elevator and rudder surfaces and the eye in their neutral positions. However, the ailerons are operative during this interval to stabilize the bomb in roll. The eye, in its neutral position, looks along the longitudinal axis of the bomb, and if in this position when the control system becomes operative, would scan a circular area of diameter A as shown in Fig. 3. It is seen that this area would not include the target, which is in the vicinity of the termination P of the free fall trajectory C. Therefore, in order to have the scanned area center around the free fall impact point when the control system becomes operative, it is necessary to provide the eye with an initial downward bias so that the area scanned is as shown at B in Fig. 3. The amount of the initial bias is determined by the altitude of release and is inversely related thereto, since the greater the altitude of release, the more nearly vertical is the axis of the bomb at 10,000 feet and the less bias angle required. As the bomb approaches the target, the bias angle should be reduced since the axis of the bomb continues to approach the vertical and the required bias angle becomes less. The eye bias device in accordance with the invention provides means for setting the initial bias angle in accordance with the altitude of release and means for gradually reducing the angle to zero as the bomb approaches the tar et.
The ap aratus for performing the above function is shown in Figs. 1a and 2. and in detail in Fig. 4. It consists of a support 39 upon which is mounted a timing device 40. An arm 41 is pivoted at 50 in the support and has pulley 22 mounted on its other end. This end of the arm is also provided with an extension 42 which serves as a stop to limit the downward movement of the arm. The arm 41 has a slot 43 provided with a number of notches designed to be engaged bv pin 44 and bar 45. The opposite end of bar 45 is provided with a rack 46 which engages pinion 47 of the timing device. The timer 40 may be wound by a clockwise rotation of knob 48 which is mounted on the same shaft as pinion 47. When fully wound, the bar 45 is in its uppermost position, as shown in Fig. 4. The timer is held in its fully wound condition by caging device 49 which is merely a magnetically operated release device to which an actuating voltage is applied by main timer 60 concurrently with energization of the control system of the bomb. The height to which pulley 22 is raised when the bar 45 is in its uppermost position is determined by which of the notches in bar 41 is engaged by pin 44. In the embodiment shown in Fig. 4, notches are provided for bomb release altitudes ranging from 8,000 to 30,000 feet in steps of 2,000 feet. The apparatus in Fig. 4 is set for a bomb release altitude of 26,000 feet. Maximum bias angle is provided when pin 34 is placed in the 8,000 foot notch and the minimum downward bias is produced when the 30,000 foot notch is used. Since cable 16 passes over pulley 22, raising this pulley increases the tension in the cable 16 and causes the eye to be rotated downward against the action of spring 13, thus providing the initial downward bias for the eye. When the main timing device 60 renders the control system of the bomb operative at or near 10,000 feet, it also sends an electrical pulse to caging device 49 over indicated connection 64 (Figs. 1a and 1b) causing it to uncage eye timer 40 which, through rotation of pinion 47, gradually lowers bar 45 and pulley 22, thus gradually reducing the bias angle to zero as the bomb nears the target.
1. A homing bomb having a control system containing an eye sensitive to radiant energy and capable of scanning an area about-its extended axis, said bomb being of the type designed to be released from an aircraft with the aid of a bombsight in the manner of a freely falling bomb and with its controls inoperative and in a neutral position, timing means in said bomb set in accordance with the altitude of release to render said control system operative at a predetermined altitude above the target, means preset in accordance with the altitude of release for rotating the axis of the eye downward through an initial angle inversely related to the altitude of release and of such value that the free fall impact point falls within the scanned area of said eye at said predetermined altitude, and means rendered operative at the same time as said control system for gradually reducing said angle to zero over the period of time required for the bomb to fall from said predetermined altitude to said target.
2. A homing bomb having a control system containing means for stabilizing the bomb in roll and means for controlling the direction of travel of said bomb, said latter means comprising an eye sensitive to radiant energy and capable of scanning an area about the extended axis of the eye, a tail structure containing elevator and rudder surfaces, means for controlling said surfaces in accordance with signals received from said eve, coupling means between said elevator and rudder surfaces and said eye tending to keep the axis of the eye pointed in the general direction of travel of the bomb, and additional means acting on said coupling means for causing the axis of the eve to assume a downward bias angle with respect to said direction of travel the instantaneous value of which is a direct function of the instantaneous altitude of the bomb grid Ian inverse function of the altitude of release of the 3. Apparatus as claimed in claim 2 in which said coupling means comprises a cable connected between said elevator surface and said eve and is so arranged that an increase in the tension of said cable rotates the eye downward. and in which said additional means comprises a movable pulley enga ing said cable and arranged to vary the tension in said cable.
4. Apparatus as claimed in claim 3 and in addition actuating means for said pul ey, said actuating means being capable of moving said pulley from a position producing a maximum increase in tension in said cable to a position producing zero increase in tension in said cable at a uniform rate.
5. Apparatus as claimed in claim 4 in which said actuating means contains adiustable means for fixing the maximum increase in cable tension in accordance with the altitude of bomb release.
6. Apparatus as claimed in claim 5 in which said control svstem is provided with a timing device adiustable in accordance with the altitude of release to function at a predetermined altitude to simultaneously render said control system operative and to initiate operation of said pulley actuating means.
7. Apparatus as claimed in claim 6 in which said pulley actuating means comprises a timing device for moving said nullev from the position producing maximum increase in cable tension to the position producing zero increase in cable tension during the time reouired for the bomb to fall from said predetermined altitude to zero altitude.
References Cited in the file of this patent UNITED STATES PATENTS 1,388,932 Centervall Aug. 30, 1921 FOREIGN PATENTS 352,035 Great Britain June 22, 1931