Patent GB-839031-A (GB)
Title: Improvements in or relating to fire control apparatus for guns
IPC: F41G5/00
Filed: 1944-03-24
Abstract: 839,031. Gun-laying systems. SPERRY GYROSCOPE CO. Inc. March 24, 1944 [March 25, 1943], No. 5537/44. Class 92 A gun-laying system of the kind in which the angle of lead is dependent on the product of the angular speed of the gun and the time of flight of the projectile is characterized in that a quantity that depends upon, but undergoes only gradual changes in response to changes of, the said product is supplied to the sighting arrangement by a slowly responsive device. By this means any change in the angular velocity of the gun results in a gradual change in the angle of lead. As shown in Fig. 1, the guns 11 are mounted for elevation on a shaft 13 and for azimuth on a fixed toothed ring 14, and to the guns is fixed a computing and stabilizing mechanism 16 including a sighting device 17. Movements of the guns about the elevation and training axes is effected by an hydraulic variable speed transmission system comprising a drive motor 34 which actuates the A-ends 35, 36 of the system, the latter being connected to drive hydraulic motors 37. 38 representing the B- ends. Motors 37, 38 drive gearing as shown to elevate and train the guns. Stabilizing and power follow-up mechanisms. In operation the gunner views the target through sight 17, and moves a handlebar 19 about a vertical or a horizontal axis through an angle proportional to the angular speed of the target in azimuth or elevation, such movement of the handlebars serving to actuate the motors 38, 37, by means of mechanism shown in Fig. 2. Thus movement of handlebar 19 about a horizontal axis displaces a vertical rack which drives a shaft 23<SP>1</SP>. This shaft is connected by shaft 23 to computer 16<SP>1</SP> to supply target elevation rate data (Erg) thereto, and by shafts to a pulley 118 which is adapted, by springs 119 and pulley 117, to apply torque to a gyro 104 about an axis 114. This causes the gyro to precess about horizontal axis 106 thereby moving an armature 124 with respect to an E-type transformer 126. The output voltage which in consequence appears across the leads 127 is applied to an amplifier 128 which actuates a torque motor 129, the arm 210 of which actuates a torque hydraulic amplifier 131 which moves the control 35<SP>1</SP> of the A-end 35 of the mechanism for driving the guns in elevation. Movement of the handlebar about a vertical axis is similarly conveyed to the computer and through the gyroscope to the motor for moving the gun in azimuth. By such means the guns are maintained parallel to the spin axis 110 of the gyro. Further, since the spin axis of the gyro remains stationary in space if the handlebar is in its central position, the gyro and hence the guns maintain their orientation in space if the aircraft or other vehicle on which they are mounted alters its direction. Computer and sighting device. As shown in Figs. 4A and 4B movement of handlebar 19 about a vertical axis supplies target rate data in azimuth to the computer by way of shafts 26, 26<SP>1</SP>, the latter serving, through rack and pinion 147 to rock a lever 148 about a movable fulcrum 149. This fulcrum is moved in accordance with the time of flight of the projectile which is a function of the slant range. To obtain the range a target dimension dial 30 is moved to a position indicating the known dimensions of the target, the dial serving also to produce axial displacement of a solid cam 143. The cam serves to displace a casing 139 associated with the sight, the casing having a circular slit 141 surrounded by a continuous light source 142 whereby a thin circle of light is projected on to a fixed conical reflecting surface 138. A knob 27, Fig. 1, is used to drive a shaft 28 for rotating the cam and thence to displace casing 139, whereby the diameter of the circle of light on the cone is varied, the cam being so designed that when the reflected image of the circle just circumscribes the target the displacement of shaft 28 represents a predetermined function of the slant range. This optical system and modifications thereof form the subject of Specification 839,032. Shaft 28 is connected by shafting as shown to a cam 151, the follower of which moves the fulcrum 149. By this arrangement the far end 153 of lever 148 moves through a distance proportional to the product of the time of flight and azimuth rate set in by rack 147, which product gives azimuth prediction angle based on gun rate. Movement of end 153 actuates a shaft leading to a differential 154 to which also leads a shaft giving a prediction correction angle #, the shaft being driven by the lift of a follower of a cam 69<SP>1</SP>. This correction mechanism forms the subject of Specification 689,029 and comprises cam positioning devices operated by slant range shaft 28, indicated air speed dial 31, and altitude dial 29, the cam being rotated by gun azimuth shaft 52 which, as shown in Fig. 1, is driven by a gear meshing with teeth on fixed ring 14. The output of differential 154 is therefore proportional to the azimuth lead angle, and its output shaft is connected through a slowly responsive device 157, 160 to a shaft 164 which moves mirror 87<SP>1</SP> of the sighting device through the correct lead angle. The elevating circuit functions in the same manner to move mirror 87, similar mechanism being provided, but the correction in this case being for super-elevation under the control of a cam 72. In order to prevent the line of sight moving in space in an opposite direction to that of the guns when the handlebar is moved, the unit 159, 160 is provided between differential 154 and shaft 164. This unit comprises a subtracting differential 157, the output of which drives a cam 162 which in turn moves, through a follower, a ball carriage 161 on a turntable 158. Carriage 161 drives a cylinder 159 on shaft 164, and a shaft extending from the cylinder is geared to the differential 157. Thus. movement of shaft 156 from differential 154 displaces the ball carriage, causing the cylinder 159 to rotate and thereby to reset the ball carriage to its neutral position, and it can be shown that shaft 164 has then been rotated through an angle proportional to that of shaft 156. The time delay involved is necessary to convert the lead angle based on gun rate to the true lead angle based upon line of sight rate. It is shown in the Specification that the delay should vary in accordance with the line of flight, and to provide for this the turntable 158 is driven by a constant speed motor through a variable speed device 166, the ball carriage of which is positioned by a cam 168 which is set by shaft 28 as shown. In a modification, Fig. 5 (not shown) the position of the fulcrum, corresponding to fulcrum 149, is controlled from the shaft 28 and also from the altitude and indicated air speed dials. This construction also incorporates a modified arrangement of the equating and delaying devices in the circuit. Modifications of the sighting instrument incorporating parabolic surfaces for causing parallel rays to be deflected through the slit on to the conical reflecting surface are also described. Fig. 11 (not shown) also describes mechanism whereby a single mirror replaces the two mirrors of the sighting device shown in Fig. 4A.