Patent GB-617237-A (GB)
Abstract: 617,237. Predictors. SPERRY GYROSCOPE CO., Inc. March 1, 1944, No. 3804. Convention date, March 1, 1943. [Class 92 (ii)] Apparatus for computing prediction corrections for guns directed at rapidly moving targets, comprises mechanical means for setting into the apparatus quantities proportional to the targets range, and azimuth and elevation position, and the rates of change of these quantities, means for mechanically deducing solely from the set range Do and the set rate of change D<SP>1</SP> a quantity that is related to the time of flight of the projectile to the targets future position, and means for deriving the gunaiming angles from the time of flight quantity and the said quantities set into the apparatus. Space diagram.-In Fig. 1, O represents the gun, To and Tp, the present and predicted future positions of the target respectiyely, OMTo the vertical plane containing the gun and To, OXQ the horizontal plane containing the gun, and OToL the slant plane perpendicular to plane OMTo and containing the gun and To. The letters A, D, E, H, where suffixed represent respectively azimuth, range, elevation and height, the suffixes o and p indicating respectively " present " and " future ". V is the velocity of the target and tp the time of flight, thus giving Vtp for the distance ToTp. The velocity is shown resolved into three mutually perpendicular components, one along the line of sight, one horizontally through To at right-angles to the line of sight, and one in plane OMTo at right-angles to the line of sight. These give respectively slant range rate (D) slant plane azimuth rate DoAs and elevation rate DoE. In the vector diagram included in Fig. 1, these are all multiplied by the time of flight tp to give three components of prediction. In the computing mechanism data is set corresponding to what is called a fictitious time of flight t<SP>1</SP>p where and the mechanism described with reference to Fig. 2 uses this expression in. combination with equations obtained mathematically from the diagram shown in Fig. 1 to orient the guns towards the target predicted position. Gun director.-The target is tracked by manipulating three handwheels 1, 35, 95, Fig. 2, associated respectively with range, elevation and azimuth. Handwheel 1 through shaft 2 and rack and pinion mechanisms imparts axial displacements to a cam 19 and to a ball. carriage 5 of a variable speed device 6. The driven cylinder 9 of device 6 and the shaft 2 both lead to differential 15 whose output shaft 16 operates a dial 10 and also rotates cam 19. The handwheel is so moved that dial 10 is made to correspond with a range indicator and thus the shaft 16 and cam are rotated by an amount proportional to the present slant range Do and the cam is translated by shaft 2 in accordance with the rate of change of range D. By suitably designing one surface of the cam a follower 21 may therefore be made to move in accordance with t<SP>1</SP>p. Handwheel 35 actuates the ball carriage 39 of a similar variable speed device 41 whose output shaft 46, which is used to drive the sighting telescope 34, moves through an angle proportional to present target elevation Eo and at a speed proportional to the elevation angular velocity E of the target. Shaft 46 is connected by shafts 51, 56, to drive a disc 57 at a speed proportional to E and as the ball carriage 25 for the disc is moved by an amount t<SP>1</SP>p, by being geared to follower 21, the driven cylinder 58 is caused to rotate at a speed proportional to the product of these factors. A shaft on cylinder 58 leads to an equating device 61, which may be a differential, to close one of two contacts 67, 68, thereby energizing a motor 69. A cam groove 72 on the shaft of the motor moves a follower 73 by an amount proportional to the tangent function of the movements of the motor, the follower serving to move a ball carriage 74 of a variable speed device whose cylinder 63 leads back to equating device 61. It is proved in the Specification that by this means the motor 69 will move by an amount proportional to the elevation component of the prediction angle (#E). The motor axially displaces a cam 79 which is rotated by an amount proportional to Eo by a drive from shaft 46, the cam being so designed that its follower 86 moves according to the expression (1-tan Eo tan #E). Azimuth tracking.-The handwheel 95, operating through a variable speed device 102 and differential 111, causes sighting telescope 96 to follow the target in azimuth, whereby shaft 112 is rotated by an amount proportional to present azimuth angle Ao and at a speed proportional to azimuth angular velocity. Shaft 112 drives a disc 31 whose ball carriage is displaced by follower 21 according to t<SP>1</SP>p, whereby driven cylinder 117 rotates at a speed proportional to At<SP>1</SP>p. Shaft 118 of the cylinder leads to an equating device 119 for merging a motor 123 which drives a shaft 125 whose cylinder 128 has a tangent groove 129. This groove moves a follower actuating a ball carriage 131 the disc 93 of which is driven, by means of a variable speed device 88 whose ball carriage is displaced by follower 86 of cam 79, at a speed proportional to (1-tan Eo tan #E). The ball carriage 131 drives a cylinder 132 leading back to the equating device. It is proved in the Specification that when equilibrium is reached the motor 123 has rotated an amount proportional to #<SP>A</SP>, this being the change in azimuth angle measured in the horizontal plane. This data #<SP>A</SP> is added by differential 134 to present azimuth data supplied by shaft 112 to actuate an azimuth transmitter 139 for the guns. A shaft 124 from the motor also gives axial displacement to a cam 143, which is rotated an amount proportional to (Eo+#Eo) by an output shaft 146 of a differential whose input shafts lead to motor 69 and to the elevation tracking mechanism. The follower 147 of cam 143 actuates a shaft 151 leading to a differential 152 to which shaft 146 also leads. The output shaft of differential 152 leads to a further differential 168, to which is also fed data corresponding to super-elevation by a shaft 169. Output shaft 171 of differential 168 actuates the elevation transmitter 172 for the guns. In a modification, Fig. 3 (not shown), the range handle is operated in a similar manner to actuate a range dial through a variable speed device, but the elevation and azimuth handles are employed to apply torques to a gyroscope, the precessional movements of which cause the actuation of motors. Various solid cams and equating devices are employed, these being constructed and arranged in accordance with formulµ given in the Specification to produce the required movements of the guns.