Patent GB-435658-A (GB)
Title: Improvements in ranging devices
IPC: F41G5/08
Filed: 1934-11-15
Abstract: 435,658. Range-finders &c. RICORDEL, A. L., 162, Rue St. Charles, Paris. Nov. 15, 1934, No. 32930. [Class 97 (i)] Auxiliary sighting-apparatus for use with range-finding apparatus to enable the speed and direction of travel of a moving target, particularly an aircraft, to be determined, and the range and bearing of the target to be continuously obtained, comprises a rotatable friction roller mounted so that its horizontal axis of rotation can turn freely in azimuth and urged, relatively to the surface on which it bears, in two directions at right-angles to each other at speeds proportional respectively to the component speeds of the target in, and at right-angles to, the sighting plane. The axis of the roller sets itself in accordance with the resultant movement, and the direction of this axis in azimuth indicates the direction of travel of the target. In one form the roller bears on a stationary plate and is connected to a sighting device which is operated to follow the target, the changes in the elevation of the sighting line causing the roller to move towards or away from the centre of the plate and the changes in azimuth causing the roller to move tangentially. In another form a freely mounted sphere receives component rotations about axes at right-angles to each other proportional to the component speeds of the target, and the roller is driven by the sphere and sets itself so that its axis is parallel to the axis of the resultant rotation of the sphere. Fig. 13 shows an apparatus of this kind, based on the velocity values represented in Fig. 11, in which O represents the observer and Ao the target assumed to be moving in the horizontal plane P in the direction AoA with velocity V. This velocity is resolved into components Vh and VL respectively in, and at right-angles to, the sighting plane S and the component Vh is further resolved into components Vr, Vs respectively along and at right-angles to the line OAo. Then if Do is the range, Dh the horizontal range, So the initial angle of sight, Ws and Wa respectively the changes in elevation and azimuth of the target, it is seen that Ws=Vs/Do and Wa=VL/DoCosSo= VL /Dh. The apparatus shown in Fig. 13 comprises separate sighting-devices 125, 98 for following the target in altitude and azimuth respectively, and a freely mounted sphere 81 driven as above described by rollers 87, 88, operated by handwheels 91, 92. The shaft 90 turned by the wheel 92 carries a friction roller 93 operating a disc 94 connected to the sight 98, the distance of the roller from the centre of the disc being made proportional to Dh by a device 99 resolving the range Do into its components, the range being represented by the displacement of a nut 101 along a screw 100. Thus, if the handle 92 is turned to cause the sight 98 to follow the target in azimuth, the rotation of the handle is proportional to VL, the rotation of the sight being equal to VL/Dh. The shaft 89 driven by the wheel 91 drives a roller 108 which rotates a sphere 109 having two driven rollers 110, 111 at rightangles to each other, the roller 108 being set so that its axis is at an angle So to that of the roller 110, so that, if the speed of the wheel 91 is proportional to Vh, the speeds of the rollers 110, 111 are respectively proportional to Vr and Vs. The rotation of the roller 110 thus represents the change in the range Do, and the shaft 112 of this roller is geared to a shaft 115 controlling the displacement of the nut 101 on the screw 100. The shaft 115 also operates a scale 134 for continuously indicating the range. The shaft 112 is also connected by shafts 115, 117 to a shaft 118 carrying a screw 119 engaging a non-rotatable nut 120 which controls the displacement of a roller 121 over a disc 122 so that the distance of this roller from the centre of the disc is maintained proportional to the range. The roller 121 is driven by the roller 111 rotating proportionally to Vs, so that the rotation of the disc 122 is proportional to Vs/Do, i.e. to Ws, Fig. 11. The disc 122 drives the altitude sighting-device 125 and is also connected to the range-resolving device 99 and to the roller 108 so as to maintain the correct value of the angle of sight in these parts of the apparatus. The initial values of the range, elevation, and azimuth of the target are set by wheels 130, 132, 107. The roller 82 driven by the sphere 81 is mounted in a pivoted frame so that it sets itself with its axis parallel to that of the resultant rotation of the sphere. The frame carries a pointer 83 indicating on a scale 84 the direction of travel of the target. The roller 82 may also operate a tachometer 86 to indicate the speed of the target. To enable the apparatus to be used to maintain the range, altitude, and elevation of the target during periods of invisibility of the latter, the roller 82 can be used to drive the sphere 81, the roller being actuated by a constant speed motor 137 through a disc 138 and roller 139, the distance of which from the centre of the disc is proportional to V. A form of apparatus is also described which takes into account the vertical component of the velocity of the target if the latter cannot be assumed to be moving in a horizontal plane.