GB836590A - Improvements in range-finder sights - Google Patents

Abstract

836,590. Range-finder sights. BEACONING, OPTICAL & PRECISION MATERIALS CO. Ltd. April 11, 1956 [Sept. 21, 1955], No. 11036/56. Class 97(1) [Also in Group XXI] A range-finder sight in which range is determined by an adjustable optical system operating on the coincidence or split-image principle and the required tangent elevation angles of the barrel of the weapon to which the instrument is clamped are provided by an aiming reticle which is moved vertically across the field of vision in correlation with the movement of the adjustable optical system comprises means for additional deviation of one of the two laterally spaced incident light beams so as to accommodate modifications of the ballistic curve of the weapon with changed firing conditions. The adjustable optical system comprises a deviator in the form of contra-rotating wedges or a pivoted plane-parallel plate, and in these cases the beam is additionally deviated so as to modify the original tangent elevation angle of the weapon e=f(R) obtained for a given range R, by an increment # e which is determined by the equation where a is the angle of arrival of the projectile at a range R for initial firing conditions, N is a constant determined by the design parameters of the instrument, and #q q is a quantity indicating the angular amount by which the mechanism of the instrument is reset to provide for a perfect fit at an arbitrarily chosen reference range Ro of the modified ballistic curve of the weapon in changed firing conditions and an approximate fit at other firing ranges. Alternatively, the optical deviator may be a wedge movable along one of the beams of light, and in this case the increment # e is determined by the equation The invention may be applied to the known range-finder shown in Fig. 3 in which the optical deviator comprises optical wedges 7a, 7b, which are contrarotated for ranging purposes by a control knob 9, and in which a vertically moving sighting reticle 4 is mounted by a pivoted lever 5 which is moved by a cam 6 on the frame 8b of the wedge 7b. In order to provide the additional deviation, in accordance with the law first mentioned above, the instrument of Fig. 3 is modified so that as shown in Fig. 4 the cam 6 is rotatably mounted on the frame 8b and is geared at 12 and 10b to a knob 11b, rotation of which moves cam 6 relatively to frame 8b through the required angular displacement A q which can be read off a scale on knob 11b as it moves past a pointer on a disc 11a coupled at 10a to the frame 8b. When knob 9 is rotated to bring the range-finding images into coincidence, cam 6 moves with the frame 8b due to the friction therebetween. In further known forms of range-finder, where the deviator is a pivoted or slidable wedge, operated by a rotatable knob carrying a cam for adjusting the reticle, the required additional deviation is provided by arranging the cam so that it can be rotated relatively to its shaft, (Fig. 7 not shown), through the necessary displacement #q.