Patent GB-369130-A (GB)
Abstract: 369,130. Sighting-instruments for use on aircraft. NAAMLOOZE VENNOOTSCHAP NEDERLANDSCHE INSTRUMENTEN COMPAGNIE, 44, Javastraat, The Hague. Aug. 1, 1931, No. 22019. Convention date, Aug 8, 1930. [Classes 97 (i) and 97 (ii).] In a sighting apparatus mounted to partake in the oscillations of an aircraft and having means for adjusting the altitudinal angle of the part of the sighting line outside the instrument, the effective movement of means provided to stabilize the sighting line transversely to the plane defined by the altitudinal adjustments is reduced in accordance with the inclination of the sighting line outside the instrument to the horizontal. In the simple form shown in Fig. 2, the sighting line is adjusted by turning the telescope tube 24 with its objective 1, ocular 2, and reversing prism 23. The mark for stabilizing the sighting line comprises a cardanically supported, pendulous, semicircular wire 25 adapted to touch the image plane of the telescope. The part of the wire being used as a mark at any time and consequently the amount of its stabilizing movement depends on the altitudinal angle of the sighting line. The telescope shown in Fig. 1 is rotatable about a normally vertical axis in the aircraft and comprises an eyepiece 2, reflector 3, objective 1, and rotatable reflector 4 for adjusting the altitudinal angle of the sighting line. In the image plane is a mark 6 on an arm 7 fixed to a pendulum 9 pivoting about an axis X-X. A further stabilizing mark 10 is attached by an arm 22 to spindle 21 having an arm 20 terminating in a ball 19 which engages in a slot 18 in an extension of the pendulum 17. The latter pivots about an axis Y-Y in a slide 15 which is caused to move up or down by the engagement in a slot 14 on the slide 15 of a pin 13 on an arm 12 which is caused to rotate at twice the rate of the reflector 4 by gearing 5, 11. Rotation of the reflector 4 alters the position of the axis Y-Y and thus the point of engagement of the ball 19 with the pendulum causing the extent of stabilizing movement of the mark 10 to depend on the position of the reflector 4. In a modification a semitransparent reflector combines the fields of two objectives. A pair of reflectors mounted on a common spindle are arranged in front of the objectives and are adapted to reflect into them the image of a target and the image of a sighting mark comprising a cardanically suspended, pendulous, semicircular wire. In a further modification the rotatable reflector is arranged between the eyepiece and the objective the latter being carried together with a reversing prism by an arm geared to rotate about the axis of rotation and at twice the angular speed of the reflector. The sighting mark comprises a cardanically mounted, pendulous, semicircular wire having its centre and centre of rotation in the face of the reflector. In the further form shown in Fig. 7, the rotatable reflector 56 is carried by a sector 57 geared to a toothed wheel 60 which carries a support 32 for the pivoted semicircular wire sighting, mark 25 and a plate 62 supporting gear wheels 63, 64. The latter are geared to a toothed wheel fixed to the wheel 60 so that a mounting 66 carried by the wheel 64 and provided for a pendulum 67 rotatable about the axis S-S is maintained vertical notwithstanding rotation of the wheel 60. The sighting mark 25 is caused to move about its pivots 68 by the engagement of an arm 69 with an extension 72 of the pendulum 67.