GB580645A - Improvements in or connected with rangefinders, heightfinders and other optical observation instruments - Google Patents

Abstract

580,645. Seats for rangefinders. BARR & STROUD, Ltd., STRANG, J. M., and FOSTER, C. Nov. 23, 1943, No. 19551. [Class 52 (ii)] [Also in Group XXIV] An observer's seat is adjustable downwards under his weight subject to control by and in accordance with the movement of the eye-piece of the rangefinder as the latter is turned to increase the elevation of the angle of sight, the movement of the seat being thus effected without the use of external power. The base 7 of the seat S is supported on a pair of levers 4 pivoted on the base brackets 2, and is partly controlled by a pair of parallel radius rods 5 pivoted at 6 on the brackets ,2. A coil spring 8 is secured at 3 between the levers 4 and its lower end is anchored to the base brackets 2, the spring tending to urge the seat upwards. The seat supporting levers 4 are coupled to a transverse oil reservoir 11 beneath which is an oil cylinder 9 mounted in trunnions 10 between the base brackets 2. When the rangefinder gear is operated so that the eye-piece is lowered, a flexible shaft 13 from this drive operates a worm drive 17-18, autolock free wheel 19, and spindle 15, (see Group XXIV). Thereby a cam 16 is turned to depress rod 23 which opens valve 22 to allow oil to escape through 21 to the top of the hollow piston 20 and to a reservoir 11. The seat therefore sinks under the observer's weight and the reservoir 11, moves angularly relative to the links 4 and therefore relative to a gear box 14 which turns the cam 16 so allowing valve 22 to close and thus holding the seat in the desired lower position. Further depression of the eye-piece gives a further depression of the seat. To elevate the seat the observer takes his weight off the seat whereupon the spring 8 turns the links 4 and radius rods clockwise in Fig. 1. Valve 22 leaves its seat and allows oil to pass from above to below the piston 20. The seat continues to rise as far as the observer desires it. For hand adjustment, a knob 25 is turned to operate through the free wheel autolock 19 so turning the cam 16 to allow the seat to lower independently, and also allows initial setting of the cam 16. To render inoperative the control of the seat from the rangefinder gear, a lever 26 pivoted at 27 is moved by hand to slide the spindle 15 and its cam 16 endwise, so rendering the cam inoperative and so fixing the seat position. A key and keyway in the gear box 14 allows this sliding motion. In a modification of the hand control, Fig. 6, hand rotation of the head 31 moves a stud 34 in a helical groove coupled to the spindle 15 which thereby is moved axially and puts its cam 35 out of gear. The whole arrangement is mounted on a turntable base.