Patent GB-208266-A (GB)
Title: Improvements in fire control apparatus, determination of quadrant of enemy's course
IPC: F41G5/20
Filed: 1922-09-28
Abstract: 208,266. Barr & Stroud, Ltd., Barr, A., and Stroud, W. Sept. 28, 1922. Courses, indicating. - The direction of the deviation of an enemy ship from the broadside-on position, i.e. whether the fore and aft line of the ship lies in the quadrants XZ or YW, Fig. 17, the line of sight being VT, is determined by the utilization of two instruments capable of measuring small angles which are situated on the observer's ship as far apart as possible to points CA, Fig. 1, respectively, and are used to measure the angle subtended by the bow and starn of the enemy ship. To enable the angle measured at the point C to be compared with the angle at the point A for the purpose in view, it is corrected by increasing in the ratio TC/TP, P being the position of the perpendicular from point A on the line C, T. The lengths TP, TA being substantially equal, the corrected angle at the point C will be equal to the angle at the point A when the ship is broadside-on. In all other positions the angles will be unequal, the enemy ship moving away if the angle at A be greater than the angle at P, Fig. 2. The ratio TC/TP is equal to 1 + B cos a, where a is the bearing angle at point C and R is the range. This correction is effected by means of a Wheatstone bridge circuit, Fig. 4, having arms of the magnitudesindicated, the slider S being used to adjust for the range. When no deflection is recorded on the galvanometer the target is broadside on; deflection on either side indicating the quadrant occupied by the target. Alternatively, the ratio. may be determined and the result indicatedmechanically, the equation for the broadside on position 1 + B/R Cos a = a/c being modified to B/R Cos a = a - c / c for this purpose, and the factorson each side of the equation are represented by pointers operated by independent mechanisms,. the pointers coinciding for the broadside-on position. In the apparatus utilizing the Wheatstone bridge method, the angles measured at A and C are transferred to the known form of variable resistance shown in Fig. 9, and the factors representing R and R + B Cos a are supplied by the. variable resistances shown in Fig. 10, the resistance 9 being of similar construction to that of Fig. 9 and the resistance 10 is provided with an additional independently variable resistance 19 to provide for the factor B Cos a. The apparatus for the mechanical indication of the result is shown in Figs. 11 and 13. Ther range-receiver 22 communicates the range R to the nut 24 carrying the slide 25 having a rack 26 at its outerend actuated by a pinion 30 rotated by a rack 45 operated from the shaft 40 to which the value of a is communicated. The distance between the shaft axis 40 and the pin 42 represents to scale the distance B. The variation of a is communicated to the stirrup 28 pivoted on the slide 25 and carrying the rod 29, pivoted on the axis 31. The inclination of the rod 29 is a measure of the valve of B cos a / R The ratio of ac / c is indicated by the rod 29<1>, Fig. 13, in which the valve c is transmitted to the receiver 22<1> and thence to the slide 25<1>. The pinion 30<1> is driven by the jockey wheel 74 of the differential gear 71, 72, giving the difference between a and c the value of a being communicated to the receiver 70. By superimposing the two mechanisms, the broadside-on position will be indicated by coincidence of the marks 48, 48<1>, and the non-coincidence will indicate the direction of the deviation from that position. In the event of the angle-measuring instruments being carried on independent ships means are provided for varying the length of the link 41, Fig. 11. Specification 126,798, [Class 106 (i), Calculating &c.], is referred to.