Patent GB-141069-A (GB)
Title: Improvements in shoal water indicators
IPC: G01C13/00
Filed: 1920-03-31
Abstract: 141,069. Sperry, E. A. Feb. 12, 1919, [Convention date]. Differential and fluid speed indicators; electric and magnetic speed indicators. - Consists of a shoal water indicator and alarm for ships, the instrument being based on the fact that the ratio of the power exerted by the ship's engines to the speed attained by the ship increases as the depth of water below the ship decreases, and the invention consists in combining the indications of instruments actuated according to these two quantities in order to give an alarm when the ship approaches shallow water and to give a continuous indication of the depth of water below the ship. The construction shown in Fig. 1 comprises a speed indicator consisting of a Venturi tube 9 projecting below the ship, pressure tubes 15. 16 being respectively connected to the throat 11 of the Venturi tube and to a portion of larger diameter, and also to flexible chambers 17, 18 which differentially actuate an arm 19 connected by an adjustable link 20 to a bellows 23. The bellows is connected to a recording-apparatus 33 and to a flexible chamber 27 carrying a rack-bar 28 which actuates a pinion 29 carrying an arm 30 having a contact point 31. To give an indication of the power exerted, each of the propeller shafts 37, 38, 39 carries a gear 40 meshing with a gear 41 which operates a double crank 42 connected to a bellows 45. Each bellows is connected to a reservoir 48 which is connected through a pivoted valve 152, which can be cut out by a by-pass 51<1>, to a Venturi tube 50<1>, the throat of which is connected to a flexible chamber 52 carrying a rack-bar 53 operating a pinion 54 which carries an arm 55 having a contact point 56. Variation in the ratio of power to speed causes relative movement of the arms 30, 55, the contacts being closed when the depth is less than a predetermined value, to actuate alarms 57, 59. To delay the action of the device until a normal speed is attained, the valve 152 is connected to a retarded relay 60, or a time delay 63 started by the " full-speed ahead " signal 65 may be provided. To facilitate adjustment of the initial setting of the arms 30, 55, at least one of the chambers 27, 52 is adadjustable. The alarm device may be combined with depth-indicating means consisting of a differential, Fig. 5, the outer members 74, 76 of which are actuated by the rack-bars 28, 53 while the spindle carrying the intermediate member 72 drives a gear 69 engaging with a pinion 68 on a shaft 67 carrying a pointer 65 moving over a scale 66. The modified form of log shown in Figs. 2 and 4 comprises a casing 2<1> within which is a rotator 84 connected to a recording instrument, the casing also having horizontal Venturi passages 80, 81 connected by pipes 15<1>, 16<1> to the pressure chambers. In a modification, a continuouslyoperated means for supplying air is connected to the bellows 23 provided with an exhaust valve which is moved by the arm 20 to adjust the operative area of the valve. In a further modification, two dynamo-electric machines are actuated, one by the log rotator and the other by the propeller shaft, and are differentially connected to a measuring device graduated to indicate depth and carrying an alarm device. To compensate such a device for varying speeds, an automatic rheostat is connected across at least one of the machines.