Patent GB-627721-A (GB)
Title: Improvements in or relating to measuring devices for fluid-containing tanks
IPC: G01F23/36
Filed: 1946-11-01
Abstract: 627,721. Calculating-apparatus. LIQUIDOMETER CORPORATION. Nov. 1, 1946, No. 32481. Convention date, Nov. 15, 1945. [Class 106 (i)] [Also in Group XXXVIII] For measuring the liquid contents of a tank, a pilot structure or replica of the tank formed by a plurality of capacitor plates arranged in an electrical circuit, is mounted in the tank in such manner that the degree of immersion of the plates in a liquid having a dielectric constant different from air is a measure of the level of the liquid in the tank. As shown in Fig. 1, the pilot structure or model tank 100<SP>1</SP> is open and mounted inside the main tank 100 on a pantograph formed by two rods 102, 102<SP>1</SP> so that the model must remain upright as it rises or falls. On an extension A<SP>1</SP>F of the rod 102 is mounted a float 105 chosen so that the position F is in the plane of the liquid and so that the extension bears the same ratio to the rod as do the dimensions of the model to those of the tank. Thus the extent to which the model is submerged will be proportional to the liquid level in the main tank, and.the contents of the model may be measured by a capacitative detecting- device. In Fig. 2, the model consists of a number of parallel spaced plates 125, 1251, connected alternately to form a condenser, the plates being connected in a circuit including an A.C. source and a milliammeter, Fig. 5 (not shown). The float is replaced by four spherical floats 110. In a modification, Fig. 3, the model 152 also consists of a number of parallel spaced plates, shaped to agree with the cross-section of the main tank, but is suspended in a closed sphere 142 containing a fixed amount of liquid. By means of a float 145 on an arm 146 secured to a fixed pivot 147, and suitably chosen pantographic connections, including a link 149 passing through the spherical container 142 in a liquid-tight manner, the model 152 is moved so that it is submerged an amount corresponding to the level of the liquid in the main tank, a correcting arm 155 moving up as the model moves down to ensure the level of the liquid in the sphere 142 remains constant. The Specification as open to inspection under Sect. 91 comprises also an arrangement shown in Fig. 1, (Cancelled), wherein the main tank 10 has a level-detecting device 13 containing a float 15 which alters a variable resistance 22 as the level changes. The model tank 101 has two electrodes 26, 26<SP>1</SP> forming a condenser of capacity dependent upon the liquid level. This condenser and the resistance 22 form arms of a resistance/capacity bridge, and initial adjustments of the other two arms 35, 36 are such that the bridge balances whenever the liquid level in the model corresponds with that in the main tank. When the bridge is out of balance current flows through an amplifier 60, its phase depending upon whether the condenser 26, 261 is of too high or too low capacity, and energizes one of two windings 61, 61<SP>1</SP> of a reversing motor 62 which operates a pump 29 to pump liquid from the model to a reservoir 30 or vice versa until the bridge is balanced. The reservoir 30 is marked so that its remaining contents give a measure of the liquid in the model and thus of the contents of the main tank. By means of multiple switches 40, 53 and a multiple valve 28, all driven by a motor 82, a number of tanks and their appropriate models may be connected in turn to the measuring apparatus, so that the container 30 gives a measure of the total contents of all the tanks. To reduce errors due to shaking of the reservoir 30 its contents may be measured by suspending it from a weighing scale, or the reservoir may be in the form of a coiled capillary tube. This subject-matter does not appear in the Specification as accepted.