Patent GB-717648-A (GB)
Title: Improvements in pressure indicating devices
IPC: G01L7/18
Filed: 1952-11-13
Abstract: 717,648. Pressure-gauges. DYER, J. V., and HOSKYNS, H. W. W. Nov. 13. 1952, No. 28615/52. Addition to 681,199. Class 106 (2) A pressure indicating device in which small movements of mercury in a tube of relatively wide bore are utilized to effect larger movements of another and lighter liquid in a. fine measuring tube of relatively small bore to indicate the pressure being measured comprises a vertically arranged coarse measuring tube 9 open to the gas pressure to be measured and connected to a container 14 for mercury, a vertically arranged fine measuring tube 3 open to the atmosphere at the upper end through a container 1 for a light liquid and having at its lower end a container 4 adapted to be filled partly with mercury and partly with the light liquid. A further vertically arranged tube having a small bore section 6 and a wide bore section 7 is connected at the upper end to the coarse measuring tube 9 and at its lower end to the container 4 of the fine measuring tube, the arrangement being such that relatively small movements of mercury in the large bore tube are utilized to effect greater movements of the light liquid in the fine bore tube. The invention is shown diagrammatically in Fig. 1 wherein a low pressure corresponding to atmospheric pressure at a high altitude is introduced through a suction connection 13 and air filter 11 to a tube 10 joining two U-tube systems, one comprising the coarse measuring tube 9 and mercury container 14 open to ground atmospheric pressure through an air filter 16 and the other comprising the fine measuring tube 3 open to atmosphere through a container of a light liquid i and an air filter 2 and joined to the wide bore tube 7 through a mercury container 4 and fine bore tube 6. A scale 18 for the coarse tube 9 is calibrated from 0 to 60,000 ft. or 100,000 ft. and a scale 17 for the fine tube 3 is calibrated from 30,000 ft. to 60,000 ft. or 100,000 ft. When the pressure corresponds to 30,000 ft. the meniscus 19<SP>1</SP> enters the wide bore 7 and further small changes of level cause large displacements of level 20 of the light liquid in the fine tube 3, a plunger 5 being provided to adjust the level so that the readings on the fine and coarse scales agree, thus correcting for temperature changes. A millibar scale 18' may be included in order that the coarse scale may be adjusted for variations in ground level atmospheric pressure. The light liquid may be paraffin, toluene or a silicone compound, e.g. D.C. 200 with a viscosity of 2 cs. If it is desired to measure pressure up to 15 1bs. per square inch connection is made to connection 16 and the suction connection 13 is left open to atmosphere, pressure being read off scale 18 upwardly with increasing pressure. In a particular embodiment, Fig. 4, the various tubes and containers are mounted upon a vertical frame 22 with suitable couplings 23 interconnecting the various tubes and containers some of which are preferably made of glass, some of steel and some of light alloy. The containers 4, 14 are formed in the lower and upper ends of a unit 26 in a casing 25 at the base of the frame 22. The plunger 5 has an operating knob 27 and is disposed within a chamber 4<SP>1</SP> extending from the unit 26. The fine and coarse tubes 3, 9 are disposed vertically side by side on the frame 22 with the tube 7 offset between and in front of them.