Patent GB-650450-A (GB)
Title: Improvements in or relating to fluid-pressure meters
IPC: G01L7/24
Filed: 1947-08-08
Abstract: 650,450. Differential pressure gauges. ELECTROFLO METERS CO., Ltd. Aug. 8, 1947, No. 21822. Convention date, Nov. 30, 1939. [Class 106 (ii)] In a flow meter using a differential gauge of the hydrostatic ring balance type, the high and low pressure chambers of the ring body are connected to the upper ends of flexible connections which extend radially of the pivot of the ring and are connected at their lower ends to a fixed part of the meter communicating with the pressure sources, these flexible connections including tubes having helical portions adapted to bend and situated in a plane passing through the axis of the pivot of the ring body. As shown, the meter is in a casing 11 mounted on a pedestal or a panel 21, and includes a base 13 supported on levelling-screws 14. The base has a ball-bearing 15 pivotally supporting a bar 16 carrying an annular tubular body 17 in which is mercury &c. The body 17 is divided by a partition, each side of which is connected to a fluid-pressure source, for example, the opposite sides of an orifice in a fluid conduit, by means of vertically extending tubes 29. Tubes 32 connect the tubes 29 to a bored block 34 on the body 17, and flexible tubes 39 connect the block to bored blocks 40 secured to the base 13 below the bearing 15 and on opposite sides thereof. The tubes 39 are formed with helical portions 41, and are deflected when the ring body 17 swings about its bearing 15 due to a pressure difference in the body. Since the tubes 39 resist rotation of the body 17, an adjustable compensating weight 42 is provided on the block 34. The body 17 is normally held central by a weight 45 thereon. The bar 16 carrying the body 17 has secured thereto an arm 46, Fig. 3, formed with a cam surface 47 engaged by a cam surface 52 on a lever 49 pivoted on a fixed pivot 51 and carrying a weighted extension 53. The cams control the rotation of the ring body 17 and are preferably so shaped that an indicator pointer or pen 26 moved by the ring 17, and co-operating with a chart 24 driven by a clock mechanism 25, will be given a relatively large motion during condi. tions of low flow velocity in the fluid conduit to which the meter is attached, and preferably so that the meter will give readings proportional to the square root of the differential pressure. The point of contact between the cam surfaces 47, 52 is always on a line connecting the axis of the body 17 and the axis of pivot 51. A damping baffle is provided in the lower part of the body 17. The tubes 29 extend through an opening in the casing 11 which is provided with a removable cover 37. In a modification, in order to save mercury, the ring 17 is reduced in cross-section in that quadrant which is always full of mercury; the tubes 29 are also eliminated, and the high and low pressure sides of the ring are separated by a block to which the flexible tubes are connected. A single weight adjacent the outside of the ring compensates for the reduced portion of the ring and the resistance to bending of the flexible tubes. In another form, the pointer or pen is actuated by a modified cam construction comprising a cam arm, secured to the ring body, engaging a cam surface to which the pen is directly secured. In this form, as shown in Fig. 15, the ring body 68 has upturned ends 82 to which pressure pipes 83 are connected. A plug 84 in each end 82 has a cross-bore 85 opposite the pipe, an axial bore 86 having a seat for a valve 88, and a perforated cage 87 for the valve. The valve, which will float in mercury but sink in water, prevents escape of mercury when excessive pressures occur.