GB642677A - Improvements in or relating to pressure responsive indicating instruments - Google Patents

Abstract

642,677. Indicating-apparatus; pressure gauges. ELECTROFLO METERS CO., Ltd. Aug. 8, 1947, No. 21823. Convention date, Dec. 16, 1939. [Classes 106 (ii) and 106 (iv)] An indicating instrument comprises a condition responsive element, a lever or yoke 86 pivotally mounted at 90 on a fixed axis and connected to the element to be rocked thereby, a flat balance spring 98 engaging a slot in an extension 92 in one end of the lever 86, a bellcrank arm 102 having one portion parallel to and adjustably connected with the spring 98 so that the effective length of. the latter can be varied, and means operated by a screw 46 to tilt the bell-crank 102 about its pivot to vary the initial loading of the spring, and thus zeroize the indicator pointer. The bell-crank 102 has one portion slotted at 104, and secured to the spring 98 by blocks 106 (not shown) and a clamp screw 107; the other portion is slotted to guide a nut 110 which is engaged by the screw 46. An extension 116 of one pivot axle 88 secured to the yoke 86 is adapted to move a pivoted point 18 through a lever 118 (not shown) and a link 120 connected to the pointer near to the pivot 16 of the latter. Counterbalance weights 122 are threaded on an extension of the pointer. The invention is described as applied to a differential pressure gauge for measuring draught, and the instrument comprises a die cast casing 10 with a top cover 26, a transparent side cover 14, and a translucent dial 22 over which an indicator 20 on the pointer 18 moves. A flange 28 and several tapped holes in the base 12 facilitate mounting the instrument. The base 12 is formed with an inwardly-projecting flange 30 supporting a flexible diaphragm 32. A cover 34 clamped by screws 36 encloses the diaphragm. Passages lead from tapped holes in the casing to both sides of the diaphragm. A stem 76 on the diaphragm is pivoted to end of a lever 82 which passes through a fluid-tight seal 84 in the cover and is secured to the yoke 86. The pivots 88 secured to the yoke are aligned in the plane of the seal 84. The sensivity of the instrument can be altered by slackening the screw 107 and sliding the blocks 106 and spring 98 towards or away from the pivot 90. To measure greater pressures, the effective area of the flexible diaphragm 32 can be limited by introducing ring supports within the pressure chamber, one on each side of the diaphragm.