Patent GB-888366-A (GB)
Title: Improvements in apparatus for measuring or recording the flow of liquid in open channels
IPC: G01F1/00
Filed: 1957-08-27
Abstract: 888,366. Flowmeters. CONSERVATORS OF THE RIVER THAMES, and GREEN, W. Aug. 27, 1958 [Aug. 27, 1957[, No. 26952/57. Class 69 (1). [Also in Group XIX] Apparatus for measuring or recording the rate of discharge of liquid flowing through an open channel in accordance with the Chezy formula Q = C A#mi (where Q is the rate of discharge, C is a constant, A is the prevailing cross-sectional area of the liquid in the channel, m is the hydraulic mean depth and i is the hydraulic gradient), comprises adjacent stilling wells k, l open at g, h respectively to upstream and downstream ends of a length of channel which is of substantially uniform cross-section; a multiplying mechanism having two inputs and an output; a differential mechanism adapted to be actuated by change in the difference between the levels of liquid in the stilling wells k, l and adapted to apply to one input of the multiplying mechanism a displacement which is a function of the quantity #i; a depth following mechanism adapted to be actuated by change in the depth of liquid flowing through the channel, and adapted to apply to the other input of the multiplying mechanism a displacement which is a function of the quantity C A#m; and a recording or indicating device arranged to be actuated by the output of the multiplying mechanism so as to produce an indication or record of the value C A#mi. The differential mechanism comprises drums 13 (Fig. 4), fixed to a spindle 14 which is rotatably mounted and bodily movable in a linear path along rails 28. The drums 13 are coupled to floats b, d by flexible cables j, n wound on the drums 13 in the same sense but leaving the drums in opposite directions parallel to the rails 28 for connection to the floats b, d. A counter torque is applied to the drums 13 by a weight 39 which keeps the cables j, n taut. A difference in the distances through which the floats move will result in unequal forces in the cables j, n which cannot be counterpoised by the weight 39 and a linear force will be imparted to the spindle 14 causing the drums 13 to move along the rails 28. Bodily displacement of the drums 13 actuates cam mechanism 52. The cam 52 rotates a shaft 57 to which the member 63 is fixed. A follower 104 is mounted for movement with a slidable rack 105 in mesh with a gear-wheel 106 coupled to an angularly movable arm 111 of the indicator or recording mechanism. The depth following mechanism includes a horizontal shaft 64 (Fig. 3), on which a drum 70 is fixed. A cable O attached to a depth float c (Fig. 1), is wound on the drum 70. A counterweight 73 opposes the motion of the float c. Fixed to the shaft 64 is a gear-wheel 74 which meshes with a larger gear-wheel 75 secured to a cam-shaft 76 (Fig. 7). Two snail cams 85, 88 are fixed to the cam-shaft 76. A recording drum 69 on which a chart is fixed is rotated by a clock mechanism (Fig. 5, not shown), secured to a vertical spindle 84 (Fig. 3). A roller 91 actuated by the snail cam 85 is disposed between the arms of a bracket attached to the spindle 84. The spindle 84 is prevented from rotating by a screw which projects into a longitudinal groove in the spindle 84. The actuating edge of the snail cam 88 imparts vertical displacement to a roller 96 supported between the arms of a forked bracket 97 attached to the end of a vertical rod 98. This causes the housing 99 of the multiplying mechanism attached to the end of the rod 98 to move vertically with respect to a bracket 101 in which the shaft 57, to which the member 63 is fixed, rotates. No relative vertical movement can occur between the recording drum 69 and the pen-arm 111. Relative motion between the pen and chart results from rack movement produced by the horizontal component of the vertical chart displacement induced by the inclinable member 63. The snail cams 85, 88 rotate in response to fluctuations in water level by means of the depth float mechanism and in doing so impart a vertical displacement to the recording drum and pen arm proportional to the quantity C A#m. This displacement is modulated by the inclinable member 63. If measurement of the discharge is all that is required the clockdriven chart may be replaced by a suitably graduated scale and the pen arm replaced by a pointer. The differential mechanism may be replaced by a bellows element, diaphragm or capsule which produces a linear displacement proportional to the difference in pressure acting upon it.