Patent GB-284083-A (GB)
Title: Improvements in or relating to weirs and sluice gates
IPC: E02B7/20
Filed: 1927-01-27
Abstract: 284,083. Butcher, A. D. D. Jan. 27, 1927. Movable weirs.-In a weir or sluice gate of the type comprising crest-forming means movable relatively 'to, and in engagement with fixed abutment means across the channel, and adapted to measure the discharge of water, the crest member and the abutment means are so constructed and arranged as to present a contour substantially unaltered by changes in the height of the crest, so that the coefficient of discharge is constant. means being provided upstream of the crest and moving 'therewith to indicate directly the head of water above the crest and hence the discharge. Preferably the abutment means comprises an upright plate or the like, and the movable crest member consists of a rigid plate structure of the width of the channel having a substantially upright flat portion in parallel engagement with the abutment means and another portion extending downstream from the upper part of the first and connected thereto by a curved portion forming the crest. The measuring-device consists of a scale rigidly attached to the crest member. The upstream side of the crest is adapted to produce only a short backwater curve, so that the scale may be located near the crest. The means provided ior raising and lowering the crest are arranged to present no obstruction to the flow of water. The weir comprises a fixed member a, Fig. 2, secured across the stream, and a movable member b of fixed shape built up of plates b<1>, b<2> secured to a frame d', d<2>, d<3>, and attached to a pair of vertical channels e sliding within the grooves of the channels c to which is attached the vertical plate a. The upper ends of the channels e are connected by a member f, Fig. 1, and a horizontal member g is secured to the upper ends of the channels c. The crest member b is of a contour arranged to suit existing conditions, and to make the backwater curve as short as possible. The downstream end of the crest member is produced at a downward inclination to o, Fig. 2, so as to support the jet of water, the distance X o being approximately 1.25 h, where h is the maximum head. The inclination of the extended portion is about 1 in 5, but both the distance X o and the inclination are such as to maintain constant the relation of discharge to head. The scale i for measuring the head is secured to a frame r bolted to the channels e. The scale may be graduated uniformly, or so as to indicate directly the discharge. Slotted holes s' may be provided for adjustment. The backwater curve being made as short as possible by a suitable design of the crest avoiding abrupt change in section and keeping the approach to the crest short, the scale may be located near the crest. In the example shown, the distance from the crest is not less than 1.5 h, in which case the error due to the backwater curve is less than 1 per cent. The control gear for the weir comprises screw and nut mechanism, the screw t being secured to the fixed channel member g, and the nut forming part of a hand wheel v rotatably mounted in the member f. Leakage between the members a and b is minimized by providing a horizontal bar k secured to the top of the plate a, and a second bar h' secured to the bottom of the plate b2.