Patent GB-769934-A (GB)
Title: Improvements in or relating to a method and mechanism for the actuation of a quick-action shut-off device for pressure-pipe lines
IPC: F03B15/18
Filed: 1955-02-22
Abstract: 769,934. Valves. GES. DER L. VON ROLL'SCHEN EISENWERKE AKT.-GES. Feb. 22, 1955 [Feb. 22, 1954; Feb. 7, 1955], No. 5354/55. Class 135. A mechanism to operate a valve to shut off the flow in a pressure pipe-line includes a member which is displaced against a return force by the flow in the pipe-line, and the valve is operated to the shut down position both in a predetermined extreme position of the displaceable member and also when a certain displacement rate in the direction of the said extreme position is exceeded. In an embodiment, a hinged paddle 5 situated in the pipe-line 1 is moved in the direction of the arrow 7 by flow in the line to cause a lever 29 to pivot up or down. Lever 29 carries a weight 39 which can slide between stops 32, 33, and the weight is connected through levers and links 43, 44, 46, 47 to a further hinged paddle 6 in the pipe-line 1. The weight 39 is pulled towards the stop 32 by a spring 42 and it carries an eye 40 which engages over a toothed rack 36 which runs between the stops 32, 33 and is spring pressed upwards. A further lever 50 carrying a loading weight 54 is hinged to the casing carried by the pipe-line 1 and is connected to the lever 29 through a piston and cylinder dash-pot 57. A screw 63 adjusts the rate at which oil can flow from one side of the dashpot piston to the other. Lever 50 normally rests against a stop 53 but, when it is raised, a projection 55 carried by the lever can actuate the mechanism by which the flow in line 1 is cut off. For an increase in flow in the pipe 1 which is not too rapid, lever 29 swings upwardly until a projection 64 on the lever 50 engages an abutment 65 on the rack 36 and causes the latter to be lowered and disengaged from the eye 40 on weight 39. Paddle 6 can now swing in the same direction as paddle 5 and the weight 39 will be pushed along lever 29 towards stop 33, and this increased moment acting on the lever 29 causes the latter to be swung downwards so that paddle 5 takes up its normal vertical position again. Provided the increases are not too rapid, the flow in pipe-line 1 can increase until the weight 39 abuts against stop 33. For any further increase in flow, the paddle 5 will not be brought back to its vertical position and lever 29 will rise until it forces lever 50 upwardly to cause actuation of the valve shutting off the flow in the pipe-line. As the teeth on rack 36 are of a saw-toothed formation, weight 39 can be drawn back by the paddle 6 when the flow decreases to a low value once again. Should there be a sudden increase in flow as, for example, due to a burst pipe, the by-pass around the piston in the dashpot will not be able to cope with the increased flow and lever 50 will be raised by the raising of lever 29 and the shut-off valve will be actuated once again. By providing dampers on the shafts of paddles 5, 6, the effect of temporary surges in line 1 can be eliminated. A suitable damper for the purpose comprises a rotary vane with its two arms working in chambers on the two sides of a partition in a fixed cylinder, there being adjustably restricted passages through the partition at both ends thereof. When such dampers are provided, rack 36, arm 50, and dashpot 57 may be omitted, and the latch 40 then acts on a lever to release and cause actuation of the valve to cut off flow in line 1. In a further modification, weight 39 is normally fixed in position on lever 29 and the latter is carried by the rotatable casing of the damper around the shaft of the single paddle provided. Non-return valves are also provided in the rotary vane of the damper. The cut-off valve in line 1 is then actuated by appropriate movement of the damper casing.