Improvements in or relating to butterfly valves

1,107,380. Valves. LOEWY ROBERTSON ENGINEERING CO. 7 Dec., 1965 [5 Oct., 1964], No. 40496/64. Heading F2V. A butterfly valve has a lost-motion connection with its actuating mechanism whereby it can also function as a check valve. As shown, the valve member has a pivotal axis along its diameter, the axis being parallel to, but spaced downstream from, the sealing edge of the valve member. A first stub shaft 15 carries a key 20 that co-operates with opposite ends 24a, 24b of a slot in a pinion driven via a worm by hand wheel 27. A second stub shaft (14, Fig. 5, not shown) carries a lever 25 having a weight 26 adjustably mounted thereon. The weight may be located on a bent outer part of the lever. To open the valve, the pinion is first rotated to bring end 24a of its slot into contact with key 20 and then rotated further to open the valve. When the valve is open, the weight 26 lies almost vertically above the axis. To allow the valve to act as a check valve, the pinion is now rotated to bring end 24b of the slot into contact with the key, whereby flow stoppage or reversal allows the weight to close the valve.