17 fulcrum member 21 will now move only u00bc inch such motion is transmitted to the sliding stem 7 and ultimately to valve 4 it can also be stipulated that the pneumatic signal has a range of 3 15 psi with an assumed diaphragm area of 25 square inches the resultant downward force on movable plate 14 will be 75 to 375 pounds in order to keep the force acting on the linkage elements low for strength considerations and reasons of friction my preferred invention uses a set of upper springs 15 that absorb about one halve of the above force the desired spring rate of upper springs 15 should therefore be 375 u2212 75 2 u00d7 0 75 200 pounds per inch it follows that the remaining force of 37 5 to 187 5 pounds has to be absorbed by the amplifying linkage mechanism with a three to one advantage the resultant force acting on fulcrum member 21 is now 112 5 to 562 5 pounds this makes the required spring rate of the lower coiled compression spring 22 562 5 u2212 112 5 0 25 1800 pounds per inch in order to fully understand the advantages of my invention let us assumne that valve 4 is a 2 inch size sliding gate valve here fluid enters from 23 and exerts a pressure on a sliding plate 24 which is then pressed against a stationary plate 25 the sliding plate 24 furthermore is connected to a valve stem 26 which in turn connects to sliding stem 7 in order for my actuating device 1 to move the sliding plate 24 it has to overcome friction forces generated between plates 24 and 25 for example for a fluid.