Pneumatic pressure transmitter

A pneumatic pressure transmitter for accurate pressure setting having a pressure regulating means comprising a frame with a supply pressure chamber, a control pressure chamber and a reference pressure chamber, a loading diaphragm which separates the control pressure chamber and the reference pressure chamber, a loading spring for putting a reference force on the the loading diaphragm;

• an exhaust port in the centre of said diaphragm, means for ventilation of excess pressure from the control pressure chamber;
• the control pressure chamber contains an inlet port in communication with the supply pressure chamber;
• an inlet plug means for closing the inlet port;
• a stem having a shouldermount (10) on its surface, and an exhaust plug at one end for closing the exhaust port;
• a two arm lever with a pivot fixed at the frame, one arm of said lever is fork shaped and rests by its prongs on the shouldermount, the other arm pushes the inlet plug closing the inlet port;
• a balance diaphragm separates the supply pressure chamber from the control pressure chamber and creates a balance force proportional to the difference between supply and control pressure, that force is applied to the other end of the stem;
• an auxilliary spring means for putting an additional force at the stem;
• said inlet and exhaust ports, stem with the exhaust plug and shouldermount, lever, inlet plug, loading diaphragm, balance diaphragm and auxilliary spring interact in such a way, that force created by the balance diaphragm and the auxilliary spring pushes the stem and, through the shouldermount, pushes the fork shaped arm of the lever, while the other arm of said lever pushes the inlet plug and closes the inlet port;
• when the reference force is counterbalanced by the pressure in the control pressure chamber, the loading diaphragm with the exhaust port moves onto the exhaust plug and closes the exhaust port;
• the balance force together with the force of the auxilliary spring is sufficient to keep the both ports closed;
• whereby a surplus pressure in the control pressure chamber lifts the loading diaphragm with the exhaust port and opens said port, while the fork shaped arm of the lever prevents the stem with the exhaust plug from following the exhaust port;
• the other arm of the lever pushes the inlet plug and keeps the inlet port closed;
• lack of pressure in the control pressure chamber moves the loading diaphragm in the opposite direction, and that action closes the exhaust port, pushes the stem, removes or reduces the force from the fork shaped arm of the lever and, consequently, from the inlet plug, whereby the force of supply pressure opens the inlet port.