Pneumatic controller

A pneumatic controller comprising:

• (a) a proportional band changing mechanism including:
• an input link adapted to receive a deviation input of a set value and a measured value,
• a feedback link adapted to receive a feedback force,
• means for connecting said input link to said feedback link,
• a proportional band changing lever connected to a connecting point of said input link and said feedback link and pivotally supported in-between said links,
• a flapper means adapted to be displaced by the force applied to said feedback link, and
• means for limiting the displacement of a portion of said connecting means within a certain range when an excess deviation force is applied to said input link;
• (b) an air injection nozzle cooperating with said flapper;
• (c) means for applying a feedback force to said feedback link in response to the back pressure from said nozzle;
• (d) means for producing an automatic output pressure in response to a back pressure from said nozzle;
• (e) means for transferring said automatic output pressure to a manual output pressure;
• and
• (f) a comparator for comparing said automatic output pressure with said manual output pressure and transmitting an output corresponding to a difference between said pressures to said proportional band changing mechanism through said transfer means in the manual mode.