Digital pneumatic modulator

In a facility management system having first sensor means for sensing a preselected facility parameter and for providing a signal in response to such sensing, pneumatic control means operably connected to said sensor means for providing a pneumatic control signal in response to the signal provided by said sensor means, controlled device means for selectively affecting the prselected facility parameter, and pneumatic cylinder means operably connected to said controlled device means whereby the selective introduction and exhaust of pressurized air to and from said pneumatic cylinder means will control the extent to which said controlled device means will affect the preselected facility parameter;

• an improvement comprising a parallel control system that utilizes said first sensor means and said pneumatic control means as a backup system, the improvement including:
• a. second sensor means for sensing the same preselected facility parameter as said first sensor means and for providing a signal in response to such sensing;
• b. electronic control means operably connected to said second sensor means for electronically comparing the signal provided by said second sensor means with a predetermined signal that relates to a desired status for the sensed parameter and for providing an electronic control signal in response thereto;
• c. a digital pneumatic modulator including:
• i. first and second solenoid valves, each such valve having a pneumatic pathway formed completely therethrough that may be selectively blocked and unblocked by appropriate energization and de-energization of said solenoid valves, and means pneumatically connecting the first solenoid valve to the pneumatic control means to receive pressurized air therefrom;
• ii. a pneumatic T intersection unit having a first and second pneumatic pathway formed therethrough, one end of said first pneumatic pathway being pneumatically connected to the pneumatic pathway of said first solenoid valve and the other end of said first pneumatic pathway being pneumatically connected to the pneumatic pathway of said second solenoid valve, the latter valve including an exhaust port, and the second pneumatic pathway being formed to have one end pneumatically intersect said first pneumatic pathway, and to have the other end serve as an output port;
• iii. a flow control unit having a pneumatic pathway formed therethrough with a selectively variable obstacle disposable therein, one end of said pneumatic pathway being pneumatically connected to the output port of said second pneumatic pathway of said pneumatic T intersection unit and the other end of said pneumatic pathway being operably connectable to said pneumatic cylinder means;
• wherein said first and second solenoid valves are operably connected to said electronic control means such that said solenoid valves may be selectively energized and de-energized thereby, said pneumatic cylinder means is pneumatically connected to the pneumatic pathway of said flow control unit, and a supply of pressurized air is pneumatically connected to the pneumatic pathway of said first solenoid valve;
• whereby said electronic control means will control said controlled device via said pneumatic cylinder means by transmitting electronic control signals to said digital pneumatic modulator which signals control the solenoid valves of said modulator to thereby selectively introduce and exhaust pressurized air to and from said pneumatic cylinder means.