Abstract: An override board of a programmable logic controller includes a manual switch such as a push button for manual selection between a first “auto” mode where the output is controlled by the programmable logic controller, a second mode where the output is energized, and a third mode where the output is de-energized. The override board can be switched back to the “auto” mode electronically, without physically obtaining access to the controller and without moving the manual switch. The override clear signal is preferably provided on a power connection with the programmable logic controller and to a microprocessor on the override board which controls the output mode.

Abstract: A pneumatic control converter, preferably acting as a pneumatic thermostat, includes a pneumatic section, and electronic section and a piezo electric linkage section. A piezo electric rotary motor drives a rotary cam, with a cam follower linked via a W-shaped flexure linkage to bias the ball nozzle which controls the pneumatic control output pressure. The input to the piezo electric rotary motor is an electrical signal dependent upon electronically sensed pressure relative to the programmed set point. The pneumatic control converter consumes little electrical energy and is preferably battery powered, and the pneumatic control output pressure can be maintained even in the absence of electric power.

Abstract: A pneumatic control converter, preferably acting as a pneumatic thermostat, includes a pneumatic section, and electronic section and a piezo electric linkage section. A piezo electric rotary motor drives a rotary cam, with a cam follower linked via a W-shaped flexure linkage to bias the ball nozzle which controls the pneumatic control output pressure. The input to the piezo electric rotary motor is an electrical signal dependent upon electronically sensed pressure relative to the programmed set point. The pneumatic control converter consumes little electrical energy and is preferably battery powered, and the pneumatic control output pressure can be maintained even in the absence of electric power.

Abstract: An override board of a programmable logic controller includes a manual switch such as a push button for manual selection between a first “auto” mode where the output is controlled by the programmable logic controller, a second mode where the output is energized, and a third mode where the output is de-energized. The override board can be switched back to the “auto” mode electronically, without physically obtaining access to the controller and without moving the manual switch. The override clear signal is preferably provided on a power connection with the programmable logic controller and to a microprocessor on the override board which controls the output mode.

Abstract: The invention is an override board releasably mounted in a programmable logic controller. The override board is used to control an individual output of the programmable logic controller. The override board includes a manual switch mounted to a printed circuit board assembly. The manual switch has an “auto” position, an “on” position and an “off” position. An output device is also mounted to the printed circuit board assembly and is electrically connected to the manual switch. Placing the manual switch in the “auto” position transfers control of the override board to the programmable logic controller. Placing the manual switch in the “on” position energizes the output device. Placing the manual switch in the “off” position de-energizes the output device.

Abstract: In a pneumatic variable air volume controller, a linear relationship is achieved between the actual air velocity in a duct carrying conditioned air to a defined area and a pneumatic pressure signal representing the temperature in that area; and this linear relationship is used to vary the volume of air flowing in the duct. This is achieved by comparing a pneumatic pressure control signal which is a linear representation of the velocity pressure in the duct to a pneumatic pressure control signal which varies as the square of a thermostat pneumatic pressure signal which itself varies in a linear manner with respect to the temperature in the controlled area.

Abstract: A multi-stage pressure-to-electric switch assembly includes a top casing provided with a pressure receiving chamber, a bottom casing integrally secured to the top casing in closing relation to the pressure receiving chamber, and a diaphragm clamped between the top casing and the bottom casing to be in sealing, closing relation to the pressure receiving chamber. This diaphragm is provided with three spaced-apart pressure response switch control portions, each portion including a switch control button. Three two-position electrical switches are fixedly supported with respect to the bottom casing. Three hollow, externally threaded switch control sleeves are aligned between the diaphragm control buttons and the switches. A switch operating control nut is threadably mounted on each of the switch control sleeves, and a switch operating plunger extends through each control sleeve between the diaphragm button and a switch.

Abstract: A variable volume air conditioning system of the type having a duct for distributing air to a room, a damper for regulating the flow of air through the duct, and a damper actuator responsive to damper drive control signals for controlling the damper. A thermostat located in the room provides a stat signal representative of a desired flow of air through the duct. An actual flow signal representative of the actual flow of air through the duct is provided by a sensor. The stat signal and actual flow signal are compared by a comparator which provides the damper drive control signals as a function of the comparison. A wire transmission line couples the actual flow signal from the sensor to the thermostat so that service personnel can easily monitor system performance.

Abstract: A rotary actuator for a damper shaft controls the angular position of the damper shaft in accordance with variations in fluid pressure inside of the actuator. The actuator includes a housing, a flexible diaphragm within the housing separating it into a fluid-tight compartment and a second compartment open to the atmosphere. The fluid-tight compartment is provided with a fluid pressure receving port open to a control source of variable pressure. The piston and piston rod are slidably mounted in the second compartment in contact with the diaphragm. The piston rod includes a longitudinally extending rack, and a crank arm rotatably mounted in the housing has a gear segment in meshing relationship with the rack. The actuator shaft to be controlled extends through the housing and is mounted in the crank arm to support the rotary actuator, and the rotary actuator is clipped to an air conditioning duct to prevent it from rotating on the damper actuator shaft axis.

Abstract: A flat, elongate, laminated plate of ceramic piezoelectric material is fixedly mounted on one end to permit movement of the other end responsive to the application of a variable electronic control signal to electrodes on the outer surfaces of the laminated plate. The movement and force applied by the movable end of the plate controls the release of air pressure from the pressure chamber so that the pressure in the chamber varies in response to the variations of the electronic control signal.