Fluidic proximity sensor and related process

Proximity sensing apparatus, comprising in combination:

• a sensor head defining a longitudinal axis thereof;
• the sensor head having an air inlet and being adapted to discharge air in a direction substantially parallel to the axis;
• a two-nozzle flapper valve forming first and second air gaps;
• the valve being operatively associated with the sensor head whereby movement of the sensor head relative to the valve and along the axis is accompanied by dimensional variation in the air gaps;
• fluidic oscillator means in fluid communication with the valve for outputting first and second series of pressure pulsations collectively indicative of the dimensional variation.

A process for producing two series of pressure pulsations that are collectively indicative of the proximity of a sensor head to a surface, comprising the steps of:

• directing pressurized air through the sensor head and toward the surface to produce an air bearing which tends to maintain a nominal clearance between the surface and the sensor head;
• moving an object incident to a variation in the nominal clearance;
• changing dimensions of two air gaps in substantially equal and opposite directions incident to movement of the object;
• increasing air pressure in a first air passage and decreasing air pressure in a second air passage in response to change in the dimensions;
• producing a first series of pressure pulsations in response to increased air pressure in the first air passage;
• and
• producing a second series of pressure pulsations in response to decreased air pressure in the second air passage.