21521 Pneumatic Edge Guide Sensor

The Model 21521 Pneumatic Sensor is a wide adjustable gap, deep throat nozzle designed primarily for use with non-polarizing films such as polyethylene. It senses the edge position pneumatically and transmits this information to a pneumatic-hydraulic controller. Many design features are included such as an integral air purge that eliminates clogging, or handwheel adjustment for fine or coarse adjustments.

Principle of Operation
This non-contact sensor directs a stream of very low pressure air across the edge of the web as illustrated below. The recovery pressure is proportional to the web position. 

A small air bleed through the purge orifice (patented) puts a positive pressure at both sensing orifices and prevents foreign material from entering the sensor and clogging the orifices. This preventative measure does not affect the control at the recovery orifice. 

The proportional pressure signal is generally transmitted to a diaphragm on a hydraulic controller. The very low pressure at which this sensor operates will not offset even the lightest film, and requires only a pressure reducing valve to operate from normal plant air supply.


  •  Non-Clogging Design
    The sensor is supplied with an integral air purge (patented) which eliminates any possibility of clogging in applications where lint or dust is encountered.

  • Minimum Edge Deflection
    Ultra-low recovery pressure as low as ¼ inch water column. Ideal for operation on light films such as ¼ mil polyethylene. 

  • Ruggedness Constructed of sturdy metal casting. Not affected by vibration. 

  • Handwheel Position Adjustment Coarse adjustment (for large width changes, for example) accomplished by merely sliding on square bar installed on machine. Fine adjustment accomplished by handwheel.

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