The Knotts Company
Thomas Diaphragm Piston

Diaphragm Piston


Diaphragm pumps work by reduction of a volume using a flexible membrane driven by a crank.

  • Suitable for pressure and vacuum or combined
  • Gas tightness to the outside
  • Durable plastic or corrosion resistant coated aluminum
  • High variablility
  • Long-life diaphragms
  • Balanced for low vibration
  • Low noise level 
  • Liquid media models available - suitable for aggressive media applications
  • Permanently lubricated bearings
  • Flow rates up to 3.2 cfm (91 l/min), end vacuum 29.2 in.Hg (-990 mbar), pressure 44 psi (3.0 bar)


In dry running diaphragm pumps, a flexible diaphragm in the pump head is moved up and down via the conrod and through the action of an eccentric on the motor shaft. On the downstroke, air is drawn into the pump chamber and expelled on the upstroke. One-way flap valves mounted within the pump head control the direction of flow of air. Equally suitable for use as a vacuum pump or compressor, they are characterized by low noise, high efficiency and gas tightness.

Models are available with AC or DC drive. They are available in single and multiple head models, which can be configured in series or parallel, with vacuum to 1 mbar abs, pressure to 2.8 bar and flow rate in the range from 0.3 l/min to 90 l/min.

Diaphragm pumps are ideally suited to applications where the attributes of efficiency and gas tightness are important such as: sampling pumps for portable gas detectors, gas analyzers, medical autoclaves, various laboratory applications or wherever efficient, compact vacuum pumps or compressors are required.


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