Self-Cleaning Filter Patent

Nederman MikroPul and Pneumafil patents

US Patent No. 4,725,292

This is the patent number displayed on the front cover of Pneumafil’s 50th year bound corporate history 1946 — 1996. It is one of the most important, and monetarily successful patents used by the company; second only to the LUWA AG-Pneumafil patents that helped start the company in 1946.

The invention covered by this patent is known as the “AUTOMATIC PANEL FILTER” (APF). The “APF” was an instant success in the textile fiber/dust air filtration market, and it is still the primary filter when very clean air is required by OSHA in the workplace. Thousands of APFs have been sold by Pneumafil and LUWA to date. Basically the “APF” has a robotic vacuum cleaner that goes in and out between filter media covered cells, and left or right as required to clean the entire filter. The robot is guided by a programmable logic controller via sensor inputs. The “APF” occupies 1/4th the floor space, fits in low ceiling heights, and has less emission than competitive type filters.

Patent Specifications
Name: Self-Cleaning Filter
U.S. Patent No.: 4,725,292
Date Issued: February 16, 1988
Inventor: Roger D. Williams
Assigned To: Pneumafil - Luwa Corp

The patent has many covered claims, but the most important are:

  1. The robotic cleaning mechanism, has a vacuum plenum in the shape of a common flat-belt conveyor with a driven pulley and a tensioning pulley at the opposite end. The plenum has a slot on each side for vacuum air to pass through. The conveyor belt that covers the slot on each side has 3-4 round holes in it that act as nozzles. This arrangement allows the vacuum air to be focused at the nozzles with full concentrated suction, all while moving around the same vacuum plenum.
  2. The vacuum plenum coupled with a synchronized robotic drive that allows filter panels to be cleaned on both sides of the mechanism at once, and with a cleaning pattern that cleans 50% of the media surface entering the media covered cells, and the other 50% when exiting the cell. This Cleaning method allows a portion of the media to still be covered by a dust cake to assist dust capture.