Dating back to the 1860s, they were designed for collecting and conveying shavings, sawdust, chips, dust from emery and buffing wheels, and similar materials which could be conveyed on a current of air.
The standard version was a 6-blade, steel plate fan(Design 1). In the 1920s two additional "Slow-Speed" types were introduced: 18-blade and 13-blade, forwardly-curved fans(Design 2 and 3). In the late 1930s the tradename Planovane was used.
Schematics and basic cfm performance data available for Designs 1,2 and Planovane