Foundry mixer, continuous

A. Binder for Foundry Sand. The major industrial use o furan resins is as a binder for foundry sand. Low levels of resin binder (0.8 to 27 ) are used to bond the sand as cores and molds for molten metal. By use of continuous mixers and appropriate levels of strong, acidic catalysts, set and strip times as low as 45 seconds at ambient temperature are attainable (see Figures 1 and 2). The furan resins work ideally in this application since they have sufficient thermal stability to retain the shape of the mold until the metal sets, then subsequently carbonize to allow shake-out of the sand after the metal hardens. 

However, 1 have discovered that effective mixing and binding effect is obtained with sand if the concentrated silica sol is mixed first with the sand to form a uniform and continuous film on the surface of the sand grains. The concentrated sodium silicate solution is then added to the sand mass in a second, separate step and the sodium silicate then mixed with the colloidal silica film on the surface of the sand, gelling in situ to form an intimately and uniformly mixed binder within the sand mass. The sand mix thus formed in the mixer can be molded by any of the various processes available in foundry practice and hardened to form strong molds or cores. 

The Banbury mixer prospered through the 1920s, but not the Wanning family that owned the Birmingham Iron Foundry. In 1927, it was merged with Farrel Foundry and Machine to form Farrel Birmingham (later Farrel Inc.). They continued to manufacture the Banbury mixer [30]. 

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