Abstract: Mixing apparatus develops a clamping pressure on a container to be mixed by bringing a pair of pressure plates together through the application of driving force developed by cranking a crank arm. A pawl and rachet arrangement prevents rotation of the crank arm in a direction which would loosen clamping pressure, unless a pawl unlocking knob is activated. Clamping pressure is limited by a clutch plate arrangement. Mixing apparatus is enclosed within a cabinet having a door interlock system which also automatically activates a brake for positively stopping further movement of the mixing apparatus.