Mechanical operation

A blender consists of a housing, motor, blades, and food container. A fan-cooled electric motor is secured into the housing by way of vibration dampers, and a small output shaft penetrates the upper housing and meshes with the blade assembly. Usually, a small rubber washer provides a seal around the output shaft to prevent liquid from entering the motor. Most blenders today have multiple speeds. As a typical blender has no gearbox, the multiple speeds are often implemented using a universal motor with multiple stator windings and/or multi-tapped stator windings; in a blender with electromechanical controls, the button (or other electrical switching device or position) for each different speed connects a different stator winding/tap or combination thereof. Each different combination of energized windings produces a different torque from the motor, which yields a different equilibrium speed in balance against the drag (resistance to rotation) of the blade assembly in contact with the material inside the food container. A notable exception from the mid-1960s is the Oster Model 412 Classic VIII (with the single knob) providing the lowest speed (Stir) using the aforementioned winding tap method but furnishing higher speeds (the continuously variable higher speed range is marked Puree to Liquify) by means of a mechanical speed governor that balances the force provided by flyweights against a spring force varied by the control knob when it is switched into the higher speed range. With this arrangement, when not set to the Stir speed, motor speed is constant even with varying load up to the point where power demanded by the load is equal to the motor's power capability at a particular speed. The more modern version of this arrangement is electronic speed control found on some units.