Bowl top with tower and pusher
Today's food processors still use Verdan's basic design. A heavy motor drives a vertical shaft that turns a blade to chop, blend or puree food, depending on the length of operation. The position of the blade is low, using gravity to keep chopping large, heavier pieces while the smaller pieces rise or drift to the sides of the bowl. The action is started and stopped, or pulsed, repeatedly to allow for contents shifting as the blade chops, making finer chops as the pulses continue. Continuous operation pulverizes or purees foods. Accessory blades have been added, including blades for shredding and slicing that are mounted close to the top of the bowl to process food lowered through an opening. This opening is generally built into a sort of tower and a removable "pusher" keeps fingers away from the sharp blade. All cutting attachments are made of steel except dough blades and egg white blades which are generally plastic. The towers and pushers have holes in the bottoms for adding liquids to the food.
An original Cuisinart admonishes to "read instructions before using"
Since the blades are so sharp, food processors are built with the type of safety features not found in many small appliances until quite recently. The first machines had one speed with two choices---"pulse" and "on." Today's processors may have a choice of speeds but generally have "off" and "on" switches for each speed. The motors have trip switches that prohibit operation if the bowl and lid are not properly seated. Machines are available from a number of makers and in a number of sizes from a one or two cup mini used to chop a bit of onion for a recipe to large 12 to 15 cup bowls for whole holiday dinner dishes.