US 4,629,131 · Granted 1986-12-16

How Cuisinart's Magnetic Lock Stopped Fingers From Meeting Spinning Blades

Imagine a food processor that won't start spinning until you've snapped the bowl in place AND locked the cover down tight. This patent uses two magnets with unique patterns that only line up correctly when everything is positioned safely. It's a clever way to make sure nobody reaches in when the blades are spinning.

Curated and verified by the IsItPatented Editorial team

The plain-English version

What it protects

The claim covers a safety system that uses two specially oriented permanent magnets, each divided into non-symmetrical polarity quadrants, that prevent a food processor motor from running unless both the bowl and cover are mounted in their correct positions simultaneously. What's protected here is the specific arrangement and coding pattern of these magnets—a physical lock that only opens when the right combination of positions is met.

Why it matters

Food processors are powerful tools with sharp, fast-moving blades, and accidents happen when people aren't careful or forget steps. This patent represents a shift toward passive safety: instead of relying on users to remember a warning label, the machine itself refuses to operate unless it's set up right. For Cuisinart, this kind of innovation became a selling point in an increasingly competitive kitchen appliance market where safety and reliability drive purchasing decisions.

Real-world use

Every time someone clicks a Cuisinart food processor bowl into place and latches the cover, they're relying on this magnetic safety interlock to ensure the motor won't fire up until both steps are complete.

Original USPTO abstract

An improved safety interlock for a food processor of the type including a control system for preventing actuation of a powerful motor drive, so that the food processing tool does not rotate, unless two conditions have been met; namely, (1) a bowl is mounted in its operating position on the base housing, and (2) a cover is held securely in its operating position on the bowl. The improved safety interlock provided in one embodiment of the invention uses two permanent magnets. One magnet is associated with actuator means and the other magnet is associated with switch means which prevent operation of the motor unless actuated. These two magnets are oriented generally in vertical planes relative to the horizontal top deck of the base housing. Each magnet is divided or coded into respective polarity quadrants, said quadrants of each of these magnets being non-symmetrical with respect to mutually perpendicular axes. The two magnets are arranged so that the control for the motor drive of the food processor can only be magnetically actuated when both the bowl and the cover are mounted securely in their respective predetermined operating positions.

Patent details

Publication number: US 4,629,131
Filing date: 1981-02-25
Grant date: 1986-12-16
Assignee: Cuisinarts, Inc.
Inventor(s): PODELL; ALLEN F.
CPC class: F16P3/10

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