Grades 3–5 · Machines
How does a can opener travel around a lid?
A common rotary can opener has two wheels with different jobs. One has a sharp edge that cuts the metal lid. The other has a rough or toothed edge that grips the can’s raised rim. The handles support these parts in the right positions.
In the diagramOne wheel grips; one wheel cutsA top-cutting opener · enlarged schematicRim seen from the sideCutterFeed wheelLid seen from aboveCut: 50% of rimGrip advances the rim past the cutting edge.
The turning knob or crank drives the gripping wheel, called the feed wheel. Its teeth press against the rim and help prevent slipping. As the wheel turns, the can’s edge moves past the cutter. Depending on what is held still, the opener can travel around the can or the can can turn beneath the opener.
The cutting wheel stays near the rim and rolls as the cut advances. A longer movement along the rim produces a longer cut, until the cut circles the lid. The feed wheel provides movement; the cutter concentrates force along a narrow edge. This drawing shows a top-cutting type. Other designs cut at a different part of the seam.
About this explanation
Starting knowledge: Understands a turning wheel and the difference between an edge and a flat surface.
Sources
- A. K. Steckmann, United States Patent Office — US1859478A: Can opener
- Zyliss — A More Comfortable & Efficient Can Opener: The Lock N’ Lift