# How the Floppy Disk's Protective Jacket Cleans the Disk > An IBM patent from 1972 describing a protective, non-removable cover for a magnetic disk that uses a built-in cleaning material to wipe the disk surface while it spins. - **Patent:** US 3668658 - **Original title:** Magnetic record disk cover - **Owner:** International Business Machines Corp - **Granted:** 1972 - **Status:** Public domain (expired) - **Times cited:** 79 - **Field:** consumer_electronics, mechanical, semiconductors ## What it does This patent describes a protective sleeve for a magnetic disk that remains stationary while the disk spins inside it. The inside of this sleeve is lined with a special porous, antistatic material that stays in physical contact with the disk surface. As the disk rotates, this lining acts like a constant wiper, removing dust and contaminants that could otherwise cause read or write errors. The cover also includes a specific opening, or transducing aperture, which allows the magnetic read/write head of the computer drive to touch the disk surface to access data. ## What it does NOT cover - Does not cover disks that are intended to be removed from their protective covers by the user. - Does not cover storage systems where the disk and the protective cover rotate together as a single unit. - Does not cover cleaning mechanisms that are separate from the disk's permanent housing. - Does not cover optical storage media like CDs or DVDs. ## The clever bit The innovation lies in using the disk's own rotation against a stationary, low-friction, porous lining to achieve self-cleaning, effectively turning the protective sleeve into a maintenance tool. ## Real-world examples 1. The 8-inch floppy disk 2. The 5.25-inch floppy disk ## Why it matters This technology was essential for the commercial viability of the floppy disk. By integrating a cleaning layer directly into the jacket, IBM ensured that the fragile magnetic surfaces could survive the dusty, uncontrolled environments of early office and home computing without frequent data corruption. ## Frequently asked questions ### What does How the Floppy Disk's Protective Jacket Cleans the Disk cover? An IBM patent from 1972 describing a protective, non-removable cover for a magnetic disk that uses a built-in cleaning material to wipe the disk surface while it spins. ### Who owns patent US 3668658? International Business Machines Corp owns this patent, granted in 1972. ### When does this patent expire? This patent has expired and is now in the public domain — anyone can use the invention freely. ### What is patent US 3668658 cited by? This patent has been cited by 79 later patents that build on its ideas. ### What problem does this patent solve? This technology was essential for the commercial viability of the floppy disk. By integrating a cleaning layer directly into the jacket, IBM ensured that the fragile magnetic surfaces could survive the dusty, uncontrolled environments of early office and home computing without frequent data corruption. ### What does this patent NOT cover? Does not cover disks that are intended to be removed from their protective covers by the user. **Full plain-English explainer:** https://patentbrief.org/patent/us/3668658/floppy-disk-diskette **Original patent:** https://patents.google.com/patent/US3668658 --- _Source: PatentBrief — https://patentbrief.org. Patent facts are from public records; the plain-English explanation is PatentBrief's._ ## Related patents Semantically similar inventions in the PatentBrief corpus: - [How Early Hard Disk Drives Accessed Data Quickly](https://patentbrief.org/patent/us/3503060/hard-disk-drive) — A 1970 patent detailing a mechanical system for moving read-write heads across magnetic disks to retrieve stored information rapidly. - [How Flash Memory Cells Use an Erase Gate to Clear Data](https://patentbrief.org/patent/us/4531203/nand-flash-memory) — This 1985 patent describes the foundational structure of flash memory, introducing an 'erase gate' that allows data to be electrically wiped from a memory cell. - [How IBM's Storage Controllers Keep Data Backups in the Right Order](https://patentbrief.org/patent/us/5682513/cache-queue-entry-linking-for-dasd-record-updates) — A method for storage controllers to track and sequence data updates in a specific order, ensuring that remote backups remain consistent with the original data during a system failure. - [How James Spangler Invented the First Portable Electric Vacuum Cleaner](https://patentbrief.org/patent/us/889823/vacuum-cleaner-spangler) — A 1908 patent for a portable suction-based cleaning device that combined a rotating brush with a fan to lift dust into a bag. - [How Ampex Invented Modern Video Recording on Magnetic Tape](https://patentbrief.org/patent/us/2956114/videotape-recorder-ampex) — This 1955 invention enabled the recording of high-frequency television signals onto magnetic tape, replacing the expensive and low-quality film recording methods of the era.