# US 4,398,404 A · Key disengagement preventive device for magnetic tumbler cylinder locks

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- Number: US 4,398,404 A
- Document ID: US4398404A
- Status: Granted
- Kind: A
- Application number: 06/218,515
- Filed: 1980-12-22
- Granted: 1983-08-16
- Earliest claimed: 1980-03-10
- Assignees: Miwa Rokku Kogyo Kabushiki Kaisha
- Inventors: Kiyoyasu Wake
- Web page: https://patentgrep.com/patent/US4398404A

## CPC

- E05B 47/0044: {Cylinder locks with magnetic tumblers (E05B47/0041, E05B47/0042 take precedence)}
- Y10T 70/7057: Permanent magnet
- Y10T 70/7565: Plural tumbler sets
- Y10T 70/7605: Pin tumblers
- E05B: LOCKS; ACCESSORIES THEREFOR; HANDCUFFS
- Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION

## Abstract

The present invention relates to a magnetic tumbler cylinder lock mechanism having enhanced safety because of a key disengagement preventive device that prevents the key from disengagement from the key hole when the lock mechanism is in the fully locked or fully unlocked position.

## Claims

### Claim 1

A magnetic tumbler lock mechanism having an outer cylinder and an inner cylinder rotatably about an axis of rotation said mechanism comprising:
a key receiving recess, rectangular in cross section formed in said inner cylinder and adapted to receive a flat key having key magnets therein and a spline means projecting from one flat surface thereof for keying engagement with axially moveable pin means;
a tumbler groove positioned non-axially in said outer cylinder to receive a tumbler magnet movable into locking engagement with said groove;
a non-axially positioned tumbler magnet means mounted in said inner cylinder and adapted to move parallel to and across the face of said key from a first locked position to a second disengaged position upon insertion of said key into said key receiving recess;
a key disengagement preventive device comprising an upper pin segment and a lower pin segment mounted in a pin hole extending through said inner cylinder and said outer cylinder; and,
spacer means positioned within said tumbler groove preventing travel of said lower pin segment into said tumbler groove;
whereby engagement of said key into a key hole moves said upper and lower pin segments outwardly so that a border surface between the upper pin segment and the lower pin segment is aligned with a shear line permitting relative rotation of said inner cylinder with respect to said outer cylinder and preventing removal of said key except upon re-alignment of said pin segments.

### Claim 2 (depends on 1)

The magnetic tumbler cylinder according to claim 1, wherein a plurality of key disengagement preventive pins are provided, segments thereof having differing lengths.

### Claim 3 (depends on 1)

The magnetic tumbler cylinder according to claim 1, wherein said pin segments are urged inwardly of said cylinder by spring means.

### Claim 4 (depends on 1)

The magnetic tumbler cylinder according to claim 1, wherein a pin hole is provided which reaches a central portion on one side of the key hole.

### Claim 5 (depends on 1, 2)

The magnetic tumbler cylinder according to claim 1 or 2, wherein pin holes are provided on an axis extended lengthwise in the shape of cross-section of the key hole.