Patent US4439808A successfully refreshed from Google Patents.
US4439808A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Electromagnetic lock
Assignee: Allegion UK Ltd
•
Filing: 1981-07-28
•
Granted: 1984-03-27
•
Expires: 2001-07-28
Abstract
Abstract An electromagnetic lock for, for example, a door comprising an electromagnet attached to the frame and a magnetizable member attached to the door the magnetizable member being attracted to the electromagnet when the door is in its closed or otherwise locked position, shoulders being provided on or adjacent the electromagnet and magnetizable member whereby if the door is forced to overcome the electromagnetic attraction the shoulders engage to prevent unauthorized unlocking of the door.
Inventors
- 👤 Peter J. Gillham
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-07 13:54
CPC Classifications
E; E05; E05C; E05C19/00; E05C19/16; E05C19/166; E05C19/168; Y; Y10; Y10T; Y10T292/00; Y10T292/08; Y10T292/096; Y10T292/1014; Y10T292/1021
Claims Analysis
Total Claims: 10
Claim 1
Independent Claim
285 words
An electromagnetic lock for locking together two relatively movable members in a predetermined relative position, comprising: electromagnet means, a magnetisable member, means to energise the electromagnet means to cause an electromagnetic field, magnetic flux cancelling means for cancelling the magnetic flux in the electromagnet means when the electromagnet means is switched off, said flux cancelling means including a circuit including charge storage means connected so that, when the electromagnet is switched off, the electromagnet discharges through itself and then charge from the charge storage means is applied to the electromagnet means to neutralise the residual magnetic flux, and mounting means for mounting the electromagnet means and magnetisable member each to a respective one of two relatively movable members in such a position that, as the relatively movable members move to the predetermined position, the magnetisable member and the electromagnet means move towards one another generally transversely of the axis of the electromagnetic field, whereby, when the two relatively movable members are in said predetermined position, said movable magnetisable member may move towards said electromagnet means generally along the axis of the electromagnetic field under the action of the electromagnetic field to normally hold said two relatively movable members in said predetermined relative position, shoulder means being provided on or connected with said magnetisable member and said electromagnet means whereby when said relatively movable members are in said predetermined position and said movable magnetisable member and electromagnet means are moved relatively axially towards one another said shoulders may engage to retain the two relatively movable members in said predetermined position even if the two relatively movable members are forced in such a manner to overcome the electromagnetic attraction between said magnetisable member and said electromagnet means.
Claim 2
Dependent Claim
285 words
An electromagnetic lock for locking together two relatively movable members in a predetermined relative position, comprising: electromagnet means, a magnetisable member, means to energise the electromagnet means to cause an electromagnetic field, magnetic flux cancelling means for cancelling the magnetic flux in the electromagnet means when the electromagnet means is switched off, said flux cancelling means including a circuit including charge storage means connected so that, when the electromagnet is switched off, the electromagnet discharges through itself and then charge from the charge storage means is applied to the electromagnet means to neutralise the residual magnetic flux, and mounting means for mounting the electromagnet means and magnetisable member each to a respective one of two relatively movable members in such a position that, as the relatively movable members move to the predetermined position, the magnetisable member and the electromagnet means move towards one another generally transversely of the axis of the electromagnetic field, whereby, when the two relatively movable members are in said predetermined position, said movable magnetisable member may move towards said electromagnet means generally along the axis of the electromagnetic field under the action of the electromagnetic field to normally hold said two relatively movable members in said predetermined relative position, shoulder means being provided on or connected with said magnetisable member and said electromagnet means whereby when said relatively movable members are in said predetermined position and said movable magnetisable member and electromagnet means are moved relatively axially towards one another said shoulders may engage to retain the two relatively movable members in said predetermined position even if the two relatively movable members are forced in such a manner to overcome the electromagnetic attraction between said magnetisable member and said electromagnet means.
Claim 3
Dependent Claim
50 words
An electromagnetic lock as claimed in claim 1 in which the magnetisable member extends, when the two relatively movable members are in said predetermined position, to both sides of the electromagnet means and includes two shoulder means to prevent relative movement of the two relatively movable members in either direction.
Claim 4
Dependent Claim
31 words
An electromagnetic lock as claimed in claim 1 in which the shoulders of or connected with the electromagnet means and the magnetisable member overlap, when engaged, to less than 10 mm.
Claim 5
Dependent Claim
29 words
An electromagnetic lock as claimed in claim 1 or 3 in which the shoulders of the electromagnet means and the magnetisable member overlap, when engaged, to approximately 4 mm.
Claim 6
Dependent Claim
36 words
An electromagnetic lock as claimed in claim 1 in which the means for mounting the magnetisable member to its relatively movable member comprise a pin adapted to pass through a slot in the relatively movable member.
Claim 7
Dependent Claim
29 words
An electromagnetic lock as claimed in claim 1 in which the means to energise the electromagnet means includes a switch means operable by a key, card or the like.
Claim 8
Dependent Claim
36 words
An electromagnetic lock as claimed in claim 1 in which the means to energise the electromagnet means includes a proximity switch to provide an indication when the two relatively movable members are in said predetermined position.
Claim 9
Dependent Claim
50 words
An electromagnetic lock as claimed in claim 7 in which said proximity switch comprises a reed switch, one component of which is adapted to be mounted on one of said relatively movable members and the other component of which is adapted to be mounted on the other relatively movable member.
Claim 10
Dependent Claim
52 words
An electromagnetic lock as claimed in claims 7 or 8 in which said proximity switch is connected to a delay means whereby it will only indicate that the two relatively movable members are in said predetermined relative position after they have been in that position for a predetermined short period of time.
References Cited (Backward Citations)
GB252872A
Cited
GB265396A
Cited
GB278523A
Cited
US1958940A
Cited
US2673108A
Cited
US2727772A
Cited
US3751088A
Cited
US3851314A
Cited
US3859571A
Cited
US4100810A
Cited
US4148092A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1987-03-27 | 1987-09-26 | 1988-03-27 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1991-03-27 | 1991-09-26 | 1992-03-27 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1995-03-27 | 1995-09-26 | 1996-03-27 | $7700.00 | Window Closed / Lapsed |