Electronic combination lock with magnetic anti-attack interlock

• US 5,271,253 A
• Filed: 03/16/1992
• Issued: 12/21/1993
• Est. Priority Date: 03/16/1992
• Status: Expired due to Fees

• Current Assignee: Mas-Hamilton Group (dormakaba Holding AG)
• Original Assignee: Mas-Hamilton Group (dormakaba Holding AG)
• Inventors: Dawson, Gerald L., Cassada, Thomas E.
• Primary Examiner(s): Cuomo, Peter M.
• Assistant Examiner(s): JAYNE, DARNELL M
• Application Number:
  US07/851,511
• Time in Patent Office: 645 Days
• Field of Search: 70/276, 70/413, 70/303 A, 70/333 R, 70/1.5, 70/1.7, 70/277, 70/150, 292/251.5
• US Class Current: 70/276
• CPC Class Codes: E05B 17/2092 Means responsive to tampering or attack providing additional locking for safes E05B65/0082
• CPC Class Codes: E05B 2047/0021 Geared sectors or fan-shaped gears
• CPC Class Codes: E05B 2047/0092 including means for preventing manipulation by an external magnetic field, e.g. preventing opening by using a strong magnet
• CPC Class Codes: E05B 37/08 with tumbler discs on a single axis, all the discs being adjustable by a rotary knob which is not shifted for adjusting the discs E05B37/0044 takes precedence
• CPC Class Codes: E05B 47/0012 with rotary electromotors actuators with rotary electromotors per se H02K7/06, H02K23/68
• CPC Class Codes: Y10T 292/11 Magnetic
• CPC Class Codes: Y10T 70/25 With reset mechanisms
• CPC Class Codes: Y10T 70/55 Dogged bolt or connections
• CPC Class Codes: Y10T 70/7057 Permanent magnet
• CPC Class Codes: Y10T 70/7424 Tampering prevention or attach defeating

Abstract

To prevent the opening of an electronic combination lock by using a strong magnet to operate a stepper motor, a magnetic interlock is included in the lock structure. A magnetic pin is held in a retracted position by a small magnet when a strong attack magnet is positioned to attempt to open the lock, the magnetic pin is attracted from the holding magnet and extended to bridge the bolt and lock housing, blocking the retraction of the bolt.

Claims

1. An anti-attack interlock mechanism comprising a housing;

a bolt slidably disposed within said housing for movement to an extended position and to a retracted position;

a magnetically actuable means for enabling retraction of said bolt;

means responsive to said magnetically actuable means for moving said bolt between said positions;

a recess disposed within said bolt and extending to a surface of said bolt slidably engaged with said housing;

a recess disposed in said housing aligned with said recess disposed within said bolt and extending to a surface of said housing in sliding engagement with said bolt;

a magnet disposed in said bolt recess;

a slidable interlocking member of a magnetically permeable material disposed within said bolt recess and axially aligned with said magnet;

a magnetically permeable focusing means for focusing magnetic flux disposed within said frame recess;

said recesses, said magnet, said focusing means and said interlocking member all oriented such that the axis of each is coaxial with the axis of the others when said bolt occupies a position extended from said retracted position sufficiently to secure a container to which said housing is attached;

whereby application of an attack magnet to said housing to magnetically affect said magnetically actuable means to permit withdrawal of said bolt from said extended position creates transient magnets of said focusing means and said interlocking member and thereby attracts said interlocking member into proximity of said focusing means to span said recesses preventing movement of said bolt to said retracted position and upon removal of said attack magnet said focusing means and said interlocking member cease to be transient magnets and said interlocking member is magnetically attracted to said magnet within said bolt recess restoring said interlocking member to an inoperative position.

2. The anti-attack interlock mechanism of claim 1 wherein said axes lie in a plane parallel to the axis of movement of said bolt and further lie to form an acute angle with the axis of movement from said extended position to said retracted position.

3. The mechanism of claim 1 wherein said interlocking member is provided with end surfaces oriented parallel to said surface of said bolt and said surface of said housing.

4. The mechanism of claim 3 wherein said focusing means is provided with one end surface oriented parallel to said surface of said housing and disposed recessed within said frame.

5. The mechanism of claim 4 wherein said magnet is constituted of a material with a coercive force greater than the maximum flux present at said magnet when said attach magnet is applied to said housing.

6. The mechanism of claim 1 further comprising a magnetically permeable shield at least partially surrounding said magnetically actuable means.

7. The mechanism of claim 4 further comprising a magnetically permeable shield at least partially surrounding said magnetically actuable means.

8. The mechanism of claim 6 further comprising a non-magnetic spacing means interposed between said magnet and said interlocking means.

9. A magnetic anti-attack interlock for a bolt lock having a magnetically affected enabling means for enabling said lock to open comprising:

a bolt;

a housing;

said bold disposed within said housing for movement to an extended position and to a retracted position;

a magnet having a north and south pole disposed within said bolt;

a magnetically attractable interlocking means held by said magnet in an ineffective position and displaceable from said magnet by a strong external magnetic field to a position bridging said bolt and said housing, thereby preventing withdrawal of said bolt to said ineffective position.

10. The magnetic anti-attack interlock of claim 9 whereby said magnet is fabricated of a material having a coercive force of at least 3,440 Oersteds.

11. The magnetic anti-attack interlock of claim 9 wherein said magnet is oriented to present to said interlocking means one of aid north and south poles, said one of said north and south poles chosen to act as a repelling pole in conjunction with a like north or south pole of said interlocking means when said interlocking means is transitorily magnetized by an external magnetic field.