Tamper resistant lock assembly

Details Tamper resistant lock assembly Tamper resistant lock assembly

2002-07-10

2004-05-18

Gall, Lloyd A. (Department: 3676)

Locks

Special application

For closures

C070S079000, C070S131000

Reexamination Certificate

active

06735991

ABSTRACT:

BACKGROUND
1. Technical Field
The present disclosure relates generally to a tamper resistant lock and, more particularly, to a tamper resistant lock having a novel strike and bolt design to prevent keyless operation of the lock.
2. Background to Related Art
Locks for retaining doors, drawers or other movable members in a closed position are well known. Such locks are commonly used on doors to homes, merchandise cabinets, desk drawers, etc. to protect the internal contents of a structure. These locks may include a key operated bolt which is mounted on a movable member, e.g., a door, and a strike which is mounted to a stationary member, e.g., a door jam. The strike includes a recess for receiving the bolt. The bolt is movable between a first extended locking position to a second retracted release position. Typically, the bolt is spring biased to the locking position and is movable to the release position by inserting a key into the lock and turning the key.
Generally, the bolt of a lock assembly includes an angled face and a rear retaining wall. The angled face is positioned to engage the strike when closing the movable member such that engagement between the angled face of the bolt and the strike urges or cams the bolt to the release position. In the release position, the bolt is able to pass over the strike to permit the movable member to close. When the rear retaining wall of the bolt passes over the edge of the strike defining the recess, the bolt is biased by the spring into the recess to lock the movable member in the closed position.
Typically, a clearance exists between the movable member and the stationary member which provides access to the bolt. One problem associated with the locks described above is that a flat tool, e.g., a credit card, can be inserted into the clearance into engagement with the angled face of the bolt. If a sufficient force is applied by the flat tool against the angled face of the bolt, the bolt can be moved from the extended position to the release position to facilitate opening of movable member without the use of a key.
Accordingly, a need exists for an improved lock assembly which cannot be released without the key associated with the lock assembly.
SUMMARY
In accordance with the present disclosure, a tamper resistant lock assembly is disclosed which is configured to prevent keyless operation of the lock. The tamper resistant lock assembly includes a lock housing having a bolt slidably supported therein and a strike. The lock housing is secured to a mounting plate which adapted to be fastened to a movable member such as a door. The strike is adapted to be fastened to a support member such as a door jam at a position to facilitate engagement between the bolt and the strike when the movable member is in a closed position. The strike includes a C-shaped catch member having a base portion, a sidewall portion, a transverse extension and a lip portion. The lip portion extends along an axis which is, preferably, substantially parallel to the sidewall of the catch member such that the lip portion, transverse extension and sidewall of the catch member define a recess having an opening which is configured to receive an engagement portion of the strike when the movable member is in the closed position.
The engagement portion of the strike also includes a sidewall portion, a transverse extension and a lip portion. The lip portion of the engagement portion is, preferably, substantially parallel to the sidewall portion of the engagement portion such that the lip portion, sidewall and transverse extension of the engagement portion also define a recess having an opening.
When the engagement portion of the presently disclosed strike is engaged by the catch member of the presently disclosed bolt, the lip portion of the bolt will position itself within the recess of the engagement portion of the strike and the lip portion of the strike will position itself within the recess of the catch member of the strike to provide interlocking engagement which resists tampering.


REFERENCES:
patent: 1530655 (1925-03-01), Dowling
patent: 2573450 (1951-10-01), Kallas et al.
patent: 4813250 (1989-03-01), Yeh
patent: 5044181 (1991-09-01), Roop et al.
patent: 6374650 (2002-04-01), Newman

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