# US 4,397,168 A · Door reinforcement and lock guard plate

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- Number: US 4,397,168 A
- Document ID: US4397168A
- Status: Granted
- Kind: A
- Application number: 06/379,302
- Filed: 1982-05-18
- Granted: 1983-08-09
- Earliest claimed: 1980-04-18
- Assignees: TRE Corporation
- Inventors: Anthony J. Rotondi; Richard O. Mullich
- Web page: https://patentgrep.com/patent/US4397168A

## CPC

- E05B 17/2084: {Means to prevent forced opening by attack, tampering or jimmying (E05B15/1614 takes precedence; for ignition or steering locks B60R25/023)}
- Y10T 70/7921: Armoring
- Y10T 70/8568: Escutcheons
- E05B: LOCKS; ACCESSORIES THEREFOR; HANDCUFFS
- Y10T: TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION

## Abstract

An L-shaped guard plate for reinforcing a door in the area of the door lock assembly. The L-shape provides a strengthening function without introducing any misalignment in the position of the lock bolt of a door with respect to the strike plate carried in a door frame. The device is thus both effective and easily installed on most doors. The guard plate may include integral tabs which engage slots in the housing of the lock unit. The tabs serve to provide increased resistance to the application of rotational forces to the lock unit.

## Claims

### Claim 1

In a door system comprising:
a frame including a lock bolt opening and a doorstop;
a door carried within the frame;
a door lock assembly connected to the door, said assembly including a lock bolt extending from an edge of the door into said lock bolt opening when the door is closed, the improvement comprising:
a one-piece L-shaped guard plate having a first leg which fits over the side of the door opposite said doorstop, said first leg including a first opening through which a portion of the door lock assembly extends, and a second leg which covers a portion of the door edge, said second leg including a second opening through which the lock bolt extends, wherein the side of the door facing the doorstop has a substantially flat surface along the length of the doorstop, whereby said guard plate can be installed in an existing door system without causing misalignment of said lock bolt with respect to said lock bolt opening.

### Claim 2 (depends on 1)

The system of claim 1 wherein said door lock includes a lock unit having a housing portion including at least one slot and wherein said guard plate includes at least one integral tab extending into the first opening and engaging said at least one slot, said tab and slot arrangement providing increased resistance to the application of torsional forces to the lock unit.

### Claim 3

A door system having increased security, comprising:
a frame including a lock bolt opening and a door stop;
a door carried within the frame;
a door lock assembly connected to the door, said assembly including a lock bolt extending from an edge of the door into said lock bolt opening when the door is closed; and
a one-piece L-shaped guard plate having a first leg which fits over the side of the door opposite said doorstop, said first leg including a first opening through which a portion of the door lock assembly extends, and a second leg which covers a portion of the door edge, said second leg including a second opening through which the lock bolt extends and wherein said second leg includes an extension which is folded over so that it is generally parallel with the second leg, said extension including a third opening corresponding to the second opening, thereby providing a two layer second leg.

### Claim 4 (depends on 1)

The system of claim 1 wherein said first leg includes at least one generally horizontal reinforcing rib.

### Claim 5 (depends on 1)

The door system of claim 1 wherein said door lock assembly further includes a latch unit having a knob extending from an additional opening in said first leg.

### Claim 6 (depends on 1)

The system of claim 1 wherein said door lock includes a lock unit having a housing portion including at least one integral tab and wherein said guard plate includes at least one slot engaging said at least one tab, said tab and slot arrangement providing increased resistance to the application of torsional forces to the lock unit.