Note: Descriptions are shown in the official language in which they were submitted.
~æ~
This invention relates to a door lock guard, and in
particular to a security door lock guard for preventing un-
authorized opening of the door.
Conventional mortise loc}cs are rel~tively easy to
open or unlock using a plastic credit card or another thin
article. The article is merely inserted between the door and the
door jamb to move the bolt of the lock into the door. Many
devices designed to prevent unauthorized openin~ of such door
locks have been proposed. Examples of door lock guard devices
are described in Canadian Patents Nos. 230,669, issued to S.
O'Hara on May 1, 1923; 700,205, issued to A.J. Gravelle on
December 22, 1964; 847,202, issued to E.L. Thompson on July 21,
1970; 856,109, issued to F.M. Sushan on November 17, 1970;
979,051, issued to D. Nemetz on December 2, 1975 and 1,126,786,
issued to H. Heffel on June 29, 1982, and United States Patents
Nos. 2,127,891, issued to E.M. Starling on August 23, 1938;
2,631,881, issued to F.A. Trachsler on March 17, 1953; 3,279,840,
issued to A. Barone on October 18, 1966; 3,290,081, issued to
F,M, Sushan on December 6, 1966 and 4,130,311, issued to F.M,
Sushan on December 19, 1978,
While the patented devices achieve the desired result,
most such devices are somewhat complicated, and consequently
expensive to mass produce. It will be appreciated that simplicity
both in terms of structure and operation is of primary importance
for devices of the type in question. In spite of the extent
`3~f~
of previous activity in this area, there still exists a need
for a simple, yet effective door lock.
The object of the present invention is to meet such
need by providing a relatively simple, efEective door lock
guard.
Accordingly, the present invention relates to a door
lock guard for use with a conventional mortise lock of the type
including a handle actuated bolt for slidable mounting in
one side edge of a door for mating with a recess in a door jamb,
said guard comprising
striker plate means adapted to be mounted on a door
jamb, said striker plate means including planar body means for
opposing said one side edge of the door, a first opening in
said body means for receiving the bolt, flange means at one end
of said body means perpendicular to said body means for extending
partly along the outer edge of a door in the closed position,
and a second opening in said flange means; and
latch plate means for mounting in said one edge of
the door for slidably receiving said bolt, said latch plate
means including a projection on one side thereof for mating
with said second opening when the door is in the closed position
to prevent the insertion of a plastic credit card or other thin
article between the striker plate means and the latch plate
means in the area of the bolt.
The invention will now be described in greater detail
with reference to the accompanying drawing, which illustrates
a preferred embodiment of the invention, and wherein:
Figure 1 is an exploded, perspective view of a
conventional lock and a lock guard in accordance with the
present invention; and
Figure 2 is a schematic cross section taken through
one side edge of a door showing the use of the lock guard of
Fig. 1.
STRUCTURE
Referring to the drawing, the lock guard of the present
invention is intended for use with a conventional door lock 1 of
the type including a sliding bolt 2. The lock 1 is mounted in
one side edge 4 of a door 5, so that the bolt 2 can slide into
and out of a recess (not shown) in a door jamb 6 (Fig. 2) during
closing and opening of the door. While the door jamb 6 as shown
is of one piece construction, it will be appreciated that except
when using metal, such jambs are usually constructed using two
or more pieces of wood.
The lock-guard includes two basic elements, namely a
striker plate generally indicated at 7 and a latch plate generally
indicated at 8. The striker plate 7 is similar to a conventional
striker plate and is mounted in a door jamb 6 opposite to the
bolt 2 when the door 5 is in the closed position. The plate 7
is defined by a planar body 10. Top and bottom holes 11 in the
body 10 receive screws (not shown) for mounting the striker
`; ' ~
plate 7 in the door jamb 6. The striker plate 7 is mounted
in a recess 12 (Fig. 2) cut in door jamb 6. The usual curved
end 13 is provided on the inner end of the body 10. A large
central opening 14 is provided in the centre of the body 10
for receiving the bolt 2.
A flange 16 perpendicular to the body 10 of the striker
plate 7 extends outwardly therefrom, so that the flange is
located at the front of the outer edge 17 of the door 5 when
the latter is in the closed position. An elongated opening 18
is provided in the flange 16.
The latch plate 8 (like the conventional latch plate)
is defined by a rectangular, planar body 20 with holes 21 near
the top and bottom ends thereof for receiving screws (not shown).
The latch plate 8 is mounted in a recess 22 in the side edge 4
of the door 5. A central opening 24 slidably receives the
bolt 2 of the lock 1. A rectangular projection 25 extends
outwardly from one side of the body 20 beyond the outer edge
17 of the door 5 for mating with the opening 18 when the door
is in the closed position.
During installation of the striker plate 7, a recess
26 is cut in the door jamb 6 in alignment with and having
essentially the same length and width as the opening 18. The
recess 26 is sufficiently deep that t:he door 5 can be fully
closed, with the projection 25 extending through the flange 16
into the recess 26. Thus, it is impossible to insert a credit
-- 4
card or other thin article into the space between the bodies
10 and 20 of the striker plate 7 and the latch plate 8,
respectively to effect unauthorized opening of the door 5.
It will be appreciated that the elements of the door
lock guarddescribed hereinbefore can readily be mass produced
from thin metal sheets, with a minimum of labour. Installation
of the lock guard is only slightly more complicated than the
installation of a conventional striker plate and latch plate, the
recesses for receiving the lock guard plates being only slightly
larger in area, with one additional projection-receiving recesses
in the door jamb.
-- 5 --
.~
.
