A NEW OR IMPROVED ALARUM SUITABLE FOR STREET AND OTHER DOORS
Year: 1885

page_text: I GEORGE FREDERICK ANDREWS of 3 Basslow Villas, East Dulwich Surrey, Civil
Engineer do hereby declare the nature of my invention for A NEW OR IMPROVED
ALARUM SUITABLE FOR STREET AND OTHER DOORS and in what manner the same
is to be performed, to be particularly described and ascertained in and by the
following statement :-
The object of this invention is to provide an effective cheap and convenient
alarum suitable for street and other doors-Such alarum may be fitted either to
draw back door locks or to door locks actuated by turning the handle.
Fig 1 of the accompanying drawings illustrates the application of my invention
to an ordinary draw back street door lock.
I fit the lock spindle (1) with a washer (2) to which a curved link (3) is pivotted
that works to and fro as the lock spindle is operated-The other parts of the
mechanism are carried on a base plate A-and consist of a toothed segment (4)
that gears into a cogged wheel (5)-This latter gears into a second smaller cog
wheel (6) mounted on a short spindle which also carries a third cog wheel (7) that
acts upon the short arm of a bifurcated striking lever (8) This striking lever is
controlled and regulated by a stud (9) and spring (10) and when actuated the long
arm strikes a gong (11) thus giving an alarm.
The operation of my invention is as follows Upon the handle of the door being
drawn back the link (3) forces back the toothed segment (4) thus operating the
train of wheels (5) (6) (7) and causing the periphery of the latter to come in
contact with and depress the short arm of the striking lever (8) thus causing the
long arm thereof to strike the gong and upon releasing the handle of the lock this
action is repeated and a second alarm is given.
In applying my invention to Office and other door locks which are actuated by
turning, instead of drawing back the handle (which application is illustrated at
Fig 2 of the accompanying drawings) I dispense with the washer (2) link (3) and
toothed segment (4) and in lieu thereof I mount a cog wheel B or a toothed
segment upon the lock spindle which is rotated with the lock spindle and so
actuates the other parts of the mechanism in the manner already described.
In order to allow of the door being opened or closed without sounding the gong
I fit the striking lever with a detent as shewn in Fig 2 which consists of a slotted
slide (12) a small lever (13) and a projecting plate or stop (14).

page_text: The mechanism carried on the base plate A is protected and concealed by a
suitable face plate not shewn in the drawings while the detent lever (13) is
provided with a pin projecting through such face plate and furnished with a knob
or stud to allow of such detent lever being easily operated.
When such detent lever is pushed forwards and forced behind the projecting
stop as shewn in dotted lines at Fig 2 the short arm of the striking lever is held
back thus preventing contact between it and the periphery of the cog wheel (7)
and consequently also preventing the long arm striking the gong.
Having now particularly described and ascertained the nature of my said
invention and in what manner the same is to be performed I declare that what
I claim is
1° The improved combined construction and arrangement of an alarum suitable
for and to act in combination with a draw back door lock substantially as herein-
before specified and shewn.
2° The modified construction and arrangement of such alarum to allow of its
application to and combination with a door lock operated by a turning handle
substantially as herein before specified and shewn.
3° Fitting such alarum with a detent constructed and arranged substantially in
the manner and for the purpose hereinbefore specified and shewn.
WHAD ULK
wwwwwy
ELT & Co.,
33, Southampton Buildings, Holborn, London,
Agents for the Applicant.