IMPROVEMENTS IN BURGLAR ALARMS
Year: 1884

page_text: COMPLETE SPECIFICATION.
I ALEXANDER MELVILLE CLARK of the firm of A. M. and Wm. Clark of
53 Chancery Lane in the County of Middlesex, Fellow of the Institute of Patent
Agents do hereby declare the nature of the invention for " IMPROVEMENTS IN
BURGLAR ALARMS and in what manner the same is to be performed, to be
particularly described and ascertained in and by the following statement:-
"
Reference is to be had to the accompanying drawings forming a part of this
specification, in which similar letters of reference indicate corresponding parts in
all the figures.
The object of this Invention is to facilitate the attachment of alarms to door
knobs and promote certainty in the operation of such alarms.
The Invention consists in a burglar-alarm constructed with a spring clamp
connected with a bar jointed to a suspended frame carrying a clock work and gong
and a sliding rod provided with a spring and having fingers to engage with the
escapement anchor and a catch attached to the suspending bar whereby the alarm
can be readily suspended from a door knob and will be sprung by the movement of
the said knob, as will be hereinafter fully described.
Figure 1 is a side elevation of the apparatus, Figure 2 is a front elevation of the
same partly in section through the line x-x Figure 1. Figure 3 is a sectional plan
view of the same taken through the line y-y Figure 1.
A represents a small frame to which is attached a clockwork B and one or more
gongs C. The upper end of the frame A or an angle plate connected with the said
frame is loosely jointed to the lower end of the bar D, to the upper end of which is
attached, or upon it is formed, a forked arm E. The forked arm E is so shaped as
to fit upon the upper side of any ordinary door knob T. To the bar D is attached
a second bar F to the upper end of which is attached, or upon it is formed a forked
arm G. The arm G is so formed as to fit against the lower side of an ordinary door
knob so that the bars D F will be securely clamped to the said door knob, and
when the said knob is turned the said bars D F will be carried with it. The
bars D F and the forked arms E G are made of elastic material so that the said
forked arms can be readily sprung upon and from a door knob.
With the escapement anchor H of the clock work B is rigidly connected the bell
hammer I which is so formed as to be thrown against the gong or gongs C by the
vibration of the said escapement anchor H. J is a rod which passes through tho

page_text: upper gong C and through guide holes K Q formed in the frame A. The lower
end of the rod J is bent inward to form a finger L, or has an inwardly projecting
finger L attached to it. The finger L passes in beneath the escapement anchor H
or beneath the shank of the bell hammer I rigidly connected with the said escape-
ment anchor H so that the rod J when raised will press the said escapement anchor
against the escapement wheel of the clock work B and thus lock the said clock
work. To the upper end of the rod J is attached, or upon it is formed, a finger M
which projects inward to rest when the said rod J is raised to lock the clockwork
upon a catch N attached to the bar D. Upon the rod J is placed a spiral or other
shaped spring O, the lower end of which rests upon a collar or pin attached to the
said rod J or upon the finger L and its upper end rests against the frame A so that
the said spring will be compressed when the said rod J is raised and hung upon the
catch N. The catch N can be covered by a cap R sliding upon the upper part of
the rod J to prevent the finger M from being accidentally pushed off the catch N
when winding up the spring of the clockwork or when applying the alarm to or
removing it from the door knob. With this construction when the door knob is
turned the bar D F will be turned with it, while the frame A and its attachments
will be held vertical by gravity, causing a movement in the joint connecting the
bar D F and frame A, which movement carries the finger M off the catch N and
allows the rod J to be thrown downward by the elasticity of the spring O-
releasing the clockwork and allowing the hammer I to be operated to sound an
alarm by the movement of the escapement. If desired the aların may be suspended
from any suitable support and connected with a door or window by a cord or
wire so that the alarm will be sprung by any movement of the said door or
window.
I am aware that alarms similar to the present have before been attached to door
knobs in which the turning of the knob throws out of line the joint of a pendulum
containing the alarm bell and clockwork to sound the same, thus freeing the means
of restraining the clock work and allowing it to sound the alarm, and I do not claim
the same broadly.
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 combination with an alarm gong, clock work for sounding it, an escape-
ment in the clockwork, and a jointed connection adapted to suspend the alarm
upon a door knob, the portion above the joint being provided with a fixed catch,
of a vertically sliding rod, a spring forcing said rod downward, a finger at its top
to rest on said fixed catch, and a finger at its lower end adapted to hold the
escapeinent engaged, whereby the turning of the knob will disengage the catch
from the upper finger, freeing the rod, releasing the escapement, and allowing the
gong to be sounded as described.
2nd In a burglar alarm, the combination with the suspending bar D F carrying
the operating parts of the mechanisin, of the forked arms EG, substantially as
herein shown and described, whereby the alarm can be readily secured to and
suspended from a door knob as set forth.
3rd In a burglar alarm the combination with the suspending bar D F, the finger M
and the fixed catch N, of the cap R, substantially as herein shown and described,
whereby the said finger can be locked in place upon the said catch as set forth.
Toted this 1st day of Jour 1884