IMPROVEMENTS IN ELECTRIC BELL INDICATOR AND THIEF DETECTOR
Year: 1877

page_text: LETTERS PATENT to Alfred George Stockwell, of Prospect Row, Woolwich, in
the County of Kent, for the Invention of "IMPROVEMENTS IN ELECTRIC BELL
INDICATOR AND THIEF DETECTOR."
Sealed the 14th August 1877, and dated the 17th February 1877.
PROVISIONAL SPECIFICATION left by the said Alfred George Stockwell at
the Office of the Commissioners of Patents on the 17th February 1877.
ALFRED GEORGE STOCKWELL, of Prospect Row, Woolwich, in the County of Kent.
"IMPROVEMENTS IN ELECTRIC BELL INDICATOR AND THIEF DETECTOR."
The object of this Invention is to save time and inconvenience necessary for
readjusting the indicators as now used, and giving a longer action to a self-
adjusting indicator; also to indicate which part of the house or premises is being
entered.
Hitherto the means employed to indicate the source of alarm has necessitated the
readjustment of the indicator before a second call from the same source could be
effected, or in case the domestic should be absent one minute after the bell has
sounded, the self-adjusting indicator has come to a standstill.
My new self-adjusting indicator consists of an ordinary horse-shoe electro-magnet
fixed on an incline from the vertical line, having a compound pendulum hung in a
perpendicular position before it, which is attracted to the magnet on the electric
circuit being completed of battery No. 1. The lower part of the pendulum is
thereby set in motion and contact is made by a spring against an upright, so
forming the circuit of battery No. 2 which rings the bell. On the circuit being
broken the part of the pendulum, acting as an armature loses its hold on the magnet,
and by 2 negative points fixed therein in conjunction with the contact spring is
repelled therefrom, giving double action to the pendulum, which oscillates to and fro
with great rapidity, thus indicating, from the moment the bell has sounded for
about 5 minutes, the source of alarm by the name or number painted on the cover
or face of the indicator..

page_text: To use the same for thief detectors they are to be connected to the doors
windows, &c., by secreted contact springs in the following manner:-For the door,
a groove is made in the top of the frame in which a flat spring is allowed to work
freely, being secured by screws at one end, and so set that the other end bears with
considerable pressure upon a metal plate, bringing it parallel with the frame; in this
position (the door being open) the electric circuit is completed, the pendulum is set
in motion, and the bells ring. Near to the free end of the spring is a solid metal
rubber by which when the door is closed the spring is elevated from its horizontal
position, and the circuit being broken, it remains so till the door is reopened, the
spring holding connection with the battery and the plate with the bell, thus being.
brought together the electric circuit is completed.
For the windows an additional spring is placed under the metal plate, which
instead of the plate holds the connection with the bell (the plate in this case being
used as a stop), a recess is made in the sash for the rubber to free itself when the
window is closed. The connections with the doors and windows are shut off during
the day by simply turning a small lever.
SPECIFICATION in pursuance of the conditions of the Letters Patent filed by
the said Alfred George Stockwell in the Great Seal Patent Office on the
16th August 1877.
ALFRED GEORGE STOCKWELL, of Prospect Row, Woolwich, in the County of
Kent. "IMPROVEMENTS IN ELECTRIC BELL INDICATOR AND THIEF DETECTOR."
My Invention relates to electric bell indicators and electric thief detectors, and
has for its object the saving of time and inconvenience necessary for readjusting
those as now used, and giving a longer and improved action to a self-adjusting
indicator; also to give a continuous alarm and indicate which part of the house or
premises is being burglariously entered.
Hitherto the means employed to indicate the source of alarm has necessitated the
readjustment of the indicator before a second call from the same source could be
effected, or in case the attendant should be absent one minute after the bell; has
sounded; the self-adjusting indicator has come to a standstill.
My improvements to remove these inconveniences, the indicator being self-
adjusting, and consists of a compound pendulum which is hung in a perpendicular
position before an electro-magnet, which is fixed on an incline from the vertical
line, the pendulum being attracted to the said magnet on completion of electric
circuit, the lower part is thereby set in motion and contact is made by a spring
against an upright, thus forming the circuit of a secured battery which rings the
bell. On the circuit being broken the part of the pendulum acting as armature
loses its hold on the magnet, and by two negative points fixed therein in con-
junction with the contact spring, is repelled therefrom, giving double action to the
pendulum, which oscillates to and fro with great rapidity, and adjusted thus to
indicate from the moment the bell has sounded for 1 minute to 5 minutes,
subsequently the source of alarm by the name or number painted or engraved on
the cover.
To use the same as thief detectors they are to be connected to the windows,
doors, etc., by secreted contact springs, and a continuous ringing bell to complete
the apparatus, so that when a window, door, etc., is opened and the indicator set in
motion, the bell is made to ring, and by a lever which is actuated by the hammer a
second contact is made and the bell keeps ringing (after the first circuit is broken)
until the inmates are aroused.
I will now proceed to describe my Invention in detail, reference being made
to the accompanying Drawing and the letters and figures marked thereon.
Figure 1 is the indicator complete; Figure 2 is an elevation of the-same with

page_text: the box cover removed to show more clearly the mechanism and arrangement of.
the apparatus and their various conditions of action; thus the lower part of No. II.
is swinging to and fro, which indicates from whence the bell is now ringing.
No. III. shows the continuation of action after the bell has ceased; No. I. shows its
normal and readjusted positions; Figure 3 is a plan of the same; Figure 4, an
end view showing the construction of the pendulum which is made in five different
sections, viz., A, B, C, D, E; the first portion A is simply a piece of ordinary wire
having a small boss fastened at each end; one holding a disc and the other the
second portion B, which is a flat steel spring which gives elasticity to the lower
part of the pendulum, causing it to oscillate while the bell is ringing, as shown in
Figure 2, No. II.; the third portion C is a piece of soft iron into which a small cylinder
is fixed, holding the lower pendulum and the contact spring F, see Figure 2, No. I.,
the fourth portion D is a second flat steel spring which gives elasticity to the whole
of the pendulum, and has a very slight resistance to the attractive power of the
electro-magnet; the fifth portion E is a foot piece from which the whole pendulum
is suspended and holds also the connection with the second battery.
Figure 5 is an elevation of the continuous ringing bell made after the same
manner as ordinary electric bells, with the addition of a small apparatus, viz., a
contact lever which is made as follows:-T is a foot piece having a cylindrical
centre; L is a lever, the under part of which has a corresponding cylindrical centre
with two small teeth projecting; the foot piece also having small inclined recesses
for the said teeth to work in; a long cylindrical screw passes through the centre of
the lever and screws into the foot piece, allowing the lever to work freely.
A spiral spring is also secured by the same screw, and bears with considerable
pressure upon the lever, which being struck with the hammer of the bell forces the
teeth down the incline recesses, and brings the lever L in contact with the upright P,
completing the direct circuit (electric), and the bell continues to ring (after the
first circuit is broken) till stopped by those alarmed, by bringing the lever back to
its perpendicular position at S, where it remains so long as the bell is undisturbed;
the direct current is brought in at centre terminal D, and contact is made by the
lever against P, as before stated; Figure 6 is an end view of the same showing the
lever as described.
Figures 7, 8, 9, 10, and 12 are the contact springs for windows, etc., and are
made in two forms, viz., double and single; the double is shown in Figure 9, and
consists of a metal plate having a long wide spring fastened to the lower end of it,
and having a hole in it to allow the metal rubber on the spring to come through;
a second spring is also attached to the plate at the other end, but having a piece of
insulating material between; one spring therefore holds connection with the battery,
the other to the bell or indicator, and being fixed in the window frame where the
sashes meet a sinal recess is made in each sash for the rubber to free itself, as
shown in Figure 8, when the window is closed, and on the sash being opened the
springs are brought together, see Figure 7, and the electric circuit is completed;
Figures 10 and 11 are the single contacts, the springs in this case are screwed into
grooves made in the window frame, but have the same action as the others, the
metal plate only being done away and substituted by a small stop piece placed
across the end of the rubber spring; this arrangement to be used where the others
cannot be properly concealed.
a'
Figures 12, 13, and 14 are different views of the contact springs for doors;
groove is made in the frame of the door, see Figure 13; H is a strong metal
spring having a rubber at one end and secured by screws at the other, and so set
that it bears with considerable pressure upon the plate I; Figure 14 is a section
showing the door closed; Figure 12, a section showing the door open and contact
made, in which position the pendulum is attracted to the electro-magnet and the
spring F, see Figure 2, at II., is brought against the upright P, connects the positive
and negative wires of the second battery, which rings the bell.
Having described the nature and object of my said Invention, and in what
manner the same may be carried into effect, I claim the arrangement and application

page_text: of compound pendulums, secreted contact springs, and lever apparatus to bell in the
manner and for the purpose herein set forth and illustrated by the accompanying
Drawing.
In witness whereof, I, the said Alfred George Stockwell, have hereunto set
my hand and seal this 15th day of August, in the year of our Lord One
thousand eight hundred and seventy-seven.
ALFRED GEORGE STOCKWELL. (L.S.)