Mechanism for Alarm Bells.
Year: 1890

page_text: Date of Application, 10th May, 1890-Accepted, 19th July, 1890
COMPTEIE STECIFICATION.
Mechanism for Alarm Bells.
We, JOHN SMITH BROWN of No. 7 Great Eastern Street, London E.C. Factor;
and GEORGE GRAHAM of No. 26 Montague Road, Victoria Park London, E. Brass-
finisher do hereby declare the nature of this invention and in what manner the same
is to be performed, to be particularly described and ascertained in and by the
following statement :-
By this invention we obtain a simple and substantial mechanism for converting a
backwards or forwards pressure upon a lever or button into a series of strokes upon.a
bell, the same being primarily adapted to cycle bells but is also applicable to other calls
and alarms.
The combination consists of an Archimedean or quick pitch screw which is caused
to revolve upon its axis by means of a nut upon a lever traversing it in the direction
of its length; a hammer jointed to an arm fixed to the screw flies outwards by cen-
trifugal force and strikes the bell; or the screw may traverse the nut and cause it to
revolve, the hammers being upon the nut.
In constructing alarms with one bell for cycles we use a base plate of rather less
diameter than the interior of, the bell, this has a pillar in the centre to carry the
bell, and two lugs near the edge to carry the ends of the screw, a pin is fixed at
the opposite side as a pivot for the lever, and a stud near the edge-midway
between one of the lugs and the pin-carries the spring which returns the .lever;
on the reverse or under side of the plate is a screw clamp for attachment to the
cycle.
The screw may be cut out of solid metal with one, two, or more threads of
quick pitch, but we prefer to use a length of flat wire twisted with the required
number of turns, at one end (or both ends) of the screw a small arm is fixed and
to this the hammer is jointed by a free rivet; the ends of the screw are pointed,
one working in a hollow centre in the lug, and the other end in a hollow screw
in the other lug, this provides for adjustment in case of wear.
The lever is made with a shaped finger piece to project outside the bell, and at its
inner end has a horizontal slot to form a nut through which the screw passes, or, if a
separate nut is used a vertical slot is made which bears the trunnions of the nut and
allows for the varying length.
The spring is attached to the stud in the plate and to a stud upon the lever, this
returns the lever to its position of rest and causes it to press against the hammer, thus
avoiding any probability of the alarm rattling or speaking through vibration.
In constructing an alarm with two bells the parts are the same as above described
except that the bells are both carried upon a long central pillar, from which an arm,
with the fixing clamp upon it, radiates, and passes out between the two bells; the pin
for lever and the lugs for the screw are also carried upon arms instead of upon a flat
plate. If only one hammer is used it will strike the upper bell in one direction and
the lower on the return; when a "chime" is required a hammer is used at each end
of the screw on alternate sides, and a small lump is cast on each bell, one
opposite each hammer, each hammer will then strike one bell and the strokes will
alternate.
A "chime" alarm also suitable for calls &c. may be made with a hollow central
pillar divided in the centre, and an internal screw plunger; a nut which carries
hammers to strike against internal lugs upon the bells works in the pillar; when
the plunger is pressed down the nut revolves and causes the hammers to strike the
bells; the plunger is returned by a spring.
In the accompanying drawings Figs. 1 & 2 show the elevation and the plan of the
single alarm, A is the bell, B is the plate, C is the clamp, D is the pillar E. E. are the
lugs, F is the Archimedean screw, G is the arm upon it, H is the hammer, I is

page_text: the adjustment screw,
K is the finger piece of lever, L is the fulcrum, M is the slot
forming the nut, N is the spring attached to the studs O. P., Q is the screw to fix
bell.
Figs. 3 & 4 show the elevation and plan of the double or chime alarm A A are the
bells, B is the arm carrying the clamp, C is the clamp, D is the pillar E. E. are the
lugs, F. is the Archimedean screw, G is the arm upon it, H is the hammer, I is
- the adjustment screw, K is the finger piece of lever, L is the fulcrum, M is the slot
forming the nut N is the spring, QQ are the screws for fixing the bells, R is the arm
carrying the lever.
Fig. 5 shows the elevation of the chime alarm with central plunger, A A are the
bells, A¹ A¹ are the lugs upon them, B is the frame, C is the clamp D is the central
tube, F is the screw plunger, H, H. are the hammers, K is the button M is the nut,
N is the spring, QQ are the nuts for fixing the bells.
Having now particularly described and ascertained the nature of our said inven-
tion, and in what manner the same is to be performed, we declare that what we
claim is :-
1. The Archimedean or quick pitch screw with nut formed upon a lever for actuating
the hammers of alarm bells, substantially as described.
2.. The Archimedean screw, with nut propelled by a lever for actuating the hammers
.of alarm bells, substantially as described.
3. The revolving nut and the Archimedean screw plunger, for actuating the hammers
of alarm bells, substantially as described.
.. 'Dated this 10th day of May 1890.
JOHN SMITH BROWN.
GEORGE GRAHAM.