Improvements in and relating to Electric Fire Alarms.
Year: 1893

page_text: COMPLETE SPECIFICATION.
Improvements in and relating to Electric Fire Alarms.
1, EMIL CARL CHRISTIAN KROGH, a citizen of the United States of America,.
residing at Monmouth, in the County of Warren and State of Illinois, one of the
United States of America, Mechanic, 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 :-
My invention relates to fire alarms of the class employing an electric circuit to
actuate the alarm, which circuit is normally open, but is closed by the action of a
thermostat actuated by a rise in temperature in the surrounding atmosphere due to
the presence of a fire.
To this end, and others to appear, the invention consists in the construction and
combination of parts hereinafter specified, and shown in the accompanying drawings,
in which-
Figure 1 is a perspective view of my device;
Figure 2 a view partially in section and partly in elevation, and
Figure 3 a detail perspective view of the contact adjusting. cam.
In carrying out my invention I employ an alcohol filled drum or capsule, A,
that constitutes one terminal of the electric circuit, an adjustable rod B consti-
tuting the other terininal, a spiral cam C to adjust said rod, dial D, and a pointer
or indicator E.
The cam C is mounted on the inner end of a shaft F, journaled in a bearing or
sleeve that is supported by an open frame of four rods, f¹ secured to two diametri-
cally extending bars d, d.
Upon its outer end the shaft F is provided with an enlargement or button g by
which it may be rotated, and also moved longitudinally inward, to carry rod B into
contact with the capsule A and thus close the circuit.
The hand or pointer E is carried by said shaft F. The rod B does not engage
the cam, but a second rod bis employed which is connected to a lateral extension of
the rod B. A coiled spring encircles the rod b and presses the same yieldingly
against the cam. This arrangement of rods enables me to have the capsule A and
the dial D concentric, instead of eccentric.
To prevent the rod b from passing out of contact with the spiral cam C when the
latter is rotated from its highest to its lowest surface, I provide a projection & to
strike said pin and thus limit the rotation of the cam.
As the frequent use of the device as an ordinary call might disarrange the
adjustment of the device to a certain temperature, I have provided a lock to
prevent such derangement, consisting of a toothed wheel mounted on the shaft F,
and a pawl I to co-operate therewith. Said pawl is pivotted to one of the rods f¹
and made quite wide, as shown, so as to always engage the wheel, whatever may
be the position to which it may be moved by the longitudinal movements of
the shaft.
The pawl is held locked in engagement with the teeth of the wheel by a collar i
mounted on one of the rods f' which engages the top of the pawl. Said collar is
normally held outward in engagement with the pawl by a coiled spring i encircling
the rod . To disengage the pawl from the wheel it is simply necessary to press
the collar i inward against the tension of the spring until it is out of the path of
outward swing of the pawl.
Having now particularly described and ascertained the nature of my said inven-
tion and in what manner the same is to be performed, I declare that what I
claim is :-
1. In combination with a temperature actuating contact of a thermostat, a

page_text: longitudinally movable contact rod adapted to be pressed into engagement with the
first named contact, substantially as described.
2. In combination with the temperature actuating contact of a thermostat, the
longitudinally movable rod forming a contact held normally away from the other,
the adjusting cam, and the shaft carrying the same adapted to be moved
longitudinally to force the rod contact against the other contact, substantially as
described.
3. In combination with the temperature actuating contact of a thermostat, the
longitudinally movable rod forming a contact, held normally away from the other,
the adjusting cam, the longitudinally movable shaft carrying said cam, and the
locking device to hold said shaft from rotation when moved longitudinally, sub-
stantially as described.
4. In combination with a temperature actuating contact of a thermostat, the
longitudinally movable contact rod held normally from the other, the adjusting cam,
the longitudiually movable shaft carrying said cam, the toothed wheel to hold said:
shaft from rotating, and the spring pressed collar to engage said pawl.
5. In combination with the temperature actuating contact of a thermostat, the
longitudinally movable contact rod forced normally from the other, the adjusting
spiral cam to move said rod, and the stop to limit rotary movement of the cam,
substantially as described.
Dated this 1st day of March 1893.
JENSEN & SON,
77, Chancery Lane, London, W.C., Patent Agents.