Year: 1889

page_text: Figure 3 an end view of our improved device.
A metallic tube or rod S is so attached to a plate P of insulating material that the.
one end will remain immovably fixed in a bearing f, whilst the other end can move
backwards and forwards in an appropriate guide . This metallic tube will be
caused to contract when the temperature is lowered and to expand when the
temperature is raised, this movement, caused by the said contraction and expansion,.
being transmitted to a suitable two-armed lever H.
The fulcrum of this lever is arranged near the free end of the rod or tube S, so that
the latter can operate on the short arm a of the lever H, the consequence of this
arrangement being, that when the second or longer arm of the said lever H is made
of sufficient length the slight movement transmitted to the arm a by the expansion or
contraction of the tube or rod S will be considerably increased at the extreme end A
of the long lever arm. The rotation of the lever H around its fulcrum caused for
instance by the expansion of the rod, rail or tube overcomes the power of the
spring G, which serves to return the said rod or tube to its original position as soon
as the same is subjected to contraction.
The end A of the lever H plays between two contacts or contact springs k¹, k², in
such manner that as soon as the temperature rises beyond a fixed temperature the
end A of the lever H will come in contact with the contact spring k', and when the
temperature is lowered beyond the fixed limit, with the contact spring k².
The end A of the lever H and also the contact springs are armed with
platinum, and it will be readily seen from the accompanying drawing that when
contact is made on the one side a bell will be operated and when the contact is made
on the opposite side a second bell will be set in operation, and in this manner the
excessively high and also the exceedingly low temperature indicated or signalled.
The course taken by the current in the apparatus is as follows:-
the
The current enters at the terminal which is in connection with the lever H;
contact springs k¹, k² being connected with the terminals 1, 12, said terminals being
each in connection with one of the electric bells from whence the current returns to
the battery. Adjusting screws e¹, e² are arranged for adjusting the distance of the
contact springs from the end of the lever according to the temperature.
In order to make the contact between the end A of the lever H and the contact
springs, a frictional contact and to render the same certain, the said springs are bent
outwards, so that when the parts come in contact friction will be made with the
surface of the springs. If the apparatus is to be employed as signalling devices or
indicators for maximum temperatures, the same is screwed to the ceiling or other

page_text: elevated parts of the room or building; if the same is, however, to be used as
signalling devices or indicators for minimum temperatures, for instance for hospitals,
hot houses and such like, the apparatus is arranged in a low position. If the
apparatus is to be employed for both purposes the same is fixed in medium position.
Having now described and ascertained the nature of our said invention, and in
what manner the same is to be performed, we declare that what we claim is :-
A device for electrically indicating or signalling maximal or minimal temperatures,
consisting of a metallic tube, rod or rail, rigidly fixed at one end onto an insulated
plate, whilst the other end can move freely in longitudinal direction to the tube, rod
or rail S, and of a two-armed lever, against the short end of which the metallic tube,
rod or rail operates in combination with a contact device formed by the long arm of
the lever and two frictional contact springs attached to the insulated plate, which said
arm comes in contact with one spring when the temperature exceeds the maximum
temperature and with the other contact spring when the temperature sinks below the
minimum temperature, substantially as set forth and shown.
Dated this 21st day of November 1889.
PHILIP M. JUSTICE,
Associate Agent.