Improvements in or relating to Mechanism for Controlling and Indicating Temperature Limits.
Year: 1899

page_text: Improvements in or relating to Mechanism for Controlling and
Indicating Temperature Limits.
We, ERNEST HOWARD GRIFFITHS, F.R.S., of 12, Park Side, Cambridge, in the
County of Cambridge, Fellow of Sydney College, Cambridge, and WILLIAM CECH.
DAMPIER WHETHAM, of 5, St. Peters Terrace, Cambridge, aforesaid, Fellow of
Trinity College, Cambridge, do hereby declare the nature of this invention
to be as follows:-
This invention relates to mechanism for controlling and indicating tempera-
ture limits. According to this invention a spring or other force is held inactive
until a temperature has been reached which will bring about the melting of an
alloy, metal or other suitable substance. The alloy, metal or other substance is
so arranged that while solid it will prevent the movement of a body which is
in connection with suitable mechanism for sounding an alarm, cutting off or
controlling a supply of heat, or for performing other operations.
As an example of a method of carrying this invention into operation, the
following mechanism may be employed:-
Within a tube, having one end closed, is arranged a rod, whose end is immersed
in an alloy, metal or other suitable substance in the bottom of the tube. The
upper end of the rod projects beyond the tube and is connected by spring-con-
trolled or other mechanism, with or without the interposition of a ratchet or
similar mechanism, with means for controlling, for example, the supply of gas
to a burner. By the employment of a ratchet the device can be set so as to
enable the gas, when the limiting temperature is reached, to be turned off com-
pletely or only partially, any convenient means being utilized to arrest the
mechanism at the desired point.
The operation of the device is as follows:--As soon as the desired temperature
limit is reached, the alloy melts and leaves the rod or body free to turn or move
endwise, and with the result that the supply of heat is cut off. Where the device
is arranged for the rod to rotate when released, the employment of the ratchet
enables the apparatus to be reset without necessitating the re-melting of the
alloy.
As examples of applications of this invention it may be mentioned that it can
be employed for indicating the sterilising temperature of milk and controlling
the heat supply when this temperature is reached. The mechanism may also be
used in connection with fire alarms and extinguishers.
An important use to which the invention may be put is to apply it to a steam-

page_text: boiler, where it can sound an alarm or open a valve, when the limit of safety in
temperature and pressure is reached.
It will be seen from the above that the invention may be conveniently employed
in conjunction with any apparatus where ranges and regulation of temperature
are in question.
In order to prevent oxidation of the alloy or other substance employed it is
advisable to cover the exposed surface with vaseline, oil or other suitable sub-
stance.
Improvements in or relating to Mechanism for Controlling and
Indicating Temperature Limits.
We, ERNEST HOWARD GRIFFITHS, F.R.S., of 12, Park Side, Cambridge, in the
County of Cambridge, Fellow of Sydney College, Cambridge, and WILLIAM CECIL,
DAMPIER WHETHAM, of 5, St. Peters Terrace. Cambridge, aforesaid, Fellow of
Trinity College, Cambridge, 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:-
This invention relates to mechanism for controlling and indicating tempera-
ture limits, and has for its object to construct a mechanism which will be capable
of being readily reset after it has operated.
According to this invention a rotatable member controlled by a force is held
inactive by a fusible lock until a temperature has been reached which will bring
about the fusing of this lock. Mechanism is provided tending to rotate this
member, there being an operative connection between the driving mechanism
and the member of such a nature that the apparatus can always be reset without
having to renew or re-fuse the fusible lock.
In applying the invention the fusible lock is formed by a small quantity of
alloy metal or other suitable substance contained in a tube, one end of which is
closed, the rotatable member being a rod, one end of which is immersed in the
alloy in the tube. Upon the outer end of the rod may be mounted a ratchet
wheel, a star wheel or some other equivalent device which will enable the con-
nection between some mechanism tending to rotate this rod to be reset at any
time after a temperature limit has been reached which will bring about the
fusing of the alloy, this resetting device being such that no refusion or renewal
of the alloy or other parts of the mechanism is necessary in order to restore the
apparatus to its operative state.
In the accompanying drawings:-
Figure 1 is an elevation partly in section showing one application of this
invention for the purpose of controlling the limit of the temperature employed
for heating a liquid such as milk.
Figure 2 is a perspective view of the alloy containing tube.
Figure 3 is a sectional elevation of the invention as applied for use as an
indicator of temperature limits as in the case of a fire alarm.

page_text: Figure 4 is a plan of Figure 3, the enclosing casing of the mechanism being
removed.
Like letters indicate like parts throughout the drawings.
The tube A has one end A¹ closed, and at this closed end of the tube is placed
a small quantity B of an alloy metal or other suitable substance, which will fuse
or become viscous or fluid at a given temperature. A rod C is placed in the
tube A in such a manner that one end will be immersed in the alloy B the
latter forming a lock between the tube A and the rod C. Upon the outer end C²
of the rod C is fixed a ratchet wheel, star wheel or equivalent device 1).
A
In applying the invention to an apparatus such as is shown in Figure 1 for
heating fluids such as milk, a saucepan or pot E of ordinary construction is
utilised, this pot having a lid F provided with a handle F and a flange F2 which
just fits within the top of the pot E, this lid being of usual construction.
hole F3 is bored through the handle F1 and the part of the lid F which lies beneath
the handle, the hole being of such a size as to allow the ready passage of the
tube A. Attached to the top of the tube A is a strip of metal G, the ends of
which are turned down as at G', the space between the turned down ends being
approximately equal to the width of the handle F1 of the lid F. If now the alloy
carrying tube A is passed through the hole F³ in the handle F and lid T and
the flanges or turned down ends G of the strip G are placed so as to lie at either
side of the handle F, it will be seen that the tube will be rigidly held in relation
to the lid which in turn will be practically rigidly connected with the pot E
owing to the friction between the flange F and the top of the pot. In this case
a star wheel 1) is mounted upon the upper end C2 of the rod C, this star wheel
being constructed as shown in the drawings of a disc I provided with several
radially projecting fingers De.
In the arrangement shown in Figure 1 the pot E is intended to be heated by
the flame from a gas burner or stove H of some well-known construction, the
burner being provided with a cock H for controlling the supply of
gas thereto.
On the spindle of this cock is rigidly mounted a bell-crank-lever K K', the
arm K of which has pivotally connected to is free end a link L having at its
free end a hook or bent finger L. The other arm K' of the bell-crank-lever is
provided at its free end with a weight M. The parts are so arranged that when
the pot E is on the stand of the burner 1 the hook L' on the end of the link L
can be engaged with one of the fingers 12 of the star wheel D, the weight M
being thus held in a raised position and
the gas
cock H being
open. If now the contents of the pot E reach that temperature at which
the alloy B in the tube A will fuse, the fusion of this alloy will release the rod C,
which the weight M through the lever K K and link L and star wheel D) is
always tending to rotate. The rod C thus released will be rotated when the
hook will slide off and become dis-engaged from the finger D2 of the star
wheel D and the weight M, thus released will fall thereby turning the
lever K K and the cock and shutting off the gas. As the alloy will once more
become solid directly the temperature falls below the limit the star wheel D) will
once more be rigidly connected to the lid of the pot and the apparatus can be
reset by engaging the hook L' with another finger on the star wheel D).
If it is desired that in place of completely shutting off the gas the latter may
be only partially turned off, and thus the supply of heat to the pot E merely
reduced and not entirely stopped, a quadrant plate N may be mounted adjacent
to the cock H and by means of a pin N¹ which can be inserted in holes N2 in
the plate N, the movement of the lever and consequently of the cock H
can be arrested at any desired point. Of course if preferred the quadrant plate N
may be mounted upon the lever KK a stop pin being suitably arranged on the
burner adjacent to the cock and in such a position that it will come in contact
with the pin N¹ on the plate N when the latter is moved.
In the construction illustrated in Figures 3 and 4 the force tending to rotate

page_text: the rotatable member C is that of a coiled spring. The tube A. containing the
Fusible lock B is rigidly attached to a plate provided with a flange or bracket
for enabling it to be attached to a wall or the like. The rod C carries on its
upper end a ratchet wheel D and pivotted either on an extension of the rod C
or on a concentric pin, is a lever P carrying a spring controlled pawl P1 which
engages with the ratchet wheel D. A coiled spring Q is attached at one end
to the plate at some point 02 the other end of the spring being attached to
the lever P at some point such as P. The lever l' is provided with a projecting
pin P for enabling it to be readily moved by the finger. The lever P is entirely
or partially composed of insulating material and can be moved about its pivot
so as to be brought between two electric contacts R and S. The contact R con-
sists of a metal stud in the plate and insulated from this plate, the contact S
consists of a metal spring strip the end of which lies over the contact arm.
contacts Rand S may be connected up in any electrical circuit, for example an
electric bell circuit, but the circuit might well include mechanism for performing
some operation such as turning on water sprays or the like..
The
In its normal position when set the lever P is rotated until it lies between the
contacts R and S, the lever being retained in this position by the pawl P¹ which
engages with the ratchet wheel D, which is in turn together with the rod C held
rigidly by the fusible lock B. If now the temperature limit is reached, the
alloy B will fuse and the rod C, ratchet wheel D) and lever P will all be rotated
by the spring Q, the removal of the insulating lever P from between the con-
tacts R and S completing the electrical circuit and ringing the alarm bell or
performing some other operation in accordance with the arrangement of the
circuit. As soon, however, as the temperature falls below the limit the apparatus
can be reset by merely moving the lever P about its pivot until it again lies
between the contacts R and S, the pawl P¹ passing smoothly over the teeth of
the ratchet wheel 1); the apparatus will now be once more held in readiness for
operation owing-to-the-lock B having again become solid-
It is to be understood that this invention is applicable to many and various
purposes, the applications above described and illustrated in the accompanying
drawings being merely by way of example. The above described mechanisms
may obviously be modified and adapted to meet various requirements, thus in
the case of the application of the invention for use in cooking the lever con-
trolling the gas supply or other source of heat may be spring controlled instead
of being weighted or the pot may be carried upon a holder on the end of a rota-
table spring controlled or weighted arm which will be free to turn as soon as
the alloy is fused. Again, in the case of the fire alarm the electrical-contact-
controlling lever may be operated by a weight instead of by a spring.
Having now particularly described and ascertained the nature of our said in-
vention, and in what manner the same is to be performed, we declare that what
claim is:
-
1. In an apparatus for controlling or indicating temperature limits the com-
bination with a fusible lock of a device such as a ratchet and pawl whereby the
apparatus can be re-set without necessitating renewal or refusion of the fusible
lock.
2. An apparatus of the kind described in which the controlling or indicating
portion can be reset without returning the locking part to the point from which
it started.
3. In an apparatus for controlling or indicating temperature limits the com-
bination with a receptacle containing a fusible substance, of a rod within this
receptacle partially immersed in the fusible substance and a device such as a
ratchet wheel carried upon the rod substantially as and for the purpose described
or illustrated in Figure 2 of the accompanying drawings.
4. The complete apparatus for controlling the supply of gas to a gas burner

page_text: substantially as described or illustrated in Figures 1 and 2 of the accompanying
drawings.
5. The complete fire alarm substantially as described or illustrated in Figures 3
and 4 of the accompanying drawings.
BOULT & WADE,
Agents for the Applicants.