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

page_text: Date of Application, 12th June, 1899
Complete Specification Left, 12th Mar., 1900-Accepted, 28th Apr., 1900
Improvements in or relating to Mechanism for Controlling and
Indicating Temperature.
We, ERNEST HOWARD GRIFFITHS, F.R.S., of 12, Park Side, Cambridge, in the
County of Cambridge, Fellow of Sydney College, Cambridge, HORACE DARWIN,
of The Orchard, Huntingdon Road, Cambridge, Scientific Instrument Manufac-
turer, and WILLIAM CECIL DAMPIER WHETHAM, of 5, St. Peter's Terrace, Cam-
bridge, in the County of Cambridge, Fellow of Trinity College, ('ambridge, do
hereby declare the nature of this invention to be as follows:
This invention relates to mechanism for controlling and indicating tempera-
ture and has for its object to construct an apparatus which upon a temperature
limit being reached will cut off or control a supply of heat, sound an alarm or
1erform some other operation, but as soon as the temperature falls again below
The limit the apparatus will automatically re-set itself so as to be ready to repeat
its controlling or indicating operation should the temperature limit be again
reached.
According to this invention a spring or other force is held inactive by means
of an alloy, metal, or other substance until a temperature has been reached,
which will bring about the melting of this substance. The latter when in its
solid state forms a connection between two members, one of which holds the
force inactive while the other is of the nature of a ratchet or similar mechanism.
Mechanism driven by clockwork or otherwise is combined with the above appa-
ratus and so constructed that at stated intervals a movement is made which tends
to return the controlling and indicating mechanism to its set or primary posi-
tion, if this mechanism has become operative owing to the temperature limit
having been reached.
With the above mechanism it will be seen that it is possible to maintain a
constant or approximately constant temperature, as in the event of the tempera-
ture exceeding the desired limit, the mechanism which for example may be
arranged to control the supply of heat, comes into operation and cuts off this
supply of heat until the temperature falls below the desired limit. When this
occurs the automatic re-setting mechanism operates to once more turn on the
supply of heat and re-set the whole apparatus, so that it can again come into
opeiation if the temperature limit is again reached or exceeded.
It is obvious that this mechanism is capable of very wide adaptation, and that
the details of construction may be varied to suit requirements. Thus, for
example, the controlling mechanism may be so arranged that it will control the
supply of gas to a burner, when on a temperature limit being reached the
alloy will be fused and the gas will be turned off or down, in the former case
the apparatus being preferably so arranged that a pilot burner will be left alight.
As soon however as the temperature falls below that at which the alloy will
remain fused, the apparatus" will, by means of the clockwork mechanism, be
re-set and at the same time the gas will be turned on again to the burner.
As an example of how the apparatus may be modified it may be mentioned

page_text: that in place of the spring being held inactive by the alloy a body may be
held up against the force of gravity by this alloy, the clockwork mechanism
raising this body against gravity for the purpose of re-setting the apparatus.
The clockwork or other automatic re-setting mechanism may comprise a spring-
controlled lever carrying a pawl which engages with the ratchet member of the
controlling device, a spindle carrying a cam, and rotated intermittently or con-
tinuously by the clockwork operating to move the lever against the spring, this
reciprocation of the lever tending to rotate the ratchet and re-set the device in
the event of its having become operative. The alloy may be carried in a tube
with rods or connections from the two members of the controlling device inserted
into it, the tube being so arranged that it may be inserted through the lid of a
saucepan or otherwise arranged. The whole device comprising the controlling
and indicating mechanism and the clockwork re-setting mechanism may be
arranged upon the end of the tube in some convenient manner so that the whole
apparatus may readily be transported. The mechanism may be so arranged
that in addition to controlling the temperature an alarm may be sounded either
by electricity or otherwise. The apparatus may be combined with separate
mechanism eperated by electricity or clockwork or otherwise, this mechanism
serving to control the supply of heat or perform other operations, the control-
ling mechanism being connected to the operating mechanism by electrical or
other connections.
Hal 1 1011.
上 L1000
E. H. GRIFFITHS.
HORACE DARWIN
W. C. D. WHETHAM.
Boult & Wade,
Agents for the Applicants.
Improvements in or relating to Mechanism for Controlling and
Indicating Temperature.
We, ERNEST HOWARD GRIFFITHS, F.R.S., of 12, Park Side, Cambridge, in the
County of Cambridge, Fellow of Sydney College, Cambridge, HORACE DARWIN,
of The Orchard, Huntingdon Road, Cambridge, in the County of Cambridge,
Scientific Instrument Manufacturer, and WILLIAM CECIL DAMPIER WHETHAM,
of 5, St. Peter's Terrace, Cambridge, in the County of Cambridge, 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 and has for its object to construct an apparatus which upon a temperature
limit being reached will cut off or control a supply of heat, sound an alarm or
perform some other operation, but as soon as the temperature falls again below
the limit the apparatus will automatically re-set itself so as to be ready to repeat
its controlling or indicating operation should the temperature limit be again
reached.
According to this invention a spring or other force is held inactive by means
of an alloy, metal, or other substance until a temperature has been reached,
which will bring about the melting of this substance. The latter when in its
solid state forms a connection between two members, one of which holds the
force inactive while the other is of the nature of a ratchet or similar mechanism.
Mechanism driven by clockwork or otherwise is combined with the above appa-

page_text: ratus and so constructed that at stated intervals a movement is made which tends
to return the controlling and indicating mechansm to its set or primary posi-
tion, if this mechanism has become operative owing to the temperature limit
having been reached.
With the above mechanism it will be seen that it is possible to maintain a
constant or approximately constant temperature, as in the event of the tempera-
ture exceeding the desired limit, the mechanism which for example may be
arranged to control the supply of heat, comes into operation and cuts off this
supply of heat until the temperature falls below the desired limit. When this
occurs the automatic re-setting mechanism operates to once more turn on the
supply of heat and re-set the whole apparatus, so that it can again come into
operation if the temperature limit is again reached or exceeded.
It is obvious that this mechanism is capable of very wide adaptation, and that
the details of construction may be varied to suit requirements. Thus, for
example, the controlling mechanism may be so arranged that it will control the
supply of gas to a burner, when on a temperature limit being reached the
alloy will be fused and the gas will be turned off or down, in the former case
the apparatus being preferably so arranged that a pilot burner will be left alight.
As soon however as the temperature falls below that at which the alloy will
remain fused, the apparatus, will, by means of the clockwork mechanism, be
re-set and at the same time the gas will be turned on again to the burner.
As an example of how the apparatus may be modified it may be mentioned
that in place of the spring being held inactive by the alloy a body may be
held up against the force of gravity by this alloy, the clockwork mechanism
raising this body against gravity for the purpose of re-setting the apparatus.
The clockwork or other automatic re-setting mechanism may comprise a spring-
controlled lever carrying a pawl which engages with the ratchet member of the
controlling device, a spindle carrying a cam, and rotated intermittently or con-
tinuously by the clockwork operating to move the lever against the spring, this
reciprocation of the lever tending to rotate the ratchet and re-set the device in
the event of ifs having become operative. The alloy may be carried in a tube
with rods or connections from the two members of the controlling device inserted
into it, the tube being so arranged that it may be inserted through the lid of a
saucepan or otherwise arranged. The whole device comprising the controlling
and indicating mechanism and the clockwork re-setting mechanism may be
arranged upon the end of the tube in some convenient manner so that the whole
apparatus may readily be transported. The mechanism may be so arranged
that in addition to controlling the temperature an alarm may be sounded either
by electricity or otherwise. The apparatus may be combined with separate
mechanism operated by electricity or clockwork or otherwise, this mechanism
serving to control the supply of heat or perform other operations, the control-
ling mechanism being connected to the operating mechanism by electrical or
other connections.
In the accompanying drawings:
Figure is a plan of an apparatus constructed in accordance with this inven-
tion to make an electric contact as soon as the temperature of a heated body
exceeds a predetermined limit, this figure showing the parts in their normal
position while the temperature of the body remains within the limit.
Figure 2 is a plan of the apparatus showing the position assumed by the
parts when the temperature limit has been exceeded and the electric contact
made.
Figure 3 is an elevation of the apparatus looking in the direction of the
arrow 3 indicated in Figure 1.
Figure 4 is a sectional elvation of the apparatus on the line i 4 of Figure 1.
Figure 5 is a section on the line 5 5 of Figure 1.
Like letters indicate like parts throughout the drawings.
A tube A with ene end closed has attached to its open end a ratchet wheel B.

page_text: In the end of the tube A is placed a certain quantity of fusible alloy, metal, or
other substance (. Lying within the tube A and with its extremity immersed
in the fusible substance (is a rod D, on whose outer end is mounted a disc E,
which bears against the face of the ratchet wheel B. The tube A passes through
a plate F to which is preferably attached a tube G which encloses and serves as
a casing for the tube A. The tube A and ratchet wheel B can be rotated within
the tube G carrying with it the rod 1 which is connected to the tube A by the
fusible substance (, which forms a lock. The fusible lock (is of such a nature
that should a predetermined temperature be exceeded this lock will be fused
and the rod 1) thereby released, so that it can be rotated within the tube A inde-
pendently of the latter.
Between the inner face of the ratchet wheel B and the plate F is disposed a
lever H which is pivotted on the hub B¹ of the wheel B. The lever H carries
a spring-controlled pawl J, which engages with the teeth of the ratchet wheel B,
and the lever H is moreover itself controlled by a spring K which tends to
move the lever H and, by reason of the engagement of the pawl J with the
wheel B, causes the rotation of the latter. The lever H carries a projection H¹
and a suitably shaped rotating cam L upon a shaft L' is so situated in relation
to the projection H¹ on the lever H that as the cam rotates the lever H will be
oscillated, the return movement of the lever being effected by the spring K.
This oscillation of the lever H tends through the engagement of the pawl I
with the ratchet wheel B to bring about the rotation of the latter.
Projecting from the dise E on the end of the rod D is a lever E¹, of which
the extremity E2 is formed as a spring contact piece adapted to rest either on a
stud M on the face of the plate or rest upon a contact stud N which passes
through a hole in the plate F, and is insulated from the latter by insulating
pieces N. Stops 001 limit the movement of the lever E¹. A spring attached
at one end to the lever E and at the other end to a projection on the plate F
exerts a pull on the lever E', this pull tending to rotate the rod D in the oppo-
site direction to which the spring K through the lever H tends to rotate the
ratchet wheel B and tube A. The spring P is weaker than the spring K so
that the latter can overcome the opposing pull of the spring P. A strap Q
which lies across the outer end of the rod D) and is attached at Q to the plate F
prevents the rod 1) from moving axially. In a suitable position upon the plate 1
is a spring controlled pawl R which engages with the ratchet wheel B.
The apparatus operates as follows:
The cam L is constantly rotated at a fixed rate by means of clockwork or other
mechanism, not shown in the drawings, connected to the shaft which is shown
hollow. The cam L at each rotation causes a slight movement of the lever H which
though undergoing a steady pull from the spring K is unable to oscillate beyond
a very limited extent. This is due to the engagement of the pawl J with the ratchet
wheel B, the latter being rigidly connected by the fusible lock (' with the rod D)
and the lever E' on the end of the latter, lying against the stop 0. Figure 1
shows the parts in this position. If now the predetermined temperature limit
is exceeded the lock (' is fused and consequently the connection between the
od 1) and the tube A is severed, with a result that owing to the pull exerted
by the spring P the rod D is rotated and the lever E moved so that contact is
made with the stud N, and an alarm sounded. The range of movement of the
lever E in this construction is limited by the stop 01. The parts now assume
the position shown in Figure 2. While this is happening the cam L still con-
tinues to rotate and the wheel B being now, owing to the fusion of the lock C',
unrestricted is rotated step by step at each oscillation of the lever H. In con-
sequence of the alarm having been sounded, or as a result of some other function
having been performed by electricity, the temperature of the body heated is
reduced. When this temperature falls below the predetermined limit the locking
metal (once more solidifies with the result that the rod 1) and lever E are
caused to move with the wheel B and tube A, the step by step 1otation of which

page_text: steadily continues. The movement of the wheel B is checked as soon as the
lever comes against the stop when the parts once more come to rest in
their normal position, as shown in Figure 1. The apparatus being thus auto-
matically re-set is ready to operate as soon as the temperature again exceeds the
predetermined limit.
The electric connections are made at S to the stud N and to the lever E', or
to some other suitable part of the mechanism, or if desired to the plate F
itself, which is in metallic contact with the lever E. Though the mechanism
has been above described as arranged for completing an electrical circuit it is
obvious that it may be arranged in many other ways so as to cause other func-
tions to be performed, such as controlling a supply of heat by turning a gas
cock.
Having now particularly 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:-
-
1. An automatically-resetting fusible-lock apparatus for controlling or indi-
cating temperature limits.
2. The combination with a fusible-lock apparatus of automatic resetting
mechanism for the purpose described.
3. A fusible-lock device, which, consequent on a variation in temperature
beyond predetermined limits, sounds an alarm or performs some function and
subsequently automatically resets itself when the temperature has returned
within the limits.
4. In an apparatus for controlling or indicating temperature limits the com.
bination with a fusible lock, of an automatically-operating device whereby the
apparatus resets itself without necessitating renewal or refusion of the fusible
lock.
5. In an apparatus for controlling or indicating temperature limits, the com-
bination with two movable members such as A and D having a fusible lock
between them, of mechanism tending to move one member independently of the
other as soon as the lock has been fused and mechanism which automatically
operates to move the second member and thereby cause the first member to be
returned to its position of rest as soon as the lock has solidified substantially as
described.
6. In an apparatus for controlling or indicating temperature limits the com-
bination with a fusible-lock device such as A CD of springs or other forces
tending to cause independent movement of the members of the fusible-lock
device and a rotating cam which in conjunction with ratchet and pawl mechanism
tends to impart a continual step by step rotary motion to one or both of the
members of the fusible-lock device according to whether the lock Citself is in
the fused or unfused state substantially as described.
7. The complete apparatus for controlling or indicating temperature limits
substantially as described or illustrated in the accompanying drawings.
1011 Ja
1000
BOULT, WADE & KILBURN,
Agents for the Applicants.