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Патент USA US2119894

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June 7, 1938,
Original Filed Nov. 6, 1934
' 24
£7 43
" v20
Patented June 7, 1938
August A. Strand, Malden, Mass.
Application November 6, 1934, Serial No. 751,713
Renewed November 5, 1937
1 Claim. (Cl. 158-28)
The invention relates to‘ heat controlling de
’ vices, and more particularly to special safety de
vices of the type used with oil burning heating
furnaces and generally known as primary con
‘The objects of the invention include the provi
sion of a relatively inexpensive, dependable, high
ly e?icient and sensitive device of the type above
Various further and more speci?c objects, fea
tures and advantages will clearly appear from
the detailed description given below, taken in
connection with the accompanying drawing which
forms a part of this speci?cation and illustrates,
15 merely by way of example, embodiments of the
In the drawing:
Fig. 1 is a section taken through the control;
Fig. 2 is a section taken on the line 2—2 of
Fig. 1;
Fig. 3 is a section on the line 3—3 of Fig. 1;
Fig. 4 is a wiring diagram illustrating dia
grammatically the relation of the pyrostat, the
thermostat and the oil burning equipment.
In the following description and in the claim,
various details will be identi?ed by speci?c names
for convenience, but they are intended to be as
generic in their application as the art will permit.
Like reference characters denote like parts in
the several ?gures of the drawing.
In the drawing accompanying and forming
part of this speci?cation, certain speci?c disclo
sure of the invention is made for the purposes of
to U! explanation, but it will be understood that the
details may be modified in various respects with
out departure from the broad aspect of the in
Referring now to the drawing, and more par
40 ticularly to Figs. 1 and 2, the regulating equip
ment, or control device, is installed for the most
part in a box denoted in general by III. The box
comprises a metal body II and a pair of remov
able metal covers I2 and I3. Installed within
45 the box is an insulating panel I4 on which is
mounted the safety timing device I5, which de
termines the permissible time in which the oil
burner must start, the clutch and switch indi
cated by I‘! controlled by stack coil I6, auxiliary
50 ignition switch I00 controlled by stack coil I6,
and starting relay I8. In general, the switches
and relays are mounted on one side of the panel
I4 with the connections and binding posts on the
other side of the panel.
For mounting the box III, a hole is cut in the
?ue adjacent the oil burning furnace and the
box I0 is mounted in a manner illustrated par
ticularly in Fig. 1. The box may be mounted
either on a vertical or horizontal portion of the
?ue. In the form indicated, the box is mounted
on a horizontal portion of the ?ue, indicated by
20. If the flue 20 were vertical, it would merely
be necessary to turn the box I0, 90°, as will be
understood by those skilled in the art.
The hole in the stack ?ue 20 is indicated by ~ .,.
2I and a plate 22 provided with hooks 23 is ?tted
to the curvature of the stack 20. A two-part
strap 24 having hooks which engage the hooks
23 and having a pair of ears through which a
tightening bolt (not shown) passes, ?rmly clamps
the box to the flue. It Will be understood that
the plate 22 is curved to ?t the particular curva
ture of the ?ue and the strap 24 is cut to ?t
the circumference of the ?ue.
A hollow sleeve 21 passes through the plate 22
and has a large nut 29 and a small nut 28 ?rmly
clamped against the plate 22. Lock nut 30 is
provided to insure locking of the assembly. The
sleeve 21 projects from the plate 22 and passes
through a hole in the wall of the box body I I and
has a pair of nuts 3I for clamping the box body
to the sleeve.
Passing through the sleeve 21 and free to rotate
therein is a rod 32 having a toothed wheel 33
and a cam I III of insulating material secured
thereto, as indicated in Fig. 1. Rod 32 also has
a pin 34' engaging the end of sleeve 21 for hold
ing the rod 32 in axial position.
The stack coil I6 is made of suitable bi-metallic
material, as is Well known in the art, and one
end is secured to nut 29 by screw I29 and the
other end is secured to the rod 32 by another
screw, as will be understood by those skilled in
the art. Thus, the raising and lowering of the
temperature in the stack winds and unwinds the
stack coil, causing rotation of the control rod 32.
Referring now to the stack switch and clutch
II, the toothed wheel 33 cooperates with a yield
able strap 35 mounted on an insulating bar 36.
The strap 35 has a ?nger I35 which engages in 45
the notches of the notched wheel 33 so that ro
tation of the wheel operates the switch con
tacts 39.
The stack switch comprises a switch frame 31
suitably bolted to the insulating panel I4 and
having opposed ears 90 and 9 I, each of which has
small recesses.
Seated in these recesses are
switch elements 38 and 40 connected by coil
spring 4| which furnishes the toggle action and
also holds the switch elements in their depressed 55
seats. The switch element 49 is H-shaped, as
indicated in Fig. 1, and carries the insulating
block 35. The switch element 38 is U-shaped
and carries the spring contacts 39 engageable
with stationary contacts 92 and 93.
Thus, when the stack begins to cool, a small
rotation of the toothed wheel 33 in the direction
of the arrow operates to throw the toggle switch,
causing the contacts 39 to close with a snap
ii) action. For example, assuming the full operating
temperature of the stack to be about 700° F.,
contacts 39 will close at, say, 550° F. Further
rotation of the toothed wheel 33, caused by fur
ther cooling of the stack, merely causes the spring
15 ?nger M5 to yield and engage succeeding teeth
of the toothed wheel. When the stack begins to
heat up, a small rotation of the toothed wheel 33
in the opposite direction will then cause the con
tacts 39 to open with a snap action. Further ro
tation of the toothed wheel 33, caused by fur
ther heating of the stack, merely causes the
spring ?nger £35 to yield and slide over the toothed
wheel as during cooling of the stack.
Referring to the auxiliary ignition switch iilil,
25 this switch is for the purpose of keeping the igni
tion in operation until the ?re is hot enough to
maintain itself without going out.
The auxiliary ignition switch comprises a collar
liiii secured to the rod 32 by an appropriate set
screw. Located adjacent the collar iil? is an in
sulating member Iii! loosely mounted on rod 32.
Insulating member l?i is provided with a flange
iii’! having a notch H35 in which is disposed loosely
pin H24 attached to collar N95 for a purpose
35 hereinafter described more in detail.
The insulating member lili is provided with a
raised cam portion I08 having gradually sloping
ends on which rides a spring contact member ia'iii
which cooperates with a ?xed contact I63 also
secured to the insulating base Hi. The insulating
member iili is maintained in axial position by
the collar E95 on the one hand, and the spring
contact member E82 bearing against the annular
?ange ID‘! on the other hand.
The construction of the auxiliary ignition switch
is such as to give a quick break between contacts
H22, H33. These contacts are closed whenever
the temperature of the stack is substantially be
low full operating temperature. For example, as
60 suming the full operating temperature of the
stack to be about ‘700° F., contacts H32, “)3 close
at, say, about 550° F. and remain closed at all tem
peratures below this point.
Heating of the stack causes rod 32 to rotate in
a direction indicated by the arrow in Fig. 3. As
full stack temperature is approached, say, at
550° F. in the example given above, the rod 32
has driven the insulating member 10! so that
the rounded projection on leaf spring N32 is just
60 about to ride off of cam surface N18.
The cam
surface ma having a sloping end, the contact
Hi2 will ride oif of cam surface Hi8 quickly caus
ing a quick break between contacts I02, I03.
This quick break action is caused by the loose
65 ?t of pin H14 in notch “15 which permits the in~
sulating member lill to ride freely on shaft 32
in the direction of the arrow in Fig. 3 under the
action of the spring contact I02 operating on the
end of cam surface E06.
When the stack is cooling and the insulating
member I!!! is rotating in a direction opposite
to the arrow in Fig. 3, the gradually sloping end
of cam surface I 08 permits spring contact N32
to ride up this surface closing contacts I02, I93.
Referring now to the safety timing device I5,
this device is for the purpose of giving the oil
burner a given time in which to start the ?re.
If the fire does not start, say, Within 90 seconds,
the safety device turns off the oil burner and its
starting apparatus.
The safety timing device 15 comprises, in gen
eral, an asbestos insulating mandrel 45 mounted
in a pair of square asbestos blocks 46 and having
a coil of resistance wire 47 wound thereon. A
bi-rnetallic strip 48 is anchored to a ?xture 148
?xedly secured to the insulating base 14 and car
ries a piece of insulation 49. The heating coil
4'! and bi-metallic strip 48 is enclosed in a box
like housing H5 screwed to the insulating base
and through which projects the insulating 15
piece 49.
The operation. of the safety timing device [5
opens the contacts 53, 59 and closes the contacts
54, 60. The former removes power from the oil
burning equipment and ignition and the latter
operates a buzzer 1'! located at a convenient place
to call attention to the fact that the oil burner
did not start.
The spring contact 53 is anchored at one end by
bracket ISO to the insulating base M and nor— 25
mally tends to take a position with the contacts
53, 59 open.
Upward movement of the spring contact 53 en
gages an insulating plate {5! which causes leaf
spring 54.- to engage contact 60 to ring the buzzer. 30
Spring member 53 is held down, however, by a
latch 52 pivoted at I52 and locked by trigger 5i
pivoted at “it. A rod 5'! passes through trigger
5! and through insulating piece 49 and a coil
spring 58 surrounds rod 51.
For manually starting the oil burner after the
oil burner has failed to start and the timing de~
vice has been operated, a push-button 55 is pro
vided. The push-button passes through the wall
of the box body H and engages a leaf spring I55 40
carrying an insulating ?nger 5B which engages the
catch 52 to reset the pyrostat.
Thus, when electric energy is applied to the
heating coil 41, the bi-metallic strip 48 is heated
and moves slowly upwardly. At the end of the
permissible period, say, 90 seconds, it has moved
upwardly suf?ciently to lift the trigger 5!, re
leasing catch 52 and causing the spring contact 53
to break with contact 59 and causing engagement
of contacts 54 and 6B.
The attendant hearing the buzzer knows that
the oil burner failed to start. He then pushes
the push-button 55 which causes insulating plate
50 to engage the cam surface 55!? of the catch 52,
causing the latter to seat within the angle seat ,
E53 of the trigger 5i. Setting of catch 52 causes
contacts 53, 59 to make and contacts 54, 6!! to
Referring now to the starting relay I8, this
relay comprises a coil 65 wound on an insulating 60
sleeve 55 which is secured to a brass supporting
angle 80 secured to the insulating base l4.
Within the insulating sleeve 66 is an iron bushing
Hit. The armature of the relay comprises a rod
61 having a magnetic armature piece 68 which
has a brass guide strap ‘H secured thereto which
is adapted to slide along the surface of insulating
base !4 to keep the relay armature in proper
At the top of the armature rod 6'! is an insulat~
ing piece 59 which supports a spring strap 10
engaging contacts '52. When current passes
throughwinding 65, the iron armature 68 moves
upwardly, closing contacts Hi and 12.
Referring now to Fig. 4, which discloses the 75
wiring diagram, similar reference characters are
used as ‘far as possible to indicate corresponding
parts. The thermostat, which may be of the low
voltage type, 'is mounted in a part of the building
it is desired to keep at constant ‘temperature and
is connected in circuit with a step-down‘trans
former ‘I8, a relay ‘I6 and a “safetystat” ‘I5.
The safetystat may be mounted on the furnace
opening the stack contacts 39, thereby removing
voltage from the safety timing device I5.
If the
stack was cold at the time the ?re starts, the
contacts 39 will open at, say, 200° F.
As the temperature of the stack rises still fur
ther, ‘continued rotation of the rod 32 in direc
and may be an aquastat in the case of a hot
tion ‘of the arrow in Fig. 3 causes the cam sur
water heating system, a pressurestat in the case of
a ‘steam heating system or another thermostat in
the case of a hot air heating system. The safety
stat is normally closed and plays no part in the
face I96 to ride off spring contact I92, causing a
ordinary operation of the temperature control but
15 only operates under abnormal conditions, as will
be understood by those skilled in the art.
The buzzer ‘IT, or other alarm, is located in a
convenient part of the building and may operate
on the full 110 volt alternating current. If a
20 low voltage buzzer is desired, obviously, a step—
down transformer similar to transformer 19 may
be ‘interposed between the buzzer TI and the
A. C. line.
In the form shown, the oil burning equipment
25 may include a motor, an oil valve and an ignition
device, as indicated. The particular construc
tion of this equipment forms no part of the pres
ent invention and will vary with the different
types of oil burning systems.
For example, the
30 motor may operate an air fan for supplying air for
combustion. In some cases, no oil valve is re
quired, but when one is provided, it is automati
cally opened at the same time the motor is
started. The ignition device Will supply a hot
35 spark for igniting the combustible mixture of oil
and air.
It will be understood that any type of thermo
stat may be used with this control equipment.
The thermostat shown is a low voltage thermo
40 stat operable on, say, 14 volts. The present pyro
stat may also operate with a 110 volt thermostat
of the type disclosed in copending application
Serial No. 569,916, ?led October 20, 1931. The
manner of substituting the 110 volt thermostat at
the points A, B and C is explained in copending
application Serial No. 716,058, ?led March 1'7,
1934, Heat controlling device.
Referring to Fig. 4, assume the oil burner is
out and the temperature of the room in which the
thermostat is located is above the temperature at
which the thermostat contacts will close. The
following will then be the condition of the con
55 trol device. The stack contacts 39 are closed,
the safety contacts 59 are closed, starting relay
contacts 12 are open, the main thermostat con
tacts are open, the contacts of relay 15 are open.
and the contacts of safetystat 15 are closed.
the stack causes the stack coil I6 to turn the rod
32 in the opposite direction to the arrow in Fig. 2,
auxiliary ignition contacts I92, I93 will be closed
since at this time the stack temperature will be
considerably below the ignition cut-off tempera
ture (of 550° F., for example).
When the temperature of the room drops to the
set temperature, main thermostat contacts close,
applying energy to the relay 16, closing its con
tacts, and applying energy to the safety heating
coil 41, the ignition, the starting relay I8 and
the motor and oil valve.
The starting relay I9
operates, closing contacts 12 which applies volt
age to the motor, oil valve and ignition independ
ently of contacts 39. The solenoid 65 of the start
ing relay I8 also is maintained energized inde
pendently of the contacts 39. If the ?re starts
75 up before the safety device I5 operates, the heat in
quick break between contacts I92, I93.
The oil burner continues to burn until the tem
perature of the room goes above set temperature
when the thermostat contacts open, causing con
tacts of relay ‘I6 to open, removing energy from 15
the motor and oil valve and unlocking the start
ing relay I8, opening contacts 12. The oil burner
goes out and, as soon as the stack cools only a
small amount, the rotation of the rod 32 in the
direction of the arrow in Fig. 2 closes the stack 20
contacts 39. Auxiliary ignition contacts I92, I93
will also close as soon as the stack temperature
falls below the predetermined value at which cam
IN is set to operate them. This may be at about
the same time as contacts 39 close or it may be 25
somewhat before or after they close.
The closing of the stack contacts 39, as well
as the auxiliary ignition contacts, by a small tem
perature drop in the flue places the apparatus
almost immediately in readiness to start the oil 80
burner should the temperature of the room drop
below the set temperature, and it is not necessary
to wait until the stack cools down to place the
apparatus in readiness to start.
If for any reason the oil burner does not start 35
up within the time limit of the safety timing de
vice I5, say, within 90 seconds, the upward move
ment of the bi-metallic strip 49 raises trigger 5I,
releasing catch 52 and permitting the spring con
tact 53 to break with contact 59, removing volt- =
age from ‘the motor, oil valve, ignition and safety
timing device I5. The upward movement of
spring contact 53 closes contacts 54 and 69, caus
ing the buzzer 11 to ring, calling attention to the
fact that the oil burner did not start.
The attendant upon hearing the buzzer presses
the push-button 55 which closes contacts 53 and
59, opening the buzzer contacts 69 and 54.
Closing of the main contacts 59 and 53 applies
voltage to the motor, oil valve and ignition as 59
well as to the safety timing device I4. If the ?re
does not start within, say, 90 seconds, the safety
timing device I4 will again operate, opening con
tacts 53, 59 and closing contacts 54, 69 to again
call attention to the fact that the oil burner failed 55
to start.
If the electric power should fail when the tem
perature of the room is above the set tempera
ture. nothing will happen since there is no power
on the control system. If the electric power 60
should fail when the temperature of the room is
below the set temperature and the thermostat is
calling for heat, the contacts of relay 16 open,
contacts of the starting relay I8 open, and the
power is removed from the motor and oil valve 65
causing the ?re to go out.
As soon as the electric power goes on, contacts
of relay ‘I6 close and the system again starts up
in the regular way, providing the stack contacts
39 and ignition contacts I92, I93 are closed. If
the electric power had not been oif for suf?cient
time to cause the stack to cool off and thereby
close the stack contacts 39 and ignition contacts
I92, I93, the oil burner will not start up until
the stack does cool off the slight amount neces 75
sary to close contacts 39 and also the amount
necessary to close contacts I02, I03.
It should be noted that the stack contacts 39
open directly as soon as the ?re starts and then
close directly as soon as the ?re stops and the
stack temperature drops a small amount. Igni
tion contacts 902, I83, however, remain closed for
a considerable time after the ?re has started in
order to insure starting. When the ?re stops,
10 they close at about the same time as contacts 32.
if for any reason the ?re should go out for a short
interval, either because the electric power fails or
because the house is over-heated for a short pe
riod from some other source, such as from a
kitchen oven, the system does not have to wait
until the stack gets cold for the ?re to start.
In case of flame failure, due to water in the oil
(with motor going and the oil valve open) a small
drop in temperature in the stack closes the stack
20 contacts 39 and ignition contacts I02, I03, turn~
ing on the ignition and putting power on the safe
ty timing device it‘). If the ?re does not start
within the time limit of the safety device I5, the
safety contacts 53, 59 open and the ignition is
25 turned off, the motor stops, the oil valve closes,
starting relay !8 releases and the buzzer TI rings.
Whenever the ?re does not start (or restart in
case of temporary failure of flame due to any
cause) after the time set when the ignition is
30 turned on, the safety device I5 operates to shut
down the oil burning system and to ring the
buzzer. The attendant must press the push-but
which resets the safety timing device I 5
and the system restarts in the regular way, as
35 above described. If the oil burner refuses to start
after a number of repeated attempts by pushing
push-button 55 something is wrong and repairs
must be made to the system.
Thus, a control system has been described
which is relatively simple, is made of inexpensive
40 parts and is very easy to assemble. The system
takes care of failure of the ?re to start within a
predetermined period. It takes care of failure of
the electric power. As soon as the ?re goes out,
the stack only has to cool a relatively small de
45 gree to place the system in condition for restart
ing when the thermostat calls for heat.
The system also provides for prolonged opera
tion of the ignition to insure complete starting
of the oil burner and eliminating the necessity
50 for “recycling”. The auxiliary ignition contacts
are especially useful in certain cases, as for ex
ample, on some types of rotary burners because
in some cases, without the auxiliary ignition con
tacts, the ?re will start up sufficiently to operate
the stack switch I‘! cutting off ignition and then
go out because suf?cient heat has not been de
veloped within the walls of the ?re box to main
tain the proper combustion.
Both the main control of the ignition and the
60 auxiliary ignition control are necessary because
the auxiliary switch holds on the ignition until
the ?re is really established, while the main con
trol switch I? opens the circuit to the safety
mechanism I5 to prevent its operating if the ?re
actually starts, although full temperature is not
obtained until some time subsequent. It will be
noted that the main or stack contacts 39 operate
with any predetermined change in stack temper
ature, while the auxiliary contacts I02, I03
operate at a ?xed temperature.
It will be understood that the alarm illustrated
by the buzzer 'Il may be any kind of an audible
or visible alarm. Furthermore, it will be under
stood that the control device may be mounted
in any part of the furnace where it will be sub
ject to the heat of the ?ame, as for example, in
the ?re door as well as in the ?ue, as illustrated.
Furthermore, it will be understood that the safe
tystat ‘i5 may be located in the 110 volt side, for
example between the point C and the relay ‘I6 20
on the low voltage thermostat control, if desired.
This application is a continuation in part of
application Serial No. 716,058, ?led March 17,
1934, Heat controlling device.
While certain novel features of the invention
have been disclosed and are pointed out in the
annexed claim, it will be understood that various
omissions, substitutions and changes may be
made by those skilled in the art without depart
ing from the spirit of the invention.
What is claimed is:
In a system for controlling oil burners or the
like having a control switch; a starting relay
comprising a solenoid and a pair of starting con
tacts; a stack switch having a ?rst pair of con
tacts and a bridging member, and auxiliary con
tacts; a safety heating device including a heat
ing coil and a switch controlled thereby; a fuel—
feeding device; and an ignition device; a main
circuit comprising said control switch, said safety
switch and a network therebetween all serially
connected across the power line, said network
comprising a ?rst circuit including said starting
contacts and said fuel-feeding device serially
connected between said control switch and said 45
safety switch, a second circuit including the ?rst
contacts of the stack switch and the safety heat
ing coil serially connected between said control
switch and said safety switch, athird circuit in
cluding the bridging member of the stack switch,
the auxiliary contacts of the stack switch and
the ignition device serially connected, the igni
tion device being disposed next to said safety
switch, said solenoid being connected to the
bridging member of said stack switch and to said 55
safety switch, and an interconnection between
said bridging member and a point in said ?rst
circuit between the starting contacts and said
fuel-feeding device.
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