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Патент USA US2111431

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March 15, 1938.
w. o. LUM
2,111,431
CONTROL MECHANISM
Filed March 31, 1934
Inventor‘:
20
26
1/5
Wa Pier‘ 0. Lum
b9 M7
8. 2M
His Attorney.
Patented Mar. 15, 1938
2,111,431
UNITED STATES
PATENT OFFICE
2,111,431
oomor. MECHANISM
Walter 0. Lum, Schenectady, N. Y., assignor to
General Electric Company, a corporation of
New York “
Application March 31, 1934, Serial No. 718,395
8Claims. (Ul. 158-—42.1)
My present invention relates to control mecha
nisms, particularly safety circuit control switches
and to furnace control systems embodying safety
circuit control switches. One of the objects is
5 to provide an improved mechanism for trans
mitting motion whereby a safety control switch
may be operated from one ~control position to
another in response either to a single reciproca
tion of a given amplitude of a reciprocating mo
.10 tion transmitting element or to a series of re
ciprocationsof lesser amplitude of the element.
Another object is to embody such a safety con
trol switch mechanism in a furnace control sys
tem.
.15
In order that the principles underlying my in
vention may be clearly understood I have de
scribed and illustrated different embodiments
thereof in a control switch mechanism and also
described and illustrated the manner in which
20 such switch mechanism may be embodied in a
furnace control system.
In the operation of oil burner equipment there
is danger of conditions arising such that abnor
mal pressures, sometimes of an explosive nature,
25 will develop in the combustion chamber. It has
been the practice to provide safety doors or like
vent means to relieve these abnormal pressures.
Since such abnormal pressures are due to im
proper functioning of the burner mechanism, it
so is desirable to deenergize the fuel supplying ap
paratus and control therefor immediately upon
the occurrence of the abnormal pressure, and
mechanism for effecting such deenergization of
the oil burner equipment in response to abnormal
35 pressures forms the subject matter of my co
normal pressure will cause the pressure release
door to vibrate to an extent su?lcient only to
allow the escape of puffs of undesirable fumes
without being sufficient to completely operate the
safety switch to open-circuit position. In other
words, the amplitudes of the successive outward
movements of the door, which is biased to return
to closed position, will not be sumcient to move
the elements of the safety switch a sufficient dis
tance with respect to each other to disengage 10
them.
It is desirable, however, to deenergize
the oil burner equipment upon the occurrence of
such relatively small pulsating abnormal pres- .
sures as well as upon the occurrence of abnormal
pressures of explosive proportions, since both 15
denote improper operation of the burner equip
ment. A further and more speci?c object of
my invention is, therefore, the provision of im
proved, simple and reliable control mechanism
for insuring deenergization of an oil burner 20
equipment upon either a single opening of the
oil burner pressure relief door to a predetermined
degree or a series of openings of the door to
lesser degrees.
'
Fig. 1 is a schematic showing of an oil burner
furnace, partially cut away, to which my inven
tion is applied; Fig. 2 is a detailed perspective
showing of the elements of one embodiment of
my invention; and Figs. 3, 4, and 5 illustrate
successive steps in the operation of the mecha
nism shown in Fig. 2. Figs. 6, 7, and 8 illustrate
another embodiment of my invention and suc
cessive steps in the operation thereof, and Fig. 9
illustrates schematically the manner of applying
this last embodiment to an oil burner furnace 35
pending application, Serial No. 596,067, filed similar to that shown in Fig. 1.
Referring to the drawing, an oil burner fur
March 1, 1932 and assigned to the assignee of
the present invention. In the apparatus therein nace I0 having a combustion chamber ii, is
equipped with a motor operated pump and com
described, a safety switch, connected to an ex
40 plosion relief door by means of a chain or like pressor unit I2 for supplying fuel and air to an
atomizing nozzle 13. The combustion mixture
connection, is automatically operated to stop op
discharged from the nozzle into the combustion
eration of the fuel supplying apparatus and con
chamber is ignited by means of electrodes 14 and
trol therefor in response to actuation of the re
the products of combustion pass from thence
lief door by pu?back or other abnormal pres
45 sure conditions within the combustion chamber. through the stack breaching l5 into the smoke
There also may occur in the operation of oil pipe it which leads to the stack. A pressure re
burner equipment, improper operating conditions
lief port I1 is incorporated in the top of the
which will not be of such nature as to cause ab
stack breeching, and a pressure relief door 20,
pivotally mounted on the breeching as shown at
2 I, is biased by means of spring 22 to close the re 50
normal pressure of explosive proportions but
50 which will cause irregularly recurring pulsations
of abnormal pressure of relatively small mag
nitude. It has been found in the operation of an
oil burner apparatus equipped with safety mech
anism‘such as described in my above referred to
55 application, that such small mutations of ab
lief port.
Electrical energy for the operation of the
burner mechanism and the electrodes is supplied
from lines 23, 24 through a safety switch which
is shown at 25 as consisting of a terminal box
2
0,111,4a1
26 secured to the stack breeching by means of
mounting plate 21 and provided with a socket II
to which the electrical leads from lines a, 24 are
brought by means of conduit 2!. A movable
switch element in the form of a plug 80 having
contacts II, II. is provided for bridging the ter
minals in the socket 20.
In accordance with my present invention, a
one-way force transmitting mechanism is pro
'10 vided for connecting the door 20 with the contact
carrying plug it and for e?'ecting disengaging
movement of the plug either in a single step in
response to opening of the door to a predeter
mined distance or in a series of steps in response
16 to a series of openings of the door to lesser dis
tances. The principal element of this mechanism
is a link member, in the form of a hook-shaped
' segment II. pivotally mounted at 83 upon clamp
I4 secured to the free end of the door It. The
segment engages a slotted stirrup I. attached to
the plug Ill and is arranged to depend from the
pivotal mounting with its free end extending
through the slot and its inner face 31 in frictional
engagement with the underneath side of the
25 closed end of the slot in the stirrup. This inner
face 31 of the segment is in the form of an irre
versible cam surface. successive points of which
as illustrated by points a and b, are at progres
sively shorter distances from the pivot point If,
80 and therefore from the free end of the door 20.
It is preferred that the cam surface be continuous
for reasons hereinafter to be set forth. A weight
ll is amxed to the hook-shaped segment at some
point horizontally o?set from the vertical line of
motion of the pivot point It so that it will provide
a relatively large gravitational force acting about
the lever arm, consisting of the portion of the
segment between the weight and the pivot point,
to tend to swing the segment in a counterclock
40 wise direction as viewed in Figs. 2 to 5 inclusive.
45
50
55
60
In the operation of the oil burner equipment
conditions may arise in the combustion chamber
which will produce abnormal pressures of sum
cient magnitude to blow open the door 20. When
the door is blown open by a pu?'back, explosion
or similar large abnormal pressure the movement
thereof will be su?icient to disengage the con
tacts II and II of the plug 30 from the terminals
in the socket 28 in a single stroke to deenergize
the oil burner and ignition equipment. It will be
apparent that upon upward movement of the door
20 the frictional engagement of the inner surface
of the hook-shaped segment 35 with the end of
the stirrup 36 will ‘become a positive engagement
to provide a positive operating connection be
tween the door and the movable plug so that
outward movement of the door will pull the plug
upward a distance proportional to the amplitude
of the movement of the door, and a single open
ing of the door to a predetermined degree will be
su?lcient to completely disengage the contacts of
the safety switch 25.
There might also arise in the operation of the
oil burner conditions such that pulsating pres
65 sures of small magnitude may occur within the
combustion chamber, and these pulsations will be
sumcient to impart to the pressure relief door only
a vibratory opening movement such that each
upward movement of the door will be of insu?i
70 cient amplitude to completely disengage the con
tacts of the safety switch 25. Such conditions
are, of course, undesirable since they denote im
proper operation of the oil burner equipment and
will also allow continued escape of combustion
75 gases from the pressure relief port into the space
surrounding the oil burner furnace. Hence it is
desirable to have the oil burner equipment de
energized after repetition of this pulsating con
dition for a certain length of time. Figs. 8, 4,
and 5 illustrate in two steps the operation of the
safety switch in response to vibration of‘ the
pressure release door 20, but it is to be understood
that this is merely illustrative and that it may
take a much larger number of successive steps to
completely ‘disengage the contacts of the safety
switch. When the door 20 is at rest in closed
position and the plug II is completely seated in
the socket 28 which is the normal condition for
proper operation of the furnace, a point on the‘
cam surface 31 having a connection distance de
noted a will engage the stirrup 38. Upon a slight
upward movement of the door Ill due to a pulse’
tion of abnormal pressure the plug III will be
caused to follow the movement of the door II in
proportion to the extent of opening thereof. This 20
will effect a partial disengagement of the plug
contacts from the terminals of the box It as
shown in Fig. 4. Now upon return of the door
to its closed position, were it not for the weight
II the segment would tend to retain its original
position as shown in the dotted lines of Fig. 4,
and would tend to push the plug back into the
socket in the terminal box 20. However, the bias
ing effect of the weight ll tends to cause the
segment to rotate in a counterclockwise direction. 80
thus forcing a succeeding bearing point of the
cam surface into engagement with the stirrup I‘,
such successive bearing point having a connec
tion distance such as b which is shorter than
that of the connection distance a of the bearing
point which ?rst engaged the stirrup ll. . This
will produce a shorter connection distance be
tween the door and the plug 30 so that succeed~
ing upward movements of the door will produce
added increments of upward movement of the 40
plug and will eventually e?'ect complete disen
gagement of the contacts 8| and 32 from the
terminals oftheterminalbox It asillustratedin
Fig. 5. It will thus be seen that my improved
linkage mechanism provides means for imparting 45
progressive increments of movement to the mov
able switch element or plug 30 upon successive
vibration of the pressure relief door 20, and that
a predetermined summation of the outward
movements of the door will effect complete dis 50
engagement of the safety switch to deenergize the
electrical circuit of the oil burner and ignition
equipment. It is also apparent that the continu
ity of the cam surface provides for in?nitely small
changes in connection length so that the mecha 55
nism,will function regardless of the amplitude
of movement of the door.
Figs. 6 to 9 inclusive illustrate a modi?ed form
of my invention wherein the linkage mechanism
is particularly adapted for use with a‘pressure
relief door having substantially horizontal move
ment. The operating link in this embodiment is
in the form of a closed segment 4| having an in
ner bearing face ll similar to the irreversible cam
surface I‘! of the link ll in the embodiment ?rst
M
described. A weight 42 of arcuate shape similar
to that of a portion of the segment is riveted or
otherwise fastened to the segment as shown at II
and 4 .
Terminal box 20 is incorporated in the wall of 70
the furnace l0, and the socket therein is ?ush
with the wall. Plug 30 is provided with one or
more projecting ears 45 for engagement with the
inner surface of the segment. The segment is
'pivotally secured by means of pin 40 upon the
,
3
9,111,481
end of rod 41 which passes through an opening
48 in the adjacent side of the stack breeching
and through the interior thereof to the opposite
side where it is fastened to the pressure relief
door 50 which is arranged to close the port ‘I
in the wall of the breeching. Guide means 52
are provided to steady the rod and aid in hold
ing it and the door in position, and spring means
53 are provided to bias the door in closed position.
The operation of the mechanism of the em
10
bodiment last described is similar to that de
scribed in connection with Figs. 2 to 5 inclusive.
Under normal conditions in the furnace, the pro
:Iection 45 will be engaged by a bearing point on
the cam surface which has a connection distance
a. Outward movement of the door 50 will cause
the rod 41 to slide in the guides 48 and 52. This
will cause segment 40 to pull on the plug 30 and
eifect partial disengagement of the contacts 3|
20 and 32 to an extent proportional to the distance
of opening of the door, as for instance, to a posi
tion such as shown in Fig. 7. Subsequent return
of the door to closed position releases the fric
tional force between the bearing surface 4i of
25 the segment and the projection 45, and allows
the segment to swing in a counter-clockwise di
rection under the in?uence of weight 42 until a
succeeding bearing point having a shorter dis—
tance, such as b, is forced into engagement with
the projection. Thus, successive outward vibra
tions of the door impart progressive increments of
movement to the movable switch member or plug
and will completely disengage the contacts of
the plug from the terminals in the terminal box,
as shown in Fig. 8, after a predetermined sum
mation of said increments of movement. when
the plug is completely disengaged it will hang
suspended from the segment by means of the pro
jecting ear 45 which will rrst upon the lower por
40 tion of the segment 40, and the plug must be
manually reset to reestablish the energizing cir
to closed position and arranged to open different
distances in response to abnormal pressures of
different magnitudes within the combustion
chamber, and means for effecting either continu
ous movement of the switch means from one of
said circuit controlling positions to the other in
response to a single opening of the door to a pre
determined distance or step by step movement
of the switch means from said one circuit con
trolling position to the other in response to a
series of lesser openings of the door.
2. The combination with a furnace having a
combustion chamber, electrically operated fuel
burner means therefor and an energizing circuit
for said electrically operated means, of electrical 15
switch means movable between two circuit con
trolling positions to control the energization of
said circuit, a pressure relief door normally biased
to closed position and arranged to have different
degrees of opening in response to abnormal pres 20
sures of different magnitudes within the com
bustion chamber, and means interconnecting the
door and the switch means including a one-way
force transmitting mechanism
for effecting
movement of the switch means from one of said 25
circuit controlling positions to the other in re
sponse either to a single opening of the door to a
predetermined degree or to a predetermined sum
mation of openings of the door to lesser degrees.
3. The combination with a furnace having a 30
combustion chamber, electrically operated fuel
burner means therefor and an energizing circuit
for said electrically operated means, of switch
means movable between two circuit controlling
positions to control the energization of said cir 35
cuit, movable pressure responsive means opera
tively associated with the furnace to vibrate in
response to pulsating abnormal pressures within
the furnace combustion chamber, and means in
terconnecting the pressure responsive means and 40
the switch means for effecting progressive move
cuit of the oil burner. It will be evident that the . ment of the switch means from one of said cir
link may be made in the form of two segments, cuit controlling positions to the other in re
having similar contours, ?xedly secured to each sponse to repeated vibration of the pressure re
other in spaced apart side by side relation and sponsive means due to repeated pulsations of ab
pivotally mounted on opposite ends of the pivot normal pressure in the combustion chamber.
4. The combination with a furnace having a
pin 46, and the bearing surfaces of these two combustion
chamber, electrically operated fuel
segments may be arranged to engage projecting
burner
means
therefor and an energizing circuit
ears 45 on opposite sides of the plug 30.
From the foregoing description it will be seen for said electrically operated means, of switch
50
means operable to control the energization of said
that by my invention I have provided a mecha
circuit and means for insuring deenergization of
nism for greatly increasing the safety and relia
said
circuit upon the occurrence of pulsating ab
bility of operation of an oil burner furnace. The
embodiments of the invention herein illustrated normal pressures in the combustion chamber in
cluding a pressure relief door operatively asso
.» and described have been selected for the purpose
of setting forth the principles involved. It will ciated with the furnace and vibratorily movable
in response to said pulsating abnormal pres
be apparent, however. that the invention is sus
sures, biasing means for holding the door nor
ceptible of being modi?ed to meet different con
ditions of use and that its use is not limited to a mally in closed position, and means intercom
necting the door and the switch means including
60 switching mechanism for an oil furnace safety
switch but maybe employed with equal advan
tage in any situation where a control mechanism
having similar characteristics is desired. Such
modifications are believed to be within the spirit
65 and scope of my invention and are intended to be
covered by the appended claims.
What I claim as new and desire to secure by
Letters Patent of the United States, is:
1. The combination with a furnace having a
70 combustion chamber, electrically operated fuel
burnermeans therefor and an energizing circuit
for said electrically operated means, of electrical
switch means movable between two circuit con
trolling positions to control the energization of
75 said circuit, a pressure relief door normally biased
45
50
55
60
a one-way force transmitting mechanism for im
parting progressive increments of movement to
said switch means toward open circuit position
in response to a series of successive vibrations of
the door due to said pulsating abnormal pres
65
sures.
5. In combination, electric circuit controlling
means having a switch element movable between
two circuit controlling positions, and means for
transmitting motion to said element including a
movable element and a one-way force trans
mitting mechanism interconnecting said switch
element and movable element for effecting move
ment of the switch element from one to the
other of said circuit controlling positions in re
75
4
2,111,4s1
spouse to either a single movement of said mov-_
able element through a predetermined distance
or the repeated movement 0! the movable ele
ment through a lesser distance.
6. In combination, circuit controlling means
having a switch element movable between two
circuit controlling positions, and means for trans
mitting motion to said element including a re
ciprocating element, and a one-way iorce trans
10
mitting mechanism mechanically interconnect
ing said switch element and said reciprocating
element for moving said switch element from one
to the other oi’ said circuit controlling positions
in response to either a single reciprocation oi the
reciprocating element through a predetermined
distance or a series of reciprocations of said
reciprocating element through a lesser distance.
7. In combination, circuit controlling means
having a switch element movable between two
20 circuit controlling positions, and mechanism for
transmitting motion to said element including ‘a
pair oi’ members having a one way interlocking
engagement for movement thereof as a unit with
said switch and biased to have relative movement
therebetween in the opposite way to provide a
movable connection of varying lengths with the
switch element.
8. In combination, circuit controlling means
having a switch elementmovable between two
circuit controlling positions, and mechanism for
transmitting motion to said element including a 10
pair oi’ relatively movable members, one being
pivotally mounted and having a one way inter
locking engagement with the other member and
biased to successively shorten the distance be
tween the mounting point of said one member and
the other member upon reciprocation done 01’
said members to eiiect progressive increments
of movement of the switch element between said
positions.
WALTER 0. LOB.
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