U.S. patent number 3,848,211 [Application Number 05/421,525] was granted by the patent office on 1974-11-12 for electrical switch construction and an electrical control system utilizing the same or the like.
This patent grant is currently assigned to Robertshaw Controls Company. Invention is credited to William J. Russell.
United States Patent |
3,848,211 |
Russell |
November 12, 1974 |
ELECTRICAL SWITCH CONSTRUCTION AND AN ELECTRICAL CONTROL SYSTEM
UTILIZING THE SAME OR THE LIKE
Abstract
An electrical switch construction comprising a housing carrying
a pair of movable spring switch blades respectively having contacts
thereon that are normally placed out of electrical contact with
each other by the normal bias of the switch blade. A pair of cams
are rotatably carried by the housing and are respectively
engageable with the switch blades, one of the cams when in one
position relative to the housing being adapted to hold its
respective switch blade in electrical contact with the other switch
blade to complete an electrical circuit therebetween. The other of
the cams when in one position thereof relative to the housing being
adapted to hold its respective switch blade out of contact with the
other switch blade even though the one cam is in its one position
whereby the electrical circuit can not be completed. A movable
actuator is carried by the housing and is adapted to simultaneously
engage the cams and move the same to the respective one positions
thereof whereby the switch construction is trip-free. A latch
member is carried by the housing for holding the one cam in the one
position thereof if the latch member is not tripped to an
unlatching position thereof.
Inventors: |
Russell; William J. (Milford,
CT) |
Assignee: |
Robertshaw Controls Company
(Richmond, VA)
|
Family
ID: |
23670897 |
Appl.
No.: |
05/421,525 |
Filed: |
December 14, 1973 |
Current U.S.
Class: |
337/64; 219/265;
337/82; 337/101; 200/39R; 337/72; 337/99; 431/254 |
Current CPC
Class: |
F23N
5/206 (20130101); H01H 73/30 (20130101) |
Current International
Class: |
H01H
73/30 (20060101); F23N 5/20 (20060101); H01H
73/00 (20060101); H01h 071/16 () |
Field of
Search: |
;337/52,55-57,64,70,72,75,77,82,94,99,101,103,105
;219/260,262,264,265 ;200/38,39 ;431/254,255,258 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Grimley; Arthur T.
Attorney, Agent or Firm: Candor, Candor & Tassone
Claims
What is claimed is:
1. An electrical switch construction comprising a housing means, a
pair of movable spring blades carried by said housing means and
respectively having contact means normally placed out of contact
with each other by the normal bias of said switch blades, a pair of
cams rotatably carried by said housing means and being respectively
engageable with said switch blades, one of said cams when in one
position relative to said housing means being adapted to hold its
respective switch blade into electrical contact with the other
switch blade to complete an electrical circuit therebetween, the
other of said cams when in one position thereof relative to said
housing means being adapted to hold its respective switch blade out
of contact with the other switch blade even though said one cam is
in its said one position thereof to thereby prevent completion of
said electrical circuit, a movable actuator carried by said housing
means and being adapted to simultaneously engage said cams and move
the same to said respective one positions thereof, and latch means
for holding said one cam in said one position thereof.
2. An electrical switch construction as set forth in claim 1
wherein trip means is carried by said housing means to move said
latch means from its latching position with said one cam whereby
the natural bias of said switch blades moves said switch blades to
an open condition thereof to open said circuit.
3. An electrical switch construction as set forth in claim 2
wherein said latch means comprises a bimetal member for latching
with said one cam when said bimetal member senses one certain
temperature and for warping away from said one cam to unlatch
therefrom when sensing another certain temperature.
4. An electrical switch construction as set forth in claim 3
wherein said trip means includes a heater means for said bimetal
member to provide said other certain temperature when operated a
certain amount.
5. An electrical switch construction as set forth in claim 4
wherein said trip means includes means for adjusting the same so
that the amount of time said heater means is to be operated before
said latch member moves to an unlatching position thereof can be
selected within certain limits.
6. An electrical switch construction as set forth in claim 1
wherein said cams are rotatably carried by said housing means in
side-by-side relation.
7. An electrical switch construction as set forth in claim 6
wherein said cams are rotatably mounted to said housing means by
the same shaft means.
8. An electrical switch construction as set forth in claim 7
wherein said actuator must be moved from an unactuated position
thereof to an actuated position thereof to move said cams to said
one position thereof, said housing means having biasing means
tending to always move said actuator from said actuated position
thereof to said unactuated position thereof.
9. An electrical switch construction as set forth in claim 7
wherein said cams are so constructed and arranged that when said
switch blades are out of contact with each other by the normal bias
thereof said cams have surfaces disposed in aligned relation that
are respectively engaged simultaneously by said actuator to be
moved in unison by said actuator when said actuator is moved from
said unactuated position thereof to said actuated position thereof
whereby actuation of said actuator will not cause said switch
blades to contact each other unless said latch means holds said one
cam in its said one position thereof when said actuator
subsequently moves back from said actuated position thereof to said
unactuated position thereof.
10. An electrical switch construction as set forth in claim 9
wherein the switch blade operated by said one cam has a cut-out
therethrough through which said other cam projects to engage its
respective switch blade.
11. An electrical control system comprising an electrical power
source, an electrically operated control device, and an electrical
circuit means for interconnecting said source to said device to
operate the same, said circuit means having an electrical switch
construction therein, said switch construction having a housing
means, a pair of movable spring switch blades carried by said
housing means and respectively having contact means normally placed
out of contact with each other by the normal bias of said switch
blades, a pair of cams rotatably carried by said housing means and
being respectively engageable with said switch blades, one of said
cams when in one position relative to said housing means being
adapted to hold its respective switch blade into electrical contact
with the other switch blade to complete an electrical circuit
therebetween whereby said source is interconnected to said control
device to operate the same, the other of said cams when in one
position thereof relative to said housing means being adapted to
hold its respective switch blade out of contact with the other
switch blade even though said one cam is in its said one position
thereof whereby said electrical circuit cannot be completed when
said cams are respectively in said one position thereof, a movable
actuator carried by said housing means and being adapted to
simultaneously engage said cams and move the same to said
respective one positions thereof, and latch means for holding said
one cam in said one position thereof.
12. An electrical control system as set forth in claim 11 wherein
trip means is carried by said housing means to move said latch
means from its latching position with said one cam whereby the
natural bias of said switch blades moves said switch blades to an
open condition thereof to open said circuit whereby said source is
disconnected from said control device.
13. An electrical control circuit as set forth in claim 12 wherein
said latch means comprises a bimetal member for latching with said
one cam when said bimetal member senses one certain temperature and
for warping away from said one cam to unlatch therefrom when
sensing another certain temperature.
14. An electrical control system as set forth in claim 13 wherein
said trip means includes a heater means for said bimetal member to
provide said other certain temperature when operated a certain
amount.
15. An electrical control system as set forth in claim 14 wherein
said trip means includes means for adjusting the same so that the
amount of time said heater means is to be operated before said
latch member moves to an unlatching position thereof can be
selected within certain limits.
16. An electrical control system as set forth in claim 11 wherein
said cams are rotatably carried by said housing means in
side-by-side relation.
17. An electrical control system as set forth in claim 16 wherein
said cams are rotatably mounted to said housing means by the same
shaft means.
18. An electrical control system as set forth in claim 17 wherein
said actuator must be moved from an unactuated position thereof to
an actuated position thereof to move said cams to said one position
thereof, said housing means having biasing means tending to always
move said actuator from said actuated position thereof to said
unactuated position thereof.
19. An electrical control system as set forth in claim 17 wherein
said cams are so constructed and arranged that when said switch
blades are out of contact with each other by the normal bias
thereof said cams have surfaces disposed in aligned relation that
are respectively engaged simultaneously by said actuator to be
moved in unison by said actuator when said actuator is moved from
said unactuated position thereof to said actuated position thereof
whereby actuation of said actuator will not cause said switch
blades to contact each other unless said latch means holds said one
cam in its said one position thereof when said actuator
subsequently moves back from said actuated position thereof to said
unactuated position thereof.
20. An electrical control circuit as set forth in claim 19 wherein
the switch blade operated by said one cam has a cut-out
therethrough through which said other cam projects to engage its
respective switch blade.
Description
This invention relates to an improved electrical switch
construction as well as to an electrical control system utilizing
such a switch construction or the like.
It is a feature of this invention to provide an electrical switch
construction that is trip-free.
It is well known in the art that safety electrical switches have
been designed to be trip-free, i.e., a switch that must be manually
reset after it has tripped to the open circuit condition after a
fault in the circuit has been automatically detected and which at
the same time cannot by means of the resetting means be held in a
circuit closed position to thus negate the safety function of the
switch. For example, see the U.S. Pat. to Roberts et al, No.
2,745,922.
Accordingly, it is a feature of this invention to provide an
improved trip-free electrical switch of the above type.
In particular, one embodiment of this invention provides an
electrical switch construction having a housing means provided with
a pair of movable spring switch blades carried by the housing means
and respectively having contact means normally placed out of
contact with each other by the normal bias of the switch blades. A
first cam is rotatably carried by the housing means and is
engageable with one of the switch blades, the first cam when in one
position relative to the housing means being adapted to hold its
respective switch blade in electrical contact with the other switch
blade to complete an electrical circuit therebetween. A second cam
is rotatably carried by the housing means and is engageable with
the other of the switch blades, the second cam when in one position
thereof relative to the housing means being adapted to hold its
respective switch blade out of contact with the other switch blade
even though the first cam is in its one position thereof whereby
the electrical circuit can not be completed when the cams are
respectively in the one positions thereof. A movable actuator is
carried by the housing means and is adapted to simultaneously
engage the cams and move the same to the respective one positions
thereof whereby the switch construction is trip-free. A latch
member is adapted to hold the first cam in its one position thereof
if the latch member is not moved to a tripped condition thereof.
The actuator by being simultaneously engageable with both of the
cams will move the cams in unison when the actuator is being moved
from an unactuated position thereof to an actuated position thereof
whereby the cams hold the switch blades in an open condition
thereof when the actuator is in the actuated condition thereof.
However, as the actuator is moved back to the unactuated condition
thereof, both cams tend to follow such movement but the first cam
will be latched by the latch member if the latch member is in a
latching position thereof whereby the switch blades can be reset in
electrical contact with each other.
Therefore, it is an object of this invention to provide an improved
electrical switch construction having one or more of the novel
features set forth above or hereinafter shown or described.
Another object of this invention is to provide an electrical
control system utilizing such an electrical switch construction or
the like.
Other objects, uses and advantages of this invention are apparent
from a reading of this description, which proceeds with reference
to the accompanying drawings forming a part thereof and
wherein:
FIG. 1 is a cross-sectional view of the improved electrical switch
construction of this invention, the electrical switch construction
being illustrated as being utilized in an electrical control system
of this invention that is schematically illustrated in FIG. 1.
FIG. 2 is a view similar to FIG. 1 and illustrates the electrical
switch construction in its tripped condition.
FIG. 3 is a fragmentary, cross-sectional view taken on line 3--3 of
FIG. 1.
FIG. 4 is a view similar to FIG. 1 and illustrates the tripped
electrical switch construction while an attempt is being made to
reset the same.
While the various features of this invention are hereinafter
described and illustrated as being particularly adapted to provide
an electrical switch construction that is trip-free, it is to be
understood that the various features of this invention can be
utilized singly or in any combination thereof to provide an
electrical switch construction for other purposes as desired.
Therefore, this invention is not to be limited to only the
embodiment illustrated in the drawings, because the drawings are
merely utilized to illustrate one of the wide variety of uses of
this invention.
Referring now to FIG. 1, the improved electrical switch
construction of this invention is generally indicated by the
reference numeral 10 and comprises a housing means 11 carrying a
pair of spring switch blades 12 and 13 respectively interconnected
at the lower end thereof to terminal means 14 and 15 that project
from the housing means 11 and carry at the upper ends thereof
contact means 16 and 17 that are adapted to be placed in electrical
contact with each other in the manner illustrated in FIG. 1 to
complete an electrical circuit therebetween. However, the normal
bias of such switch blades 12 and 13 is to tend to hold the
contacts 16 and 17 out of electrical contact with each other in the
manner illustrated in FIG. 2 so as to open the electrical circuit
therebetween for a purpose hereinafter described.
The electrical switch construction 10 of this invention is adapted
to be utilized in an electrical control system of this invention
that is generally indicated by the reference numeral 18 in FIG. 1
and includes an electrically operated control device 19 which, in
the embodiment illustrated in FIG. 1, comprises an electrical
igniter means for igniting fuel when the same issues from a burner
means 20 that has fuel directed thereto by a control device 21
which when turned to an "on" position thereof directs fuel to the
burner means 20 as well as closes a main "on-off" switch 22 for the
electrical circuit 18.
In particular, the main switch 22 of the electrical circuit 18 is
adapted to open and close a switch member 23 in a power source lead
24 which is interconnected to the terminal 15 of the electrical
switch construction 10. Thus, if the switch blade 23 is in an open
condition, the power source L1 is disconnected from the terminal 15
and when the switch blade 23 is in a closed condition the power
source L1 is interconnected to the terminal 15 of the switch
construction 10. Similarly, the main switch 22 includes a switch
blade 25 disposed in a lead 26 that is interconnected to one side
27 of the igniter 19 and to ground at the other end thereof, the
igniter 19 is disconnected from the ground and when the switch
blade 25 is in a closed condition thereof the igniter 19 is
interconnected to ground.
The other side 28 of the igniter 19 is interconnected by a lead 29
to the terminal 14 of the electrical switch construction 10.
In this manner, when the switch blades 12 and 13 are disposed in
the closed condition illustrated in FIG. 1 and the operator turns
the control device 21 to an "on" condition thereof, the main on-off
switch 22 closes the switch blades 23 and 25 in their respective
lines 24 and 26 and the igniter 19 is placed across the power
source L1 and ground whereby the ingiter 19 will be operating in an
attempt to ignite fuel now issuing from the burner 20 since the
control device 21 has been moved to an "on" condition thereof to
also direct fuel to the burner 20.
However, the electrical switch construction 10 of this invention is
so constructed and arranged in a manner hereinafter set forth that
should a sensor 30 of the system 18 detect that the burner 20 has
not been ignited within a certain time period, the sensor 30 will,
in effect, cause the electrical switch construction 10 to be
tripped to the open condition illustrated in FIG. 2 and thereby
terminate the operation of the igniter 19 until the switch
construction 10 is manually reset from the open or tripped
condition illustrated in FIG. 2 back to the closed position
illustrated in FIG. 1 in a manner hereinafter described.
A bimetallic latch member is disposed in a chamber 32 of the
housing means 11 and has an L-shaped end 32 interconnected to a
flexure member 33 that is fixed to the housing means 11 by a fixed
support 34, the other end 35 of the bimetallic latch member 31
being turned over in such a manner that the same is adapted to
engage against an angled surface 36 of a first cam 37 rotatably
mounted to the housing means 11 by a shaft 38 carried by the
housing means 11.
The cam 37 is so constructed and arranged that the same has a part
39 adapted to engage against the spring blade 12 and bias the same
to the right in the manner illustrated in FIG. 1 when the cam
member 37 is disposed in the position illustrated in FIG. 1 so as
to maintain the contact 16 of the blade 12 into full electrical
contact with the contact 17 of the blade 13 as such position of the
cam 37 not only biases the blade 12 to the right, but such position
of the cam 37 also biases the blade 13 to the right so that the
blade 13 is always spring biased against the contact 16 of the
blade 12 when the cam 37 is in the latched position illustrated in
FIG. 1. Because the spring blades 12 and 13 are tending to rotate
the cam 37 in a clockwise direction in FIG. 1, the turned end 35 of
the latch 31 prevents such movement of the cam 37 so that the cam
37 is latched in the position illustrated in FIG. 1 maintaining an
electrical circuit between the switch blades 12 and 13 for the
purpose previously described.
However, the bimetallic latch member 31 is adapted to be warped to
the left to move the latching end 35 thereof out of the path of the
surface 26 of the cam 37 when the bimetallic member 31 is heated to
a certain degree by an electrical heater 40 that is carried by the
bimetallic latch member 31 and has one end 41 thereof electrically
interconnected by a lead 42 to a terminal 43 of the housing means
10. The other end 44 of the electrical heater 40 is interconnected
by a lead 45 to a fourth terminal 46 of the housing means 11.
The terminal 46 is adapted to be interconnected by a lead 47 to
ground while the terminal 43 is interconnected by a lead 48 to one
side 49 of the sensor 30 while the other side 50 of the sensor 30
is interconnected by a lead 51 to the terminal 15.
In this manner, when the igniter 19 is initially turned on by the
main "on-off" switch 22 being moved to a closed position by the
control device 21 being turned to an "on" condition thereof,
electrical current is adapted to flow not only through the sensor
30 but also through the electrical heater 40 whereby the electrical
heater 40 begins to heat up the latch member 31 to tend to warp the
same to the left and thereby open the electrical circuit being
provided by and through the switch blades 12 and 13 for the igniter
19. However, if the operating igniter 19 during such time period
ignites the burner 20, the sensor 30 senses such flames at the
burner 30 and disconnects the electrical circuit through the sensor
30 so that the electrical heater 40 is disconnected from the power
source L1 whereby the latch member 31 will remain in its latched
position as illustrated in FIG. 1 to maintain an electrical circuit
through the switch blades 12 and 13 and thereby maintain the
igniter 19 operative.
However, if during such time period the burner 20 is not ignited by
the igniter 19, the sensor 30 has caused the heater 40 to continue
to operate for a certain length of time whereby the bimetallic
member 31 is heated up and thereby warped to the left to pull the
latch end 35 thereof away from the surface 36 of the cam 37 whereby
the natural bias of the switch blade 12 rotates the cam 37 from the
position illustrated in FIG. 1 to the position illustrated in FIG.
2 so that the natural bias of the switch blades 12 and 13 hold the
blades 12 and 13 in an open condition thereof to terminate the flow
of current to the igniter 19 and, thus, turn off the igniter 19,
until the electrical switch construction 10 is reset in a manner
hereinafter described.
An ambient temperature compensating bimetal member 52 has a lower
L-shaped end 53 thereof also interconnected to the flexure 33 by
the same fastening member 54 that fastens the L-shaped end 32 of
the bimetal latch member 31 thereto as illustrated. The upper end
55 of the bimetal member 52 has a suitable opening (not shown)
passing therethrough and receiving a reduced part 56 of a threaded
adjusting member 57 therein, the threaded adjusting member 57 being
threaded in a threaded bore (not shown) passing through a nut 58
carried in suitable recess means 59 in the housing means 11.
The reduced portion 56 of the threaded adjusting member 57 carries
a disc-like member 60 on the outer end thereof and a washer-like
member 61 is loosely telescoped onto the reduced part 56 of the
adjusting member 57, the member 61 being urged to the right in FIG.
1 toward the disc 60 by a compression spring 62 disposed between
the slideable disc 61 and the nut 58 as illustrated. In this
manner, the end 55 of the compensating bimetal member 52 is held
against the disc 60 of the adjusting member 57 by the disc 61 under
the force of the compression spring 62.
In this manner, rotation of the adjusting member 57 at the
bifurcated end 63 thereof that projects out of the housing means 11
at an opening 64 thereof will cause axial movement of the adjusting
member 57 relative to the housing means 11 and thereby adjust the
position of the upper end 55 of the compensating bimetal member 52
which, through its lower end 53, will change the position of the
flexure 33 and, thus, the position of the latching bimetal member
31 so that the time period required for the heater means 40 to be
operating before the bimetal member 31 will move to its unlatching
position relative to the cam 37 can be adjusted within the limits
of the adjusting member 57.
In particular, when the threaded adjusting member 57 is threaded
into the housing means 11 the flexure 33 is flexed to the right in
FIG. 1 and thereby requires a longer time period for the bimetal
member 31 to be heated by the heater 40 before the same will move
to an unlatching position thereof. Conversely, when the threaded
adjusting member 57 is rotated in a manner to move the end 55
thereof to the left in FIG. 1, the flexure 33 is likewise moved to
the left and thereby requires a lesser time period for the heater
means 40 to heat the bimetal member 31 to cause the same to move to
an unlatching position thereof.
Similarly, the ambient temperature compensating bimetal member 52
is so constructed and arranged that as the same is heated up by an
increase in the temperature in the atmosphere, the same warps in a
direction that tends to move the flexure structure 33 to the right
in FIG. 1 to offset the likewise heating up of the bimetal member
31 by the ambient temperature that tends to warp the bimetal member
31 to its unlatching position. Thus, the bimetal member 52
compensates for such increased ambient temperature. Conversely, a
drop in ambient temperature tends to cause the bimetal member 52 to
move to the left and thereby carry the flexure 33 to the left an
amount equal to the amount that the decreased ambient temperature
caused the bimetal member 31 to move to the right and thereby
offset that additional amount of time that the heater 40 would have
to heat the bimetal member 31 to overcome the decreased ambient
temperature.
Therefore, it can be seen that the bimetal member 31 is ambient
compensated by the bimetal member 52 and can be adjusted within
limits by the adjusting member 57 so as to provide the desired time
delay that is required for the heater means 40 to be operated
before the bimetal member 31 will move to its unlatching
position.
An actuator or reset button 65 projects out through an opening 66
formed through an outer surrounding part 70 of the housing means 11
and is carried on an end 67 of a spring member 68 that has its
other end 69 fastened to the part 70 of the housing means 11. The
bias of the spring member 68 is such that the same tends to
maintain the spring member 68 against the undersurface 71 of the
housing part 70 whereby a turned end 72 of the spring member 68
merely projects into an opening 73 formed in the housing means 11
and leading to the chamber 32 thereof. However, when the button 65
is moved downwardly by an operator pushing inwardly on the same,
the end 72 of the spring member 68 is moved into the chamber 32 of
the housing means 11 and engages against the cam 37 at the surface
36 thereof to pivot the cam 37 in a counterclockwise direction
about the shaft means 38 so that the abutment 39 thereof that
engages against the spring blade 12 will bow the blade 12 to the
right in the manner illustrated in FIG. 4 in an attempt to reset
the switch construction should the latch member 31 be in a
resetting or relatching position thereof.
Another cam member 74 is also rotatably mounted to the housing
means 11 by the shaft means 38 in side-by-side relation to the cam
37 and has an abutment 75 for engaging against the other spring
blade 13 in the manner illustrated in the drawings, the cam member
74 being adapted to project through a cutout 76 in the spring blade
12 in the manner illustrated in FIG. 3.
The cam member 74 has a surface 77 that is adapted to be
simultaneously engaged by the end 72 of the reset spring member 68
as the same is engaging the cam 37 when the end 72 is moved
downwardly by the push button 65 in the manner illustrated in FIG.
4 whereby such movement of the actuator 65 from the unactuated
condition thereof of FIG. 2 to the actuated condition thereof of
FIG. 4 causes the cam members 37 and 74 to be simultaneously
engaged and rotate in unison in a counterclockwise direction so
that the ends 39 and 75 thereof will simultaneously move the switch
blades 12 and 13 to the right while maintaining the same out of
electrical contact with each other in the manner illustrated in
FIG. 4. During such movement, if the latch end 35 of the bimetal
member 31 is in the path of counterclockwise movement of the cam
37, the cam 37 merely cams by the same to the right to the position
illustrated in FIG. 4. Upon release of the push button 65 from the
acuated position illustrated in FIG. 4, both cam members 37 and 74
tend to rotate back in a clockwise direction under the natural bias
of the respective switch blades 12 and 13 back to the natural
condition illustrated in FIG. 2. However, if the latch member 31
has its end 35 disposed in the path of movement of the surface 36
of the cam member 37, the same will prevent the cam member 37 from
being driven back in a clockwise direction so that the same will
hold the switch blade 13 in its biased condition illustrated in
FIG. 1 so that clockwise movement of the cam 74 will permit the
switch blade 13 to move into electrical contact with the switch
blade 12 in the manner illustrated in FIG. 1.
The operation of the electrical switch construction 10 of this
invention in its use in the control system 18 will now be
described.
Assuming that the switch construction 10 is in the latched
condition illustrated in FIG. 1 wherein the cam member 37 is held
by the end 35 of the latch member 31 from being rotated in a
clockwise direction by the natural bias of the spring blade 12, the
spring blades 12 and 13 are electrically interconnected together at
the contact means 16 and 17 thereof. Thus, an electrical circuit is
adapted to be provided from the power source L1 through the igniter
19 to the ground when the control device 21 is moved to an "on"
position to close the main switch 22 as previously described.
Thus, when the operator desires to turn on the burner means 20, the
operator turns the control device 21 to the "on" position thereof
to close the main switch 22 as well as to direct fuel into the
burner 20. The closing of the main switch 22 places the igniter 19
across the power source leads 24 and 26 so that the ignitor 19 is
operating as the fuel issues from the main burner 20. At the same
time, the sensor 30 is now placed across the power source lead 24
and ground lead 47 so that the sensor 60 permits electrical current
to flow through the heater 40 to tend to heat up the latching
bimetal member 31. However, the bimetal member 31 remains in its
latched condition for the predetermined amount of time as
determined by setting the adjusting member 57 in the manner
previously described.
During such time period as set by the adjusting member 57, if the
igniter 19 ignites the fuel issuing from the burner 20, the sensor
30 senses the flames at the burner 20 and opens the electrical
circuit therethrough to disconnect the heater 40 from the
electrical power source so that the latching bimetal member 31 will
remain in the condition illustrated in FIG. 1 and the switch
construction 10 will remain in its latched condition.
However, should the sensor 30 not sense flames at the burner 20
after the lapse of the time period as set by the adjustment member
57, the heater 40 will have operated in such a manner to cause the
bimetal member 31 to warp to the left and thereby move the end 35
thereof away from the surface 36 of the cam member 37 whereby the
cams 37 and 74 are driven back in a clockwise direction by the
natural bias of the spring blades 12 and 13 to the position
illustrated in FIG. 2 to not only disconnect the heater 40 from the
electrical circuit, but also to disconnect the igniter 19
therefrom.
Thereafter, should a person desire to reset the switch construction
10, that person must push inwardly on the actuator 65 from the
unactuated condition thereof illustrated in FIG. 2 to the condition
illustrated in FIG. 4 whereby the end 72 of the spring member 68
will act simultaneously against the surfaces 36 and 77 of the cam
members 37 and 74 to rotate the same in a counterclockwise
direction from the position illustrated in FIG. 2 back to the
position illustrated in FIG. 4. Such movement of the cams 37 and 74
maintain the spring blades 12 and 13 out of contact with each other
during such actuated movement of the actuator 65.
A subsequent release of the actuator 65 when in its actuated
condition illustrated in FIG. 4 will permit the cams 37 and 74 to
be rotated back in a clockwise direction by the natural bias of the
spring blades 12 and 13 if the bimetal member 31 has not cooled
sufficiently to place the end 35 thereof in the path of movement of
the surface 36 of the cam 37. If the bimetal member 31 has cooled
sufficiently, the end 35 prevents the clockwise movement of the cam
37 so that the same remains in the position illustrated in FIG. 1
and the natural bias of the spring blade 13 causes the cam 74 to
move in a clockwise direction and thereby place the contact 17
thereof in electrical contact with contact 16 of the blade 12 in
the manner illustrated in FIG. 1 whereby the switch construction 10
has been reset to its "on" condition so that the control system 18
can now be operated in the manner previously described.
Thus, it can be seen that the electrical switch construction 10 of
this invention is substantially trip-free because movement of the
reset member 65 to its actuated condition will not permit the
switch blades 12 and 13 to be held in a closed position thereof
because the switch blades 12 and 13 will only be moved to a closed
condition when the actuator 65 is released and if the latching
member 31 is in a latch position thereof.
Therefore, it can be seen that this invention not only provides an
improved electrical switch construction, but also this invention
provides an improved electrical control system utilizing such a
switch construction or the like.
While the form of the invention now preferred has been illustrated
and described as required by the Patent Statutes, it is to be
understood that other forms can be utilized and still come within
the scope of the appended claims.
* * * * *