Solenoid valve having coaxial armatures in a single coil design

A solenoid valve having a coil, a pair of armatures including an inner armature slidable within a coaxial outer armature and the outer armature slidable within the coil, and a pair of valves. One of the valves is at or near the end of the outer armature extending from the coil, and the other valve is at or near an end of the inner armature extending from the valve-bearing end of the outer armature. Thus, both valves are at the same side of the solenoid valve assembly. When a magnetic force is applied by a current flowing in the coil, at least the inner armature is drawn in a direction into the coil so as to open the valve at its end. An increased magnetic field caused by increased current in the coil eventually results in the outer armature being drawn into the coil, thereby also opening the valve at the end of the outer armature. The valve is suitable for use in many fluid control applications, but is especially useful for control of gases and for control of intermittent gas ignition systems.

BACKGROUND OF THE INVENTION 
This invention relates to electromagnetically operated valves, and more 
particularly to an improved solenoid valve having coaxial armatures in 
which only one coil is necessary. 
Three-way solenoid valves are known and have been used to control fluid 
flow, including gaseous fluid flow. For example, U.S. Pat. No. 5,218,996 
discloses a solenoid valve having three operating positions for the 
purpose of rendering the system more efficient when regulating fluid 
pressure. The disclosed solenoid valve has inner and outer coaxial coils 
and first and second coaxial armatures. A first ball valve is secured to 
and movable with the first armature, and a second ball valve is secured to 
and movable with the second armature. A first compression spring urges the 
first armature downward into a position wherein the first ball valve 
normally closes an exhaust port. A second compression spring urges the 
second armature downward into a position wherein the ball valve is open. 
When one of the coils is energized, the first armature moves against the 
resistance of the first compression spring to open the first valve. The 
independent armatures allow only one of the valves to be open at a given 
time, but allows both valves to be closed at the same time. 
U.S. Pat. No. 4,619,289 describes another solenoid-controlled valve that is 
said to be capable of achieving changeover and control at three positions 
by exciting only one particular solenoid. The solenoid has first and 
second coaxial armatures or members. The armatures are independently 
moveable along the axis via a solenoid coil. 
While the previously known solenoid valves are useful for the purposes for 
which they are described, there is still a need for a valve having 
built-in sealing redundancy, which is particularly useful, desirable and 
required in low-pressure/high-pressure fluid applications. 
BRIEF DESCRIPTION OF THE INVENTION 
There is thus provided, in accordance with one aspect of the invention, a 
solenoid valve assembly comprising: a coil having a coil axis; a first 
armature and a second armature, the first and second armatures being 
moveable in first and second opposite directions along the coil axis and 
having valve coupling portions extending out of the coil in the first 
direction; a first valve and a second valve, the valve coupling portion of 
the first armature being operatively connected to a portion of the first 
valve in a manner so that movement of the first armature along the coil 
axis moves the first valve between open and closed positions, the valve 
coupling portion of the second armature being operatively connected to a 
portion of the second valve in a manner so that movement of the second 
armature along the coil axis moves the second valve between open and 
closed positions; and at least one of the first and the second armatures 
is responsive to a magnetic field generated by the coil. The armatures 
preferably comprise inner and outer armatures, which may be coaxial, and 
the inner armature is preferably free to slide inside the outer armature. 
The coil and the inner and outer armatures may be configured so that 
magnetic flux generated by the coil can selectively engage and disengage 
one or both of the armatures. The outer armature may be made of plastic or 
a non-magnetic material, and may be a hollow tube closed at an end 
opposite the valves. In this case, a first spring may be disposed between 
the inner armature and the closed end of the outer armature, the inner 
armature may be free to slide within the outer armature, and a second 
spring may be configured to bias the outer armature outward from the coil, 
wherein application of current to the coil causes a magnetic field 
generated by the coil to retract the inner armature inward towards the 
coil. The first spring may then be compressed until the outer armature is 
retracted inward towards the coil, or a member of the inner armature 
outside the outer armature may strike a member at the open end of the 
outer armature to thereby retract the outer armature inward, towards the 
coil. 
In accordance with another aspect of the invention, there is provided a 
solenoid valve assembly comprising: a coil; a well slidable within the 
coil and having an open, first valve coupling portion extending out of the 
coil in a first direction and a closed end within the coil; a shaft 
slidable within the well and having a second valve coupling portion 
extending outside of the open, first valve coupling portion of the well; a 
first valve and a second valve, the first valve coupling portion 
operatively coupled to the first valve for opening and closing the valve 
and the second valve operatively coupled to the second valve coupling 
portion; a first spring configured to bias the well to close the first 
valve; and a second spring configured to bias the shaft to close the 
second valve; wherein the coil is configured to generate a magnetic force 
on at least one of the well and the shaft to oppose the bias force of the 
spring thereon. The open, first coupling portion of the well may be 
flanged, and an end of the well opposite the open end may be closed, with 
the second spring disposed inside the well. The first spring may be 
disposed outside the well. The shaft may be magnetic and the well 
nonmagnetic, and the second valve and well may be configured so that, when 
current is applied to the coil to generate a magnetic force, the second 
valve strikes the flange of the well. The shaft and the well may be 
configured to move as a unit thereafter in response to magnetic force from 
the coil. 
In accordance with yet another aspect of the invention, there is provided a 
method for controlling flow of a fluid through a path comprising: 
magnetically operating a first valve on a portion of a first armature 
extending outward from a coil of a solenoid valve assembly to control the 
flow of fluid through the path, the coil having a coil axis; and operating 
a second valve on a portion of a second armature extending from the coil 
of the solenoid valve assembly to control the flow of fluid through the 
path; wherein the armatures are moveable along the axis of the coil in 
first and second opposite directions, and the outwardly-extending portions 
of both the first and the second armatures extend outward from the coil in 
the first direction. In this method, the first and the second armatures 
may be coaxial, and the step of operating the second valve may comprise 
either or both of compressing a biasing spring with the inner armature 
until the outer armature and inner armature move as a unit in the second 
direction or striking a flange on the outer armature with either or both 
of a portion of the inner armature or the first valve. 
It is thus an object of this invention to provide an electromagnetically 
operated valve that provides redundant valve operation in a minimum of 
space. 
It is a further object of this invention to provide an electromagnetically 
operated valve that can provide redundant valve operation with only one 
electromagnetic coil. 
It is an additional object of this invention to provide a method of 
controlling a flow of fluid through a path employing coaxial valves and 
requiring only a single electromagnetic coil. 
It is an additional object of this invention to provide an 
electromagnetically operated valve that is suitable for controlling gas 
flow in a device such as a gas furnace, a gas water heater, a gas space 
heater, a gas clothes dryer, a gas boiler, a gas-operated fireplace, or a 
gas cooking appliance, and other devices in which redundant valve 
operation may be advantageous. 
The manner in which these and other objects of the invention are achieved 
will be apparent to one skilled in the art upon study of the figures and 
the accompanying description.

DETAILED DESCRIPTION OF THE INVENTION 
Without intending any loss of generality, the devices and methods of this 
invention will be described in conjunction with gas fuel control valves, 
inasmuch as the invention is considered particularly advantageous when 
employed in such devices. It will be recognized, however, that the devices 
and methods of this invention may be applied more generally to various 
other fluids, both gaseous and liquid, and may be used advantageously to 
control the flow of such fluids in devices other than those that are 
described herein. In addition, where the discussion refers to control of a 
current flowing in a coil, it will be recognized that control of either 
current or voltage may be possible, with equivalent results. 
FIG. 1 is a cross-sectional view of a solenoid valve assembly 10 of the 
present invention. Valve assembly 10 comprises a coil 14, an outer 
armature 16, an inner armature 18, a first valve seal 20, and a second 
valve seal 22. A portion of outer armature 16 slidably surrounds inner 
armature 18, and is preferably coaxial therewith. A cover member 12 is 
provided over coil 14. Valve assembly 10 is mounted on a body 24 of a 
device such as a gas control valve. An inlet port 26 in body 24 is 
provided for the entry of gas. 
Armatures 16 and 18 pass through a bore 36 in body 24. Inner armature 18 
extends past the end of outer armature 16 through chamber 28, which 
connects with inlet 26. Inner armature 18 is free to slide inside outer 
armature 16, and outer armature 16 is free to slide inside coil 14. An 
outlet path 30 connects to chamber 28. First valve seal 20 at or near an 
end of outer armature 16 is biased by a spring 21 to rest on a first valve 
seat 32 (which may be a part of body 24) so that when coil 14 is not 
energized, flow of gas from inlet 26 to chamber 28 is prevented. 
Similarly, second valve seal 22 at the end of inner armature 18 extending 
beyond the end of outer armature 16 is biased by a spring 23 so that it 
rests on a second valve seat 34 to prevent flow of gas from chamber 28 to 
outlet 30. 
Although spring 21 is shown here as providing a bias force between a 
portion of body 24 and valve seal 20, it is not necessary that the bias be 
provided directly to the valve seal 20. For example, the bias force could 
instead be provided to a flange on outer armature 16. Similarly, the bias 
force of spring 23 could be provided to a flange of inner armature 18 
rather than directly to valve seal 22. However, unlike spring 21, which 
has one end stationarily compressed against a portion of body 24, spring 
23 is compressed between valve seal 22 (or a flange on inner armature 18) 
and an end portion of outer armature 16. 
In operation, when no current is applied to coil 14, valve seals 20 and 22 
rest against their respective valve seats 32 and 34, shutting off flow of 
gas from inlet port 26 to chamber 28 and from chamber 28 to outlet path 
30. To open these paths, current is applied to coil 14 to generate a 
magnetic field. This magnetic field can engage one or both of the 
armatures 16 and 18, depending upon the amount of current flowing in the 
coil (and hence, the strength of the magnetic field) and the relative 
spring constants of springs 21 and 23, for example. In the embodiment 
shown in FIG. 1, inner armature 18 is spaced from the sealed end 38 of 
outer armature 16 and outer armature 16 is spaced from cover member 12 
when valve seals 20 and 22 are in the "off" position. Thus, valve seal 20 
may disengage from valve seat 32 before valve seal 22 disengages from 
valve seat 34, or valve seal 22 may disengage from valve seat 34 before 
valve seal 20 disengages from valve seat 32, or both may disengage 
essentially simultaneously when sufficient current is applied to coil 14. 
When both are disengaged, gas flows into inlet port 26 as indicated by 
arrow A, into inner bore 28 as indicated by arrow B, and out through 
outlet path 30, as indicated by arrow C. 
When current through coil 14 is reduced or removed and the magnetic field 
generated by the coil weakens, the bias forces of springs 21 and 23 act to 
cause outer armature 16 and inner armature 18 to slide outwardly from coil 
14. Depending upon the balancing of the forces on inner armature 18 and 
outer armature 16, one or the other of valve seals 20 and 22 will come to 
rest first on their respective valve seats 32 and 34, or both valve seals 
will come to rest simultaneously. It will thus be seen that a redundant 
valve construction is achieved wherein two valves are provided in a small 
space, with a single coil efficiently used to supply an operating magnetic 
flux. 
A cross sectional view of another solenoid valve assembly 10' of the 
present invention is shown in FIG. 2. This embodiment comprises a coil 14, 
a redundant shaft 16' and a main shaft 18'. Coil 14 is wound on a bobbin 
52 with metallic sleeves 54. Redundant shaft 16' slides in a tube 50 
inside bobbin 52 and sleeves 54. A gasket 56, plate 58, and coil bracket 
64 are provided for mounting purposes. Coil bracket 64 may also 
advantageously shape and confine the magnetic field of coil 14. 
Redundant shaft 16' (which need not be metal, and could be plastic or made 
of various other materials) is sealed at an end 38 inside tube 50, but is 
otherwise hollow. Main shaft 18', which is of a magnetic material that is 
attracted into the central tube 50 of coil 14 when coil 14 is energized, 
is slidably engaged within redundant shaft 16', but is biased away from 
end 38 of redundant shaft 16' by an internally mounted spring 23'. A 
redundant valve seal 20' is fixedly attached at or near an end of 
redundant shaft 16' opposite end 38. Preferably, a plate 62 is also 
affixed just behind redundant valve seal 20' by retaining ring 60, and end 
19 of redundant shaft 16' is flanged to hold valve seal 20' in place. 
Spring 21 provides a bias to redundant shaft 16' to force redundant valve 
20' to rest on redundant valve seat 32', which thereby is closed to the 
passage of fluid. In the embodiment illustrated, spring 21 is disposed 
around a portion of redundant shaft 16' extending outside of tube 50, and 
provides pressure between an outer flange 51 of tube 50 and plate 62 or 
retaining ring 60 behind plate 62. Other placements of spring 21 that 
provide bias for the closure of redundant valve 20' on redundant seat 32' 
may be used. In this position, spring 23' inside redundant shaft 16' 
biases main shaft 18' further outward, seating main valve 22' on main seat 
34' somewhat beyond end 19 of redundant shaft 16'. 
When a sufficient amount of current passes through coil 14, a magnetic 
field is generated that pulls main shaft 18' into tube 50. This results in 
main valve 22' being lifted off of main seat 34', which thereby opens the 
main portion of the valve. As the main shaft 18' is lifted, spring 23' is 
compressed. As an increased amount of current passes through coil 14, the 
main shaft 18' is lifted sufficiently and spring 23' is compressed 
sufficiently to overcome the bias of spring 21 and to lift redundant shaft 
16'. This causes redundant valve 20' to be lifted off redundant seat 32', 
opening the redundant valve. At a sufficiently large current, both valves 
are fully open. As current in coil 14 is reduced, the process proceeds in 
reverse, first seating redundant valve 20' on redundant seat 32', and next 
seating main valve 22' on main seat 34', thereby closing both valves. FIG. 
3 is a schematic representation, in cross-section, of the solenoid valve 
assembly 10' of FIG. 2 installed in a gas control valve 100. A few 
additional details of assembly 10' are shown, including terminals 66 of 
coil 14, a printed circuit (PC) board 68, and a manual switch 70 that may 
be used to manually control current applied through terminals 66 to coil 
14. Aside from solenoid valve assembly 10', gas control valve 100 also 
comprises a filter screen 72 at inlet 26 for removing debris particles 
that may be present in a flow of gas A, a control gas orifice 74, a 
diaphragm 76, a main regulator valve 78, a servo regulator 80, a regulator 
vent 82, a by-pass path 84, an outlet sense port 86, an outlet filter 
screen 88, and an outlet 90. Except for solenoid valve assembly 10', gas 
control valve 100 is similar to White-Rodgers 36E Combination Gas Control 
Valve available from White-Rogers Division, Emerson Electric Co., St. 
Louis, Mo. The interested reader is referred to U.S. Pat. No. 3,727,836 to 
Visos et al., directed to a manifold gas valve, which describes the 
operation of a regulator and diaphragm operator, and which is hereby 
incorporated by reference in its entirety. (U.S. Pat. No. 5,199,456 to 
Love et al. shows and describes solenoid constructions that have 
previously been used in gas control valves. The gas valve described in 
Love et al. has a moveable metallic plunger and a coaxially mounted 
stationary metallic core member, and may be contrasted with those of the 
invention.) 
The reader is reminded once again that the figures are not necessarily 
drawn to scale. In the case of FIG. 3, it is particularly noted that the 
gap between redundant shaft 16' and tube 50 is exaggerated, and should 
preferably be about 0.010 inch. The gap between the main shaft 18' and the 
redundant shaft 16' is also preferably 0.010 inch. By comparison, 
redundant valve 20' and redundant seat 32' may typically separate in 
operation by as much as 0.250 inch. Of course, while these gaps and 
separations may be typical and/or preferred, these and other dimensions of 
the solenoid valve itself may be adjusted as necessary for different 
applications. 
FIG. 4 is a flow block diagram of the structure of FIG. 3. Gas enters at 
inlet 26 and passes through filter screen 72. When redundant valve 20' is 
lifted from redundant seat 32', gas flows through the redundant valve and 
is divided into two flows. One of these flows passes through the 
main/regulator valve 78, the filter screen 88, and outlet 90. When main 
seat 34' and main valve 22' are open, the other flow is directed through 
the main valve, past the control gas orifice 74, and to the back of 
diaphragm 76, to servo regulator 80 and servo by-pass 84. The flows of 
servo regulator 80 and to servo by-pass 84 are then reunited at outlet 
sense port 86 and this second flow rejoins the first to pass through 
filter screen 88. 
FIG. 5 is a schematic representation, in cross-section, of a control valve 
100' incorporating yet another solenoid valve assembly 10" of the present 
invention. Except for solenoid valve assembly 10" and modifications made 
in body 24' to accommodate assembly 10", the remainder of the construction 
of control valve 100' is similar to the White-Rodgers 36E Combination Gas 
Control Valve discussed above. 
When an appropriate AC voltage is supplied by a controller (such as a 
thermostat, which is not shown in FIG. 5) and when manual switch 70 is in 
the "on" position, built-in rectifier circuitry (not shown) supplies 
rectified DC current to coil winding 14. The current through coil 14 
generates a magnetic field that is concentrated and shaped by coil 
brackets 64 and sleeves 54 to provide an operating force on shaft 18'. 
This magnetic force is sufficient to override the main return spring 23', 
which provides a biasing force on shaft 18' in an opposite direction to 
the magnetic field, which pulls shaft 18' into coil 14. Shaft 18' slides 
within redundant shaft or well 16' (which may be non-magnetic) and moves 
towards the closed end 38 of redundant shaft 16'. This movement lifts the 
main valve 22' off its seat 34', thereby opening a gas path 30 and 
compressing main return spring 23' until main valve 22' strikes flanged 
end 19 of redundant shaft 16' 
The impact force of main valve 22' striking the flanged end 19 of redundant 
shaft 16' combines with the magnetic force provided by coil 14 to override 
the biasing force of "redundant" return spring 21 and inlet gas pressure, 
thereby lifting redundant valve 20' off its seat 32'. (See FIG. 5A, which 
shows both valves in their open state) Main shaft 18' and redundant shaft 
16' continue to move as a unit within the non-magnetic closed end tube 50 
until the magnetic and spring forces reach equilibrium wherein both valves 
are open, thus allowing high capacity flow of gas from inlet 26 to the 
inner chamber 23. Gas flow to the outlet is momentarily blocked by 
regulator valve 15. The pressure differential between the inlet and the 
outlet causes gas to flow through the open path 30 to the control gas 
orifice 74. The limited amount of gas coming through the control gas 
orifice 74 is split into two paths, one going to the servo diaphragm 81 
and one going to the back of the regulator diaphragm 76. Pressure 
differential caused by the gas going to the back of the regulator 
diaphragm 76 forces the diaphragm to flex, pushing against regulator shaft 
92. This force overrides the regulator spring 94 and the regulator shaft 
92 lifts the regulator valve 15 off its seat 96, allowing high capacity 
regulated flow from the inner chamber 23 to outlet 90. 
As long as appropriate current is supplied, the forces on the solenoid 
shaft 18' remain in equilibrium and high capacity flow is allowed from 
inlet 26 to the inner chamber 23. Gas flow to outlet 90 is regulated by a 
balance of pressures. This balance is adjustable and controlled by the 
regulator spring 80. The biasing force of spring 80 is adjusted by turning 
the regulator adjust screw 98. This force controls the amount of gas 
allowed to flow past the servo regulator seat 102 and into the gas path 86 
leading to outlet 90. The balance of pressure caused by this adjustment 
controls the position of the regulator diaphragm 76, which in turn 
controls the position of the regulator valve 15. The position of this 
valve relative to its seat 96 controls the flow of gas from inlet 26 to 
outlet 90. The effect of fluctuations in the inlet pressure within the 
specified range of operation are damped and effectively eliminated by this 
system. The inlet filter 72 and the outlet filter 88 prevent particles 
from entering the valve and interfering with proper operation. 
When current to the valve coil 14 is interrupted, either by the controller 
(e.g., the thermostat interrupts AC voltage) or by turning off the manual 
switch 70, the magnetic field collapses. The force equilibrium that holds 
the main 22' and redundant 20' valves off their seats 34' and 32' 
respectively is eliminated and return springs 23' and 21 force the valves 
closed. Closing redundancy is achieved by the independent closing of the 
two valves 20' and 22', the closing of either of which is separately 
capable of shutting off the gas flow. Redundant valve 20' directly shuts 
off the gas flow by closing against its seat 32'. Main valve 22' 
indirectly shuts off the gas flow by closing the gas path 30. A bleed or 
servo by-pass across the servo regulator seat 102 (actually, a small slot 
in diaphragm 81) allows the pressure in the back of regulator diaphragm 76 
to equalize with the outlet 90 pressure. This allows the regulator spring 
94 to return the regulator diaphragm 76 to its original position, closing 
regulator valve 15. 
A difference between the solenoid valve assembly 10" shown in FIG. 5 and 
assembly 10' shown in FIG. 3 is the structure by which the outer armature 
is lifted by upward movement of the inner armature. In the solenoid valve 
assembly of FIG. 3, as spring 23' is depressed, main valve 22' is lifted 
off main valve seat 34', opening the main valve. As spring 23' is 
depressed more, redundant valve 20' is eventually moved off its seat 32' 
by redundant armature 16'. In the structure of FIG. 5, inner shaft or 
armature 18' moves upwardly, lifting its valve 22' off seat 34'. As the 
inner armature 18' continues to move upwardly, its valve 22' impacts 
flanged end 19 of outer or redundant armature 16'. This impact and the 
continued upward movement of shaft 18' causes shaft 18' to lift redundant 
valve 20' off its seat 32'. 
It will thus be seen that the solenoid valve constructions of this 
invention having a single coil with co-axial armatures and a valve on each 
armature at the same side of the solenoid valve is useful to provide a 
redundant valve construction in a smaller space than previously known for 
structures having similar function. Two mechanically independent valves 
may be provided in a small space, both of which are supplied with an 
operating flux from a single coil. Those skilled in the art will recognize 
that the inventive solenoid valves of this invention may be useful in many 
applications and for control of many different types of fluids, and are 
especially useful for control of gaseous fuel flow. Inasmuch as many 
modifications within the spirit of the invention will be apparent to those 
skilled in the art, the scope of the invention should be determined by 
reference to the claims appended below and the full scope of equivalents 
as provided by applicable laws.