Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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SELF-LATCHTNG SOLENOID VALVE ASSFM»LY
AND C:O1VTROL C1'H(~U1T
BAC>C~'GRO~UN1) OF THE INVENTrON
Field ofthe InyEntion
The rresGnt invention relates, Sencrally, 1v solenoid actuatett valves arid,
more
cPrcifically, to self latchin; solenoid ac;tuatcd valves cold control circuits
for operating
same.
2. Description ot~dhe Xeluled Art
Solenoids are well known electrornechcuucal devices used to convert electrical
energy into mechanical energy and particularly into short stroke mechanical
motion. hs
such, solenoids have long been employed to actuate valves iii response to an
electrica.!
signal. For example, it is known in the related art to employ a solenoid to
bias a valve
member in one direction against the biasing force or a return spring. When
power to the
solenoid is intemipted, the return spring biases the value member back to its
first position.
In certain applications, valve members must be positively maintained in
different
predetermined positions to control the flow of fluids, such as air, through
the valve. nne
embodiment employed in the related art to achieve this results eliminates the
return spring
employed to bias the valve member to a specific location and replaces it with
a cer.~,~
solenoid. T'fie second solenoid is powered to positively m«ve the valE~c~
rn.ember to a
predetermined position and maintain i1 there until the second sc~lenoi~t is de-
energi~d and
the first solenoid is energized to rrtove the valve memhPr hack to the other
position.
However, this approach suffers from the disadvantage that double solenoid
operated valves
t nerease the Size. weight, enst and aompl~city of the valve. Furthc.~r, t n
the cast of pupp~l-
type valves, at Ieast one onil must be powered at adl times to ensure that the
vat vc member
is properly seated in the predetermined position. An unexpected, iuaclvcrtent
or even
planned shrtt down aF power to the solenoid results in a loss uC control of
the valve.
2S Ariditionally, in applications when: the efficiency of the solenoid is of
concern, such as
where there is a limited source of electrical power, solenoids which must he
oontinually
powered to hold a valve member in a spccifi~ position or double solenoid
actuated valves
are ~enerolly unacccptablc.
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2
To decrease the power dissipated by the solenoid, and particularly in
~prlications
where the solenoid is to be retained in the actuated position fir cignificant
time pariods,
latching mechanisms are employed in the related art to hold the rneehsnical
output of the
solenoid in one position or the other withnut_continuous power reduircd tv tha
sulcnctid.
To this end, conventional self latchirl6 solenoids known in flit ralatcWu~:
typically employ
a movable pole piece and a fixrd permanent ~ua~nef which are subject tc) an
electri>magnetic flux tc~ bias a valve ~«Ctnber_ LJsually, current flowing
through the coil in
one direction causes the pole picc;e to move away from the permanent magnet
and to be
attxactcd to aclulhcr stationary element in the solenoid thereby actuating the
valve member.
Power to the coil is then interrupted but the latent magnetic force acting on
the movable
pole piece causes it to remain magnetically attracted to the stationary
portion of the
solenoid or ''latched" in its last position.
Control circtuts are used to reverse the direction of current through the
solenoid coil
thereby reversing the direction of electromagnetic flux. Reversing the
direction of current
through the coil reverses the "polarity" afthe movable pole piece, driving it
in the apno~Tre
direction toward the permanent magnet where it again becomas''latci,arJ''
after the power
to the solenoid has been interrupted. The return spring is then typically free
to bias the
valve member in the opposite direction_ In this way, the valve member may be
emr~vad to,
and maintained in, any Isrndet~rmined position by actuation ofthc solenoid
aflar a relatively
short Ptrlse of electrical Current through the solenoid coil.
While the Self latching solcnoi~t aclualc;d valves tctlown in the related art
have
general ly workrd well famhCir intended purposes, there continues to be a head
for Smaller,
faster acting selF latching solenoid actuated valves having low power
consumption. This
is especially true for small pneumatic valves used, for example, to control
small air
cylinders. In addition, there continues to be a need for control circuits
which result in
lower power consumption than those circuits known in the related art.
SUMNrARY t1F THE INVENTION
The present invention overcomes these deficiencies in the related art in a
self-
latching solenoid valve assembly including a valve body having a pressurized
air cutsPly
inlet port for cc~mcnunic;ating with a source of pressurized air and at least
one cylinder pmt.
A valve membcris supported in the valve body so as to be movable between
predetermined
puaicioizs to seltrc;tivety direct pressurirxd air ti~om the inlet port to at
mast one cylinder
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port. A biasing member is employed for moving the valve member in one
~iirPCt~on and
a solenoid assembly is used to move the valve member in the nPposite
direction. The
solenoid assembly includes a housing with a solennid coil fiupported therein
and a hxcd,
ferromagnetic pole piece having apasSage extending therathrottgh with
apushpumnnuvabJy
supported in the passage. In addition, a ferromagnetic latch is suppurla;d by
the housing
and spacPrl floor the pole pieca. A permanent magnet is disposed between the
latch and
the pole piece. The permanent ~uaguct is movable toward the pole piece order
the
influence of an clcctromagnetiv flux generated by a pulse of current. flowing
through the
coil lo om dirCC~i~n thereby driving the permanent magnet against the pushpin
to move the
valve member to one predetermined position. Additionally, the permanent magnet
is
movable away from the pole piece and tc>ward the latch under the influence of
an
electromagnetic flux generated by a pulse ofcurrent flowing through the coil
in an opposite
direction. .When this occurs, the biasing member moves the valve member to the
other
predetermined position.
1 S 'fhe present invention also includes d circuit for controlling a valve
assernhly This
circuit is necessary in applications where electrical isolation of the two
control signal
supply lines is required to prevent damage of control cirr..uits caused by a
reverse polarity
feedback signal or other transient si ~nai. The circuit includes a solenoid
having a. coil. The
coil has a first end and a second c'~d. The iircuit also includes a first
swiCching circuit
2U electriraily connected to the first and second ends of thG coil to allow
curre~lt to pass
tharethrough in a fit direction to n tows Ctrc permanent magnet against the
pushpin in a first
axial direction. The circuit further includes a second switching circuit
eleetric;ally
conncxacd to the Crm and second ends of the coil to allow a current to pass
therethrough
in a second direction to move ttte permanent magnet away from the pushpin in a
second
25 axial direction. further, when either switching circuit is allowing current
to flow through
the coil, it electrically isolates one negative control source from the other.
In addition, the use of a pair of switching circuits electrically connected to
the coil
results in a relatively low voltage drop across the circuit when compared with
conventional
circuits known in the related art.
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BRIEF DI~~CR1PT10N OF THE DRAWINGS
Other advantages ofthe invention will be readily appreciated as the same
becomes
better understood by reference to the following detailed description when
considered t n
connection with the accompanying drawings, wherein.
Figure 1 is a perspective view of the self=latching solenoid valve 3c~~mbly of
the
present invention;
Figure 2 is a cross-sectional side view of the self latching solenoid valve
sssombly
showing the permanent magnet latched to the pole piece.:
Figure 3 is a cross-sectional side view of a self latching solenoid vtilvc
assembly
of the present invention showing the permanent masnat adjuccnt to the latch;
and
figure 4 illustrates the electrical control circuit employed to reverse the
direction
of the current through the coil.
D»:TATL»D DESCRirTrON OF THE ritEFEIRZZED EMl3c)DiMFNTfS)
A self latching soicnuid valve assembly of the present invention is generally
indicrxtcd at 10 in Figeu~s I through 3 where like numerals are used to
describE like
structure. Tltc solenoid valve assembly 1 U mclades d valve body 12 and a
solenoid
a~scmbly I 4 mounted to W a valve be>dy 12. The valve body 12 includes a
pressurized air
supply inlet port 16 for communicating with a source of pressurized air wd at
least one
cylinder port 18, ?U. A valve member 22 is supported in the valve body 12 so
as to he
movable between predetermined positions to selectively dimcL pressurized air
from the
inlet port 1b to at least one of the cylinder ports 18, 20.
Mare specifically, the valve body 12 is rectangular in shape and includes a
valve
bore 24 extending axially through the valve body 12 which provides fluid
communication
between the air supply inlet passage 16, a pair of cylinder passages 1 A, 2U
and a pair of
exhaust ports 26, 27. As shown in the drawings, the valve member is a poppet
valve ?2
which is supported within the valve bore 24 far reciprocal movement therein to
control the
flow of fluid through the valve body 12. The poppet valve member 22 is
preferably an
aluminum insert over molded and bonded with rubber in specific arena of th~~
valve
member 22 and ground to specifc dimensions to form valve alements '~fl, 32,
34. 'f'th~
valve elements 30, 32, 34 engage adjacent valve seats 3d, 35. 40, 41 r,-
esented in the valve
bore 24 for sealing various flow passages as the valve member 72 is
reciprocated betwaen
petitions within the valve bore 24.
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A cup shaped retainer 42 is threadably disposed at one end of the valve bore
24.
A threaded insert 44 is located in the bcue 24 opposite the retainer 42. A
biasing member
46, such as a coiled retttm spring, is positioned between the retainer 42 and
one end of the
poppet valve member 22. 'fhe return spring 46 applies a. constant biasing
force against the
S poppet valve member 22 and to the left as viewed in Figure 2. On the other
hand, the
poppet valve member 22 is actuated in the opposite direction, or to the right
as viewed lo
figure 2, under the influence ofthe solenoid assembly I4 as v~rill be
described in ~:reater
detail below. As described above and shown in the drawings, the valve assembly
employs
a four way valve. However, those having ordinary skill in ttie art ~uvill
appreciate that the
t 0 present invention as described and claimed herein may also be employed
with two way,
three way or any other type of solenoid actuated valve.
The solenoid a~embly 14 includes a housing, generally indicated at 4R The
housing 48 includes apole plate SU abutting the valve body 12, a cap 62
disposed nProsite
the pole plate 50 and a. solenoid can or frame 54 extending therebeiween The
frame 54
supports a coil 56 including a conductive wire 58 conventionally wrapped:round
a bobbin
60. 'fhe conductive wire 58 is connected to a source of electricAl current
through leads,
generally indicated at 62. The Leads 62 are supported in the can 57 and
include feed pins
Cr4, electrical contacts 66 and lead wires 68. The lead wires 6R arP
roperatively connected
to the soutre of electrical current. The direction of the crtrrant through the
coil S6 and thus
the direction of the electromagnetic force generated thereby is controlled by
tZ control
circuit, generally indicated at 7U in Figure 4 as will be described in greau:r
detail below.
A top plate 55 is mounted adjacent to the h~hhin EU and between a portion of
the fi-a.me 54
and the cap 52.
The pole plate 50 includes an opening ?2 extending thercthrough. 'fhc
sulc;noi.d
assembly 14 further includes a ferromagnetic pole piece 7~! having a stepped
~i~r~tivn 7$
with a srnallc;r Cross-sectinnal area than the rest vftho pole piece 74. ThC
stGppGd portion
78 is received in the opening 7~ r.~f the pole plate SO for mechanically f
xing tlm pole piece
74 to the pole plate S(7. A thin piece ofnon-nv~netic stainless steel SO caps
the pole piece
74 opposite the pole; Plate s0. A centrally located passage 82 extcttds
through the pole
3U piece 74. A P'irshpin 84 is movably supported in the passage 82.
The car S7. of the solenoid housing 48 includes a thrcttded bore 8ti, .A
ferromagnetic latch RR is threadably mounted to the solenoid housing 4S in the
bore Rti bvt
sErcuc;ed from the pole piece 74. The latch 88 is made of iron but may be
tiix~ic of any
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b
ierroniagnetic material. A permanent magnet 90 is disposed between the latch
8R anrl the
pole piece 74, A bushing 92 guides the magnet 90 within the bobbin bU. TMe
pernnanent
magr<et 90 is movable toward the pole piece 74 'under the influence of an
elrctrornagnetic
flux generated by a pulse of current flowing throui.;h the coil 56 in one
direction. This flux
> drives the permanent magnet 9U against the pushpin 84 to mc,vP the. valve
member ?2 to
one predeterrninedposition. Furthermore, the permanent magnet 90 is movable
away from
the pole piece 74 and toward the latch 88 under the iWluence of an oppositcIy
dircctad
electromagnetic flux generated by a puiaP of current flowing through the coil
SG in the
opposite direction. When this occurs, the biasing member46 moves the wdlve
member 22
1 U to another predetermined position, for e~:nmplc to the Icft as shown In
Figure 3.
To this end, the pushpin t34 presents lm cmia.~. ad head 94 which is disposed
adjacent
one. e.nd of the poppet vu,lvc; member ?? iur wnlactlng it when tile permanent
magnet 90
contacts the pushpin. 84. Irr addition, the enlarged head 94 oi~ the pushpin
$4 limits the
movement ofthe pushpiei 84 within the passage 82 of the pole piece 74 under
the iniluenee
1.5 ot'thc biasing me~r~bcr 46 through the valve member 22 when the permanent
magnet 94 has
moved wwaz~ci the latch 88. 'I-he limited movement of the pushpin 84 presents
a gap 96
t~twoen the permanent magnet 9U and the pole piece 74 as shown in 1~ figure 3.
As illustrated in r figure 2, a space t 02 is defined between the latch 8R and
the
permanent magnet 90 when the permanent magnet is moved toward the pole piece
74.
2U 1-'urthermore, the position of the latch 88 toward and away from the
permanent magnet 9U
may be adjusted by adjusting the position of the threaded latch 8$ within the
threaded bore
86 in the cap 52. Accordingly, the six of the space 1 U2 between the latch 88
and the
permanent magnet 90 when the permanent magnet has moved toward the pole piece
74
may be adjusted. In this way, the attractive force between the latch 88 and
the pennanent
25 magnet 9U may be modulated.
The permanent magnet 90 may be of any suitable type but preferably is a. rare
e~erth
neodymiaun-iron~boron magnei_ The permanc.'nt magnet 90 dernes north anct
south poles
at opposite ends thereof' as indicated in the figures. However, it will be
appreciated by
those having ordinary skill in the art that the poles may he reversed. A
protective cap E~8
30 is bonded to the north pole and a protective cap 100 is bonded to the south
pole. Thcsc
caps 98, 100 protect the permanent magnet 90 as it is cycled toward the pole
pierc 7~ amd
the latch 88.
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7
Referring to Figure 4, a circuit, generally indicated at 70, is shown for
evntmllinQ
the self latching solenoid valve assembly 1 U. The circuit 70 includes a
solenoid I 4 having
a coil 56 and a permanent magnet 9U. The electrical leads 62 of the coil Sli
extend out o1'
a first end 1 SO and a second end 152 of the solenoid 14. t'.urrent travels
through the coil
S 56 through the lead 62 at either end 15h, 152. The di.reclion of the current
as it passes
through the ends 1 S0, 1 S2 determines whether the permanent magnet 90 will be
bia..sed in
a first axial direction or a second axial direction apposite that of the first
axial direction.
Connected to the first end 1 SO ofthe solenoid l4 is a first switching circuit
154 and
a second switching circuit 156. The first switching circuit l S4 allows
current ro flow
U through the solenoid 14 in one direction and the second switching circuit I
5h allows
current to flow through the solenoid I4 in a second direction opposite in
directic,n to that
of the first direction.
2'he first switching circuit 154 includes a first transistor 1 S8 and a second
transistor
160. 1n the embodiment shown in Figure 4, the firsttransistor l :5R is a pup
bipolar junction
IS transistor. The second transistor 160 is a MOSFET. 'the reaccns for using
two different
types of transistors is to reduce the overall voltage rlrnp across tha
trainsistar3 1 ~8, I 6o a5
well as tct reduce the bias requirements. A base 162 of the first transistor
16Q is cannccteci
to a gate 164 of the second t~cc8ztsistor 160 through .j resistor 166. The
gate 164 of the
second transistor 16U is also connected to a drain 168 of the second
transistor 160 through
~0 a resistor I 7U. The drain 1 (i8 and resister 1 ?0 are. also eonnectad to a
negative input
control source 172. 'the negative input control snuree 17? provides the input
rcyuired to
determine whether the self latching valve assEmbly 10 is to he forocd in the
dirGCtiun
providod in the first switching aitruit 154. A collector 174 of the first
t~~ausisl.ur 1'78 is
connected to the first end 1 SO of the solenoid 1~1 ;and a source of 17f ur
the second
25 tt~tlsistor I60 is ccmnected to the. second end 1 S2 of the solenoid 14.
~1u Ctnitter 17$ Of the
~~tL'st tt'anSi~r 1 SS is connected to the power supply, 24 volts iu lttis
embodiment.
The cecond switching circuit 156 mirrors the first swil,c;hing circuit in that
tt
incior~ies a third transistor I 80 srtd a fourth transistor 182. fhe
differences are that the third
transistor 1 g0 is a bipolar junction transistor with ita wllactor 184
electrically cotanLeted
'itl to the second end 152 of the solc;noid 14 and the Cuurlh transistor 182
is a MC)Sl?ET with
its rnurce 1 Sfi electrically connected to the first cud 1 SO of the solenoid
14. A, resistor I 88
is connected between the gate 19U of the fourth transista~ 182 and the base 1
X72 of the third
tra~imur I 8U. Another resistor t 94 is connected between the date 190, tlm
resistor 158,
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g
and the drain 196 of the fourth transistor 182. The resistor 194 and the drain
196 are also
cc.~rtnecied to a negative input control source 198 providing input to sW tch
the self latching
valve assembly 10 in the opposite direction as that from the negative input
172. Power is
received by the solenoid 14 through the emitter 200 o.f he third transistor
180 which is
connected directly to the power supply.
A red LED 202 and a green LED ?04 are connected to the first end 150 and the
second end 1 ~? of the solenoid 14. These L.EDs 202, 204 are conneeti:d in
opposite
directions such that when the solenoid 14 is aetivatc~i in one direction, the
red LED 202
will emit light and when the solenoid I4 is activated in the apposite
direction, the green
LED 204 will emit light. This allows an operator to view the assembly 10 and
know in
which mode the aelf latching valve assembly 10 should be operadnp.
UPERATIUN
In operation, current is driven through the coil 56 in one direction which
generates
an electromagnetic flux. The electromagnetic flux polarizes the ale: piece 74
attracting
the permanent magnet 90. The movable permanent magnet 9015 thus driven wward
the
pole piece 74 across the gap 96 and engages the pushpin R4, as shown in Figure
2. This
drives the pushpin $4 to the right moving the poppet valve 7.7. also to the
right and against
the hiasing force of the coil spring 46.
Power to the coil Sfi is then interrupted. 1-lc~wwer, the perrnanont magnet 90
remains in its position shown at Figure 2 and ''latcheri" to the pole piece 74
due to the
residual attractive forces that remain even in the absence of an
electromagnetic flux. In this
disposition, valve element 30 cooperatively s~~:ais with valve seat 3b ;md
vrrtvc elenzcnt 32
cooperatively seals with valve seat 4(l. Conversely, the valve element 32 is
uYcn with
respect to the valve seat :~8 and the valve element 34 is open with rcspecl to
the valve seat
41.
Vi~ith the valve member 22 shifted to the right rxs described aLuvc and shown
in
Figure 2, pressurized air t~nwing into the valve body 12 via the inlet purl 1
b passes tf~e
valve element 37. and valve seat 38, flows through the; valve L«rC 24 and out
the cylinder
passage 18. At the same time. air is exhausted from the cylimdcr passage 20
past the valve
element 34 and valve seat 4i and out the valve body 12 via the exhaust port
l7. T'lte
exhaust port 2~ is sealed by the valve element 3U and tlzc walvc seat 36.
The valve member ~~ remains in this dispc~sitiom unlit current is agaita
driven
through the coil 56 in r1n oPp~.Qiy~~ direction. This producea rut
clcctmma~uclic: flux in a
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~liccction opposite to the first flux described above_ 1'he oppositely
directed magnetic flux
clmcyrs the polarity of the pale pioce 74 which acts to repel the permanent
magnet 90.
Thus, the permanent magnet 90 moves away from the pole piece ?4 and toward the
latch
88 uuereby closing the spa~c~ 102 therebetween. 'fhe coil spring 46 biases the
valve
mmnher 2? to the !eft as shown in Figure 3. The pushpin 84 is also shifted to
the left under
tl~a influence of this biasing force acting through the valve membc;r 22.
Current to the coil
56 is then interrupted. However, the permanent magnet 9U remains in the
position shown
in Figure 3 dnd is "latched" to the latch 88 due tea the residual attractive
forces that remain
ev~c~ in the ahsence of an electromagnetic flux.
In this disposition, the valve element 32 cooperatively Seals with the valve
seat 38
and valve element a4 cooperatively seals wills valve seat 41. Conversely, the
valve
dement 3? is now open with respect to the valve seat 40 and the valve element
30 is open
with respect to the valve seat 36.
With the valve memher 22 Shifted to the left as described above and shovm in
l5 Figure 3, pressurised air Mowing into the valve body 12 via the inlet port
1.6 passes the
valve element 3~? and valve seat 40, flows through the valve bore ?4 and then
out the
cyliuciGr passage 2U. At the same time, air is exhausted from the cylinder
passage 18, past
rhc vat vc; element 30 and valve seat 36 and then out the valve body 12 via
the; exhaust port
2C~. The exhaust port 27 is sealed by the valve element 34 and the valve seat
41. ?he valve
?0 mctnber 22 remains in this disposition until current is again driven
through the coil ~fi in
an opposite direction. The valve member 22 is then shifted back to the right
as shown in
ribule 2 and described above.
Iu addition, a pair of switcheng circuits is employed to control the direction
of
cLlt'i'CIIt LU the coil and to electrically isolate one negative control input
source from the
25 c~ll~Cr negative conuol input source. This effectively prev~;nts damage to
the control
circuits ~:ausad by a reverse polarity feeclhaek signs! or other transient
signal. Switching
circuit' of the present invention provide a relatively low voltage drop across
the circuit
wlicn cu~upered with conventional circuits known in the related art.
Accordingly, the self
Iatcluy solenoid valve assembly of the present invention facilitates reduced
cost and size
30 in a fast-acting v:~lvC r~sSGmbly having self latetung capabilities.
The inveutium lees bc~n described in a~n illustrative manner. It is to be
understood
that the tcrrninolo~y wluch has been used is intended to be in the nature of
words of
~fm-ipEic~a rr~W er ttlan of limitation.
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la
Many rnodificati~ns and variatsons of the invzntion are possible in light of
the
shove taachiags. Thctefurc, within the scope ot~the appended claims, the
invention t2lay
be practiced other than as spcv:ifically described.
