Improved magnetostrictive materials are combined in a novel arrangement to provide a transducer of the electromechanical type particularly suited for the precise control of fluid flow. An embodiment according to this invention comprises a valve assembly having a discharge ported, cylindrical housing of a material exhibiting positive magnetostriction, a plunger of a material exhibiting negative magnetostriction disposed within the housing, the plunger provided with a tapered nose initially in close fitment within the discharge port to restrain the flow of fluids, and means to create a magnetic field around the assembly. As the materials are exposed to the magnetic field the housing expands relative to the contracting plunger, causing the plunger to separate from close, seated fitment within the discharge port, thereby allowing flow through the port. One of the materials may be selected from a non-magnetostrictive material. An alternative embodiment according to this invention comprises a magnetostrictive member interconnected to a plate slidably disposed within a conduit, said plate having an aperture adapted for alignment with the interior conduit passageway, and means to create a magnetic field around the magnetostrictive member. As the member is exposed to the magnetic field, the plate aperture is adjusted within the conduit passageway to control the flow of fluids.

BACKGROUND OF THE INVENTION 
This invention relates to magnetostrictive transducers and more 
particularly to transducers adapted for use as fluid flow control devices. 
DESCRIPTION OF THE PRIOR ART 
Although there are many electromechanical transducers, there are some 
electromechanical conversions which are more demanding on known 
transducers. In the past, because of the inherent disadvantages in the 
materials then available, magnetostrictive transducers were not able to 
generate usable magnetostrains that could be transformed into sufficient 
mechanical motion. 
The ability of a transducer in general to interconvert two forms of energy 
rests on the particular properties of the material used. Piezoelectric 
substances, like quartz, ammonium-dihydrogen-phosphate (ADP), and Rochelle 
salt acquire a charge between certain crystal surfaces when placed under a 
stress. 
Conversely, they acquire a stress when a voltage is placed across them. 
Electrostrictive materials exhibit the same effects, but are 
polycrystalline cermaics that have to be properly polarized by a high 
electrostatic field. Some examples are barium titanate and lead zirconate 
titanate (PZT). A magnetostrictive material is one that changes dimensions 
when placed in a magnetic field, and conversely, changes the magnetic 
field within and around it when stressed. Magnetostrictive materials can 
also be polarized in order to avoid frequency doubling. Heretofore, 
typical magnetostrictive materials were composed of nickel- and 
iron-alloys. Although these magnetostrictive materials exhibit some 
magnetostriction at room temperatures which enables them to be used in 
transducer devices, their uses have been extremely limited and it has 
always been desirable to obtain other magnetostrictive materials which 
have much greater magnetostriction. 
Certain heavy rare earth elements have magnetostrictions approximately 
1,000 times greater than iron and about 200 times greater than nickel. 
However, a disadvantage of these materials is that these large 
magnetostrictions are present only at cryogenic temperatures and are most 
pronounced in the neighborhood of absolute zero. At room temperature 
(about 300.degree. K.) these rare earth elements exhibit very little 
magnetostriction since their magnetic ordering temperatures fall below 
room temperature. Under these conditions, magnetostrains generated are 
typically of the order of 10-100 (.times.10.sup.-6 in/in.). A more 
desirable magnetostrictive alloy would be one that develops large 
magnetostrains and is not limited to operating temperatures below room 
temperatures. 
Several new alloys of these rare earth elements have been developed which 
possess similar thermal and mechanical properties, but which also possess 
large magnetostrictions. Maximum strains of from 300-3,000 
(.times.10.sup.-6 in/in.) at room temperatures are now attainable--over 30 
times greater than those previously attained. These alloys are generally 
ternary mixtures of two heavy rare elements which include praseodymium 
(Pr), terbium (Tb), samarium (Sm), holmium (Ho), erbium (Er), and 
dysprosium (Dy) in combination with iron (Fe). Quatenary alloys combining 
three heavy rare earth elements with iron are also promising. 
A need for precise and rapid micrometering of the flow of gases or liquids 
has long existed, and although many devices have been developed to meet 
that need, none have been very simple in design or in operation. Most have 
required several complex mechanical elements to cooperate together to meet 
whatever the requirements may have been. The need for a simple flow 
control valve exists in applications calling for microliter flow control, 
for use as a controlled leak source, for use in a mass spectrometer, for 
supplying anesthesis gases, for blending and/or bleeding of fuels in 
process control systems, and in applications calling for extremely rapid, 
precise, and controlled motions adapted to be used in an active feedback 
control system. Due to the recent advances in materials technology, 
magnetostrictive alloys combined with the above mentioned rare earth 
elements can be utilized in a novel fashion to serve as precise flow 
control devices. 
SUMMARY OF THE INVENTION 
Accordingly, it is an object of the present invention to provide an 
improved transducer. 
Another object of the present invention is to provide an improved 
magnetostrictive transducer which is small, compact, rugged, and yet 
reliable, extremely simple in design and inexpensive to manufacture. 
It is another object of this invention to provide an improved 
magnetostrictive transducer for performing energy conversions between 
electrical and mechanical systems. 
It is a further object of this invention to provide an improved 
magnetostrictive transducer which is rapidly responsive to excitations. 
A still further object of this invention is to provide a magnetostrictive 
transducer that is capable of operating at room temperatures. 
It is a still further object of the invention to provide an improved 
magnetostrictive transducer which is capable of rapidly undergoing changes 
in dimension to provide for usable mechanical motions. 
It is another object of the invention to provide a flow control device 
which can accurately control the flow of fluids. 
Briefly, in accordance with one embodiment of this invention, these and 
other objects are attained by providing a flow control valve comprised of 
a cylindrical housing, a tapered plunger, and a magnetizing means. A 
discharge port at the forward end of the housing is adapted to receive the 
tapered nose of the plunger disposed within and along the main 
longitudinal axis of the housing to initially prevent fluid flow. 
The housing is composed of a material that exhibits high positive 
magnetostriction (i.e. expands under a magnetic field) and the plunger is 
either magnetically inactive or composed of a material that exhibits high 
negative magnetostriction (i.e. contracts under a magnetic field). The 
magnetic means comprise an electrical coil encircling the longitudinal 
axis of the housing. When electrical current is passed through the coils, 
the magnetically sensitive materials either expand or contract, depending 
on the sense of the material. The relative dimensional change of these 
materials is reflected in a relative separation of the plunger nose from 
the housing port, resulting in an opening permitting precise control of 
fluid discharge from the housing. The valve may be actively controlled by 
a feedback control system utilizing sensor means downstream from the 
discharge port. Further, whether the housing is magnetostrictively sensed 
positive or negative would be determined by whether the valve port is to 
be normally open or normally closed in the absence of a magnetic field. In 
alternative embodiments the relative dimensional changes in the 
magnetostrictive materials are utilized by mechanical means 
interconnecting apertures means to align apertures. When the magnetic 
field is applied, the expansion/contraction of the magnetostrictive 
materials allows apertures to be selectively exposed resulting in a 
precise control of fluid flow.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring now to the drawings wherein like reference characters designate 
identical or corresponding parts throughout the several views, in FIG. 
1(a) there is shown disposed along a longitudinal axis a cylindrical valve 
body 10 in spaced apart relation to an internal elongated plunger 12, said 
valve body terminating at a forward end with a discharge port 14. The 
forward end of the plunger has a tapered nose 16 adapted to seat within 
the discharge port in a tight fit to initially close off fluid flow. To 
provide a magnetic field, an electrical wire is wrapped around the valve 
housing, starting with the input at 18 and ending with the output at 20, 
thereby defining a coil 22. 
The valve body is preferably comprised of a material that exhibits large 
magnetostriction. Depending on whether the application calls for a valve 
that is normally open or normally closed when no magnetic field in acting, 
a material exhibiting negative magnetostriction or one that exhibits 
positive magnetostriction would be selected. When the material is exposed 
to a magnetic field, the former material will contract and the latter 
material will expand. The valve shown in FIG. 1(a) depicts the situation 
where the valve is normally closed and the body is composed of a material 
exhibiting large positive magnetostriction. The plunger is preferably 
composed of a material that exhibits negative magnetostriction. However, 
either the body or the plunger could be made from magnetically inactive 
materials such as brass or aluminum, but this would not provide as great a 
relative displacement between the valve members as would be provided if 
the two members were to be composed of oppositely-sensed magnetostrictive 
materials. For inverse operation, the signs of the magnetostrictive 
materials would be interchanged. 
Using new and highly magnetostrictive rare earth alloys, movements of 
0.001-0.005 in, can easily be attained without the use of any mechanical 
advantage mechanisms. Rare earth alloys exhibiting large positive 
magnetostrictions are those comprised of iron with terbium (Tb) or 
praseodymium (Pr), with the former being the better. Several suitable 
alloys are TbFe.sub.2, TbFe.sub.3, or Terfenol-D, Tb.sub.0.27 Dy.sub.0.73 
Fe.sub.2. Rare earth materials exhibiting high negative magnetostrictions 
are best illustrated by alloys of iron with erbium (Er) and samarium (Sm), 
and to a lesser extent those containing dysprosium (Dy) and holmium (Ho). 
Several suitable alloys are SmFe.sub.2, ErFe.sub.2, or Sm.sub.0.7 
Ho.sub.0.3 Fe.sub.2. These new magnetostrictive alloys help to reduce the 
amount of power required to develop saturation magnetization and 
magnetostriction. 
Upon introduction of electrical energy into the coil 22, a magnetic field 
is established that creates magnetic flux within the magnetostrictive 
material. This simultaneous energization of the two valve elements results 
in an expansion of the valve housing and a contraction of the plunger, 
thereby creating a relative displacement between the two at the discharge 
port. Referring to FIG. 1(b), the displacement allows a controlled flow to 
be initiated and in FIG. 1(c) the valve body is at maximum separation from 
the plunger, providing the maximum area for the flow. 
The valve members can easily be fabricated using any standard processes 
known in the art. For example, casting, powder metallurgy or epoxy bonding 
are all possible methods. Casting is sometimes fairly difficult because 
the materials are somewhat brittle and thus would be limited to simple 
geometrics. Power metallurgy offers a method that is simpler than casting 
and is more versatile since slightly more complex geometries could be 
manufactured. The method would lend itself well to mass production. Epoxy 
bonding is perhaps the best of the three methods, both with respect to the 
type of valve geometries that can be fabricated and as to the mass 
production of parts. For increased resistance to wear and to corrosion, 
the materials could be plated with some suitable material, for example, 
chromium. 
Referring now to FIG. 2, an alternative valve embodiment has high 
permeability magnetic material 24 in the shape of a toroid with an air gap 
26. A magnetic field is provided by a coil 28 of electrical wire wrapped 
around the torus having current input 30 and output 32. By passing current 
through the coil, magnetic flux is created in the toroid and is shown by 
dashed lines 34 in FIG. 2. In FIG. 3, magnetostrictive rod 36, secured by 
attachment means 38 at one end, has connecting means 40 at the other end 
connected to plate 42 having aperture 44, said plate adapted to slide 
within a slot 46 of a member 48 having flow passageway 50. Upon 
energization of the coil 28, a magnetic field is established through the 
air gap 26, causing the magnetostrictive rod 36 therein to expand or 
contract, which correspondingly forces the plate aperture to be adjusted 
within the passageway 50 for flow adjustment. 
Referring now to FIG. 4, an alternative valve embodiment has 
magnetostrictive control member 52 comprising a first, upper layer 54 of 
magnetostrictive material laterally joined with a second, lower layer 56 
of magnetostrictive material of opposite sign than the first to form a 
composite bar. The bar is supported at one end by holding means 58. 
Connecting means 60 interconnect the other end of the bar to a plate 62 
having aperture 64, said plate slidably disposed within slot 66 of a 
conduit 68 having a central passageway 70. An electrical wire having input 
lead 72 and output lead 74 is wrapped about the longitudinal axis of the 
composite bar to form a coil 76 which, when supplied with electrical 
current, causes a magnetic field to be established within the bar. This 
magnetic field acts to produce a change in dimension of the mateials used 
to form the bar, causing the upper/lower layers to expand/contract, and 
thereby forcing the unsecured end of the bar to move transversely with 
respect to the longitudinal axis. The transverse motion of the bar 
displaces the connector 60 causing the apertured plate to be aligningly 
positioned within the conduit passageway to control fluid flow. As shown 
in FIG. 4 the upper layer is composed of a material exhibiting large 
positive magnetostriction. Suitable materials were mentioned above. A 
similar composite bar would consist of one non-magnetostrictive element. 
Referring now to FIG. 5, another alternative valve comprises a valve 
housing 78 with enclosure 80 and plate 82 having apertures 84 thereon. A 
sectioned side view of FIG. 6(a) shows the valve initially blocking flow, 
and FIG. 6(b) shows the valve after a magnetic field has caused 
expansion/contraction of magnetostrictive valve materials to allow flow. 
The first outer plate 82 in in FIG. 6(a) is slidingly positioned adjacent 
to a second, inner, plate 86 with apertures 88, which are not in alignment 
with the apertures 84 of the first plate. A first connecting means 90 
interconnects the first apertured plate with a magnetostrictive shaft 92 
attached to the support 94 within the valve enclosure. Similarly, a second 
connecting means 96 interconnects the second apertured plate with a second 
magnetostrictive shaft 98 of opposite magnetostrictive sign than the first 
shaft, and is attached to 94. A magnetic field is supplied by means of an 
electrical coil 100 wrapped around the magnetostrictive shafts, the coil 
generally being housed within the enclosure 80. As shown, the first and 
the second magnetostrictive shafts are composed, respectively, of 
positive- and negative-sensed magnetostrictive materials. When an 
electrical current passes through the coil, the magnetic field created in 
the magnetostrictive shafts causes the first shaft 92 to expand and the 
second shaft 98 to contract, thereby causing the first and second plates 
to be displaced by the connecting means 90 and 96, with the direction of 
plate motion shown by the arrows in FIG. 6(a). Upon undergoing the 
displacement, the apertures 84 on the outer plate 82 are aligned with the 
apertures 88 on the inner plate 86, thereby permitting flow therethrough. 
FIG. 6(b) shows the result of the change in relative dimensions of the 
magnetostrictive materials, with the original dimensions of shafts 92 and 
98 shown in phantom as 92" and 98" respectively. The new shapes are shown 
as 92' and 98', respectively. 
In operation, the flow control devices according to this invention could be 
adapted for use in a feedback control loop. Typical of such an application 
would be the toroidal magnet described above relating to FIG. 2 used to 
control flow as shown in FIG. 7. A flow sensing device 106 is inserted 
into the conduit passageway downstream of the apertured plate 42. As 
fluids pass through the conduit and through the aperture 44, the sensor 
generates an output representative of that flow. A desired flow rate is 
known and can be used for comparison by comparator means 104 to produce a 
signal which is sent to a feedback control means 102. The signal compares 
the output value from the sensor with the desired value, and any 
difference other than zero would be used by the feedback control to vary 
the electrical current passing through the coil 28 of the toroid to adjust 
the magnetic field and cause the magnetostrictive shaft 36 to undergo a 
change in dimension and thereby adjust the position of the aperture in the 
conduit. 
Obviously, numerous modifications and variations of the present invention 
are possible in light of the above teachings. It is therefore to be 
understood that within the scope of the appended claims the invention may 
be practiced otherwise than as specifically described herein.