Valves and valve actuation – Electrically actuated valve – Including solenoid
Reexamination Certificate
2001-05-01
2004-04-06
Rivell, John (Department: 3753)
Valves and valve actuation
Electrically actuated valve
Including solenoid
C251S129180, C335S279000
Reexamination Certificate
active
06715732
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates in general to solenoid-operated fluid control valves of the type used in precision fluid flow regulation systems, such as those that require precise control of the rate of fluid flow, including but not limited to pneumatic and hydraulic regulation. The invention is particularly directed to an improved variation of the solenoid-driven valve control structure described in the '137 application, through which fluid flow through a fluid flow-regulating valve assembly may be controlled in proportion to the application of solenoid current.
BACKGROUND OF THE INVENTION
As described in my earlier filed '137 application, precision fluid flow control devices, such as those used in fuel supply units for aerospace systems and oxygen/air metering units employed in hospitals, as non-limiting examples, typically incorporate a solenoid-operated valve for controlling fluid flow substantially proportional to the current applied to the solenoid. It is also desirable that hysteresis in the flow rate versus control current characteristic (which creates an undesirable dead band in the operation of the valve) be maintained within some minimum value.
A standard practice for reducing hysteresis has been to physically support the solenoid's moveable armature within the bore of its surrounding drive coil by means of low friction bearings, such as Teflon rings. However, even with the use of such a low friction material, there is still significant ‘dead band’ current (e.g. on the order of forty-five milliamps), which limits the operational precision of the valve.
One proposal to deal with this physical contact-created hysteresis problem is to remove the armature support mechanism from within the bore of the solenoid coil (where the unwanted friction of the armature support bearings is encountered) to an end portion of the coil, and to support the armature for movement within the bore by means of a spring mechanism located outside of the solenoid coil.
An example of such a valve configuration is described in the Everett U.S. Pat. No. 4,463,332, issued Jul. 31, 1984. Pursuant to this patented design, the valve is attached to one end of an armature assembly supported for axial movement within the cylindrical bore of the solenoid coil and having a permanent ring magnet surrounding the solenoid. One end of the solenoid contains a ring and spring armature support assembly, located substantially outside the (high flux density) solenoid bore, and whose position can be changed, so as to adjust the axial magnetic flux gap within the bore and thereby the force applied to the valve.
Disadvantageously, however, this type of support structure requires a magnetic flux booster component which, in the patented design, is a permanent magnet. Namely, even though the objective of the Everett design is to adjust magnetic permeance and maintain linearity, the overall solenoid structure and individual parts of the solenoid, particularly the ring spring armature assembly (which itself is a complicated brazed part), and the use of a permanent booster magnet, are complex and not easily manufacturable with low cost machining and assembly techniques, resulting in a high price tag per unit.
In another prior art configuration, described in the Nielsen U.S. Pat. No. 4,635,683, the movable armature is placed outside the bore by means of a plurality of spiral spring-shaped bearings adjacent to opposite ends of the solenoid structure. Unfortunately, this structure is costly to manufacture, as it not only places a complicated and movable return spring structure in the interior of the solenoid bore, but requires precision attachment of the spring bearings at multiple spaced apart locations of the housing adjacent to opposite ends of the solenoid.
The linear motion proportional solenoid assembly described in my U.S. Pat. No. 4,954,799 entitled: “Proportional Electropneumatic Solenoid-Controlled Valve,” improves on the above designs by using a pair of thin, highly flexible annular cantilever-configured suspension springs, to support a moveable armature within the bore of solenoid, such that the moveable armature is intimately coupled with its generated electromagnetic field (thereby eliminating the need for a permanent magnet as in the Everett design, referenced above).
In order to make the force imparted to the movable armature substantially constant, irrespective of the magnitude of an axial air gap between the armature and an adjacent magnetic pole piece, my patented structure places an auxiliary cylindrical pole piece region adjacent to the axial air gap. This auxiliary cylindrical pole piece region has a varying thickness in the axial direction, which serves to ‘shunt’ a portion of the magnetic flux that normally passes across the axial gap between the armature assembly and the pole piece element to a path of low reluctance. By shunting the flux away from what would otherwise be a high reluctance axial path through a low reluctance path, the auxiliary pole piece region effectively ‘linearizes’ the force vs. air gap characteristic over a prescribed range.
The proportional solenoid structure described in my earlier filed '137 application, and diagrammatically illustrated in
FIGS. 1 and 2
, reduces the structural and manufacturing complexity of the implementation of my previously patented structure by locating a moveable, magnetic armature
10
adjacent to one end of a fixed pole piece
12
that protrudes outside a solenoid coil bore
14
, and configuring this moveable armature
10
to provide two, relatively low reluctance magnetic flux paths
21
and
22
.
The first flux path
21
is a radially directed flux path through an annular air gap
31
at one end
16
of fixed magnetic pole piece
12
. This annular shaped air gap results from the fact that the radially projecting, tapered rim portion
34
of the movable armature
10
has an interior diameter that is only slightly larger than the diameter of the end
16
of the fixed magnetic pole piece
12
protruding beyond the one end of the solenoid bore
14
. This allows for relative axial translation between the movable armature
10
and the fixed magnetic pole piece
12
as moveable armature
10
is axially translated by energizing a solenoid coil
11
. Since annular air gap
31
is very short, fixed radial distance, the magnetic flux path between the end
16
of the fixed pole piece
12
and armature
10
is a substantially constant, low magnetic reluctance radial path.
The second flux path
22
is also essentially a radial flux path through a variable geometry annular air gap
32
between a radially projecting, tapered rim portion
34
of moveable armature
10
and an inwardly projecting tapered portion
36
of the solenoid assembly housing
30
. Because the thickness of each of the mutually opposing surfaces of the tapered rim portion
34
of the moveable armature
10
and the inwardly projecting rim portion
36
of the housing
30
is tapered to an annular wedge shape at the variable geometry air gap therebetween, the magnetic field characteristic between the armature and the housing becomes saturated at each of mutually adjacent tapered rim portions
34
and
36
.
Consequently, the magnetic flux through the armature is principally confined in the radial direction, by-passing the substantial reluctance path along an axial air gap
23
between the moveable armature
10
and the lower end
16
of the fixed pole piece
12
. This causes the force imparted by the solenoid on movable armature
10
to vary in proportion to the applied current, so that displacement of moveable armature
10
against the bias of an axial compression spring
40
varies in proportion to solenoid current.
When employed in a fluid flow application, the proportional solenoid assembly of my '137 application may include an armature retainer
25
threaded into the moveable armature
10
, and mechanically coupled with a valve poppet
55
of a valve unit
50
. The armature retainer
25
and the movable armature
10
capture interior radius portio
Rivell John
Teknocraft, Inc.
The Bilicki Law Firm P.C.
LandOfFree
Proportional solenoid-controlled fluid valve assembly does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Proportional solenoid-controlled fluid valve assembly, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Proportional solenoid-controlled fluid valve assembly will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3206006