U.S. patent application number 13/408644 was filed with the patent office on 2013-08-29 for magneto-rheological elastomeric fluid control armature assembly.
This patent application is currently assigned to Vernay Laboratories, Inc.. The applicant listed for this patent is Robert Ferguson. Invention is credited to Robert Ferguson.
Application Number | 20130221255 13/408644 |
Document ID | / |
Family ID | 49001828 |
Filed Date | 2013-08-29 |
United States Patent
Application |
20130221255 |
Kind Code |
A1 |
Ferguson; Robert |
August 29, 2013 |
MAGNETO-RHEOLOGICAL ELASTOMERIC FLUID CONTROL ARMATURE ASSEMBLY
Abstract
A solenoid fluid control valve having a valve body containing a
solenoid coil, a fluid channel, and a seat, each coaxially disposed
about a central longitudinal axis of the body, and a one-piece
armature of MRE material. The armature is disposed within the fluid
channel and magnetically actuable to seal against the seat, with
operation of the solenoid coil actuating the armature with respect
to the seat to alter the closure state of a fluid port. Also, a
fluid check valve having a first valve body part defining a seat, a
fluid port, and a first portion of a fluid chamber, with the seat
including a permanent magnet element disposed adjacent the fluid
port proximate the fluid chamber. A one-piece armature of MRE
material is disposed across the fluid port and magnetically
sealable against the magnet element. The armature and magnet
element are configured to create a preselected magnetization offset
pressure portion of a valve cracking pressure.
Inventors: |
Ferguson; Robert;
(Springboro, OH) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Ferguson; Robert |
Springboro |
OH |
US |
|
|
Assignee: |
Vernay Laboratories, Inc.
Yellow Springs
OH
|
Family ID: |
49001828 |
Appl. No.: |
13/408644 |
Filed: |
February 29, 2012 |
Current U.S.
Class: |
251/129.15 ;
137/528; 251/321 |
Current CPC
Class: |
F16K 31/0651 20130101;
Y10T 137/7904 20150401; F16K 15/148 20130101; F16K 31/0658
20130101; F16K 15/023 20130101; F16K 31/084 20130101 |
Class at
Publication: |
251/129.15 ;
251/321; 137/528 |
International
Class: |
F16K 31/06 20060101
F16K031/06; F16K 15/00 20060101 F16K015/00 |
Claims
1. A magnetically-actuated, solenoid fluid control valve
comprising: a valve body containing a solenoid coil, a fluid
channel, and a seat, each coaxially disposed about a central
longitudinal axis of the valve body; and a one-piece armature
comprising an elastomer matrix containing a dispersed particulate
ferromagnetic filler, the one-piece armature being disposed within
the fluid channel and magnetically actuable to bring a sealing end
into sealing engagement with the seat; the fluid channel having a
first end including a first fluid port in fluid communication with
the seat, whereby operation of the solenoid coil actuates the
one-piece armature with respect to the seat to alter the closure
state the first fluid port.
2. The magnetically actuated, solenoid fluid control valve of claim
1, wherein the elastomer matrix is a synthetic rubber, and the
ferromagnetic filler is a particulate strontium ferrite present in
a range about 70% to about 84% by weight.
3. The magnetically actuated, solenoid fluid control valve of claim
1, wherein the combined elastomer matrix and dispersed particulate
filler have a Shore hardness of about 55 to about 85 on the Shore A
scale.
4. The magnetically actuated, solenoid fluid control valve of claim
1, wherein the valve is a normally closed valve, the valve further
comprising: a spring coaxially disposed about the central
longitudinal axis and within the fluid channel opposite the seat,
wherein the spring biases the sealing end against the seat to seal
the first fluid port.
5. The magnetically actuated, solenoid fluid control valve of claim
4 further comprising: a profiled spring contact disposed on the end
of one-piece armature opposite the sealing end, the profiled spring
contact including a peripheral land surrounding a projecting
nub.
6. The magnetically actuated, solenoid fluid control valve of claim
5, wherein the projecting nub includes a chamfered peripheral
surface.
7. The magnetically actuated, solenoid fluid control valve of claim
1, wherein the valve is a normally open valve, the valve further
comprising: a spring coaxially disposed about the central
longitudinal axis and within the fluid channel around the seat,
wherein the spring biases the sealing end away from the seat to
open the first fluid port.
8. The magnetically actuated solenoid fluid control valve of claim
7 further comprising: a profiled spring contact disposed on the
sealing end of one-piece armature, the profiled spring contact
including a peripheral land surrounding a projecting nub.
9. The magnetically actuated solenoid fluid control valve of claim
8, wherein the projecting nub includes a chamfered peripheral
surface.
10. The magnetically-actuated, solenoid fluid control valve of
claim 1, wherein the one-piece armature consists essentially of a
homogeneous suspension of the ferromagnetic filler within the
elastomer matrix.
11. The magnetically-actuated, solenoid fluid control valve of
claim 10, wherein the one-piece armature is coated with a different
polymer than that of the elastomer of the elastomer matrix.
12. The magnetically-actuated, solenoid fluid control valve of
claim 1, wherein the one-piece armature includes a guide element
for maintaining the armature in a preset orientation, and the valve
body includes a complementary guide element engaging the armature
guide element.
13. The magnetically-actuated, solenoid fluid control valve of
claim 1, wherein the one-piece armature incorporates an internal
passage or surface channel for the delivery of fluid to another
fluid port.
14. A self-actuating fluid check valve comprising: a first valve
body part defining a seat, a fluid port, and a first portion of a
fluid chamber, the seat including a permanent magnet element
disposed adjacent the fluid port proximate the fluid chamber; a
second valve body part defining a second portion of the fluid
chamber; and a one-piece armature comprising an elastomer matrix
containing a dispersed particulate ferromagnetic filler, the
one-piece armature being disposed across the fluid port and
magnetically sealable against the permanent magnet element of the
seat; the one-piece armature and the permanent magnet element being
configured to create a preselected magnetization offset pressure
portion of a valve cracking pressure.
15. The self-actuating fluid check valve of claim 14, wherein the
elastomer matrix is a synthetic rubber, and the ferromagnetic
filler is a particulate strontium ferrite present in a range about
70% to about 84% by weight.
16. The self-actuating fluid check valve of claim 15, wherein the
combined elastomer matrix and dispersed particulate filler have a
Shore hardness of about 55 to about 85 on the Shore A scale.
17. The self-actuating fluid check valve of claim 14, wherein the
permanent magnet element is an annulus of permanently magnetized
material disposed coaxially about the fluid port.
18. The self-actuating fluid check valve of claim 14, wherein the
valve is a disk valve, and the one-piece armature is configured as
a disk.
19. The self-actuating fluid check valve of claim 18, wherein at
least one of the first and second body portions includes guide
elements projecting into the fluid chamber, and the one-piece
armature includes complementary guide elements engaging the
projecting guide elements to retain the one-piece armature in
position across the fluid port
20. The self-actuating fluid check valve of claim 14, wherein the
valve is an umbrella valve, and the one-piece armature is
configured as an umbrella element having an umbrella stem, with the
one-piece armature umbrella stem being secured across the fluid
port through engagement of the fluid port with the umbrella stem.
Description
FIELD
[0001] The present disclosure is directed to fluid control valves
and, more particularly, to magnetically actuated fluid control
valves and self-actuating fluid check valves.
BACKGROUND
[0002] Direct-acting, magnetically-actuated fluid control valves
are used in a variety of applications within industry. Typically,
such valves include a solenoid coil and a metallic armature body
manufactured from a ferromagnetic alloy. The metallic armature body
is capped with an elastomeric sealing member which seals against a
seat within the body of the valve to control the flow of fluid
through the valve. A spring may bias the metallic armature body
into a normally open or normally closed position, whereupon
powering the solenoid coil of the valve magnetically actuates the
metallic armature body against the bias (either toward the seat to
seal a fluid port or away from the seat to unseal a fluid port,
respectively) to alter the closure state of the valve. The
elastomeric sealing member may provide for both fluid sealing and
impact absorption during operation of the valve.
[0003] Self-actuating fluid check valves are also commonly used
within industry, household fixtures, and consumer products.
Typically, such valves include a resilient sealing member, such as
an elastomeric ball or disc, which may be biased against a seat in
the valve body by gravity, by preloading via a spring, or by the
intrinsic resilience of the sealing member (such as in an umbrella
valve). The flow of fluid from an upstream side of the valve
displaces the sealing member from the seat, allowing fluid to flow
past the sealing member and to a downstream fluid port in the
valve. The biasing of the sealing member, as well as any flow of
fluid into the downstream port the valve (a reversed flow), drives
the sealing member toward seat and, upon sealing engagement, serves
to prevent fluid from flowing past the sealing member to an
upstream fluid port of the valve. Fluid check valves may also
desirably have a minimum "cracking pressure," defined as the
minimum upstream pressure required to open the valve and start
fluid flow through the valve. That cracking pressure is
conventionally varied by altering the preloading displacement or
spring constant of a biasing spring, by altering the preloading
displacement or modulus of elasticity of the sealing member
material, or by related means.
SUMMARY
[0004] The applicant has determined that such fluid control valves
may be advantageously enhanced, whether through simplified
construction or greater flexibility in material selection and other
design constraints, by manufacturing the sealing armature from a
magneto-rheological elastomer material or "MRE." Such materials
comprise an elastomer, such as a natural or synthetic rubber
compound, and a particulate ferromagnetic material, such as a
ferrite, prepared as an essentially homogeneous suspension. The MRE
material is subsequently molded, formed, or shaped into an armature
body shape by various mechanical and chemical processes depending
upon whether the elastomer matrix is a rubber (vulcanization), a
thermoset (thermal or chemical curing), a thermoplastic (cooling
below an elevated melting temperature), etc. Such materials, when
formed into a magneto-rheological elastomeric armature, may
simplify actuator and/or sealing armature construction, allow for
substantial reductions in valve component size, and enable more
compact valve body designs.
[0005] An MRE sealing armature may be incorporated into a solenoid
fluid control valve to provide a one-piece, magnetically-actuable
armature which effectively seals a fluid port. Even more
advantageously, an MRE sealing armature may be incorporated into a
self-actuating fluid check valve having a permanent magnet element
in order to abolish dependencies upon valve orientation, to
eliminate the need for a biasing spring, and/or to endow a
particular valve design with greater flexibility in configured
cracking pressure by altering the preload or apparent pliancy of a
sealing armature without necessarily altering a spring
characteristic or switching to a less pliant armature material. The
MRE sealing armatures and disclosed valve designs consequently
provide significant advantages such as simplified construction and
greater flexibility in design and material selection over
conventional direct-acting, magnetically-actuated or self-actuating
fluid control valve designs.
[0006] In a first aspect, the disclosure pertains to a
magnetically-actuated, solenoid fluid control valve. The valve has
a valve body containing a solenoid coil, a fluid channel, and a
seat, each coaxially disposed about a central longitudinal axis of
the valve body, and a one-piece armature of MRE material. The
one-piece armature is disposed within the fluid channel and
magnetically actuable to bring a sealing end into sealing
engagement with the seat, and the fluid channel has a first end
including a first fluid port in fluid communication with the seat,
whereby operation of the solenoid coil actuates the one-piece
armature with respect to the seat to alter the closure state the
first fluid port. It is noted that magnetic actuation may include
actuation of the one-piece armature while powering the solenoid
coil to create and sustain a magnetic field, as well as actuation
of the one-piece armature while depowering the solenoid coil to
collapse the magnetic field.
[0007] In a second aspect, the disclosure pertains to a
self-actuating fluid check valve. The valve has a first valve body
part defining a seat, a fluid port, and a first portion of a fluid
chamber, with the seat including a permanent magnet element
disposed adjacent the fluid port proximate the fluid chamber. A
one-piece armature of MRE material is disposed across the fluid
port and magnetically sealable against the permanent magnet element
of the seat. The one-piece armature and the permanent magnet
element are configured to create a preselected magnetization offset
pressure portion of a valve cracking pressure.
BRIEF DESCRIPTION OF THE DRAWINGS
[0008] FIG. 1 is a sectional profile view of a normally closed
solenoid fluid control valve in a closed position.
[0009] FIG. 2 is a sectional profile view of the normally closed
solenoid fluid control valve of FIG. 1 in an open position.
[0010] FIG. 3 is a sectional end view of a solenoid fluid control
valve showing an optional guide projection 118 in the armature and
a complementary guide channel 149 in the valve body, an optional
guide channel 119 in the armature and a complementary guide
projection 148 in the valve body, an optional internal passage in
the armature, and optional surface channel in the armature.
[0011] FIG. 4 is a sectional profile view of a normally open
solenoid fluid control valve in an open position.
[0012] FIG. 5 is a sectional profile view of the normally open
solenoid fluid control valve of FIG. 4 in a closed position.
[0013] FIG. 6 is a sectional perspective view of a self-actuating
fluid check valve incorporating an MRE sealing armature in a closed
position.
[0014] FIG. 7 is a sectional perspective view of the self-actuating
fluid check valve of FIG. 6 in an open position.
[0015] FIG. 8 is a sectional perspective view of a self-actuating
fluid check valve incorporating an MRE umbrella-type sealing
armature.
[0016] FIG. 9 is a sectional profile view of the self-actuating
fluid check valve of FIG. 8, further including an exemplary second
valve body part for forming an enclosed fluid chamber and
downstream fluid port.
DETAILED DESCRIPTION
[0017] A first aspect of the disclosure is a magnetically-actuated,
solenoid fluid control valve 100. With initial reference to FIG. 1,
the solenoid fluid control valve 100 incorporates a one-piece
armature 110 manufactured from a magneto-rheological elastomer or
MRE. The MRE generally comprises an elastomer matrix containing a
dispersed particulate ferromagnetic filler. In one exemplary
implementation, the elastomer is a vulcanized natural rubber, and
the ferromagnetic filler is a particulate strontium ferrite present
in a range about 70% to about 84% by weight. In another exemplary
implementation the elastomer is a synthetic rubber or polymer such
as EPDM (ethylene-propylene-diene monomer) or SEBS
(styrene-ethylene-butylene-styrene), and the ferromagnetic filler
is a particulate barium ferrite present in a range about 70% to
about 84% by weight. The material preferably has a Shore hardness
of about 55 to about 85 on the Shore A scale. Those of skill in the
art will appreciate that the Shore hardness of the material of
armature 110 will tend to be greater than that of the elastomer
itself due to the amount and form of the ferromagnetic filler
incorporated into the elastomer matrix, and that varying
combinations of particular elastomers and ferromagnetic fillers may
be used to manufacture the armature 110. The one-piece armature is
preferably an essentially homogeneous mixture of these materials,
yet may be coated with a different polymer than that of the
elastomer matrix, such as polytetrafluoroethylene, in order to
provide increased chemical resistance and/or increased resistance
to fouling.
[0018] The solenoid fluid control valve 100 more generally
comprises a valve body 120 containing a solenoid coil 130, a fluid
channel 140, and a seat 150 each coaxially disposed about a central
longitudinal axis "L." A first end of the fluid channel 140
includes a first fluid port 160 in fluid communication with the
seat 150, with the seat being configured for sealing engagement
with a sealing end 112 of the one-piece armature 110. In operation,
a force may bias the one-piece armature 110 with respect to the
seat 150, with the sealing end 112 entering into sealing engagement
with the seat 150 to prevent fluid flow through the first fluid
port 160 or withdrawing from sealing engagement with the seat 150
to allow fluid flow through the first fluid port 160. Another
portion of the fluid channel 140, such as the second end of the
fluid channel, includes a second fluid port 170 to permit flow
within the fluid channel 140 and through the valve 100. It will be
appreciated that the second fluid port 170 may alternately be
disposed in the sidewall of the fluid channel 140 or even in a
non-coaxially disposed segment or branch of the fluid channel 140,
rather than the axially aligned location illustrated in the
figures.
[0019] In a first embodiment, shown in FIGS. 1 and 2, the fluid
control valve 100 is a normally closed fluid control valve, and
includes a spring 180 coaxially disposed about the central
longitudinal axis L within the fluid channel 140 opposite the seat
150. This spring 180 may matingly engage with a profiled spring
contact 114 on the end of the one-piece armature 110 opposite the
sealing end 112. For example, the profiled spring contact 114 may
include a peripheral land 115 surrounding a projecting nub 116,
with the nub 116 preferably including a chamfered peripheral
surface 117 to enhance pulling force into the solenoid coil 130.
The one-piece armature 110 and fluid channel 140 are preferably
generally cylindrical, but it will be appreciated that the these
elements may have other cross-sectional profiles as well, including
generally ellipsoidal, rectangular, or square profiles, in order to
maintain the one-piece armature 110 in a preset orientation. As
shown in FIG. 3, the one-piece armature 110 and fluid channel 140
may alternately or additionally include complementary guide
elements such as projections 118, 148 and channels 119, 149 in
order to maintain the one-piece armature 110 in a preset
orientation. The one-piece armature 110 may generally have the
described cross sections while also incorporating internal passages
111 or surface channels 113 for the delivery of fluid to other
fluid ports, such as in some three-way solenoid fluid control valve
designs. Operation of the solenoid coil 130 actuates the one-piece
armature 110 with respect to the seat 150 to overcome the spring's
closing bias and seal the fluid port 160 against fluid flow.
[0020] In a second embodiment, shown in FIGS. 4 and 5, the fluid
control valve 100 is a normally open fluid control valve, and
includes a spring 180 coaxially disposed about the central
longitudinal axis L within the fluid channel 140 and around the
seat 150. This spring 180 may matingly engage with a profiled
spring contact 114 on the sealing end 112. For example, the
profiled spring contact may include a peripheral land 115
surrounding a projecting sealing nub 116, with the sealing nub 116
preferably including a chamfered peripheral surface 117 to enhance
pulling force into the solenoid coil 130, as well as to seal
against a complementary chamfered peripheral surface in a seat
recess 152 formed in seat 150. As in the first embodiment, the
one-piece armature 110 and fluid channel 140 are preferably
generally cylindrical, but may have other cross sectional profiles
as well, and may alternately or additionally include complementary
guide elements such as projections 118, 148 and guide channels 119,
149. The one-piece armature 110 may again generally have the
described cross sections while incorporating internal passages 111
or surface channels 113 for the delivery of fluid to other ports.
Operation of the solenoid coil 130 actuates the one-piece armature
110 with respect to the seat 150 to overcome the spring's opening
bias and seal the fluid port 160 to prohibit fluid flow.
[0021] Those of skill in the art will appreciate that the spring
180, particularly in a normally open fluid control valve, is an
optional component that may be provided to ensure the desired bias,
however in some normally open fluid control valves fluid pressure
may provide sufficient bias towards an open state. Similarly, in
some fluid control valves the solenoid coil 130 may be normally
powered in order to hold the valve in a normally closed state,
however this form of valve will consume more energy (which must be
dissipated as heat) than normally closed valves incorporating a
biasing spring. In yet other fluid control valves, a second
solenoid coil could be disposed within the valve body to create a
low-power/high-power coil pair which may be used to shuttle the
one-piece armature 110 between open and closed positions, with one
member of the pair ensuring the desired opening or closing bias,
and the other member of the pair being operated to overcome the
second solenoid coil's opening or closing bias.
[0022] A second aspect of the disclosure is a self-actuating fluid
check valve 200. With initial reference to FIG. 6, the fluid check
valve 200 incorporates a one-piece armature 210 manufactured from a
magneto-rheological elastomer or MRE. As in the first embodiment,
the MRE generally comprises an elastomer matrix containing a
dispersed particulate ferromagnetic filler. In one exemplary
implementation, the polymer is a vulcanized natural rubber, and the
ferromagnetic filler is a particulate strontium ferrite present in
a range about 70% to about 84% by weight. In another exemplary
implementation the elastomer is a synthetic rubber or polymer such
as a PUR (polyurethane ether or polyurethane ester) and the
ferromagnetic filler is a particulate barium ferrite present in a
range about 70% to about 84% by weight. The material preferably has
a Shore hardness of about 55 to about 85 on the Shore A scale. The
one-piece armature 210 is preferably an essentially homogeneous
mixture of these materials, but may be coated with other materials,
such as a mechanically compatible fluoropolymer, in order to
provide increased chemical resistance. The one-piece armature 210
may be configured as a disk sealing member, an umbrella sealing
member, a ball sealing member, a hinged flap sealing member,
etc.
[0023] The fluid check valve 200 generally comprises a first valve
body part 220 defining a seat 250, a fluid port 260, and a first
portion of a fluid chamber 240. The seat 250 includes a permanent
magnet element 252 disposed adjacent to, and preferably around, the
fluid port 260 proximate the first portion of the fluid chamber
240. In varying embodiments, the permanent magnet element 252 may
comprise an annulus of permanently magnetized material disposed
coaxially about the fluid port 260. Another portion of the fluid
chamber 240, e.g., another portion of the first valve body part
220, a portion of a second valve body part 230 defining a second
portion of the fluid chamber 240 (as shown in FIG. 9), or a
combination of the parts 220 and 230, defines a downstream fluid
port 270 to permit flow through the fluid chamber 240 and the valve
200. It will be appreciated that the downstream fluid port 270 may
be any opening to a downstream fluid path connected to the fluid
chamber 240, although preferably the downstream fluid port 270 is
configured so as to retain the one-piece armature 210 within the
fluid chamber 240 of the valve 200. As discussed in further detail
below, the one-piece armature 210 and the permanent magnet element
252 are configured to create a preselected magnetization offset
pressure portion of a valve cracking pressure.
[0024] In a first embodiment, shown in FIGS. 6 and 7, the fluid
check valve 200 is a disk valve, with one-piece armature 210 being
configured as a disk and held in proximity to the fluid port 260
between the first and second valve body parts 220, 230. The
permanent magnet element 252 is an annulus of permanently
magnetized material disposed coaxially about the fluid port 260,
with the magnetic properties of the annulus and disk serving to
center and reseat the one-piece armature 210 against the seat 250
in the event of a cessation of flow, or reverse flow, through the
downstream fluid port 270. In alternate embodiments, guide elements
such as projections from the valve body parts 220 and/or 230 into
the fluid chamber 240 and, optionally, complementary channels or
apertures in the one-piece armature 210 may be used to retain the
armature in position across the fluid port 260. Those of skill in
the art will appreciate that the disk and/or annulus need not be
truly circular as illustrated in the figures, but may be generally
ellipsoidal or generally polygonal as well. Those of skill in the
art will also appreciate that in other alternate embodiments, the
one-piece armature 210 may be configured as a ball and held in
proximity to the fluid port 260 between the first and second valve
body parts 220, 230, with first valve body part 220 being formed
into a funnel-like shape to further direct the one-piece armature
210 to seat within the annulus of permanent magnet element 252.
[0025] In a second embodiment, shown in FIG. 8, the fluid check
valve 200 is an umbrella-type valve, with one-piece armature 210
being configured as an umbrella element and secured across fluid
port 260 through engagement of the fluid port with the umbrella
stem. The permanent magnet element 252 is an annulus of permanently
magnetized material disposed coaxially about the fluid port 260,
with the umbrella skirt of the one-piece armature 210 reseating
against the seat 250 in proximity to the permanent magnet element
252 in the event of a cessation of flow, or reverse flow, through
the downstream fluid port 270. Those of skill in the art will
appreciate that the umbrella stem of an umbrella element is similar
to the fixed portion of a flap sealing member having a living
hinge. The one-piece armature 210 may accordingly be configured in
other embodiments to have a fixed portion secured to the first
valve body part 220 radially beyond the permanent magnet element
252, and a flap portion extending across the seat 250, permanent
magnet element 252, and fluid port 260 so as to seal the fluid port
260 to prevent fluid flow.
[0026] In general, the attractive force between an annulus of
magnetic material and a generally planer one-piece armature 210
(such as the face of a disk sealing member, the annular contact
portion of an umbrella sealing member, or the flap portion of a
flap sealing member) can be estimated by:
F = B m 2 * A * L .mu. * P f ( 1 ) ##EQU00001##
where F is the attractive force, B.sub.m is the maximum magnetic
induction of the particulate ferromagnetic filler material, P.sub.f
is the weight percent of the particulate ferromagnetic filler
material in the MRE, A is the area of surface contact between the
one-piece armature 210 and the annulus of magnetic material
(permanent magnet element 252), L is the average thickness of the
one-piece armature 210 over the area of surface contact, and .mu.
is the permeability coefficient of the medium between the one-piece
armature 210 and the permanent magnet element 252, if known (with
air being .about.1.000000). Dividing this force by the area of
surface contact yields a magnetization offset pressure, which may
be treated as a valve cracking pressure, P.sub.mo, or in cases such
as umbrella valves where resiliency of the valve material further
contributes to valve cracking pressure, a magnetization offset
pressure portion of the valve cracking pressure.
Example 1
[0027] Several one-piece armatures 210 were manufactured in the
form of disc sealing members from a sulfur-cured EPDM polymer
containing varying amounts of STARBOND HM410, a strontium ferrite
filler supplied by Hoosier Magnetics, Inc. of Ogdensburg, N.Y.
B.sub.m and .mu. for the filler were 2.2 kiloGauss and 1,
respectively. Six different disc exemplars were created from sheets
of MRE material having a thickness (L) of either 0.075 inches or
0.040 inches and one of three levels of particulate ferromagnetic
filler material: 69.6 wt. percent, 79.3 wt. percent, or 84.7 wt.
percent. The area of contact (A) between an annular permanent
magnet (circular, approximately 2 inch outside diameter and 9/16
inch inside diameter) and an armature disc (circular, approximately
2 inch diameter) was 2.04 inches.sup.2 so as to yield the estimated
cracking pressures shown in Table 1.
TABLE-US-00001 TABLE 1 Estimated Check Valve Cracking Pressure
Filler Disc Thickness (L) material (P.sub.f) Est. Force Est.
Cracking Exemplar (inches) (wt. percent) (lbs.) Pressure (psi) A
0.075 69.6 0.515 0.249 B 0.075 79.3 0.587 0.283 C 0.075 84.7 0.627
0.303 D 0.040 69.6 0.275 0.133 E 0.040 79.3 0.313 0.151 F* 0.040
84.7 0.335 0.161
Disc exemplar F was not successfully created and tested. Test
sheets molded at this thickness and filler content could not be
demolded without tearing due to adhesion to the mold and
insufficient tensile strength.
[0028] The force required to separate the disc exemplars from the
permanent magnet was measured using an Instron 4411 tensile machine
equipped with a 5 KiloNewton load cell. Each disc exemplar was
connected in turn to the grips in the crosshead of machine using
monofilament line, and the crosshead was operated at a rate of 5
inches per minute. The peak force generated during displacement of
the crosshead was identified and divided by A to calculate the
experimental cracking pressure of the one-piece armatures 210,
reported in Table 2. The test was repeated three times upon each
exemplar, and the values averaged for reporting.
TABLE-US-00002 TABLE 2 Experimental Check Valve Cracking Pressure
(Instron 4411 testing) Measured Measured Cracking Error in Estimate
of Force (lbs.) Pressure (psi) Cracking Pressure Disc Exemplar
(lbs.) (psi) (.DELTA. vs. Measured, %) A 0.510 0.246 -1 B 0.456
0.220 -29 C 0.537 0.259 -17 D 0.242 0.117 -14 E 0.268 0.130 -17 F
N/A N/A N/A
The average error in the estimate of cracking pressure versus the
experimental results was -15%, suggesting some element of
systematic error in the experimental measurement technique and/or
systematic error in the model of equation (1) due to an omitted
term. However, a general trend in cracking pressure as a function
of armature thickness and composition will be apparent to those of
ordinary skill in the art.
[0029] The various aspects and implementations described above are
intended to be illustrative in nature, and are not intended to
limit the scope of the invention. Any limitations to the invention
will appear in the claims as allowed.
* * * * *