U.S. patent application number 11/213085 was filed with the patent office on 2007-03-01 for pneumatic diaphragm having a bias weave pattern.
This patent application is currently assigned to Honeywell International, Inc.. Invention is credited to Larry K. Ball, Betty H. Kocsis, Chuck W. Plevich, James F. Stevenson.
Application Number | 20070044653 11/213085 |
Document ID | / |
Family ID | 37453404 |
Filed Date | 2007-03-01 |
United States Patent
Application |
20070044653 |
Kind Code |
A1 |
Stevenson; James F. ; et
al. |
March 1, 2007 |
Pneumatic diaphragm having a bias weave pattern
Abstract
A diaphragm is provided that includes a tubular sidewall and a
first elastomeric material. The tubular sidewall has an open end
and an enclosed end and comprises fabric having a plurality of
yarns disposed in a bias weave pattern. The first elastomeric
material is disposed over the fabric at a predetermined
thickness.
Inventors: |
Stevenson; James F.;
(Morristown, NJ) ; Ball; Larry K.; (Chandler,
AZ) ; Kocsis; Betty H.; (Phoenix, AZ) ;
Plevich; Chuck W.; (Casa Grande, AZ) |
Correspondence
Address: |
HONEYWELL INTERNATIONAL INC.
101 COLUMBIA ROAD
P O BOX 2245
MORRISTOWN
NJ
07962-2245
US
|
Assignee: |
Honeywell International,
Inc.
|
Family ID: |
37453404 |
Appl. No.: |
11/213085 |
Filed: |
August 25, 2005 |
Current U.S.
Class: |
92/96 |
Current CPC
Class: |
F15B 15/10 20130101;
F16J 3/02 20130101 |
Class at
Publication: |
092/096 |
International
Class: |
F01B 19/00 20060101
F01B019/00 |
Claims
1. A diaphragm comprising: a tubular sidewall having an open end
and an enclosed end, the sidewall comprising fabric having a
plurality of yarns in a bias weave pattern; and a first elastomeric
material disposed over the fabric at a predetermined thickness.
2. The diaphragm of claim 1, wherein the bias weave pattern is a
herringbone pattern.
3. The diaphragm of claim 1, wherein the bias weave pattern
comprises at least a first yarn crossed over a second yarn at an
angle.
4. The diaphragm of claim 3, wherein the angle is less than about
60.degree..
5. The diaphragm of claim 1, wherein the fabric comprises at least
a first pair of yarns crossed over a second pair of yarns at an
angle.
6. The diaphragm of claim 1, wherein the fabric has a yarn count of
at least 50 yarns per square inch.
7. The diaphragm of claim 1, wherein the fabric is rolled, and the
tubular sidewall includes an inner sidewall and an outer
sidewall.
8. The diaphragm of claim 1, wherein the bias weave pattern
comprises a first yarn crossed over a first pair of yarns and
crossed under a second pair of yarns adjacent the first pair of
yarns.
9. The diaphragm of claim 1, wherein each yarn of the plurality of
yarns comprises a plurality of fibers and the plurality of fibers
has a twist angle that is greater than about 45 degrees.
10. The diaphragm of claim 1, wherein the enclosed end is
clamped.
11. The diaphragm of claim 1, further comprising a backing plate to
which the enclosed end is bonded.
12. A diaphragm comprising: a tubular sidewall having an open end
and an enclosed end, the sidewall comprising fabric including a
first yarn crossed over a second yarn at an angle that is less than
about 60.degree. and forming a bias weave pattern, each yarn
comprising a plurality of fibers having a twist angle that is
greater than about 45 degrees; and a first elastomeric material
disposed over the fabric at a predetermined thickness.
13. The diaphragm of claim 12, wherein the fabric comprises at
least a first pair of yarns crossed over a second pair of yarns at
the angle.
14. The diaphragm of claim 12, wherein the fabric has a yarn count
of at least 50 yarns per square inch.
15. A method for forming a diaphragm for use in a pneumatic
actuator, the method comprising the steps of: forming a fabric tube
having a tube diameter and a uniform bias angle around its
circumference; using a preform-shaping tool having a top component
and a bottom component, where an inner surface of the top component
includes a preform shaped integrally formed therein, and disposing
the fabric tube between the top and bottom components; shaping the
fabric tube to reduces a diameter of the fabric tube and decrease
each of the bias angles to form a fabric preform having a top-hat
shape; and impregnating the fabric preform with an elastomer.
16. The method of claim 15, wherein the step of forming includes
the step of braiding threads to form the fabric tube.
17. The method of claim 16, wherein the step of braiding includes
varying the tube diameter and bias angle of the tube.
18. The method of claim 15, wherein the step of forming includes
cutting a fabric on a bias and stitching together opposite ends of
the fabric to form the fabric tube.
19. The method of claim 15, wherein the step of braiding includes
varying the fabric tube diameter and bias angle.
20. The method of claim 15, wherein the step of forming the tube
includes stitching together opposite ends of a strip of fabric cut
on the bias.
Description
TECHNICAL FIELD
[0001] The present invention relates to pneumatic actuators and,
more specifically, to a diaphragm assembly for use in pneumatic
actuators.
BACKGROUND
[0002] Pneumatic actuators may be found in various applications
such as commercial vehicles and aerospace applications. Though
pneumatic actuators may be one of the most cost-effective linear
actuators, they may be short lived when exposed to high
temperatures and pressures. Generally, the low lifespan of these
actuators may be due in part to construction of the actuator.
[0003] A typical pneumatic actuator may include at least a housing,
a diaphragm, and a diaphragm support structure. The diaphragm may
be made from a flat sheet of fabric having a number of yarns, and
may be coated on at least one side with an elastomer, which is
subsequently crosslinked. In some instances, the diaphragm support
structure may have an outer periphery that is generally cylindrical
in shape. Thus, the diaphragm may be formed into a so-called "top
hat" shape, to conform at least a portion of the diaphragm into a
shape that is consistent with the outer periphery of the diaphragm
support structure. Because the diaphragm fabric is originally flat,
with the fabric weave crossing at right angles, this new shape may
cause some of the fabric weave to distort and form a series of
"rainbow-patterns" when viewed around the side of the top hat.
[0004] During the operation of the actuator, the diaphragm may be
exposed to numerous pressure cycles. Although actuators and
presently used diaphragms are robustly designed and operate safely,
in some instances the diaphragm may become worn and potentially
become inoperative. One particular type of diaphragm failure that
may occur following repeated pressure cycles is known as a "curtain
failure." A curtain failure may be recognized as a slit in the
diaphragm fabric, and a "puckered-out" region may surround the slit
on the diaphragm fabric's elastomer side. When the diaphragm fails,
the actuator may no longer operate, or not operate correctly. Thus,
the actuator may need to be disassembled to effect diaphragm
replacement, which can increase overall cost.
[0005] Hence, there is a need for a diaphragm assembly that may be
used in a pneumatic actuator that is less prone to curtain failure
and/or is relatively inexpensive to make and/or reduces maintenance
and repair costs associated with pneumatic actuators. The present
invention addresses one or more of these needs.
BRIEF SUMMARY
[0006] The present invention provides a pneumatic diaphragm. In one
embodiment, and by way of example only, the diaphragm includes a
tubular sidewall and a first elastomeric material. The tubular
sidewall has an open end and an enclosed end and comprises fabric
having a plurality of yarns formed in a bias weave pattern. The
first elastomeric material is disposed over the fabric at a
predetermined thickness.
[0007] In another embodiment, and by way of example only, the
diaphragm includes a tubular sidewall having an open end and an
enclosed end. The sidewall comprises fabric including a first yarn
crossed over a second yarn at an angle that is less than about
60.degree. and forms a bias weave pattern. Each yarn comprises a
plurality of fibers having a twist angle that is greater than about
45 degrees. Additionally, the diaphragm includes a first
elastomeric material disposed over the fabric at a predetermined
thickness.
[0008] In still another embodiment, a method is provided for
forming a diaphragm for use in a pneumatic actuator. The method
comprises the steps of forming a fabric tube having a tube diameter
and a uniform bias angle around its circumference, using a
preform-shaping tool having a top component and a bottom component,
where an inner surface of the top component includes a preform
shaped integrally formed therein, and disposing the fabric tube
between the top and bottom components, shaping the fabric tube to
reduces a diameter of the fabric tube and decrease each of the bias
angles to form a fabric preform having a top-hat shape, and
impregnating the fabric preform with an elastomer.
[0009] Other independent features and advantages of the preferred
diaphragm will become apparent from the following detailed
description, taken in conjunction with the accompanying drawings
which illustrate, by way of example, the principles of the
invention.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1 is a cross sectional view of an exemplary pneumatic
actuator that may employ the diaphragm assembly of the present
invention;
[0011] FIG. 2 illustrates an exemplary embodiment of a diaphragm
assembly that may be used in the actuator depicted in FIG. 1;
[0012] FIG. 3 is a close-up view of an exemplary bias weave pattern
that may be incorporated into the diaphragm assembly depicted in
FIG. 2;
[0013] FIG. 4 is a close-up view of another exemplary bias weave
pattern that may be incorporated into the diaphragm assembly
depicted in FIG. 2;
[0014] FIG. 5 is a close-up view of still another exemplary bias
weave pattern that may be incorporated into the diaphragm assembly
depicted in FIG. 2;
[0015] FIG. 6 is a close-up view of a yarn that may be incorporated
into fabric of the diaphragm assembly;
[0016] FIG. 7 is a cross-sectional view of another exemplary
embodiment of the diaphragm assembly;
[0017] FIG. 8 is a cross-sectional view of a fabric shaping tool in
an open configuration; and
[0018] FIG. 9 is a cross-sectional view of the fabric shaping tool
shown in FIG. 8 in a closed configuration.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT
[0019] The following detailed description of the invention is
merely exemplary in nature and is not intended to limit the
invention or the application and uses of the invention.
Furthermore, there is no intention to be bound by any theory
presented in the preceding background of the invention or the
following detailed description of the invention.
[0020] Turning first to FIG. 1, a cross-sectional view of an
exemplary actuator 100 that may employ the diaphragm assembly of
the present embodiment is shown. As this figure illustrates, the
actuator 100 includes a housing assembly 102, that is made up of an
upper housing section 104 and a lower housing section 106. The
upper housing section 104 is coupled to the lower housing section
106 to form an internal chamber 108 within the housing assembly
102. The upper 104 and lower 106 housing sections are preferably
coupled together by, for example, threaded fasteners 110, such as,
for example, nuts and bolts, located around the circumference of
the upper 104 and lower 106 housing sections. It will be
appreciated that any other suitable structure could be used to
couple the housing sections together.
[0021] 1 An exemplary diaphragm 200 is mounted within the housing
assembly 102. In the depicted embodiment, a peripheral portion of
the diaphragm 200 is positioned between the upper 164 and lower 106
diaphragm sections, and is thereby clamped in place. It will be
appreciated that any one of numerous other suitable structures
could be used to clamp the diaphragm 200 in place. With this
configuration, the diaphragm 200 divides the internal chamber 108
into at least two portions, a first portion 112 and a second
portion 114.
[0022] A diaphragm support 116 is mounted below the diaphragm 200
and moves with, and provides support to, the diaphragm 200. In the
depicted embodiment, a diaphragm backing plate 118 is positioned
over a portion of the diaphragm 200. A threaded stopscrew 120
extends through the backing plate 118, the diaphragm 200, and the
support 116, and is threadedly coupled to a push rod 122. The push
rod 122 may be coupled to a particular component such as, for
example, a valve (not illustrated), the operation of which is be
controlled by the actuator 100.
[0023] A spring 124 is mounted within the chamber 108 between the
diaphragm support 116 and a bottom inside of the lower housing
section 106. The spring 124 is configured to bias the diaphragm
support 116 upward (relative to the view in FIG. 1). In the
depicted embodiment, the upper housing section 104 additionally
includes a fluid inlet port 126 and a fluid outlet port 128, each
of which extends through the upper housing section 104 and is in
fluid communication with the internal chamber first portion 112.
The fluid inlet 126 and outlet 128 ports allow entry and exit of
fluid from an external supply system (not shown). It will be
appreciated that the configuration and number of the fluid inlet
126 and outlet 128 ports depicted in FIG. 1 is merely exemplary,
and that other suitable configurations and numbers could be
used.
[0024] The actuator 100 illustrated in FIG. 1 and described above,
is operated by supplying a pressurized fluid, such as air or gas,
to the fluid inlet port 126 by, for example, opening an inlet valve
130. Substantially simultaneously, fluid egress from the actuator
100 is prohibited by, for example, closing an outlet valve 132.
Thus, the pressurized fluid enters the upper housing section 104
and pressurizes the internal chamber first portion 112. This causes
the diaphragm 200 to move the push rod 122 downwardly, against the
force of spring 124, to appropriately position the connected
component. When the component is no longer needed in this position,
the inlet valve 130 is shut, and the outlet valve 132 is opened,
depressurizing the internal chamber first portion 112. As a result,
the spring 124 moves the push rod 122 upwardly, to thereby return
the connected component to its original position.
[0025] Turning to FIG. 2, a detailed description of an exemplary
embodiment of the diaphragm 200 will now be provided. The diaphragm
200 is preferably cup-shaped and has a tubular sidewall 202 with an
open end 203 and an enclosed end 204. The enclosed end 204 may be
enclosed in any one of numerous manners. For example, the end 204
may be clamped or, alternatively, the end 204 may be bonded to a
plate, such as, for example, the diaphgram backing plate 118. The
diaphragm 200 is made of fabric that includes a plurality of yarns
that are in a bias weave pattern 206 wherein at least one yarn 208
is crossed over a second yarn 210, and each crossing has an angle
that is preferably less than about 60.degree..
[0026] In one exemplary embodiment of the bias weave pattern, shown
in FIG. 3, a single yarn 302 is formed over a first pair of yarns
304, then under a second pair of yarns 306, then over a third pair
of yarns 308, and so on. Additionally, a yarn 310 of the first pair
of yarns 304 is formed over a fourth pair of yarns 312, under a
fifth pair of yarns 314, then over a sixth pair of yarns 316, and
so on. This pattern is repeated throughout the fabric to form a
twill pattern 350. In still another exemplary embodiment, as shown
in FIG. 4, the yarns are positioned in the same manner as shown in
FIG. 3, however, they are spaced apart from one another providing
openings 402 that allow fluid elastomers (discussed in further
detail below) to flow therethrough during diaphragm formation. This
weave pattern forms a herringbone pattern 404.
[0027] In another exemplary embodiment, two or more yarns are
crossed over one another. For example, as shown in FIG. 5, a weave
pattern is formed by crossing a first pair of yarns 502 over a
second pair of yarns 504, then under a third pair of yarns 506,
then over a fourth pair of yarns 508, and so on. The second pair of
yarns 504 is crossed under the first pair of yarns 502, over a
fifth pair of yarns 510, then under a sixth pair of yarns 512, and
so on. This weave pattern is repeated in the fabric to form a
basket-weave pattern 550.
[0028] The fabric may alternatively include additional properties
that increase its structural integrity. In one exemplary
embodiment, the fabric has a yarn count of 50 yarns per square inch
or greater. In another exemplary embodiment, shown in FIG. 6, each
yarn 600 may be formed of a bundle of fibers, for example, three
fibers 602, 604, 606 that are twisted at an angle of greater than
about 60.degree.. It will be appreciated that each yarn 600 may
include fewer or many more fibers than that depicted in FIG. 6. In
yet another exemplary embodiment of the diaphragm assembly 200, a
cross section of which is shown in FIG. 7, the fabric is rolled and
doubled-up to form an inner sidewall 202 and an outer sidewall
228.
[0029] The yarns of the fabric may be made of any suitable material
such as, for example, polyamide (nylon), fiberglass, or polyester.
However, the fabric is preferably constructed of an aromatic
polyamide (e.g. Nomex.RTM.). It will be appreciated, however, that
various other different materials, and combinations of different
materials, may also be used.
[0030] Returning to FIG. 2, the fabric is impregnated with an
elastomer by positioning an uncured elastomer sheet on one side of
the fabric and pressing the sheet therein. In a particular
preferred embodiment, the elastomer is placed against the surface
of the fabric that is exposed to pressurized gas. Thus, it may be
either on the inner surface, the outer surface, or both. In the
depicted embodiment, the elastomer is on an outer surface of the
sidewall 202. The elastomer may be silicone, fluorosilicone, or
fluorocarbon, although other suitable materials may be used.
However, in the preferred embodiment, the elastomer is vinyl methyl
silicone (VMQ) that exhibits enhanced heat resistance. More
specifically, the preferred elastomer is a vinyl methyl silicone
material that is heat resistance enhanced with a fine iron oxide
powder (preferably less than 1%), which acts as an anti-oxidant,
and Silastic.RTM. HT-1, a heat stability additive available from
Dow Corning, in conjunction with a high temperature catalyst
2,5dimethyl-2,5-di-(t-butyl peroxy) which may be purchased under
the trademark Varox.RTM. DBPH-50, and which is available from the
R. T. Vanderbilt Co. It will be appreciated that a second layer of
elastomer may be coated over the first elastomer layer 230 to
thereby strengthen the fabric. The first and second elastomer
layers may or may not be similar material.
[0031] It will be appreciated that although the diaphragm 200 is
depicted and described herein as being constructed of a single
diaphragm, it could also be constructed of two or more diaphragms,
if so desired for a particular application.
[0032] In a preferred embodiment, the diaphragm 200 is formed from
a fabric tube structure having a uniform bias angle around its
circumference. It will be appreciated that the bias angle may vary
along the length of the tube. The fabric tube may be fabricated by
any conventional process, such as, for example, by braiding or by
stitching together the ends of a fabric strip cut on a bias to form
a tube. In an embodiment in which the tube is braided, a suitable
apparatus is set up with an appropriate number of yarns to from a
braided tube and may be instructed to construct a tube-like
structure having a diameter and bias angle that vary periodically
along its length. This process is suitable for providing a
diaphragm having a larger and a smaller diameter region, where the
larger region forms the brim of the top hat shape and the smaller
region forms the closed top section of the top hat shape.
[0033] FIGS. 8 and 9 illustrate two steps in a process of forming
an unshaped tube 712 into a fabric preform 713. As shown in the
figures, a preform-shaping tool having a top component 700 and a
bottom component 701 is employed. First, the unshaped tube 712 is
placed over the bottom component 701 and anchored at one end with a
circumferential clamp 703. The opposite end of the tube 712 is tied
off over a post 705 on the bottom component 701 using a fastener,
such as a wire 706. The tube 712 is soaked in a solution, such as,
for example, Chemlok.RTM. 607 (available through Lord Corporation
of Cary, N.C.), to enhance adhesion and to allow the tube 712 to
retain the shape of the preform 713 after exposure to high
temperature in the shaping tool. The top component 700 is then
hydraulically pressed against the bottom component 701 so that the
preform-shaping tool is in a closed configuration, as shown in FIG.
9. The force from the hydraulic press causes the tube 712 to
conform to the shape of the inner surface of the shaping tool
second component 701, the stretching of the tube 712 fabric reduces
the diameter of the tube 712 and decreases the bias angle of the
tube 712 to form a top hat region 710. As a result, wrinkles and
folds are eliminated at the outer edge 711 of the top hat region
710 and are decreased toward the interior of the top hat region
710.
[0034] In the next step of the exemplary method of forming the
diaphragm, the preform is impregnated with elastomer. For example,
first, a charge of elastomer is disposed within a two part mold
that molds the elastomer into a hat shape. After the elastomer is
appropriately shaped, the two-part mold is opened and the fabric
perform 713 is placed conformably over the shaped elastomer. The
mold is closed for a sufficient amount of time, to thereby
impregnate the fabric preform 713 with the elastomer and to cure
the elastomer. The elastomer-impregnated fabric preform is then
removed from the mold and die cut to desired required
dimensions.
[0035] The diaphragm 200 may be installed into a new actuator 100,
as part of its initial manufacturing process, or the diaphragm
assembly could be retrofitted into an existing actuator. For
example, to retrofit an existing actuator 100, an operator would
decouple the upper housing section 104 from the lower housing
section 106 by removing the fasteners 110. The stops screw 120 may
then be removed, to allow the backing plate 118 and existing
diaphragm to be removed from the housing assembly 102. The
diaphragm 200 (which may include one or more individual diaphragms)
may then be installed, with the fabric patterns properly aligned,
and the backing plate 118, stop screw 120 replaced. The upper
housing section 104 may then be coupled to the lower housing
section 106.
[0036] The diaphragm 200 increases the average time between repairs
of pneumatic actuators and significantly reduces the likelihood of
curtain failures where the actuator is in service.
[0037] While the invention has been described with reference to a
preferred embodiment, it will be understood by those skilled in the
art that various changes may be made and equivalents may be
substituted for elements thereof without departing from the scope
of the invention. In addition, many modifications may be made to
adapt to a particular situation or material to the teachings of the
invention without departing from the essential scope thereof.
Therefore, it is intended that the invention not be limited to the
particular embodiment disclosed as the best mode contemplated for
carrying out this invention, but that the invention will include
all embodiments falling within the scope of the appended
claims.
* * * * *