Note: Descriptions are shown in the official language in which they were submitted.
CA 02680299 2015-10-08
POSITION SENSING COMPOSITE CYLINDER
BACKGROUND
[0001] A fluid power composite cylinder that incorporates sensor features
to assist in
position sensing devices to sense the position of a piston within the cylinder
that cannot be
achieved with conventional metallic cylinders.
SUMMARY
[0002] The present disclosure relates to a composite cylinder that
incorporates within its
dielectric wall a conductive material that provides resistivity, capacitance,
conductance,
varying magnetic fields, and other types of features required for electronic
sensors
incorporated in (or on) the piston, piston rod, end pieces or other components
located within
the cylinder. The fluid power composite cylinders incorporate implants in the
form of linear
transducer devices within the wall of the composite cylinder to detect the
position of the
piston within a cylinder. The fluid power composite cylinders incorporating
electromagnetic
shielding materials within the wall of the cylinder to protect against
undesirable electrical
interference. Such shielding prevents cross-talk between adjacent composite
cylinders.
Since the sensing equipment is built into the cylinder, there is a reduction
in costs associated
with conventional hydraulic position cylinders.
[0002a] In accordance with an aspect of an embodiment, there is provided a
composite
cylinder having position sensing capabilities comprising a dielectric
composite cylindrical
wall having a continuous inner bearing surface and an outer surface, the inner
bearing surface
defining a primary bearing direction along an axis of the cylinder, a resin
matrix composed of
a resin, the resin at least partially lying at the inner bearing surface, a
conductive fiber
embedded within the resin matrix, the conductive fiber positioned between the
continuous
inner bearing surface and the outer surface of the dielectric composite
cylindrical wall, and a
filament material embedded within the resin matrix.
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[0002b] In accordance with another aspect of an embodiment, there is
provided a
composite cylinder having position sensing capabilities to determine the
position of a piston
within the composite cylinder by use of an electric sensor, the composite
cylinder comprising
a dielectric composite cylindrical wall having a continuous inner bearing
surface and an outer
surface, the piston adapted to slide with respect to the inner bearing surface
of the cylinder
wall, the inner bearing surface defining a primary bearing direction along an
axis of the
cylinder, a resin matrix composed of a resin, the resin at least partially
lying at the inner
bearing surface, a conductive fiber embedded within the resin matrix, the
conductive fiber
positioned between the continuous inner bearing surface and the outer surface
of the
dielectric composite cylindrical wall, and a filament material embedded within
the resin
matrix, wherein the conductive fiber is coupled to a source of electrical
power and the piston
is coupled to an electrical ground, and wherein the electronic sensor can
determine the
position of the piston within the composite cylinder.
[0002c] In accordance with yet another aspect of an embodiment, there is
provided a
composite cylinder comprising a composite sleeve having an annular side wall
formed of a
resin matrix composed of a resin material having fumed silica therein, the
resin material at
least partially at an inner surface of the side wall, a substantially
continuous filament material
embedded within the resin matrix, the substantially continuous filament
material including a
round cross-section, and a metallic jacket positioned around the composite
sleeve and having
an inner surface that is positioned to lie near the annular side wall of the
composite cylinder,
wherein opposing ends of the metallic jacket extend further than opposing ends
of the
composite sleeve so that the jacket can be coupled with an end cap.
[0003] Additional features of the present disclosure will become apparent
to those skilled
in the art upon consideration of the following detailed description of
illustrative embodiments
exemplifying the best mode of carrying out the disclosure as presently
perceived.
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BRIEF DESCRIPTION OF THE DRAWINGS
[0004] The detailed description particularly refers to the accompanying
figures in which:
[0005] FIG. 1 is a perspective view of the position sensing composite
cylinder;
[0006] FIG. 2 is a side elevational view of the composite cylinder of Fig. 1;
[0007] FIG. 3 is an exploded view of section A of Fig. 2 showing the different
layers of the
composite cylinder;
[0008] FIG. 4 is a front elevational view showing the layers of the cylinder;
[0009] FIG. 5 is a cross-sectional view of a composite cylinder having a
capacitive sensor;
[0010] FIG. 6 is a cross-sectional view of a composite cylinder having a
linear motion
transducer;
[0011] Fig. 7 is a partial, cross-sectional view of the hybrid bearing
cylinder of the present
invention;
[0012] Figs. 8-10 illustrate a series of steps used in producing the hybrid
bearing cylinder
of the present invention;
[0013] Fig. 11 is a perspective view of a completed hybrid bearing cylinder
produced by
employing the steps illustrated in Figs. 8-10;
[0014] Fig. 12 is an end view of a bearing cylinder including a metal jacket;
[0015] Fig. 13 is a cross section of the hybrid bearing cylinder taken along
line 13-13 of
Fig. 12 showing the composite bearing cylinder positioned within the metallic
jacket and also
showing the metallic jacket being secured to a pair of end caps by welding;
[0016] Fig. 14 is an end view of a bearing cylinder;
[0017] Fig. 15 is a cross section of the hybrid bearing cylinder taken along
line 15-15 of
Fig. 14 showing the composite bearing cylinder positioned within the metallic
jacket and also
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showing the metallic jacket being secured to a pair of end caps by threads
positioned at the ends
of the metallic jacket;
[0018] Fig. 16 is a side elevational view of a hybrid bearing cylinder
secured to a pair of
end caps by a series of threaded rods that extend from end cap to end cap;
[0019] Fig. 17 is an end view of the hybrid bearing cylinder of Fig. 16;
and
[0020] Fig. 18 is a cross section of the hybrid bearing cylinder taken
along line 18-18 of
Fig. 17 showing the composite bearing cylinder positioned within the metallic
jacket and also
showing the metallic jacket being secured to a pair of end caps by elongated
threaded rods that
extend from end cap to end cap.
DETAILED DESCRIPTION
[0021] The present disclosure relates to resistivity type positioning
fluid power cylinders
10. More specifically, the present disclosure relates to a fluid power
composite cylinder 10 such
as the AeroSlide cylinder manufactured by Polygon that includes a thin
cylindrical layer of a
resistive (or semi-conductive) material 202 located within the wall 201of the
dielectric cylinder
tube 203, as shown, for example, in Fig. 3. The location of the resistive (or
semi-conductive)
layer 202 in the wall 201 of the cylinder tube 203 relative to the bore
surface 205 and the
thickness and the resistivity of the resistive material 202 varies depending
on the requirements of
the electronic positioning sensor that is coupled to the cylinder 10. Examples
of sensor
components that can be used in connection with the cylinders 10 include but
not limited to
sensors requiring resistivity, sensors requiring capacitance, and sensors
requiring varying
magnetic field.
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[0022] Cylinders 10 with the position sensing components shown in Figs. 1-
6 can be
used for piston positioning sensing, piston velocity control, cycle counting
in fluid power
hydraulic cylinders. Use of this arrangement provides cost savings, and
greater monitoring of
piston and cylinder wear.
[0023] In one embodiment, a multiple of thin resistive layers 202 may be
positioned at
various locations within the wall 201 of the cylinder tube 203. The resistive
film in this
embodiment is located between dielectric layers 204 in the wall 201 of the
composite cylinder
10. In another embodiment the cylinder 10 incorporates an electromagnetic
shielding material
206 within the cylinder wall 201 or at the outer surface 207 of the dielectric
composite tube 203
to prevent undesirable electrical interference with the positioning sensor
device.
[0024] The resistive material used in the resistive layer 202 of the
dielectric composite
tubing 203 may be in the form of a polymeric gel coat formulated with the
desirable amount of
conductive filler such as carbon black to give the desired resistivity. The
polymeric gel coat may
be applied (but not limited to) during the manufacturing process at the
desired location within the
composite wall by normal gel coating techniques such a spraying or contact
application,
preferably between the conductive layer and the outer surface 207 of the
cylinder 10.
[0025] In yet another embodiment, the resistive material 202 may also
take the form of a
resistive conductive polymeric thin film or metallic film that is wrapped onto
the laminated
composite cylinder 10 at a desired location within the wall 201 of the
cylinder tubing 203, as
suggested in Fig. 5. In yet another embodiment, the resistive material may
also take the form of
conductive fibers 216 such a carbon fiber that is filament wound into the
cylinder wall during the
filament winding process used in manufacturing the cylinder 10, as suggested
in Fig. 6.
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[0026] In yet another embodiment, the resistive material 202 may take the
form of a
conductive prepreg consisting of a dielectric reinforcing material such as
fiber glass roving with
a semi-conductor polymer matrix. The resistive material 202 is not limited to
the above but may
take other forms to meet the intent of this invention.
[0027] The present disclosure also relates to fluid power capacitive
positioning sensor
cylinders 10. In this embodiment, but not limited to this embodiment, an area
variation type
capacitor is made by integrating a conductive thin foil 212 between dielectric
laminates 204 in
the wall 201 of the composite cylinder tube 203, as shown, for example, in
Fig. 5. The foil 212
forms a symmetric trapezoid orientated about the axis of the cylinder 10. The
taper in the foil
212 relative to the axial direction of the cylinder bore 205 provides a
changing exposed area to
piston 210 as the piston 210 moves in the cylinder 10. Normally the piston 210
is ground while a
voltage is applied to the foil 212. The moving piston 210 thereby creates a
changing capacitance
which is proportional to the changing capacitance area.
[0028] By tuning the capacitance at retract and extend positions of the
fluid power
cylinder 10 and knowing the capacitance change from retract to extend position
is a linear
function, the position of the piston 210 can be electronically monitored. The
dielectric
composite tube material 200 (located between the conductive foil 212 and the
bore surface 205
and the relatively small distance between the bore surface 205 and the piston
outer diameter
serves as a dielectric spacer between the conductive surfaces of the
capacitors.
[0029] The present disclosure also relates to fluid power electromagnetic
position sensor
cylinders. In this embodiment, a conductive wire 216 is wound symmetrically at
a changing
wind angle about the axis of the composite cylinder tube 203. The wire 216 is
imbedded within
the dielectric laminate of the composite tube wall 201 and preferably located
near the bore
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surface 205 and the piston 210 within the cylinder 10 is electrically
grounded. Due to the
magnetic field density changing with axial movement of the piston 210, the
position of the piston
210 is proportional to the change in electromagnetic field current, thereby
providing a means for
electronically monitoring the relative position of the piston 210.
[0030] Fig. 5 shows a capacitive sensor formed with the composite
cylinder 10. The
cylinder 10 includes the tapered conductive foil electrode 212 that positioned
to lie around the
cylinder 10. A charge is placed on the foil electrode and the metallic piston
210 and rod 214 are
grounded. The tapered foil 212 provides a changing face area as the piston 210
moves axially
producing a change in capacitance.
[0031] Fig. 6 shows a linear motion transducer formed of a variable wound
coil 217 that
is wound within the dielectric composite fluid power cylinder 10 as it is
being manufactured.
The coil wire 216 is wound into the resin material of the cylinder 10. As with
Fig. 5, a charge is
placed on the coil wire 216 and the conductive piston 210 and rod 214 are
grounded. The coil
windings vary in density across the length of the cylinder 10 to provide a
change in capacitance.
[0032] FIG. 7 shows the composite sleeve 10 having an inner surface 12.
Composite
sleeve 10 includes a resin matrix 14 with a continuous filament material 16
and, optionally, a
plurality of particulate additives 18 embedded therein.
[0033] Resin matrix 14 is composed of a resin material having fumed
silica (commonly
sold under the trade name "Cab-O-Sil") therein. Advantageously, 2% to 10% (by
weight) thereof
is employed with about 8% fumed silica being preferred. While fumed silica is
used it is
contemplated that any material having similar thixotropic properties and
tribological
characteristics such as wear resistance and hardness could be used in place of
fumed silica. An
inner layer 20 of resin matrix 14 exists at inner surface 12, thereby greatly,
due to the hardness
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imparted thereto by the fumed silica present therein. The resin material may
be made to be either
translucent or colored, as desired.
[0034] Continuous filament material 16 is helically embedded within resin
matrix 14 to
thereby add to the toughness (i.e., durability) of composite sleeve10.
Advantageously, filament
windings 26 each have a round filament cross-section 28, thereby forming a
series of rounded
filament surfaces 32 at or near inner surface 12. Inner layer 20 of resin
matrix 14 and the series
of rounded filament surfaces 32 at or near inner surface 12 together actually
define the totality of
inner surface 12. In fact, the combination of the fumed silica in resin matrix
14 and rounded
filament surfaces 32 permits the surface finish of inner surface 12 to be an
arithmetic average
roughness (Ra) of about 25 µin or greater, whereas normal metallic or gel
coated cylinders
specify an Ra of less than 10 µin.
[0035] Advantageously, continuous filament material 16 is a fiberglass
material.
Fiberglass offers advantages of good hardness, generally good durability, a
round cross-section
and translucency. Some possible choices for particulate additives 18 are
polytetrafluoroethylene
(PTFE), glass beads, fine ground silica, etc. or a combination thereof. PTFE,
commonly sold
under the trade mark "Teflon". Glass beads each offer a rounded surface and
good hardness. Fine
ground silica helps increase hardness.
[0036] FIGS. 7-11 together illustrate various steps in the production of
composite
sleeve10, including a perspective view of the finished product FIG. 11. As set
forth in FIG. 8, a
highly polished mandrel 34 is provided to act as a mold for inner surface 12.
Mandrel 34
advantageously has an arithmetic average roughness (Ra) of no more than about
10 inch. To
help achieve the desired level of roughness and promote easy release thereof
from the finished
product, mandrel 34 is chrome plated.
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[0037] The bore surface finish of the composite cylinder 10 is primarily
a reflection of
the mandrel surface finish. The normal bore surface finish of the composite
cylinder 10 ranges
from 10 Ra to 25 Ra micro-inches. The surface finish can even be higher and
can simulate
a microscopic "orange peel" surface profile resulting in less adhesion
friction without adversely
affecting the seal life as would be the case with bores of metallic cylinders.
[0038] To further aid in the release thereof from the finished product,
mandrel 34, as
shown in FIG. 7, is desirably initially coated with a release agent 36
supplied by a release agent
applicator 38 (shown schematically). Additives can be provided within release
agent 36 that will
adhere to inner surface 12. PTFE can, for example, be used as such an
additive. The coefficient
of friction can further be reduced by the migration (transfer) of the mandrel
release material from
the mandrel to the composite bore surface. Above normal amounts of low
friction additives in
the mandrel release material such as PTFE particulates can further reduce the
friction at the bore
surface by the migration process.
[0039] In FIG. 9, a resin source 40 of an appropriate resin material 42
and an associated
resin applicator 44 are provided. Resin applicator 44 is advantageously a
trowel applicator,
permitting the application of a controlled, even thickness of resin material
42 on mandrel 34.
Resin material 42 is applied, desirably in a form of a paste, upon mandrel 34.
Resin material 42
is troweled substantially evenly over entire mandrel 34, preferably to a
thickness of about 1/8
inch.
[0040] As illustrated in FIG. 10, a filament source 46 of continuous
filament material 16
is supplied and via which filament windings 26 that are formed substantially
transversely of
primary direction 26. (Mandrel 34 could be rotatably driven, as schematically
shown via arrow
48, to promote the winding of continuous filament material 16 thereon.)
Filament windings 26
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displace and otherwise become embedded in resin material 42 during this step.
After a suitable
number of filament windings 26 have been formed along the entire length of
mandrel 34 in resin
material 42, continuous filament material 16 is cut (not shown) and,
desirably, excess resin
material 42 is wiped (not shown) from the outside of now-formed composite
sleeve 10 before
resin material 42 has an opportunity to cure. Once resin material 42 cures,
mandrel 34 is then
removed from composite sleevel0 to reveal the finished product shown in FIG.
11.
[0041] Composite sleeve 10 can be used in combination with a metallic
jacket 100 to
form hybrid bearing cylinder 102, as shown, for example, in Fig. 7. Metallic
jacket 100 includes
an inner surface 104, an outer surface 106 and first and second ends 108, 110.
Composite sleeve
includes inner bearing surface 12 and machined outer surface 112. Outer
surface 112 of
composite sleeve 10 can be machined using a lathing process so that the outer
diameter of
composite sleeve 10 is the same as or slightly greater than the inner diameter
of metallic jacket
100 to allow for the metallic jacket 100 to be positioned around and secured
to composite sleeve
10 to form hybrid bearing cylinder 102.
[0042] The outside diameter of the composite sleeve 10 can be machined to
give the
desired fit between the bore of the outer metallic jacket 100 and the outer
diameter of the inner
composite sleeve 10. Normally there will be a slight interference fit for a
press fit assembly. In
situations where the composite sleeve 10 is bonded to the outer metallic
jacket 100 the outside
diameter of the composite sleeve would be slightly less than the metallic
jacket inside diameter
to allow the proper bond joint thickness.
[0043] Composite sleeve 10 includes first and second ends 114, 116, as
shown, for
example, in Fig. 7. The overall length of composite sleeve 10 is shorter than
metallic jacket 100
such that first and second ends 114, 116 of composite sleeve 10 are set in
from first and second
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ends 108, 110 of metallic jacket 100. This arrangement allows metallic jacket
100 to be either be
secured to end caps 118, 120 by use of welds 122, as shown in Fig. 7 or by
threads 124, as
shown in Fig. 9 for example.
[0044] Use of composite sleeve 10 in combination with metallic jacket 100
provides
lower seal wear and friction characteristics of composite sleeve 10 when used
with a metallic
cylinder 100. Metallic cylinder 100 can be made from steel, aluminum or
stainless steel. Hybrid
bearing cylinder 102 reduces the cost of surface preparation of the metallic
cylinders used for
fluid power, pneumatic and hydraulic cylinder applications because inner
bearing surface 12 is
already smooth due to the manufacturing process of the composite sleeve 10.
[0045] Use of composite sleeve 10 in combination with metallic jacket 100
provides
corrosion resistance to the bore surface allowing other non-compressible
fluids, such as water, to
be used other than conventional hydraulic fluids, and the design results in an
overall weight
reduction in the cylinder. The hybrid bearing cylinder 102 incorporates the
strength and stiffness
of metal cylinders and incorporates the bearing surface benefits of the
composite sleeve material
10. Use of hybrid bearing cylinder 102 reduces the overall geometric size of
the cylinder as
compared with an all composite cylinder.
[0046] With the additional strength of hybrid bearing cylinder 102 over
metal cylinders
the pressure rating of non-repairable metallic cylinders used for low pressure
hydraulic
applications can be increased for 500 psig to 1500 psig applications.
[0047] End caps 118, 120 are designed to be secured to hybrid bearing
cylinder 102 to
provide an end seal, as shown, for example, in Figs. 7 and 9. Depending upon
the application,
end caps 118, 120 may or may not include a central aperture 126 to permit the
passage of a rod
128 used in combination with a piston 130, as shown, for example, in Fig. 12.
In the provided
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examples of the disclosure, end caps 118, 120 include an end wall 132 and an
annular side wall
134.
[0048] Annular side wall 134 of end caps 118, 120 includes a first
annular recess 136
positioned to lie near first and second ends 108, 110 of metallic jacket 100,
as shown, for
example, in Fig. 7. Metallic jacket 100 can either be welded to side wall 134
of end caps 118,
120 or first annular recess 136 can include threads 124 that engage
corresponding threads formed
on the inner surface 104 of metallic jacket 100, as shown, for example, in
Fig. 9.
[0049] End caps 118, 120 also include a second annular recess 138 that is
positioned to
lie near first and second ends 114, 116 of composite sleeve 10, as shown, for
example, in Fig. 7.
Second annular recess 138 includes an annular groove 140 that is adapted to
accept an o-ring seal
142 to seal against the inner bearing surface 12 of composite sleeve 10.
[0050] End caps 144, 146 of hybrid bearing cylinder 102 of Figs. 10-12
include a series
of apertures 148 adapted to accept tie rods 150 that extend from end cap 144
to end cap 146 to
compress end caps 144, 146 against hybrid bearing cylinder 102. Use of tie
rods 150 replaces
the use of welds or threads to secure end caps 144, 146 to hybrid bearing
cylinder 102. Use of
welds or threads eliminate the need to use tie rods. Swaging, while not
illustrated in the figures,
can also be used to secure end caps 118, 120 to hybrid bearing cylinder 102.
[0051] Metallic jacket 100 can be assembled with composite sleeve 10 by
press fitting
the two components together. Another method for assembling metallic jacket 100
to composite
sleeve 10 is by thermally expanding the metallic jacket 100 prior to inserting
composite sleeve
10. Alternatively, metallic jacket 100 can be bonded to composite sleeve 10 by
use of an
adhesive or can be metal formed by use of swaging, roll forming, or drawing
processes. Use of
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metallic jacket 100 with composite sleeve 10 provides a sealing barrier for
the composite
sleeve 10 for applications that require the containment of gasses such as
helium.
[0052] While this invention has been described as having a preferred
design, the
present invention can be further modified within the scope of this disclosure.
This application
is therefore intended to cover any variations, uses, or adaptations of the
invention using its
general principles. Further, this application is intended to cover such
departures from the
present disclosure as come within known or customary practice in the art to
which this
invention pertains and which fall within the limits of the appended claims.
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