TITLE OF INVENTION
Inflatable Tube For Coupling Component and Method For Making an
Inflatable Tube
BACKGROUND OF THE DISCLOSURE
The present invention relates to flexible inflatable tubes that are
inflatable under pressure to operate or engage a coupling component used in a
mechanism such as an industrial clutch or a brake.
Clutches and brakes used in industrial machinery and equipment may
include a coupling component having an inflatable annular tube that is mounted on
a rigid annular rim. Friction shoe assemblies are connected with the tube in an
annular array. When pressurized, the tube is expanded to press the friction shoe
assemblies against another coupling component to interconnect the two coupling
components or retard relative motion therebetween.
Coupling components having this construction have previously been
made by a method that includes hand-building an inflatable annular tube, placing
the inflatable annular tube in a mold, inflating the tube, and heating the mold to
vulcanize the elastomeric material of the tube. This process is labor intensive and,
accordingly, significantly increases the cost to manufacture the tube and the clutch
or brake.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a perspective view, in partial cross-section, of an exemplary
coupling component that includes and inflatable tube according to an embodiment
of the present invention;
FIG. 2 is a perspective view of a tube shown in its finally manufactured
condition prior to assembly into the coupling component of FIG. 1;
FIG. 3 is a perspective view of a generally tubular-shaped structure
having several exposed layers supported on a mandrel, for use in the tube shown
in FIG. 2;
FIG. 4 is a flow chart illustrating a method of making a tube according to
an embodiment of the present invention;
FIG. 5 is a perspective view, in cross-section, of the generally tubular-
shaped structure of FIG. 2 according to an embodiment of the invention, showing
the fiber orientation in reinforced layers of the structure;
FIG. 6 is a detailed view of the structure shown in FIG. 4, further
illustrating the fiber orientation in the reinforced layers of the structure; and
FIGS. 7 and 8 are exploded perspective views of a valve according to an
embodiment of the present invention, for use in the tube shown in FIG. 2.
DETAILED DESCRIPTION
Referring now to the drawings, which are not intended to limit the
invention, FIG. 1 illustrates an exemplary coupling component 10 that includes an
inflatable tube 12 and an annular array of friction shoe assemblies 14. The friction
shoe assemblies 14 are engageable with the outside of a drum or second coupling
component (not shown) to interconnect the two coupling components. The
exemplary coupling component 10 may function as part of either a brake or a
clutch.
The friction shoe assemblies 14 are moved into engagement with the
drum by radial expansion of the inflatable tube 12. Thus, when fluid pressure, such
as air pressure, is conducted through a conduit 16 into the annular tube 12, the
tube expands radially inwardly. This causes the tube 12 to press the friction shoe
assemblies 14 against the drum. The friction between the shoe assemblies 14 and
drum interconnect the drum and the coupling component 10.
In the illustrated coupling component 10, a rigid annular metal rim 18 is
connected with the inflatable tube 12. The rim 18 has an annular mounting flange
20 which is used to connect the coupling component 10 with an associated
apparatus or support structure (not shown). The rim 18 has a cylindrical web 22
with a radially inner side surface which is bonded to a radially outer side wall
portion of the tube 12. Upon inflation of the tube 12 to press the friction shoes 14
against a drum or other coupling component, torque is transmitted between the
friction shoe assemblies and the rim 18. To enable the tube 12 to withstand
relatively large torque forces, one or more reinforced and non-reinforced layers 24
are provided in the tube 12 as will be described in further detail below.
Referring to FIGS. 2 and 3, a tube 12 according to an embodiment of the
present invention is shown. In FIG. 2, tube 12 is shown in its finally manufactured
condition prior to assembly into coupling component 10. The tube 12 includes an
elongated, generally tubular-shaped structure 24 of predetermined length having
two ends 26a, 26b and a joint 28 between the two ends that closes the tube 12 to
form a continuous toroidal-shaped cavity 30 (see, e.g., FIG. 1).
In an embodiment, tube 12 includes at least one reinforced layer 32
sandwiched between an inner, unreinforced layer 34 and an outer, unreinforced
layer 36. However, it will be appreciated that tube 12 may have any number of
layers, including for example, multiple reinforced layers 32 as shown in FIGS. 3
and 6, or only a single unreinforced layer 34, 36 positioned inwardly or outwardly of
the reinforced layer 32.
The tube 12 is constructed by building the elongated, generally tubular-
shaped structure 24, cutting the tubular-shaped structure 24 into predetermined
lengths and joining the ends 26a, 26b of each length at the joint 28 to form the
toroidal-shaped tube 12. While a range of elastomers may be used in the
unreinforced layers 32 to facilitate this construction, including uncured thermoset
and thermoplastic elastomers, thermoplastic elastomers provide the best blend of
efficiency and integrity when joining the.two ends. Thermoplastic polyurethane is
particularly suited for tubes used in clutches given its good overall balance of
mechanical, thermal, chemical and aging performance. Similarly, while a variety of
organic and inorganic fibers may be used in the reinforced layers, organic fibers
such as polyester, nylon, and rayon are particularly suited for use in tube 12 given
their relatively low cost, low stiffness and generally acceptable thermal
performance. Polyester fiber including multiple twisted fiber bundles similar to
bundles used in the vehicle tire and industrial hose industries—commonly referred
to as "tire cord"—is particularly, but not exclusively suited for use in tube 12;
however, it is recommended that traditional resorcinol formaldehyde latex fiber
sizing used with thermoset elastomers be replaced with isocyanate, blocked
isocyanate, or epoxy sizing to provide more robust adhesion to the thermoset
elastomer.
With reference,to FIG. 4, a method for making tube 12 according to an
embodiment of the present invention will now be described. In the illustrated
embodiment, each reinforced layer 32 may be constructed by producing a semi-
continuous sheet of elastomer coated, unidirectional fiber or fabric. As shown in
option A, a thermoset elastomer, such as urethane, may be milled and calendared
into a generally flat sheet of predetermined width within which a treated fiber or
fabric, such as tire cord, may be imbedded in accordance with methods well know
in the art. Alternatively, as shown in option B, a reinforced fiber, including without
limitation polyester, may also be twisted into cord and coated with a compatible
sizing (i.e., adhesion promoter), then woven into a unidirectional fabric of
predetermined width (e.g., about 40-60 in (15.7-23.6 cm)). The woven fabric may
then be extrusion coated with a thermoplastic elastomer (e.g., TPU) to produce a
sheet of predetermined thickness and width (e.g., about 0.04 in (0.015 cm) thick by
40-60 in (102 - 152 cm) wide). Heated nip rollers, as are known in the art, may be
used to provide adequate polymer flow and strike-through of the fiber structure.
Depending on the level of strike-through, the fabric may be coated with polymer on
either one or both sides.
A chemical cross-linking agent may be added to the thermoplastic
elastomer during extrusion coating of the fiber reinforcement (e.g., dosed into the
barrel of an extruder). When so employed, partial cross-linking between the
reinforced layer materials occurs while the thermoplastic elastomer is at a relatively
high temperature, promoting cross-linking of polymer chains between the fiber and
the resin and within the. body of the thermoplastic elastomer itself. The type and
amount of chemical cross-linking agent may be selected to facilitate a relatively low
level of cross-linking, sufficient to improve elevated temperature stability of the
reinforced layer, but low enough so that additional flow and bonding may occur
during subsequent high temperature processing operations.
In an exemplary implementation of the present invention, a medium
durometerTPU made by BASF having material number 1185A10, was mixed with
either of two experimental chemical cross linking agents (e.g., 7 w% Link 1.0 or 5
w% Link 2.0. A T-Peel test was then performed yielding a bond strength between
the layers as high as 80% of the unmodified thermoplastic at bonding temperatures
only slightly higher (e.g., 10-20°C) than required for the unmodified, fully
thermoplastic polymer. These results indicate that the polymer chains retain
sufficient mobility for adequate thermal bonding and still allow thermal
consolidation of the layers after wrapping.
Alternatively, the fiber or fabric may be coated with a chemical cross-
linking agent prior to extrusion coating. During extrusion coating, the relatively hot
thermoplastic elastomer contacts the coated fiber or fabric, activating the chemical
cross-linking agent and causing localized cross-linking of the polymer chains
between the fiber or fabric and the thermoplastic elastomer. This process
improves fiber or fabric adhesion to the elastomer and long-term creep
performance since the fiber is mechanically and chemically secured to the
elastomer. A majority of the elastomer remains uncross-linked to preserve the
thermoplastic behavior of the reinforced layer.
Similarly, each unreinforced elastomer layer 32 may be constructed by
producing a semi-continuous sheet of unreinforced elastomer, such as by sheet or
blown film extrusion. The reinforced and unreinforced sheets may then be slit or
cut into individual strips of "tape," each having a predetermined width.
In an embodiment, the tubular-shaped structure 24 is constructed by
spiral wrapping individual strips of unreinforced elastomer "tape" onto a mandrel
38. The width of each tape strip may be selected to match the minor diameter,
amount of overlap and fiber helix angle desired in a given wrap layer. To facilitate
removal of the mandrel from the tubular-shaped structure, the mandrel may be
coated with a release agent, such as zinc state or polyethylene film. While the
mandrel shown in FIG. 3 is generally circular in cross-section, non-circular shaped
mandrel may also be used, such as those having a generally oval shaped cross-
section or a cross-section substantially similar to the tube cavity 30 shown in FIG.
1.
Referring to FIG. 3, two reinforced elastomer layers 32 are spiral-
wrapped over the unreinforced elastomer layer 34; however, as noted above, the
number of reinforced layers is not limited thereto. For the spiral-wrapped
reinforced elastomer layers, the spiral angle is selected to provide an acceptable
balance of strength and stiffness of the orthotropic fibers in the principal load
direction of the tube. As shown in FIG. 5, the coordinates 1, 2, 3 of the reinforced
elastomer layers are shown adjacent the coordinates X, Y, Z of the unreinforced
elastomer layers 34, showing the relative angle G therebetween representing the
spiral angle. In FIG. 6, the spiral angles of two unreinforced layers 32 are shown
relative to the radially extending axis R and axially extending axis § of the tubular-
shaped structure 24. For example, in clutch applications, the spiral angles +/-0
may be selected to be a minimum of about +/- 45°. A second spiral-wrapped
unreinforced elastomer layer 36 may then be placed over the reinforced elastomer
layers 32 to produce a tube having a given length (e.g., about 100' (30.5m)). While
the construction method described herein includes spiral wrapping each of the tube
layers, it is not intended to be limited thereto. Alternatively, for example, the
unreinforced layers 34, 36 may be extruded and the reinforced layers 32 may
comprise a braided or spiral-applied fabric reinforcement. A chemical cross-linking
agent may also be disposed between the unreinforced layers 34, 36 and reinforced
layers 32. For example, when the unreinforced and reinforced layers are spiral
wound, the chemical cross-linking agent may be applied as a coating over each
wrapped layer excluding the outer layer. When a chemical cross-linking agent is
employed between the unreinforced and reinforced layers, the thermal
consolidation process activates the cross-linking agent to bond the layers together,
enhancing the overall structural integrity of the tubular-shaped structure and
reducing the possibility for delamination of the layers.
Prior to thermal consolidation of the layers, a nylon fabric tape or other
suitable material (not shown in FIG.) may be spiral wrapped around the outer
unreinforced elastomer 36 layer to apply a radially inwardly directed pressure onto
the layers and to protect the tubular-shaped structure 24 during thermal
consolidation. Thermal consolidation of the tubular-shaped structure 24 may be
accomplished using a variety of methods, including, without limitation, heating the
mandrel (electrical resistance, induction or heated fluid within the mandrel) or by
inserting the entire tubular-shaped structure into a heated atmosphere, such as a
steam autoclave or oven. In a steam autoclave, for example, temperature and
pressure promote molecular mobility and bonding between the layers. It was
determined that subjecting the tubular-shaped structure to saturated steam at
approximately 293°F for about 35 minutes was sufficient to bond and consolidate
the tube structure described above using a relatively low hardness polyester
thermoplastic urethane, such as Seaman 1940 PTFF
Following consolidation, the nylon tape is removed and the mandrel 38
may be extracted from the tubular-shaped structure 24, such as by using fluid •
pressure (e.g., high pressure water) to eject the mandrel. The continuous and still
relatively straight tubular-shaped structure 24 may be permanently deformed using
additional heat and pressure to obtain the generally flat shape shown in FIG. 1.
The flattened tubular-shaped structure 24 may then be cut into pieces having, a
predetermined length so that a closed toroidal-shaped tube may be formed when
the ends of the cut length are joined to form the continuous cavity 30. Prior to
joining, holes may be placed into a wall of the tube 12, such as by punching or
cutting, to accommodate air inlet and outlet valves 40 that connect the conduit 16
to the tube 12.
In the embodiment shown in FIGS. 7 and 8, the valve 40 includes an
interior valve member 42 that is inserted into the interior of the tube 12 prior to
joining and an exterior valve member 44 attached to the interior valve member prior
to joining the ends of the tubular-shaped structure 24. The interior valve member
includes a threaded male portion 46 that is adapted to thread into a corresponding
threaded female portion 48 in exterior valve member 44. A generally flat mating
surface 50 in the interior valve member 42 includes at least one annular rib 52 that
engages an interior surface of the cavity 40 to create an air-tight seal. A hexagonal
hole 54 in the interior valve member 42 is adapted to interface with a
correspondingly shaped hex-key tool (not shown), allowing the interior valve
member 42 to be rotated relative to the exterior valve member 44 from outside of
the tube 12 to assemble the valve 40.
The ends 26a, 26b of the straight tubular-shaped structure may be joined
using a thermoset or thermoplastic adhesive. For thermoplastic tubes, a solvent
bond or thermal weld may also be used to join the ends. Heat to effect a thermal
weld may be generated using various sources, including, without limitation, a
heated tool, hot gas, vibration, ultrasonic, induction, radio frequency, resistance,
infrared and laser energy.
The invention has been described in great detail in the foregoing
specification, and it is believed that various alterations and modifications of the
invention will become apparent to those skilled in the art from a reading and
understanding of the specification. It is intended that all such alterations and
modifications are included, in the invention, insofar as they come within the scope
of the appended claims.
We claim:
1. An inflatable coupling component tube 12 for a fluid-operated brake or
clutch, comprising:
an elongated, generally tubular-shaped structure 24 of predetermined
length having two ends 26a, 26b and a joint 28 between the two ends 26a,
26b that closes the tube 12 to form a generally toroidal-shaped cavity 30.
2. The tube of. claim 1, wherein the generally tubular-shaped structure 24
includes at least one reinforced layer 32 and at least one unreinforced layer
36. '
3. The tube of.claim 2, wherein the generally tubular-shaped structure 24
includes multiple reinforced layers 32.
4. The tube of claim 2, wherein the reinforced layer 32 comprises a semi-
continuous sheet of elastomer-coated, unidirectional fiber or fabric.
5. The tube of claim 4, wherein the fabric is coated with polymer on either one
or both sides.
6. The tube of claim 2, wherein the unreinforced elastomer layer comprises a
semi-continuous sheet of unreinforced elastomer.
7. The tube of claim 2, wherein the reinforced and unreinforced layers 32, 34
are spiral wrapped at a predetermined spiral angle.
8. The tube of claim 2, wherein the unreinforced layer 34, 36 is an extruded
elastomer.
9. The tube of claim 2, wherein the reinforced layer 32 comprises a braided or
spiral-applied fabric reinforcement.
10. The tube of claim 2, wherein at least one of the reinforced layer 32 and the
unreinforced layer 34, 36 includes a thermoplastic elastomer.
11. The tube of claim 2, wherein the thermoplastic elastomer is at least partially
chemically cross-linked.
12. The tube of claim 2, further including an interior valve member 42 and an
exterior valve member 44 attached to the interior valve member 42, the
interior valve member including a threaded male portion 46 adapted to
thread into a corresponding threaded female portion 48 in exterior valve
member 44 and a generally flat mating surface 50 in the interior valve
member 42 having at least one annular rib 52 that engages an interior
surface of the cavity 40 to create an air-tight seal.
13. The tube of claim 1, wherein the generally tubular-shaped structure 24
includes at least one reinforced layer 32 sandwiched between an inner,
unreinforced layer 34 and an outer, unreinforced layer 36.
14. The tube of claim 1, wherein the joint 28 includes one of a thermoset or
thermoplastic adhesive, a solvent bond, and a thermal weld.
15. A coupling component 10 for a fluid-operated brake or clutch, comprising:
an inflatable toroidal-shaped tube 12 having an annular array of
friction shoe assemblies 14 engageable with a second coupling component
to interconnect the two coupling components, the tube 12 comprising an
elongated, generally tubular-shaped structure 24 of predetermined length
having two ends 26a, 26b and a joint 28 between the two ends 26a, 26b that
closes the toroidal-shaped tube 12 to form a generally toroidal-shaped cavity
30.
16. The coupling component of claim 15, wherein the generally tubular-shaped
structure 24 includes at least one reinforced layer 32 and at least one
unreinforced layer 34, 36.
17. The coupling component of claim 16, wherein the generally tubular-shaped
structure 24 includes multiple reinforced layers 32.
18. The coupling component of claim 16, wherein the reinforced layer 32
comprises a semi-continuous sheet of elastomer-coated, unidirectional fiber
or fabric.
19. The coupling component of claim 18, wherein the fabric is coated with
polymer on either one or both sides.
20. The coupling component of claim 16, wherein the unreinforced elastomer
layer comprises a semi-continuous sheet of unreinforced elastomer.
21. The coupling component of claim 16, wherein the reinforced and
unreinforced layers 32, 34 are spiral wrapped at a predetermined spiral
angle.
22. The coupling component of claim 16, wherein the unreinforced layer 34, 36
is an extruded elastomer.
23. The coupling component of claim 16, wherein the reinforced layer 32
comprises a braided or spiral-applied fabric reinforcement.
24. The coupling component of claim 16, wherein at least one of the reinforced
layer 32 and the unreinforced layer 34, 36 includes a thermoplastic
elastomer.
25. The coupling component of claim 16, wherein the thermoplastic elastomer is
at least partially chemically cross-linked.
26. The coupling component of claim 16, further including an interior valve
member 42 and an exterior valve member 44 attached to the interior valve
member 42, the interior valve member including a threaded male portion 46
adapted to thread into a corresponding threaded female portion 48 in
exterior valve member 44 and a generally flat mating surface 50 in the
interior valve member 42 having at least one annular rib 52 that engages an
interior surface of the cavity 40 to create an air-tight seal.
27. The coupling component of claim 15, wherein the generally tubular-shaped
structure 24 includes at least one reinforced layer 32 sandwiched between
an inner, unreinforced layer 34 and an outer, unreinforced layer 36.
28. The tube of claim 1, wherein the joint 28 includes one of a thermoset or
thermoplastic adhesive, a solvent bond, and a thermal weld.
29. A method for making a coupling component tube 12 for a fluid-operated
clutch or brake, comprising the steps of:
constructing an elongated generally tubular-shaped structure 24;
cutting the elongated tubular-shaped structure 24 into a separate piece
having a predetermined length;
manipulating the separate piece to form a closed generally toroidal-shaped
tube 12 having first and second ends 26a, 26b; and
joining the first and second ends 26a, 26b.
30. The method of claim 29, wherein the constructing step includes spiral
wrapping at least one reinforced layer and spiral wrapping or extruding at
least one unreinforced layer over a mandrel.
31. The method of claim 29, wherein the constructing step includes thermally
consolidating the reinforced and unreinforced layers.

An inflatable coupling component tube 12 for a fluid-
operated brake or clutch includes an elongated,
generally tubular-shaped structure 24 of predetermined
length having two ends 26a, 26b and a joint 28 between
the two ends 26a, 26b that closes the tube 12 to form a
generally toroidal-shaped cavity 30. A coupling
component 10 for a fluid-operated brake or clutch that
includes an inflatable tube 12, and a method of making
an inflatable coupling component tube 12 are also
disclosed.