U.S. patent application number 10/843187 was filed with the patent office on 2004-11-18 for filament-wound composite boom pipe.
Invention is credited to Mayer, Martin G., Willig, John T..
Application Number | 20040228739 10/843187 |
Document ID | / |
Family ID | 33452334 |
Filed Date | 2004-11-18 |
United States Patent
Application |
20040228739 |
Kind Code |
A1 |
Mayer, Martin G. ; et
al. |
November 18, 2004 |
Filament-wound composite boom pipe
Abstract
A mobile concrete pumping vehicle including a reduced-weight
boom arm. The pumping vehicle includes a boom arm that is
extendible between a folded position and an extended position. The
boom arm carries molded and fabricated composite boom pipe
sections. Each pipe section is formed from a composite material
having a reinforcing outer layer and a wear resistant inner layer.
Preferably, the outer layer is formed using a filament winding
process while the inner layer is molded of wear resistant urethane.
Each boom section is formed by centrifugal molding a urethane tube
then secondarily winding carbon fiber onto the exterior of the
tube. The centrifugal force created by the rotating mold provides a
bubble free urethane tube. The filament winding provides the hoop
strength needed to withstand the internal pressures of the concrete
pumping process.
Inventors: |
Mayer, Martin G.; (Racine,
WI) ; Willig, John T.; (Cincinnati, OH) |
Correspondence
Address: |
Joseph D. Kuborn
ANDRUS, SCEALES, STARKE & SAWALL, LLP
Suite 1100
100 East Wisconsin Avenue
Milwaukee
WI
53202-4178
US
|
Family ID: |
33452334 |
Appl. No.: |
10/843187 |
Filed: |
May 11, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
60469870 |
May 12, 2003 |
|
|
|
Current U.S.
Class: |
417/231 ;
417/313; 417/900 |
Current CPC
Class: |
E04G 21/04 20130101;
F16L 57/06 20130101; F16L 9/121 20130101; E04G 21/0436
20130101 |
Class at
Publication: |
417/231 ;
417/313; 417/900 |
International
Class: |
F04B 017/06; F04B
035/06 |
Claims
We claim:
1. A pumping unit comprising: a multi-section moveable boom arm
having a plurality of boom sections, the boom arm being extendable
from a folded position to an extended position; and a boom pipe
supported by the boom arm, the boom pipe extending between a supply
of material and an outer end of the boom arm, wherein the boom pipe
is comprised of a plurality of joined boom pipe sections each
having a filament-wound reinforcing outer layer and a wear
resistant inner layer.
2. The pumping unit of claim 1 wherein the reinforcing outer layer
is formed from a wound layer of braided fiber applied to an outer
surface of the inner layer.
3. The pumping unit of claim 2 wherein the braided fiber is formed
from carbon fiber.
4. The pumping unit of claim 2 wherein the wear resistant inner
layer is formed from urethane.
5. The pumping unit of claim 4 wherein the urethane has a durometer
hardness rating between 90-A and 95-A.
6. The pumping unit of claim 1 wherein each of the pipe sections
includes an end coupling secured to both ends of the supply pipe
section, each end coupling being secured to the pipe section by an
adhesive.
7. The pumping unit of claim 1 wherein the pipe sections are each
capable of sustaining an internal pressure of at least 1200
psi.
8. A mobile pumping vehicle comprising: a vehicle body; a material
supply bin mounted to the body for receiving a material to be
pumped by the pumping vehicle; a multi-section movable boom arm
having a plurality of boom sections, the boom arm being mounted to
the body and extendible from a folded position to an extended
position; and a boom pipe supported by the boom arm for directing
the flow of material from the supply bin to an outer end of the
boom arm, wherein the boom pipe is comprised of a plurality of
joined composite pipe sections each having a filament-wound
reinforcing outer layer and a wear resistant inner layer.
9. The mobile pumping vehicle of claim 8 wherein the reinforcing
outer layer is formed from a wound layer of braided fiber applied
to an outer surface of the inner layer.
10. The mobile pumping vehicle of claim 9 wherein the braided fiber
is formed from carbon fiber.
11. The mobile pumping vehicle of claim 10 wherein the wear
resistant inner layer is formed from urethane.
12. The mobile pumping vehicle of claim 11 wherein the urethane has
a durometer hardness rating between 90-A and 95-A.
13. The mobile pumping vehicle of claim 8 wherein each of the
supply pipe sections includes an end coupling secured to both ends
of the supply pipe section, each end coupling being secured to the
pipe section by an adhesive.
14. The mobile pumping vehicle of claim 8 wherein the pipe sections
are each capable of sustaining an internal pressure of at least
1200 psi.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] The present application is based on and claims priority to
U.S. Provisional Patent Application Serial No. 60/469,870 filed on
May 12, 2003.
BACKGROUND OF THE INVENTION
[0002] The present invention generally relates to a concrete
pumping unit having a hinged structure, hereafter referred to as a
boom arm, including a multi-section pipe, hereafter referred to as
the boom pipe, for delivering pumped concrete to a location remote
from the pumping unit. More specifically, the present invention
relates to the use and manufacture of filament-wound reinforced
urethane pipe sections for use with a mobile concrete pumping
vehicle. The filament-wound reinforced urethane pipe section
reduces the overall weight of the boom arm while providing the
required strength and durability for the delivery of concrete or
other materials.
[0003] Presently, mobile concrete pumping vehicles and stationary
concrete pumping units are available that include a multi-section
boom arm that is folded into a compact condition during transport
and storage. Once the pumping unit is positioned at the work site,
the folded boom arm is extended to supply concrete to a remote
location. Typically, the boom arm includes a steel boom pipe made
up of multiple sections that are supported by the boom arm such
that concrete can be supplied to a remote location on the work
site. Each of the pipe sections is currently fabricated from steel
to provide the required durability and strength to withstand the
internal pressure of the concrete being pumped by the unit.
[0004] Currently, some mobile concrete pumping vehicles and
mast-mounted pumping units include a boom arm that can extend up to
175 feet from a base. When the boom arm is in its extended
position, each section of the boom arm must be able to support not
only the weight of the boom arm, but also the weight of the
individual pipe sections and the concrete contained within each
pipe section. Thus, the overall weight of the boom arm during the
delivery of concrete is a limitation as to how long the boom arm
can be constructed without adding significant reinforcements to the
boom arm to support the total weight of the boom arm including the
concrete being pumped.
[0005] One contemplated solution for reducing the overall weight of
the boom arm is to replace the steel boom pipe sections with a
lighter weight material, such as plastic. Although the plastic pipe
sections would reduce the overall weight of the boom arm, few
plastics are strong enough to prevent bursting due to the pumping
pressure of approximately 1200 psi within each of the pipe
sections. Therefore, although the idea of replacing the steel pipe
with a lighter weight, high wear resistant alternative appears
desirable, currently no pipe exists that provides the desired
weight savings while maintaining the required strength and
wearability associated with high pressure pumping operations, such
as with concrete.
[0006] Presently, concrete pumping units typically include multiple
boom pipe sections that are used to deliver pumped concrete from
its input receptacle, hereafter referred to as the hopper, to the
tip of its boom arm at a remote location on the work site. Each of
the pipe sections, both on the chassis deck and the retractable
boom arm, are currently fabricated from steel with grooved steel
sleeves welded onto the pipe section at both ends. The current
steel pipe sections are connected with a steel or aluminum clamp
that uses the grooves on the steel sleeves, along with a rubber
seal ring, to form a sealed connection that can withstand the
internal pressures of the material being pumped.
[0007] Therefore, a need exists for both a mobile concrete pumping
vehicle and mast-mounted pumping unit that utilize a supply of pipe
having a reduced weight that is strong enough to withstand the
pressures of pumping concrete. Further, a need exists for a
composite pipe section that can be utilized with a mobile pumping
vehicle that creates a significant weight reduction for the supply
pipe while providing the required durability and strength. Further,
a need exists for a boom pipe section that includes a grooved
sleeve on each end such that the composite pipe sections can be
connected in a similar manner to currently available pipe
sections.
SUMMARY OF THE INVENTION
[0008] The present invention relates to a concrete pumping unit
that utilizes a boom pipe formed from composite pipe sections each
having an inner wear resistant layer and an outer reinforcing layer
to deliver pumped concrete to the end of a hinged boom arm.
Additionally, the present invention is directed to a coupling
design that enables the composite boom pipe sections to be attached
to each other using conventional techniques.
[0009] A concrete pumping unit, such as a mobile pumping device,
includes a boom arm having a plurality of boom sections such that
the boom arm can be extended from a folded position to an extended
position to provide a supply of concrete at a desired remote
location. The boom arm sections each support one or more sections
of a boom pipe such that pumped concrete can be directed to the end
of the boom arm. Presently, each of the boom pipe sections is
formed from steel. In accordance with the present invention, the
steel pipe sections are each replaced by a lightweight, durable
filament-wound reinforced composite urethane pipe section.
[0010] Each of the filament-wound composite pipe sections includes
a wear resistant inner layer and a reinforcing outer layer of high
strength fibers. The reinforcing outer layer provides the required
hoop or tensile strength to withstand the pressure of concrete
being pumped. The wear resistant inner surface provides the
required durability for contact with the very abrasive concrete
material being pumped.
[0011] The reinforcing layer of fibers is applied using a process
called filament winding. Filament winding is a process where a
continuous fiber tow, or untwisted unidirectional filaments, are
laid down with a binder resin in a predetermined pattern over a
rotating shape or mandrel. The mandrel in this case is a molded
urethane tube. The fiber type, number of layers, cross pattern, and
matrix resin are calculated to provide the necessary hoop strength
and stiffness for the tube. The computer-controlled winding machine
controls the path the fibers are laid down during the filament
winding process. This machine also controls the rotational speed of
the mandrel and other requirements.
[0012] The fiber used to develop the reinforcing layer is
preferably carbon fiber, although other materials such as
fiberglass and Kevlar.RTM. (Aramid Fiber) are also acceptable. The
preferable binder resin is epoxy, although other binders such as
urethane and polyester are acceptable.
[0013] The wear resistant inner layer is preferably formed from
urethane having a durometer hardness rating of between 90-A and
95-A. However, other hardness ratings are contemplated depending
upon the type of material being pumped.
[0014] In accordance with the present invention, each of the
reinforced filament-wound pipe sections utilizing carbon fiber
windings and urethane weighs approximately 25% of a similar steel
pipe. Thus, the carbon fiber reinforced urethane pipe sections have
a weight of approximately 2.6 pounds per foot, as compared to
approximately 10.2 pounds per foot for a steel pipe. Thus, a mobile
pumping vehicle utilizing the composite pipe sections of the
present invention and having a boom length of 200 feet can realize
a reduction in boom force of about 152,000 ft. pounds.
[0015] The reinforced composite boom pipe sections of the present
invention are fabricated as follows. Initially, a urethane tube is
molded using a centrifugal molding method. This process uses a
machined metal pipe as the mold, where the metal pipe's inside
diameter is finished and honed to a specific diameter. This
diameter will determine the finished outside diameter of the molded
urethane tube.
[0016] The metal pipe mold is heated in a machine to approximately
250.degree. F. and spun on its axis at approximately 400 rpm. When
liquid urethane is poured into the spinning metal tube, the
centrifugal force created by the rotating tube flows the urethane
material outward against the pipe. After several minutes, the heat
cures the urethane to the point where the urethane, now formed as a
pipe, can be removed. This method provides a bubble free tube of
exacting dimensions.
[0017] The urethane, being an elastomeric or rubber like material,
cannot by itself withstand the pressures associated with the
concrete pumping process and thus must be reinforced. This present
invention provides such reinforcement by filament winding.
[0018] In filament winding, the urethane tube is wrapped with high
strength fibers using a computer-controlled machine, although
manual machines can be used with less reliability. The filament
winding process uses the urethane tube as its mandrel or the shape
that the carbon fiber is wound over. Since the urethane tube is
flexible, the tube is fitted over a metal inner mandrel held
between centers and allowed to spin while fiber and resin is
applied. The metal center mandrel provides the necessary stiffness
to the urethane during processing. The filament-winding machine
spins at low speeds, while a continuous fiber is applied to the
surface in a predetermined pattern over the entire length of the
tube. The preferred resin for securing the fibers to the urethane
tube is epoxy, although other resins can be applied, such as
urethane or polyester.
[0019] Because the fiber is applied in a back and forth motion,
each end of the tube includes a turn-around section where the
fibers do not maintain appropriate alignment. On completion of the
filament winding process, the ends of the tube are cut off to
ensure correct fiber alignment.
[0020] Once the urethane tube, now fiber reinforced, has been
removed from the metal inner mandrel and the ends cut, the tube is
post cured in an oven to achieve maximum properties. After the
curing process, metal end couplings are bonded to each end of the
tube for assembly purposes. Typically, urethane or epoxy adhesive
is used to secure the end couplings to the exterior surface of the
composite tube.
[0021] Various other features, objects and advantages of the
invention will be made apparent from the following description
taken together with the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0022] The drawings illustrate the best mode presently contemplated
of carrying out the invention.
[0023] In the drawings:
[0024] FIG. 1 is a side view of a mobile concrete pumping vehicle
of the present invention that includes reinforced composite pipe
sections on the hinged boom arm;
[0025] FIG. 2 is a back perspective view of the mobile concrete
pumping vehicle illustrating the incorporation of the reinforced
composite pipe;
[0026] FIGS. 3a and 3b illustrate the mobile concrete pumping
vehicle with the boom arm in intermediate positions between a
retracted position and a fully extended position;
[0027] FIG. 4 is a side view of a filament-wound composite pipe
section of the present invention with a pair of end couplings;
[0028] FIG. 5 is a section view taken along line 5-5 of FIG. 4
illustrating the actual configuration of the filament-wound pipe
section and the bonded connection of the end coupling;
[0029] FIG. 6 is a perspective view of the mold used to form the
urethane tube of the pipe section;
[0030] FIG. 7 is a magnified end view of the mold used to form the
urethane tube of the pipe section illustrating the set back of the
pipe section within the mold;
[0031] FIG. 8 is a schematic illustration of the position of the
mold within an oven for setting the urethane tube section;
[0032] FIG. 9 is a perspective view illustrating the filament
windings over the urethane tube; and
[0033] FIG. 10 is a section view illustrating a second embodiment
of the end coupling bound to the end of the filament-wound pipe
section.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
[0034] FIG. 1 illustrates a mobile concrete pumping vehicle 10 that
includes an extendible boom arm 12 having independent sections
14a-14c that can be unfolded and extended. Each of the sections
14a-14c supports a portion or portions of a composite boom pipe of
the present invention to provide a path for pumped concrete to flow
from a storage hopper 16 to the outermost tip of the boom arm.
[0035] Referring now to FIG. 2, the mobile concrete pumping vehicle
10 includes a plurality of individual boom pipe sections 18 that
extend along the length of each section of the extendable boom arm
12 to provide the path for concrete from the hopper 16. The
individual pipe sections 18 are joined to each other by a movable
joint such that the boom arm 12 can be extended without
interrupting the flow path for the concrete through the joined pipe
sections 18.
[0036] Referring now to FIG. 3a, thereshown is the boom arm 12
beginning to extend from the body 20 of the vehicle 12. As
illustrated in FIG. 3b, the boom arm 12 can be extended a
significant distance from the body 20 to provide a flow of concrete
out of a concrete delivery hose 22 at the outer end 23 of the boom
arm 12 to place concrete at the desired location. Currently, mobile
concrete pumping vehicles have boom arms 12 that can extend up to
175 feet from the truck body 20 to supply concrete to the desired
location.
[0037] As can be understood in FIG. 3b, each of the boom sections
14a-14c must be constructed of a material strong enough to support
not only the weight of the boom arm 12, but also the weight of the
boom pipe sections and the weight of the concrete being delivered
through the pipe sections. The weight on the boom arm 12 creates a
significant force along the length of the boom arm sections
14a-14c, thus limiting the length of the boom per cross-sectional
design and material type. Eventually, the total weight of pipes,
concrete, and arms reaches the point that a longer boom can only be
achieved with a cross-section or material that is prohibitive due
to cost, availability, and/or fabrication restraints. In addition,
to avoid an unstable condition, the mobile concrete pumping vehicle
10 will need to weigh more (via added counterweights) which is
undesirable in transportation.
[0038] Although the present invention is shown in the figures as
being particularly desirable for use with a mobile concrete pumping
vehicle, it should be understood that the composite boom pipe is
also particularly desirable when used with other types of concrete
pumping units. For example, concrete pumping units are currently
available that include an extendable boom arm where the entire
pumping unit is mounted on top of an extended mast. The boom arm is
extendable from a base such that concrete can be delivered to a
remote location at a work site. A mast-mounted concrete pumping
unit is particularly useful in constructing multiple floor
buildings. The advantages of the composite urethane boom pipe
sections are equally applicable to this type of pumping unit, since
the composite urethane boom pipe sections reduce the overall weight
of the boom arm which allows the length of the boom arm to be
increased as compared to boom arms utilizing steel boom pipe
sections.
[0039] Presently, each of the boom pipe sections 18 is formed from
a metal material, such as steel, such that each section of pipe has
a weight of approximately 12 pounds per foot. Thus, the supply pipe
for a 175 foot boom arm would have an overall weight of 1,785
pounds empty. In accordance with the present invention, the boom
pipe sections 18 of the mobile concrete pumping vehicle 10 are
replaced with a reinforced composite urethane pipe sections having
a significantly lower overall weight such that the weight of the
boom arm 12 is significantly reduced as compared to the prior
art.
[0040] Referring first to FIG. 4, thereshown is a reinforced
composite boom pipe section 24 that forms the basis of the present
invention. The boom pipe section 24 extends from a first end 26 to
a second end 28 to define the overall length of the boom pipe
section 24. In the preferred embodiment of the invention, the
length of the pipe section 24 is up to three meters, although
longer lengths of pipe are certainly contemplated as being within
the scope of the present invention.
[0041] The pipe section 24 includes a first end coupling 30 and a
second end coupling 32 that allow the pipe section 24 to be joined
to others in a conventional manner. Each of the end couplings 30,
32 includes a recessed groove 34, commercially referred to as a
Victaulic.RTM. groove, positioned between an outer lip 36 and an
inner attachment flange 38. The configuration of each of the end
couplings 30, 32 is conventional and currently utilized in securing
the pipe on mobile concrete pumping vehicles.
[0042] Referring now to FIG. 5, thereshown is a cross-section view
of the reinforced pipe section 24 of the present invention. The
reinforced pipe section 24 includes a wound reinforcement layer 40
and a wear resistant inner layer 42. In the preferred embodiment of
the invention, the wound reinforcing layer 40 is filament-wound
fiber 44, such as illustrated in FIG. 9. This wound fiber 44 can be
made from any type of fiber material, such as fiberglass, carbon
fiber or a synthetic fiber such as Kevlar.RTM. or Vectran.RTM.. In
the preferred embodiment of the invention, the fiber material 44 is
carbon fiber due to its weight and strength characteristics. The
carbon fiber 44 provides increased tensile strength for the
reinforced boom pipe section 24 while providing for a low overall
weight.
[0043] Referring back to FIG. 5, in the embodiment of the invention
illustrated, the wound reinforcing layer 40 has an approximate
thickness of 1/8 inches and is created using a cross-hatch pattern
to provide support in both the axial and radial directions. The
type of pattern is selected based on computer calculations and
testing. The typical internal pressure generated in a concrete boom
pipe is approximately 1200 psi. Since it is desirable for the pipe
section to be designed to have a safety factor of two, the
reinforced pipe section 24 should be able to withstand pressures
approaching 2400 psi. The wound reinforcing layer 40 provides the
hoop strength required, while the wear layer 42 provides a high
wear resistant inner surface for the flow of rough materials, such
as concrete.
[0044] Referring back to FIG. 5, the fiber-wound reinforcing layer
40 includes an outer layer 46 that is formed from the binder
material used in applying the filament winding. The outer layer 46
provides protection for the winding of the reinforcing layer 40 to
protect the pipe section 24 from wear due to contact during normal
usage.
[0045] Referring back to FIG. 5, in the preferred embodiment of the
invention illustrated, the wear layer 42 has a thickness of
approximately {fraction (3/16)} inches and is formed from a durable
resin, such as urethane. The urethane wear layer 42 provides the
required wear and abrasion resistance while providing low overall
weight for the reinforced pipe section 24. Urethane, and other
chemicals similar thereto, are available in a number of different
hardnesses and chemistries. The actual formulation in hardness of
the urethane wear layer 42 can be adapted depending upon the type
of material flowing through the reinforced pipe section 24. In the
preferred embodiment of the invention, urethane having a durometer
hardness rating of 90-A to 95-A are selected. However, it is
contemplated that for a non-concrete piping application, the
urethane could have a durometer hardness rating as low as 70-A, or
as high as 75-D.
[0046] Referring back to FIG. 5, the pipe section 24 includes an
end coupling 32 positioned near the outer end 28. As can be seen in
FIG. 4, a second end coupling 30 is also coupled to the pipe
section 24 near the first end 26.
[0047] As illustrated in FIG. 5, the end coupling 32 is defined by
an inner wall 50 and an outer wall 52. Preferably, the end coupling
32 is formed from a unitary section of steel in a conventional
manner.
[0048] The end coupling 32 includes an inner, annular groove 54
that is recessed from the inner wall 50. The annular groove 54 has
a diameter slightly greater than the outer diameter of the pipe
section 24 as illustrated. The inner most portion 56 of the inside
wall 50 has a diameter that generally corresponds to the outer
diameter of the pipe section 24 near the outer end 28.
[0049] As described previously, the end coupling 32 includes a
recessed outer groove 34 positioned between an outer lip 36 and the
inner attachment flange 38. The groove 34 is commonly referred to
as Vitraulic.RTM. groove as is conventionally used in mobile
concrete pumping vehicles.
[0050] The end coupling 32 is attached to the end 28 of the
composite pipe section 24 by placing a supply of urethane adhesive
58 between the inner recessed groove 54 and the outer surface 60 of
the outer layer 46 applied over the reinforcing layer 40. The high
strength adhesive 58 provides a permanent bond between the end
coupling 32 and the reinforced pipe section 24 such that the pipe
section 24 can be used in a normal manner. For example, the pipe
section 24 having the pair of end couplings 30, 32 can be connected
to either other composite pipe sections 24, or conventional steel
boom type sections, using what is commercially called a
Vitraulic.RTM. clamp. As discussed, the Vitraulic.RTM. groove 34
allows the urethane composite boom pipe to be interchangeable with
the current steel boom pipes presently available.
[0051] The inner surface 56 of the end coupling 32 contacts the
outer surface 60 of the boom pipe section 24 to prevent the
adhesive 58 from flowing out of the end 28. The surface 56 thus
traps the adhesive 58 and allows the adhesive to set and
permanently attach the end coupling 32 to the boom pipe section
24.
[0052] The reinforced composite pipe sections constructed in
accordance with the present invention utilizing urethane inner tube
layer 42 with the filament winding outer layer 40 are roughly 25%
in weight compared to the steel pipe sections. For example, the
composite pipe section 24 has a weight of approximately 2.6 pounds
per foot, while a similar steel pipe has a weight of approximately
10.2 pounds per foot. Thus, in a mobile concrete pumping vehicle
having a boom arm with an extended length of 200 feet, the mobile
concrete pumping vehicle would realize a reduction in force of
approximately 152,000 ft. pounds. This provides a significant
advantage currently not available.
[0053] The method of forming the reinforced pipe section 24 will
now be described. The first step in creating the reinforced pipe
section 24 of the present invention involves creating a urethane
tube that will form the wear layer 42. As illustrated in FIG. 6, a
mold 50 is provided. The mold 50 is typically a steel pipe that has
a polished inner wall 52 and an outer wall 54 as shown in FIG. 7.
The mold 50 preferably has a length slightly greater than the
length of the reinforced pipe section to be formed such that the
ends of the tube of urethane formed can be cut and the tube formed
of the desired length.
[0054] Referring back to FIG. 6, the mold 50 includes a first end
piece 56 that is installed on one end of the mold as illustrated.
Initially, the mold 50 is heated to an elevated temperature prior
to the insertion of the liquid urethane into the mold interior.
After the first end piece 52 is installed, a supply of liquid
urethane 58 is preferably fed through a funnel 60 and connecting
pipe 62 and allowed to flow along the axial length of the mold 50.
The amount of urethane poured into the mold 50 depends on the
desired wall thickness for the wear layer 42 illustrated in FIG. 5.
At the elevated temperatures of approximately 230.degree. F., the
viscosity of the urethane is reduced, which allows the urethane to
flow easier along the length of the mold 50. Although the
embodiment shown in FIG. 6 contemplates the simple insertion of the
liquid urethane, it is contemplated that the urethane may be pumped
into the mold interior under pressure, depending upon the specific
shape of the mold 50.
[0055] Referring now to FIG. 8, once the mold 50 has been filled
with the required supply of urethane, the mold extends along a
horizontal axis within a machine 64. The machine 64 can be operated
to spin the mold 50 about its horizontal axis, as illustrated by
arrow 66, such that the urethane is forced outward against the
smooth inner wall of the mold 50.
[0056] In the preferred embodiment of the invention, the machine 64
includes several heating elements 68 contained within enclosed,
insulated housing 70. The heating element 68 elevate the
temperature of the mold and the urethane to allow the urethane to
properly flow against the outer wall of the mold and ultimately to
cause the urethane to set.
[0057] Once the liquid urethane and the mold are heated, the speed
of rotation of the mold 50 is increased such that the spinning mold
50 creates a centrifugal force. In the preferred embodiment of the
invention, the mold is rotated at approximately 1000 rpms to
generate the required centrifugal force. During this rotation, any
air pockets that are contained within the urethane are driven to
the center to provide porosity-free part. Once again, the thickness
of the wear layer is controlled by the amount of urethane poured
into the mold.
[0058] After approximately 30 minutes of rotation and exposure to
heat, the urethane within the mold 50 becomes cured enough to allow
the tube that forms the urethane wear layer to be removed from the
mold 50. Once the urethane tube has been removed, the tube is post
cured in an oven for several hours to fully cure the urethane.
[0059] As illustrated in FIG. 7, the urethane tube 72 that
ultimately forms the inner layer has a length less than the length
of the mold, as illustrated by length A. The difference between the
length of the urethane tube 72 and the mold 50 results from the
insertion of the end cap 56 onto each end of the mold, as was
described in FIG. 6.
[0060] Referring now to FIG. 9, once the urethane tube 72 has been
formed, a reinforcing layer is applied using a filament winding
process. During the filament winding process, a continuous tow, or
untwisted unidirectional filament, is laid down with a binder resin
in a predetermined pattern over a rotating mandrel. In the present
invention, the urethane tube 72 is supported over a metal mandrel
to provide additional support for the urethane tube.
[0061] Once the inner mandrel and urethane tube are properly
supported, the fiber layers are applied to the urethane tube in a
pattern with a supply of resin. In the embodiment of the invention
illustrated in FIG. 9, the fiber layer is applied over several
passes to create a first pattern 74a and a second pattern 74b. The
multiple passes and multiple patterns of the filament winding
dictate the hoop strength of the tube and provides the required
strength for the use of the pipe section. The computer-controlled
filament winding machine controls the path that the fibers are laid
down while simultaneously controlling the speed that the urethane
tube is being rotated during the filament winding process.
[0062] Once the urethane has been fully cured, the outer ends 76
and 78 of the tube are severed. The ends of the tube must be
severed since during the filament winding process, the fiber is
applied in a back-and-forth motion and each end of the tube
includes a turn-around section where the fibers do not maintain
appropriate alignment. For this reason, the urethane tube is
created having a length longer than the length of the desired pipe
sections such that each end of the tube can be severed.
[0063] The urethane tube, which has now been fiber reinforced and
cut to its desired length, is then post-cured in an oven to achieve
maximum properties for the tube. After the curing process, the
metal end couplings 30, 32 shown in FIG. 4 are adhesively attached
to each end of the tube to create the pipe section.
[0064] Although a first embodiment of the end coupling 32 is shown
in FIG. 5, FIG. 10 illustrates a second embodiment of an alternate
end coupling 80. In the embodiment of the invention illustrated in
FIG. 10, the end coupling 80 includes a series of gripping ridges
82 formed along the inner wall that define the annular groove 54.
Each of the gripping ridges 82 extends around the entire inner
circumference of the end coupling 80. The individual gripping
ridges 82 interact with the urethane adhesive 58 to provide
improved gripping of the end coupling 80 at the end 28 of the pipe
section 24. Each of the gripping ridges 82 is formed by removing a
portion of the wall 84 of the end coupling along the inner surface
of the annular groove 54. Although numerous individual grooves are
shown in the embodiment of FIG. 10, it is contemplated by the
inventors that the size and shape of the individual ridges 82 could
be modified while operating within the scope of the present
invention.
[0065] Various alternatives and embodiments are contemplated as
being within the scope of the following claims particularly
pointing out and distinctly claiming the subject matter regarded as
the invention.
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