Note: Descriptions are shown in the official language in which they were submitted.
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COMPOSIl~ STRUCTURAL E:LEMENT AND
BACKGROUND o~ r~Nr~ON
Structural elements such as rods, tubes, and beams are
normally made by casting, extruding, or rolling techniques to
produce plastic or metal tubing, sheets, rods, beams, and the
like. These structural elements normally comprise a single
material which is chosen for its combination of physical
properties, e.g., strength and weight, as well as corrosion
resistance, color, and texture. Plastic molding and extrusion
procedures have provided the possibility of preparing plastic
structural elements with selected combinations of physical
properties, chemical properties, color, texture, etc. Fiber
reinforcement of plastic materials has provided much higher .
physical s~rength properties than the plastic material alone
could offer. In general, these fiber reinforced materials arë
made by extruding through a die a plastic melt having continu-
ous strands of fiber distributed therein The extrudate is
then solidified in the form of a continuous rod, beam, or
strand and can be cut into whatever length is desired for use.
The disadvantages of the prior art procedures are (1) that
the extrudate can not be made into a curved or non-linear ,
article, and (~) the surface properties at the;extrudate
cannot be changed from that inherent in the extruded plastic.
It i9 an object of this invention to provide a novel
structural element of fiber reinforced plastic material. It
is another object of this invention to provide processes for
manufacturing such structural elements. Still other objects
will be apparent from the more detailed description which
follows.
BRIEF SUMMARY OF TXE INVENTION
This invention relates to an alongated solid or tubular
structural element having a subs~antially identical cross ~
section over its entire length, the element having a solid ~-
core of thermoplastic or thermosetting re~in material em~
bedded in which is a plurality of elongated continuou~ strands ~ -
of lengthwise fiber reinforce~ent material, preferably in
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substantially parallel array, and a continuous ~asing around
the core.
This invention also relates to a process for preparing
an elongated structural element comprising:
(1) preparing a hollow tubular solid casing being an
integral part of the structural element;
(2) filling the interior of the casing with a polymer
material in liquid form; and distributing throughout said
polymer material a plurality of elongated continuous strands
of fiber reinforcement material substantially parallel to
each other and extending lengthwise of the casing; and
(3) allowing the polymer material to solidify with
the strands of fiber reinforcement material embedded therein.
The process and element may include a tubular shape
employing an external casing and an internal casing with the
space therebetween being filled with the polymer material and
fiber reinforcement materials. The element may also be
shaped before solidification, or thereafter by reheating,
into a helical coil or spring, or other shape like an I-beam
or an H beam or any irregular shape. Sometimes this requires
the displacement and~or removal of some of the plastic mater~
ial.
BRIE~ DESCRIPTION OF THE DRAWINGS
The invention as to its organization and method of
operation, together with further objects and advantages
thereo, is best understood by reference to the following
description taken in connection with the accompanying drawings
in which:
FIG. 1 is a side elevational view of one embodiment of
the structural element of this invention;
FIG. 2 is an end elevational view of the structural
element shown in FIG. l;
FIG. 3 is an end elevational view of a second embodi- ~ ;
ment of the structural element of this invention;
FIG. 4 is a~ end elevational view of a third embodim~nt
of the structural element o~ this in~ention;
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W092/16347 ~ ,3 Pcr/us9l/01636
FIG. 5 is an end elevational view of a fourth embodi-
ment of the structural element of this invention;
FIG. 6 is an illustration of one type of article, e.y.,
a coil spring, that can be made from the structural element
of this invention;
~ IG. 7 is an illustration of one embodimenk of the
process of this invention;
FIG. 8 is an illustration of a second ~imbodiment of
the process of this invention;
FIG. 9 is an illustration of a third embodiment of
the process of this invention;
FIG. 10 is an illustration of the structural element
of this invention with end caps attached;
PIG. 11 is an end elevational view of a hollow struc-
tural element of this invention;
FIG. 12 is an illustration of a fourth embodiment of
this invention;
FIG. 13 is an illustration of a fifth embodiment of
this invention; and ~-
FIG. 14 is an illustration of a process for c~anging
a stxuctural element having a round cross section to one ;~
having a non-round cross section.
DETAILED DESCRIPTION OF THE INVENTION
, . ,
This invention relates to articles of manufacture
which are shown in FIGS. 1-6, 10, and 11 of the attached
drawings, and to processes for preparing such articles which
are shown in FIGS. 7-9, and 12-14. ~
In FIGS. 1-6, 10 and 11 there are depicted several ~``
types of structural elements according to this invention. In
FIGS. 1-2 there is shown a cylindrical rod element having
three components; namely, an external casing 11, an internal `-
binder 12, and strands 13 of fiber reinforcement material.
These are all joined together into a slngle~unitary structure
which has an indefinite length and a substantially similar
cross section at any place along that length. ~;
External casing 11 is a flexible, semiflexible, or
rigid pipe or tubing having whatever properties are important ~ ;
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for the eventual use of the structural element. If corrosion
resistance, abrasion resistance, or weather resistance is
important, casing 11 must provide that property; and so on
for other property requirements~ Generall~, casing 11
should be a flexible or semiflexible thermoplastic material
which is compatible with binder 12 and does not react chem- ;
ically therewith. In other embodiments casing 11 may be a
metallic tube, an animal or human vein, intestine, or the
like. Preferably there is no bond between the two, although
in certain embodiments binder 12 and casing 11 may be bonded
to each other. Typical materials for casing 11 include poly-
olefins, poly~inyls, polyesters, polyacetals, polyacrylics,
polyamides, polyfluorocarbons, polycarbonates, and other
plastics of similar properties, aluminum, human or animal
tissue, and the like.
The internal space in casing 11 is filled with binder
12 and fiber reinforcement 13. ~inder 12 must be capable of
tightly adhering to strands 13. Preferably, binder 12 should
be available in liquid form for ease in manufacturing tAe
structural element of this invention, and capable of being
transformed into solid form at ambient conditions for use as
binder 12 in the structural element in ordinary use. Binder
12 may be a thermoplastic or a thermosetting material each of
which exists in both liquid and solid forms. The thermoplastic
material~ normally change from liquid to solid and from solid ~ -
to liquid by temperature changes. Thermosetting materials
normally involve two or more starting components which are
mixed together to produce a liquid which is hardened by
chemical reaction between the component and cannot later be
liquefied. Typical thermoplastic~ include polyolefins, poly- l -
esters, polyvinyls, polyacetals, polyacrylics, polyamides,
polyfluorocarbons, polycarbonates, and the like. Typical
~hermosetting binders in~lude phenol~formaldehyde resins,
melamlne resins, epoxy resins, urea-formaldehyde resins,
polyesters, and the like.
The fi~er reinforcement material 13 is a plurali~y of -
strands of fiber or fLlament that are distributed throughout 1 ` -
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the binder and are in substantially parallel arrangement
running lengthwise of the structural element. The strands
may be in a linear arrangement or in a sinuous or helical
arrangement preferably mutually parallel to each other,
although there may be embodiments where strands 13 are in any
desired nonparallel arrangement. Ideally, the strands 13
would be separated from each other and equally distributed
throughout all of the binder 12. From a practical point o~
view this may not be achieved, but preferably, the strands
are extended lengthwise throughout the structural element and
distributed as evenly as possible in the binder. Each strand
13 may be a single filament or a plurality of filaments
twisted together, or may be a single fiber or a plurality of
fibers twisted into a thread; or may be any other combination
of fibers, filaments, threads, yarns or the like that are
relatively small in diameter and relatively long and contin- ~
uous in length. Tubular filaments, threads, yarns and the ;
like are also useful as strands 13. The word "strand" herein
is meant to be generic and to include all of the above con-
figurations. The material of the strands may be organic or
inorganic. The organic strands include materials such as
cotton, wool, bagassee, hemp, polyamide, polyacrylonitrile,
polyester~ rayon and the like. Inorganic strands include ;
materials such as glass, steel, copper, aluminum, titanium,
graphite, and the like.
In order to assure good adhesion between the binder 12 ~ ;
and the strands 13, certain promoters or agents may be em-
ployed to enhance the bonds between binder 12 and strands 13.
In FIGS. 3-5 there are shown other structural elements -
of other cross sectional shapes, e.g., square (FIG. 3), ohlong
(FIG. 4), and triangular ~FIG. 5), which may be solid as show~
or tubular with an internal open space, as shown in FIG. 11. ~
Any of these shapes may be prepared in ~inite lengths and~end- ~ '
capped, as shown in FIG. 10, if it is desirable to protect the
open ends fxom the surrounding medium in which the s~ructural
element is used. Still other shapes are within the scope of
this invention since any geometric design like an H-beam, an
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I-beam or star shaped cross section is acceptable.
The structural element Df this invention can be sawed,
drilled, tapped, twisted, bent, and otherwise used to form
useful articles of manufacture. For example, the element may
be coiled into a helix to form a coil spring as shown in FIG.
6. If the structural element is made with a thermoplastic
binder 12, a preformed straight length of element may be
heated, and formed into another shape, e.g., coiled to form
the spring of FIG. 6, and cooled to solidify the binder 12,
and thereby produce a stable shape. Alternatively, the
element may employ a thermoplastic molten binder 12 in casing
and the element may be coiled into a spring or formed
into another shape before the binder 12 is allowed to sol-
idify. If the binder 12 is a thermosetting material, it must
b~ formed into the final desired shape, e.g., coiled into the
spring of FIG. 6, before binder 12 has had time to set to a
solid. There are a multitude of applications for the struc-
tural element of this invention including ropes, rpds, struc-
tural beams for chemical processing equipment, articles used
under sea water, strands or bones used in human surgical pro-
cedures, and the like.
In the process of this invention as shown in FIGS 7-9
and 12-14 a plug 17 is moved through the internal hollow of
casing 11 with binder 12 and fiber reinforcement strands 13
filling the hollow behind the plug 17 as it moves along. In
the process depicted in FIG. 7, a length of casing 11 is
fitted with a feed funnel 16 into which is fed a continuous
length of a plurality of strands 13 and at the same time is
~ed liquid or molten binder 12 from a supply reservoir 15.
Plug 17 is slidable within casing 11 and has an eye 18 to
which the hank of strands 13 is attached. A pull cable 19
is attached to the front;of plug 17 to pull plug 17 through
casing`ll by windup drum 20. As plug 17 is moved downward
toward drum 20, binder 12 fills-the interior hollow of casing
11 and~the individual strands in thè hank disperse themseives 6
throughout the entire cross section of the interior hollow of
casing 11 to eventually approach the distribution shown in
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YIGS. 2-S. It can be appreciated that casing 11 and plug 17
may take any shape, such as those in FIGS, 2-5. Furthermore,
hollow shapes as shown in FIG. 11 may be made b~ making plug
17 into an annular object and sliding between an inn~r casing
29 and an outer casing 11 (see FXG. 11). If pre~erred, inner
; casing 29 may be supported by an internal mandrel (not shown)
to support inner casing against collapse until binder 12-
hardens.
In FIG. 8 the same general arrangement as that of FIG.
7 is shown except that instead of a windup drum 20 and a cable
19 to move plug 17 there is a vacuum pump 21 to produce a
lower pressure in the space 25 ahead of plug 17 causing plug
17 to move toward vacuum pump 21.
-- In FIG. 9 there also is the same general arrangement
.~.. ~ .
of casing 11, plug 17 and strands 13, attached to eye 18. In
this instance the force to move plug 17 through casing 11 is
provided by the pressure on binder 12. Inlet pipe 22 feeds
liquid binder 12 to pump 23 which pumps binder into pressure ;p
vessel 27 which has an outlet into casing 11. Roll 14 of `~
fiber reinfor~ement strands 13 is mounted inside vessel 27 in
a pressurized space 26 designed to offset the pressure on
binder 12 emitted from pump 23. Binder 13 is supplied to ;~
space 24 under pressure and this bears against plug 17 causing
it to move to the right and fill up casing 11. ;~
In all of the embodiments of FIGS. 7, 8, and 9 the -
strandsi will be substantially linear and parallel to each
other and to the longitudinal axis of casing 11 if plu~ 17 is -
simply pulled through casing 11. If plug 11 is rotated about
its axis of travel as it is pulled through casing 11, strands
13 can be made into a sinuous or helical orientation while
the individual strands 13 remain generally parallel with each
other. ~;
It is contemplated that in certain corrosive conditions
there may be a need to completely insulate binder 12 and ~-
strands 13 from the surrounding corrosive medium. In such
instances there may ~e end caps 28 sealed onto any cut ends of ~
the structural element so as to leave only the material of the ~;
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casing e~posed as shown in FIG. 10. End cap 28 can be heat
sealed or otherwise attached to casing 11 so as to be leak
proof and therefore completely corrosion-resistant.
It is an important feature of this invention to pro-
vide elements in which the fiber reinforcing component is a
continuous strand and not a plurality of chopped fi~ers. The
continuous strands emplo~ed in this invention provide a
greatly improved modulus of elasticity as compared to that of
the strand containing short lengths of reinforcing ~ibers or
filaments. It is for this reason that an excellent coil
spring can ~e made from the structural element of this inven-
tion, while such a coil spring from the prior art would not
be operableO
FIGS. 12-14 show alternate embodiments of the process
of making the structural elements of ~IGS. 2-5 and 11. In
FIG. 12 there is illustrated a procedure to make hollow
tubular structural elements as shown in FIG. 11. Outer casing
11 is attached to funnel 16 by clamp 30. Inner casing 2~ with
a plug at its lower or forward end is introduced into funnel
16 along with plug 33 into which the forward ends of fiber
strands 13 have been embedded by previously molding plug 33
with strands 13 embedded therein. Plug 33, lnner casing 29,
and plug 34 are moved downwardly in the direction of arrow 35
while outer casing 11 and funnel 16 remain stationary and
filled with liquid binder 12. As inner casing 29, plug 34,
plug 33 and strands 13 move downwardly the annular space
between casing~ 11 and 29 fills with binder 12 and fiber
strands 13 are dispersed throughout. Plug 34 is needed to
prevent binder 12 from leaking into the interior hollow of
internal casing 29. Plug 34 may be independent of plug 33 or
attached thereto in different embodiments of this process. ~;-
Centering guides 31 and 32 keep inner casing 29 centered in
casing ll as casing 29 advances. Guides 31 and 32 are spider -
legs. Guide 31 is attached to funnel 16 with its distal ends
rubbing against inner casing 29 as it moves forward. Guides
32 are attached to casing 29 or its plug 34 with its distal
ends rubbing against outer casing 11 as inner casing 29 moves ;
SUBSTITUTE SHEET
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forward. Preferably, guides 31 and 32 are spring biased to
bear against casings 29 and 11, respectively. Furthermore,
guides 31 preferably are pivotable so as to be no obstacle
to the initial entrance of plug 33 into and through funnel 16
to the top of outer casing 11. When the desired length of 7
tubular structural element 11 has been made, the process can
be repeated by starting again with a new length of outer
casing 11.
In FIG. 13 there is shown an alternative to the process
of FIG. 9 for making the structural element by 1uid pressure
causing the movement of the plug to which fiber strands 13 are
attached. A plurality of fiber strands 13 are introduced over
a feed roller 37 in header box 38 and downward through funnel
16 into outer casing 11 which is temporarily attached to ;
funnel 16 by clamp 20. The forward ends of strands 13 are
embedded in plug 36. Casing 11 rests on a base plate 39
which will serve as a stop to plug 36 which moves downward in
the process. Binder 12 is kept in container 40 which is con-
nected by passageway 43 to funnel feeder 16 permitting the
level of binder 12 to be the same in funnel 16 and in container ~-~
40. Air pressure is maintained in tank 44 which is connected
by lines 45, 46 and 47 to both of header box 38 and binder con~
tainer 40 to equalize the pressure on both surfaces of liquid ;
binder 12. The pressure is transmitted to plug 36 causing it
to move forward in casing 11 until it reaches base plate 39.
Lid 41 is provided for adding binder 12 to container 40, and
lid 42 is provided for replacing a supply of strands 13 over
roller 37 in head box 38.
In FIG. 14 there is shown a procedure for transforming
an element of circular cross section, as in FIG. 2, to an ele~
ment of noncircular cross section, as in FIGS. 3-5, when outer
casing 11 is flexible and capable of being bent and formed -~into different shapes. The problem in such modifications is ;~that~the cross sectional area and-circumference of the begin- ~`
ning element, e.g., circular, may not be the same as those of
the final element, e.g., a rectangle. The limiting factor
normally is that the circumference or perimeter of the
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beginning element and final element must be the same i~ the
outer casing 11 is to remain smosth, continuous, and un-
wrinkled. Generally this is accomplished by ~ixing the
perimeter dimensions of the desired final element and ad-
justing the process of making the beginning element to ~it
those dimensions. It is basic geometry that for any given
cross sectional area, a circle will have the smallest perim-
eter length of any shape that encloses that area. Accord-
ingly, as an example, if the final element is to be a rec-
tangular beam having dimensions of one inch by two inches, a
perimeter length of six inches and a cross sectional area o~
two square inches; a circle of the same perimeter length o~ -
six inches will have a diameter of 1.91 inches and a cross
sectional area of 2.865 square inches. Therefore, an element
of circular cross section (2.865 square inches) must be
squeezed to a cross sectional area of 2.0 square inches to be
reshaped into a rectangular cross section of one inch by two
inches. Referring to FIG. 14, the above means that a circular
cross section element 50 with a cross sectional area of 2.865
square inches and with binder 12 in a liquid form is squeezed
by rollers 49 turning in the direction of arrows 52 as the '~
element moves past an internal solid of about 0.865 square
inch cross section to reduce the cross sectional area to 2.0
square inches.
Rollers 49 with or without the assistance of other ''
forming devices can then shape element 5I into a rectangular
cross section of one inch by two inches before binder 12 sol-
idifies. It may be seen that this procedure may be applied
to the end of the procedures of FIGS. 7-9 and 13 or before '~
binder 12 solidifies, or alternatively, a rigid element may '-
be heated to liquefy binder 12 (if it is thermoplastic) and '~ '
then subjected to the reshaping procedure of FIG. 14. While
the beginning'element may have anv shapej it preferably'is
circular'because it-is easier to make'and it-automatically
pxovides a better dispersion of strands 13 than any other'
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As seen hereinabove, the binder 12 may be thermo-
plastic in certain embodiments and thernos~tting in other
embodiments. In any event the binder needs to be a plastic
or polymer material which is capable of tightly adhering to
strands 13 and not reacting chemically with casing 11.
While the invention has been described with respect to
certain specific embodiments, it will be appreciated that ,
many modifications and changes may be made by those skilled
in the art without departing from the spirit of the invention.
I~ is intended, therefore, by the appended claims to cover
all such modifications and changes as fall within the txue
spirit and scope of the invention.
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