US5096384A — Plastic fan blade for industrial cooling towers a…

Claim 1

Independent Claim 233 words

A molded, composite, airfoil defining, synthetic resin blade for large diameter cooling tower fans having a central hub and comprising: an elongated, relatively dense internal core of synthetic resin foam material; an elongated shank extending outwardly from one end of the foam core and adapted to be coupled to the fan hub; and an essentially laminar, monolithic reinforced skin of synthetic resin material overlying the foam core, said skin having been formed over the core as a plurality of pre-prepared, initially flexible fiberglass reinforced synthetic resin sheets with the core and skin thereover having been molded in a final desired configuration thereof under pressure and temperature conditions such that the core was compressed and the fiberglass reinforced sheets converted into said monolithic skin by virtue of curing of the laminar skin between the compressed core and the mold, said blade being provided with a relatively smooth outer surface and the core having a series of stepped areas which increase in height relative to the center of the core at respective steps as the normally outermost end of the blade remote from the shank is approached, a sufficient number of fiberglass reinforced synthetic resin sheets having been applied to the core to fill spaces between the outer surfaces of the core and the mold during curing of the resin whereby the skin is of greater thickness in a direction toward the shank end thereof.

Claim 2

Dependent Claim 233 words

A molded, composite, airfoil defining, synthetic resin blade for large diameter cooling tower fans having a central hub and comprising: an elongated, relatively dense internal core of synthetic resin foam material; an elongated shank extending outwardly from one end of the foam core and adapted to be coupled to the fan hub; and an essentially laminar, monolithic reinforced skin of synthetic resin material overlying the foam core, said skin having been formed over the core as a plurality of pre-prepared, initially flexible fiberglass reinforced synthetic resin sheets with the core and skin thereover having been molded in a final desired configuration thereof under pressure and temperature conditions such that the core was compressed and the fiberglass reinforced sheets converted into said monolithic skin by virtue of curing of the laminar skin between the compressed core and the mold, said blade being provided with a relatively smooth outer surface and the core having a series of stepped areas which increase in height relative to the center of the core at respective steps as the normally outermost end of the blade remote from the shank is approached, a sufficient number of fiberglass reinforced synthetic resin sheets having been applied to the core to fill spaces between the outer surfaces of the core and the mold during curing of the resin whereby the skin is of greater thickness in a direction toward the shank end thereof.

Claim 3

Dependent Claim 52 words

A molded, composite, synthetic resin blade for large diameter cooling tower fans as set forth in claim 1, wherein said core originally was of a thickness such that the compression reduced the thickness dimension thereof to a degree that was correlated with the thickness of the laminar, monolithic skin over said core.

Claim 4

Dependent Claim 57 words

A molded, composite, synthetic resin blade for large diameter cooling tower fans as set forth in claim 2, wherein said core has been compressed such that the original thickness thereof between opposed major faces before compression was reduced from about 15% to about 40% of a combined thickness of the skin on opposed surfaces of the blade.

Claim 5

Dependent Claim 43 words

A molded, composite, synthetic resin blade for large diameter cooling tower fans as set forth in claim 3, wherein said thickness reduction of the core by compression is about 25% of the combined thicknesses of the skin on opposed surfaces of the blade.

Claim 6

Dependent Claim 56 words

A molded, composite, synthetic resin blade for large diameter cooling tower fans as set forth in claim 1, wherein the height of each of the stepped areas of the core relative to an adjacent area thereof was each originally from about 60% to about 85% of the thickness of the layers of synthetic resin immediately thereover.

Claim 7

Dependent Claim 43 words

A molded, composite, synthetic resin blade for large diameter cooling tower fans as set forth in claim 4, wherein said height of each of the stepped areas of the core originally was about 75% of the thickness of the synthetic resin layers thereover.

Claim 8

Dependent Claim 129 words

A molded, composite, synthetic resin blade for large diameter cooling tower fans as set forth in claim 1, wherein the core prior to compression during molding of the blade was of a thickness, and the blade was molded under conditions such that the final core thickness substantially satisfies the equations T.sub.U =T.sub.A-B -0.75(t.sub.A +t.sub.B) [I] T.sub.C =T.sub.A-B -(t.sub.A +t.sub.B) [II] where T U ≡ Uncompressed core thickness T A-B ≡ Thickness of the final blade between selected directly opposed points on opposite major surfaces of the blade t A ≡ Thickness of the skin at one of said opposed points on the final blade t B ≡ Thickness of the skin at the other of said opposed points on the final blade T C ≡ Final compressed core thickness.

Claim 9

Dependent Claim 35 words

A molded, composite, synthetic resin blade for large diameter cooling tower fans as set forth in claim 1, wherein the density of the core is from about 21/2 to about 4 pounds per cubic foot.

Claim 10

Dependent Claim 31 words

A molded, composite, synthetic resin blade for large diameter cooling tower fans as set forth in claim 8, wherein the density of the core is about 31/2 pounds per cubic foot.

Claim 11

Dependent Claim 34 words

A molded, composite synthetic resin blade for large diameter cooling tower fans as set forth in claim 1, wherein said core and the skin thereover have been molded in a longitudinally twisted final configuration.

Claim 12

Dependent Claim 55 words

A molded, composite synthetic resin blade for large diameter cooling tower fans as set forth in claim 1, wherein one of said sheets of pre-prepared, initially flexible synthetic resin material reinforced with glass fibers is oriented such that when applied to the core, the glass fibers primarily extended in a direction longitudinally of the blade.

Claim 13

Dependent Claim 54 words

A molded, composite synthetic resin blade for large diameter cooling tower fans as set forth in claim 11, wherein one of said sheets of pre-prepared, initially flexible synthetic resin material reinforced with glass fibers is oriented such that when applied to the core, the glass fibers extended both longitudinally and transversely of the blade.

Claim 14

Dependent Claim 52 words

A molded, composite synthetic resin blade for large diameter cooling tower fans as set forth in claim 12, wherein the synthetic resin sheet having glass fibers which extend both longitudinally and transversely of the blade being is oriented outboard of the sheet having glass fibers which primarily extend longitudinally of the blade.

Claim 15

Dependent Claim 41 words

A molded, composite synthetic resin blade for large diameter cooling tower fans as set forth in claim 12, wherein said sheets include an outer synthetic resin veil augmented with fabric having fibers which extend both longitudinally and transversely of the core.

Claim 16

Dependent Claim 28 words

A molded, composite synthetic resin blade for large diameter cooling tower fans as set forth in claim 14, wherein said fabric comprised a relatively thin glass cross-fiber sheet.

Claim 17

Dependent Claim 43 words

A molded, composite synthetic resin blade for large diameter cooling tower fans as set forth in each of claims 11 and 12, wherein each of said sheets and the veil include a quantity of chopped fiberglass roving on the innermost face portions thereof.

Claim 18

Dependent Claim 27 words

A molded, composite synthetic resin blade for large diameter cooling tower fans as set forth in claim 1, wherein said shank is embedded in the foam core.

Claim 19

Dependent Claim 57 words

A molded, composite synthetic resin blade for large diameter cooling tower fans as set forth in claim 1, wherein the core is provided with two opposed stepped areas in alignment with the innermost end of the shank, and stepped areas on opposite sides of the core which increase in height in a direction away from the shank.

Claim 20

Dependent Claim 38 words

A molded, composite synthetic resin blade for large diameter cooling tower fans as set forth in claim 18, wherein the stepped areas on each side of the core increase in width in a direction away from the shank.

Claim 21

Dependent Claim 42 words

A molded, composite synthetic resin blade for large diameter cooling tower fans as set forth in claim 18, wherein the core is tapered and thereby decreases in thickness as the outermost extremity thereof is approached in a direction remote from the shank.

Claim 22

Dependent Claim 51 words

A molded, composite synthetic resin blade for large diameter cooling tower fans as set forth in claim 20, wherein is provided at least four stepped areas on opposite major faces of the core adjacent the shank, and at least two stepped areas located centrally of the core on opposed faces thereof.

Claim 23

Dependent Claim 59 words

A molded, composite synthetic resin blade for large diameter cooling tower fans as set forth in claim 14 wherein at least one of the sheets reinforced with glass fibers that extend both longitudinally and transversely of the blade upon application thereof to the core, wraps around a significant portion of the length of the leading edge of the blade.

Claim 24

Dependent Claim 59 words

A molded, composite synthetic resin blade for large diameter cooling tower fans as set forth in claim 11, wherein said sheet of synthetic resin reinforced with glass fibers which primarily extend in a direction longitudinally of the blade contained from about 30% to 40% by weight of resin and from about 60% to 70% by weight of glass fibers.

Claim 25

Dependent Claim 58 words

A molded, composite synthetic resin blade for large diameter cooling tower fans as set forth in claim 12, wherein said sheet of synthetic resin reinforced with glass fibers which extend both longitudinally and transversely of the blade contained from about 30% to 40% by weight of resin and from about 60% to 70% by weight of glass fibers.

Claim 26

Dependent Claim 30 words

A molded, composite synthetic resin blade for large diameter cooling tower fans as set forth in each of claim 1, wherein said laminar, monolithic skin is of a polyester resin.

Claim 27

Dependent Claim 26 words

A molded, composite synthetic resin blade for large diameter cooling tower fans as set forth in claim 25, wherein said polyester resin is an isophthalic polyester.

Claim 28

Dependent Claim 29 words

A molded, composite synthetic resin blade for large diameter cooling tower fans as set forth in claim 1, wherein said skin is also reinforced with random directional glass fibers.

Claim 29

Independent Claim 280 words

A method of fabricating a molded, composite, airfoil-defining, synthetic resin blade for large diameter cooling tower fans having a central hub, said method comprising the steps of: fabricating an elongated core of relative dense synthetic resin foam material and of dimensions generally equal to those of the final blade, and a thickness dimension which is generally equal to but somewhat greater than the thickness of the final blade, said core fabricating step including forming depressions in the foam core defining a series of stepped areas therein of increasing height relative to the center of the core at respective steps as the normally outermost end of the fan blade is approached; attaching an elongated shank to the core in disposition extending outwardly from the end thereof adapted to be coupled to the fan hub; placing a skin over the core made up of a plurality of pre-prepared, flexible synthetic resin layers reinforced with glass fibers; inserting the core with the glass reinforced synthetic resin sheets thereover in a mold having a cavity which conforms to a final desired configuration of the blade; applying sufficient heat and pressure to the composite blade within the mold to cure the synthetic resin of the sheets while compressive forces are applied to the core to thereby form a laminar, essentially monolithic skin by virtue of curing of the synthetic resin sheets between the compressed core and the mold, a sufficient number of fiberglass reinforced synthetic resin sheets being applied to the core to fill a spaces between the outer surfaces of the core and the mold during curing of the resins; and removing the blade from the mold after curing of the synthetic resin material.

Claim 30

Independent Claim 280 words

A method of fabricating a molded, composite, airfoil-defining, synthetic resin blade for large diameter cooling tower fans having a central hub, said method comprising the steps of: fabricating an elongated core of relative dense synthetic resin foam material and of dimensions generally equal to those of the final blade, and a thickness dimension which is generally equal to but somewhat greater than the thickness of the final blade, said core fabricating step including forming depressions in the foam core defining a series of stepped areas therein of increasing height relative to the center of the core at respective steps as the normally outermost end of the fan blade is approached; attaching an elongated shank to the core in disposition extending outwardly from the end thereof adapted to be coupled to the fan hub; placing a skin over the core made up of a plurality of pre-prepared, flexible synthetic resin layers reinforced with glass fibers; inserting the core with the glass reinforced synthetic resin sheets thereover in a mold having a cavity which conforms to a final desired configuration of the blade; applying sufficient heat and pressure to the composite blade within the mold to cure the synthetic resin of the sheets while compressive forces are applied to the core to thereby form a laminar, essentially monolithic skin by virtue of curing of the synthetic resin sheets between the compressed core and the mold, a sufficient number of fiberglass reinforced synthetic resin sheets being applied to the core to fill a spaces between the outer surfaces of the core and the mold during curing of the resins; and removing the blade from the mold after curing of the synthetic resin material.

Claim 31

Dependent Claim 88 words

A method of fabricating a molded, composite, synthetic resin blade for large diameter cooling tower fans as set forth in claim 28, wherein is included the steps of configuring the mold, and fabricating a core of a thickness such that when the blade with the sheets of reinforced synthetic resin material thereover is placed in the mold, the thickness of the core is reduced by an amount correlated with the thickness of the laminar monolithic skin formed thereover by application of said heat and pressure to the blade.

Claim 32

Dependent Claim 75 words

A method of fabricating a molded, composite, synthetic resin blade for large diameter cooling tower fans as set forth in claim 29, wherein the size of the mold cavity and the thickness of the core are correlated such that the core is compressed to an extent that its thickness is reduced by an amount of from about 15% to about 40% of the combined thicknesses of the skin on opposite sides of the final blade.

Claim 33

Dependent Claim 71 words

A method of fabricating a molded, composite, synthetic resin blade for large diameter cooling tower fans as set forth in claim 29, wherein the size of the mold cavity and the thickness of the core are correlated such that the core is compressed to an extent that its thickness is reduced by an amount of about 25% of the combined thicknesses of the skin on opposite sides of the final blade.

Claim 34

Dependent Claim 130 words

A method of fabricating a molded, composite, synthetic resin blade for large diameter cooling tower fans as set forth in claim 29, wherein the size of the mold cavity and the thickness of the core are correlated such that the uncompressed core thickness and final compressed core thickness satisfy the equations T.sub.U =T.sub.A-B -0.75(t.sub.A +t.sub.B) [I] T.sub.C =T.sub.A-B -(t.sub.A +t.sub.B) [II] where T U ≡ Uncompressed core thickness, T A-B ≡ Thickness of the final blade between selected directly opposed points on opposite major surfaces of the blade, t A ≡ Thickness of the skin at one of said opposed points on the final blade, t B ≡ Thickness of the skin at the other of said opposed points on the final blade, T C ≡ Final compressed core thickness.

Claim 35

Dependent Claim 66 words

A method of fabricating a molded, composite, synthetic resin blade for large diameter cooling tower fans as set forth in claim 28, wherein is included the steps of forming depressions in the foam core of a depth such that the step to the next adjacent depression in a direction longitudinally of the blade is approximately equal to the thickness of one of the synthetic resin sheets.

Claim 36

Dependent Claim 61 words

A method of fabricating a molded, composite, synthetic resin blade for large diameter cooling tower fans as set forth in claim 28, wherein is included the steps of applying pre-prepared, flexible synthetic resin material sheets to the core of dimensions such that at least one of the sheets wraps around the leading edge of the blade along the longitudinal length thereof.

Claim 37

Dependent Claim 32 words

A method of fabricating a molded, composite, synthetic resin blade for large diameter cooling tower fans as set forth in claim 34 wherein said synthetic resin material is a chemically thickened polyester.

Claim 38

Dependent Claim 31 words

A method of fabricating a molded, composite, synthetic resin blade for large diameter cooling tower fans as set forth in claim 34, wherein said synthetic resin material is an isophthalic polyester.

Claim 39

Dependent Claim 35 words

A method of fabricating a molded, composite, synthetic resin blade for large diameter cooling tower fans as set forth in claim 28, wherein said temperature is of the order of 250° F. to 350° F.

Claim 40

Dependent Claim 39 words

A method of fabricating a molded, composite, synthetic resin blade for large diameter cooling tower fans as set forth in claim 28, wherein said blade is subjected to said temperature for a time of about 25 to 60 minutes.

Claim 41

Dependent Claim 45 words

A method of fabricating a molded, composite, synthetic resin blade for large diameter cooling tower fans as set forth in claim 28, wherein said pressure applied to the composite core and synthetic resin sheets is of the order of about 125 psi to 225 psi.

Claim 42

Dependent Claim 50 words

A method of fabricating a molded, composite, synthetic resin blade for large diameter cooling tower fans as set forth in claim 28, wherein is included the step of applying an outer synthetic resin veil over said sheets prior to insertion of the core with the cover thereover in said mold.

Claim 43

Dependent Claim 32 words

A method of fabricating a molded, composite, synthetic resin blade for large diameter cooling tower fans as set forth in claim 40, wherein said veil is augmented with a glass cross-fiber material.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1995-03-17	1995-09-16	1996-03-17	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	1999-03-17	1999-09-16	2000-03-17	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	2003-03-17	2003-09-16	2004-03-17	$7700.00	Window Closed / Lapsed

Plastic fan blade for industrial cooling towers and method of making same

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