US3445583A - Composite tubing - Google Patents

Description

COMPOSITE TUBING Filed Nov. 29, 1965 INVENTOR.

ALBERT E. CHROW United States Patent 3,445,583 COMPOSITE TUBING Albert E. Chrow, Chagrin Falls, Ohio, assignor to Samuel Moore and Company, Mantua, Ohio, a corporation of Ohio Filed Nov. 29, 1965, Ser. No. 510,202 Int. Cl. H01b 7/04, 7/28 U.S. Cl. 17447 Claims ABSTRACT OF THE DISCLOSURE The present invention relates to a high pressure fluid transmission hose for use with a spraying apparatus, and more particularly to such a hose having a grounding wire disposed therein.

Composite tubing or hoses areused to transport a liquid such as paint or the like from a pulsating source of power such as a hydraulic pump to a spray nozzle, such as a spray gun or the like, where the liquid is sprayed upon an object. Because a considerable amount of static electrical charge is produced along the core of the hose, it is desirable to incorporate an electrically conductive ground wire in the structure of the hose so as to drain off such static charge to prevent sudden sparking at the spray nozzle. Such sparking occurs when too much electric static charge is built up in the device and a worker uses the spray nozzle too close to a grounded conductor, such as a steel beam. In order to transmit the liquid under sufficient pressure to produce an adequate spray, the hose is generally of a high pressure construction involving a relatively strong, though flexible inner tube or core, a fibrous reinforcement layer to protect against bursting, and an outer protective coating, usually polymeric, to protect the tubing from abrasion, moisture, temperature variations and corrosion. It is desirable that such hose radially expand under the pressure pulsation in order to act as an accummulator which attenuates the pulses so as to minimize the pulsating at the nozzle and thereby produce a more smooth and uniform painting spray. The practice in the past has been to incorporate this grounding wire as one of the braids of the reinforcement. In another form, the wire was molded into the core along one side thereof in a zig-zag fashion. The difficulty with the prior art type of arrangement is that such wires often broke under pressure and thereby lost their elfectiveness as a grounding device for a static charge. One attempt which had been made to solve the problem was to make the hose less susceptible to expansion. Such approach was helpful in decreasing breakage of the wire but tended to make the hose less effective as it severely decreased in accummulator action and thus caused undesirable pulsation at the nozzle of the paint spray gun.

Another objection has been that the incorporation of the wire into the braid causes undue abrasion between the wire and the braid resulting in damage to the braid and ultimate bursting of the hose. This abrasion caused the hose to burst sooner than would ordinarily be the case.

3,445,583 Patented May 20, 1969 "ice Accordingly, it is an object of the present invention to produce a composite hose construction having a ground element or wire disposed therein whereby the hose may be capable of extensive radial expansion without a loss of the effectiveness of the grounding element incorporated therein.

Another object of the invention is to provide a grounding construction for a composite hose wherein the possibilities of rupture of the grounding element are substantially decreased and wherein the effectiveness in draining the static charge is maintained even though a rupture should occur in the grounding element.

A further object is to produce a composite tubing for the transmission of high pressure fluid such as paint from a source of hydraulic power to a nozzle such as the nozzle of a paint spray gun wherein the fluid dispensed at the nozzle is relatively uniform and free from pulsation, while at the same time providing an effective system for draining off excess static electricity charges so as to prevent sparking at the spray nozzle.

Another object of the invention is to produce a grounded high pressure hose for transmission of the fluid under pulsating pressure having good accumulator characteristics and improved fatigue failure characteristics.

Briefly stated, the foregoing and other related objects and advantages are accomplished in one form of the invention by a high pressure hose for use in transmitting paint and the like to a nozzle for spraying by the use of a polymeric inner core for transmitting the paint fluid, a grounding element spirally wound about said inner tube at widely spaced axial pitch distances, a polymeric tape juxtaposed over the spiralled convolutions of the grounding wire and covering the exposed portions thereof, a layer of fibrous reinforcement material, such as woven braid, disposed circumferentially of the aforesaid composite structure, and an outer protective covering.

Referring now to the drawings, FIG. 1 is a fragmentary partially cut-away and partially cross-sectioned elevation yiew of a section of paint hose according to the present invention;

FIG. 2 is an enlarged fragmentary cross-section of a composite paint hose having a reinforcing element disposed therein taken along the lines 2-2 in FIG. 1;

FIG. 3 is a fragmentary elevation view of a section of the inner core tube illustrating the grounding element or twisted wires, disposed spirally of the core tube in accordance with the present invention;

FIG. 4 is a vector diagram illustrating the forces exerted on a grounding element according to the prior art where the wire turns are closely spaced;

FIG. 5 is a vector diagram illustrating the forces applied to the grounding element disposed according to the present invention;

FIG. 6 is an enlarged fragmentary cross-section taken along the lines 6-6 of FIG. 1, illustrating a cross-section of the grounding element when assembled with the composite tubing and prior to rupture thereof;

FIG. 7 is an enlarged fragmentary cross-sectional view illustrating a partial disintegration of the grounding element of FIG. 6 during operation; and

FIG. 8 is a cross-sectional illustrating the action of the protective tape of FIGS. 6 and 7 after fragments break through the binder tape during operation.

Referring again to the drawings and more particularly to FIGS. 1 and 2 thereof, there is illustrated a composite tubing T made in accordance with the present invention and having an inner tube or core 10, a grounding element 12, such as a plurality of twisted wires, disposed helically of the inner tube 10 and covered by a binder tape 14 which in turn is covered by a protective tape 16. The binder tape 14 and protective tape 16 follow the helical convoluted path of the grounding element 12, as best illustrated in the right hand portion of FIG. 1. A reinforcement sheath 18 of fibrous material may be disposed circumferentially of the tubing to reinforce the tubing for high pressure operations and an outer protective sheath 20 may be disposed circumferentially of the reinforcement sheath to protect the composite product from corrosion, abrasion, and/or adverse temperatures.

One feature of the invention is that the grounding element 12 may be wound helically of the inner tube 10 and in a manner so that the spacing between adjacent convolutions in much greater than ordinarily has heretofore been the case in the prior type of tubing. As shown in FIG. 3, it is desirable to wind the grounding element 12 so that the distance y between corresponding axially spaced points on the convolutions, such as between crests 22 and 24, is at least four times the outer diameter of the inner tube 10. It is even preferred that the aforesaid pitch distance be 16 times the diameter of the tube. For example, where the diameter of the inner tube 10 is one-quarter inch, it is preferred that the pitch distance be four inches. It has been found that by greatly increasing the pitch distance, an extremely flexible hose construction may be utilized so as to permit substantial swelling or diametrical expansion of the hose so as to provide the desired accumulator action which minimizes the pulsation at the nozzle without subjecting the ground wire 10 to abnormal stresses and strains. It is preferred that the composite product expand as much as 11% of its diameter. The rupture of the grounding element 12 is caused by radially directed components of force. As shown in the vector diagram of FIG. 4, wherein a helical winding of the closely packed arrangement is made, the radial component to R is substantial. In FIG. 4, a 45 lay is shown. In FIG. 5, it is seen that where the angle of the lay is extremely acute, the radially outwardly directed component of force 0 to R is very slight as compared to its corresponding force shown in FIG. 4. It is to be understood that the angle of lay or the pitch distance may be more or less than that described but that the use of some pronounced elongation, as compared to the conventional tight winding, may be of great assistance in achieving the composite structure of the present invention.

While nylon is a preferred material for the construction of the inner tube and of the reinforcement sheath, it is to be understood that any materials which are strong enough to resist premature breaking, yet which are flexible enough to permit the expansion to achieve the accumulator effect may be used.

Preferred results are obtained wherein the grounding element is comprised of a plurality of twisted Wires. It is believed that a plurality of wires such as shown in FIGS. 6 to 8 is useful in achieving a disintegration of the grounding wire which, when used in cooperation with the other elements, retains electrical continuity as hereinafter described. Preferred results have been obtained by the use of a 9 x 2 x 34 AWG tinned copper, flattened braid, or the 8 x 2 x 34 AWG, bare oxygen-free copper.

The aforesaid axial disposition of the convolutions is utilized to minimize the occurrence of breakage over normal usage. Equally important, it is designed to decrease the extent of breakage of the grounding element when it does occur. When this feature of a minimized extent of breakage is utilized in conjunction with the application of the binder tape 14 and the protective tape 16 of the present invention, the usefulness of the grounding element as a static energy dissipator is still available even though a rupture has occurred in the element. It has been found that the electrical conductivity of the grounding element may be sustained by confining the particles in sufiiciently close physical proximity or contact with each other that the electrical conductivity is maintained even though a rupture has occurred and the element is no longer the continuous solid entity which it was during assembly.

The continuity of the electrical circuit is maintained by the disposition of a binder tape 14 which is placed over the grounding element 12, as shown in FIG. 1 and FIG. 2, so as to bind the element in position. The preferred binding tape should have good fatigue resistance and adhesive characteristics and good elongation. Preferably, the tape should be as wide as the grounding element which it covers and preferably, slightly wider. A preferred form of binder tape is inch wide by 4 mil thickness vinyl such as type 471 sold by Minnesota Mining and Manufacturing Company. Other types of binding tapes may be utilized such as Mylar adhesive, semi-plasticized vinyls, or various adhesive bearing thermo-plastic or thermo-setting resins as well as the use of impregnants such as latexes, plastisols, organisols, liquid urethanes, or epoxides. While it is not necessary to do so, the binder tape may completely cover the tube rather than merely following the path of the element, if desired. The tape must be capable of expansion so as not to be ruptured due to the action of the swelling or diametrical expansion of the tube due to the pulsation of the liquid therethrough and must be a sufficiently good binder to hold the fragmented particles 30 formed when a portion of the element ruptures, as shown in FIG. 7.

When the grounding element disintegrates after rupture, there is a possibility that one of the pieces or particles of the grounding element will break through the binder tape and cut the superimposed fibrous reinforcement sheet. Accordingly, a protective tape 16 may be provided to overlie the binder tape 14, as shown in FIG. .1. Thus, as shown in FIG. 8, should a rupture occur, the protective tape 16 shields the fibrous reinforcement 18 from the displaced grounding wire particles 32, thereby preventing abrasion, cutting or other damage to the reinforcement sheath and also confines the particles so as to maintain the electrical continuity of the grounding element. The protective tape should be abrasion and particle-penetration resistant. An example of a preferred form of tape is Mylar. Mylar is the trade name for a polyethylene terephthalate polyester tape sold by Du Pont. It is preferred that the protective tape follow the path of the convoluted wire. The tape could also be wound circumferentially of the binder tape and inner core so as to form a continuous encompassing sheath through such complete encasement is not necessary.

The outer reinforcement sheath of fibrous material may be of a conventional braid type or it may be of a series of coplanar layers. It is preferred that the braid material and construction be such as to permit sufiicient diametrical expansion to act as an accumulator for the liquid, such as paint and the like, passing through the hose so that the pulsation at the nozzle of the spray gun is minimized. A preferred material for the reinforcement layer is nylon. However, other materials, such as Dacron may be used. Dacron is the trade name of a polyester fiber sold by Du Pont.

The thickness of the grounding element will depend on the degree of conductivity required. For example, where the hose is inch in diameter, then it has been found desirable to use an element having a maximum initial resistance of .6 ohm for 25 linear feet of hose.

The outer protective sheath 20 may be of a polymeric material which provides flexibility, and good temperature and abrasion resistance. A preferred material for the sheath is polyurethane. The thickness may be in the range of .020 to .025 inch on a one-quarter inch diameter inner core.

The foregoing composite structure for a paint hose and the like provides a hose which is capable of extreme radial outward expansion 'so as to provide an accumulator effect for paint and the like passing through the hose and thereby minimize pulsation at the nozzle while at the same time providing a grounding element to drain off static electricity to prevent sparking at the nozzle sh uld the nozzle be placed in too close proximity to another conductor whereby the rupture-free life of the grounding element is greatly increased and whereby the electrical continuity and operation of the grounding element is maintained even though a rupture does occur and the fatigue life of the hose is increased.

' Whereas the prior art structure, wherein the grounding element formed a part of the braid, lost electrical continuity at approximately 1000 cycles, the structure of the present invention has operated from 50,000 cycle-s to in excess of 100,000 cycles without such loss.

The terms and expressions which have been used, are used as terms of description and not of limitation, and there is no intention in the use of such terms and expressions of excluding any equivalents of any of the features shown or described, or portions thereof, but it is recognized that various modifications are possible within the scope of the invention claimed.

I claim:

1. A composite tubing product having good burst strength, fatigue, diametrical expansion and electrical continuity characteristics for use in transmitting pressurized pulsating fluids comprising, an inner polymeric core tube having an axially extending bore for the transmission of said fluid, a continuous electrical conductive element disposed in engagement with said core tube and extending in helically convoluted relation around said core tube and substantially co-extensive in length with said tubing, a reinforcement sheath of fibrous material disposed in circumferentially engaged relation around said core tube, a flexible polymeric binder tape disposed intermediate said core tube and said reinforcement sheath, said binder tape disposed in engaged covering relation over said conductive element throughout its length and in secured contact with said core tube on opposed sides of said conductive element to maintain the electrical continuity of said conductive element upon flexure of said tubing.

2. A composite tubing in accordance with claim 1, including a polymeric protective tape disposed intermediate said core tube and said reinforcement sheath, said protective tape disposed in engaged covering relation over said binder tape throughout its length and in engaged relation with said core tube on opposed sides of said conductive element.

3. A composite tubing in accordance with claim 1, wherein said core tube is made of nylon, said binder tape being made of a polymeric material having good fatigue, elongation and adhesive characteristics, such as vinyl, and said protective tape being made of a polymeric material having good abrasion and particle-resistant characteristics, such as Mylar.

4. A composite tubing in accordance with claim 1, wherein the distance between axially spaced points on adjacent convolutions of said conductive element is greater than the maximum transverse dimension of said core tube.

5. A composite tubing in accordance with claim 4, wherein such distance is in the ratio from about 4:1 to 16: 1.

6. A composite tubing in accordance with claim 4, wherein such distance is in the ratio of about 16:1.

7. A composite tubing in accordance with claim 1, wherein said conductive element comprises a twisted braid of flattened copper base wires.

8. A composite tubing in accordance with claim 1, wherein the tubing incorporates electrical continuity characteristics after from about 50,000 cycles to in excess of 100,000 cycles to fatigue.

9. A composite tubing in accordance with claim 1, wherein said binder tape is made from a polymeric material having good adhesive characteristics.

10. A composite tubing in accordance with claim 1, including a polymeric outer sheath disposed around said reinforcement sheath and providing a protective cover for said tubing.

References Cited UNITED STATES PATENTS 646,886 4/1900 Stowe et al 174-47 646,887 4/1900 Stowe et a1 138103 X 837,512 12/1906 Seeley 17447 2,144,478 1/1939 Baumgratz 138103 2,244,635 6/ 1941! Williamson 138103 2,268,321 12/1941 Flynn 138-118 2,648,720 8/1953 Alexander 138-118 X 3,042,737 7/1962 Brumbach et al. 138125 X 3,063,303 11/1962 Cadwallader 138125 X 3,086,557 4/1963 Peterson 138 118 X 3,116,759 1/1964 Webb 138125 3,177,900 4/1965 Sharp 138-125 3,277,231 10/1966 Downey et al 17447 FOREIGN PATENTS 813,151 5/1959 Great Britain.

HOUSTON S. BELL, 111., Primary Examiner.

mg? UNI'IED S'1A'1.ES PATEN" OFFICE CERTIFICATE OF CORRECTION May 20, 1969 Patent No. 3,445,583 Dated Inventor(s) lb t E, Chrow It is certified that error appears in the above-identified patent and that; said Letters Patent are hereby corrected as shown below:

r Claim 3, line 1, should read:

A composite tubing in accordance with Claim-,2,

Signed and sealed this 15th day of August 1972.

(SEAL) Attest:

) EDWARD 'M. FLETCHER JR. ROBERT GOT-TSCHALK Attesting Officer Commissioneg of Patents

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