US 3234970 A
Description (OCR text may contain errors)
Feb. 15, 1966 w. A. BAKER ETAL 3,234,970
RESIN-BONDED FIBRE STRUCTURES Filed Jan. 26 1965 2 Sheets-Sheet l Feb. 15, 1966 w. A. BAKER ETAL 3,234,970
RES IN-BONDED FIBRE STRUCTURES Filed Jan. 26 1965 2 Sheets-Sheet 2 640-4 fl w 2% rneyr United States Patent 3,2349% RESLN BUNDED hTRUCTURES William Andrew Baker, Donald Arthur Shoemack, and Victor Bernard Murray, Bristol, England, assignors to Bristol Aeroplane Plastics Limited, a British company Filed llan. 26, 1965, Ser. No. 429,950 @laims priority, application Great Britain, Mar. 3, 96% 7,578/60; July 30, 1964, 30,232/64 13 Claims. (til. l38--125) This application is a continuation in part of application, Serial No. 91,997, filed February 27, 1961, by the present applicants, and now abandoned.
The bore of a resin-bonded or plastics-bonded fibre or filament pipe may be subjected to the scouring action of an abrasive liquid, by which we mean a liquid which carries in suspension hard, sharp particles, such for example as sand and certain clays which are encountered in oil well-drilling. T he bore may also be subject to attack by some chemicals, such for example as are encountered in chemical processing plants and also with some crude oils.
The word fibre will be used to include staple fibres and continuous filaments, and the word resin to include resins and plastics.
We have found that some fibres when bonded by resin have an adequate resistance to abrasion and to chemical attack, either because of the inherent resistance of the fibres themselves or because they bond especially well with resin, or for both reasons, but those fibres are in general too Weak and lack the necessary stiffness to be used alone in forming a resin-bonded high-strength pipe of low weight, that is to say having the necessary strength without an excessively thick Wall. We have found that they are even too Weak in themselves to form a satisfactory protective inner layer for a pipe formed basically from stronger fibres with resin bonding, as a severe blow on the outside of the pipe can produce cracks in the protective inner layer, even without any defect being apparent elsewhere.
The primary object of this invention is to provide for a pipe or other hollow structure formed by resin-bonded fibre a facing layer, either internal or external, which is resistant to abrasion or chemical attack and is leakproof.
To accomplish this object, a hollow structure formed from a basic resin-bonded fibre has for protection a facing layer of resin-bonded fibre of material such that the facing layer is more resistant to abrasion or chemical attack than would be a layer of the basic fibre which forms the body of the structure, and a second layer lying between the facing layer and the body of the structure and consisting of cloth formed from a fibre of material stronger than that of the fibre in the facing layer and bonded by resin.
The term cloth is intended to cover all flexible sheet materials formed from fibre, for example by weaving, knitting or felting, but woven cloth is preferable and it is preferably in the form of tape.
The efiect of the layer of cloth is to resist any tendency for strains or actual cracks in the body of the structure to create highly localised stresses in the facing layer which may cause cracking, and for the best possible effect the cloth should have a fine mesh. In most resinb-onded fibre pipes the fibre is incorporated as a winding, and th invention is of particular value in such pipes because at the layer of the winding adjacent to the protective facing layer they lack local tensile strength in more than one direction. However, the invention is also applicable to pipes and other hollow structures of different construction, for example in which the basic fibre is in the form of tape or mats, woven, knitted or felted,
3,2343% Patented. Feb. E5, 1966 which can be of a coarser mesh than the cloth for the second layer. The basic fibre is preferably of glass; other types of fibre may, however, be used, for example a strong cotton thread. The fibre of the cloth forming the second layer is preferably of the same material as the basic fibre.
Preferably the facing layer has fibres running in two or more intersecting directions. A particularly suitable fibre for the facing layer is acrylic fibre, which is preferably bonded by a epoxide resin. Alternative fibres are synthetic fibres which provide the necessary resistance to abrasion and chemical attack when bonded with resin, for example nylon and some polyester fibres such as those solid under the trade name Terylene.
Preferably the facing layer is also woven. It is convenient to use woven tapes which can be wound onto a mandrel, with turns overlapping if desired. Alternatively woven mats may be used. It is also possible to use knitted or felted fibres. The fibres may be continuous filament or staple.
The preferred sequence of layers for internally protected pipes is:
(1) Two layers of resin-bonded acrylic fibre tape, the inner surface of which forms the bore of the pipe.
(2) A layer of resin-bonded glass fibre tape,
(3) A layer of resin-bonded acrylic fibre tape,
(4) A layer of resin-bonded glass fibre tape and then resin-bonded glass fibre winding forming the body of the pipe.
The simplest but most laborious method of winding a pipe or other tubular structure is to wind on each layer separately, impregnating it with resin as the Winding proceeds.
A more refine-d process is to have two cassettes carried by a winding head, preferably so as to be positioned diametrically opposite each other with respect to the mandrel on which the pipe or other tubular structure is to be wound. One cassette holds acrylic tape and the other glass fibre tape, and the tape in both cassettes is impregnated with resin before leaving the cassettes. The Winding of the two tapes can then proceed simultaneously. If the widths of the two tapes are the same, single layers of the two tapes can be wound on simultaneously.
A still more developed form of winding, which can give several thicknesses of acrylic tape forming a facing layer backed by at least one thickness of glass fibre tape, can be achieved by using acrylic tape and glass fibre tape of different Widths and having a rate of traverse per revolution of the mandrel (that is to say, a pitch) which is less than the width of the narrower of the two tapes.
In one example the width of the acrylic tape which is to form an internal facing layer of a pipe is 6 inches and that of the glass fibre tape 4 inches, and the pitch is 1% inches. The two tapes are wound on simultaneously with their trailing edges in line with each other and the glass tape outermost, and are advanced axially relative to the mandrel, conveniently by traversing the mandrel, by an amount each turn of 1% inches. In this example there is thus obtained, with the use of only two tapes, two inner layers of acrylic tape, then one of glass fibre tape, then one of acrylic tape, and then a final layer of glass fibre tape. The glass fibre thread windings of the pipe itself then follows on to build up the required thickness.
The accompanying drawings show a pipe wound in this Way. In these drawings:
FIGURE 1 is a diagrammatic fragmentary section parallel to the axis of the pipe;
FIGURE 2 shows the tapes being Wound around the mandrel (which is for convenience foreshortened in diameter) to produce the inner layers of the pipe;
FIGURE 3 shows the tapes being wound on to produce the outer layers of the pipe; and
FIGURE 4 shows diagrammatically the relevant parts of a machine for winding the pipe.
The wall of the pipe as seen in FIGURE 1 includes a layer 1 of resin-bonded acrylic tape which defines the bore of the pipe, and layers 2 to of which layers 2 and 4 are of acrylic tape, and layers 3 and 5 are of resin-bonded glass fibre. Around the layers 1 to 5 there is the body of the pipe which may be formed by any number of layers of glass fibre windings, adjacent layers being preferably helices of opposite hand and at a helix angle such that the wall of the pipe has substantially the same strength in all directions. Around the body of the pipe there is a layer of glass tape surrounded by two layers 11 and 12 of acrylic tape, to protect the outside surface of the pipe. It will be seen that the tapes overlap so as to provide additional layers in localised regions; this is done to ensure that in no place is there less than the required number of layers.
The width of the acrylic tape is approximately the dimension A shown in FIGURE 1, and the width of the glass tape is approximately the dimension B. In order to produce the arrangements of layers shown, the pitch of the tapes in the internal layers 1 to 5 is the dimension C, and that of the tapes in the outer layers 10 and 2 is the dimension D.
It will be seen that edges of the inner acrylic and glass tapes are aligned at the points 13 shown in FIGURE 1. These points are on the trailing edges; in other words, the mandrel around which the tapes are wound moves to the left with respect to the tapes. When winding the outer layers 10 to 12 the mandrel is moved to the right with respect to the tapes, and the trailing edges of the two tapes are oiiset by an amount E, with the acrylic tape outermost.
The dimension C is substantially equal to /2B and to /sA; the dimension D is approximately equal to %B and to /zA.
As an alternative to 6 inches and 4 inches, the widths of the acrylic tape and glass tape may be 9 inches and 6 inches respectively (i.e. again in the ratio 3:2). Such tapes may be used for pipes of which the internal diameter is 6 inches to 18 inches or more.
FIGURE 2 shows an acrylic tape 13 and a glass fibre tape 14 being Wound around a mandrel 15 to produce the layers 1 to 5 shown in FIGURE 1.
FIGURE 3 shows an acrylic tape 13a and a glass tape 14a being wound on to produce the layers 10 to 112 shown in FIGURE 1.
Other multiple layerings can be obtained by suitable choice of width of tapes and lengths of traverse per turn.
The method of winding may consist of making the winding head and mandrel both rotatable with respect to a stationary base. With such an arrangement it is possible, by arranging that the base carries a supply of basic fibre to form the body of the pipe, to wind on at least some of the basic fibre during the winding on of the tapes which make up the internal layers of the pipe. By use of such a head the tapes can be at a different helix angle or oppositely handed to the first glass fibre thread winding.
The acrylic tape is preferably a scoured square weave, sold under the trade name Courtelle CL71. The glass fibre tape is preferably in accordance with the British Standard specification DTD5518/S2/l50/E and is caramelised; for example, it may be of .009 glass cloth, balanced 8 shaft satin weave.
FIGURE 4 shows a pipe being wound onto a mandrel 15. The apparatus for doing this includes a sleeve 16 which is mounted on a stationary base 17 (partly shown) and around which an annular member 18 forming part of a winding head can rotate. On diametrically opposite sides of the member 18 there are bars 19 and 20 which carry cassettes 21 and 22 respectively, the positions of the cassettes being adjustable along the bars. A cassette 23 for glass fibre is carried by parts 24 and 25 which are mounted on the stationary base (by means not shown).
During winding the mandrel is moved axially in the direction of the arrow 26 with respect to the base and winding head, and it rotates in the direction of the arrow 27 with respect to base. The winding head rotates in the direction of the arrow 28 with respect to the base, at a speed less than the speed of rotation of the mandrel. There is thus relative rotation between the winding head and the mandrel, and as a result resin-impregnated tapes 29 and 30 from the cassettes 21 and 22 are wound onto the mandrel with overlapping so as to produce the arrangement shown in FIGURE 1.
At the same time as tape is wound around the mandrel, glass fibre 31 from the cassette 23 is wound over the tapes. The fibre is impregnated with resin on its way from the cassette (by means not shown). After one pass of the mandrel during which fibre and tape is wound on, more fibre may be wound on by disconnecting the tapes and then reciprocating the mandrel while rotating the mandrel in the same direction.
The winding head is driven by a belt 32 from a pulley 33. The speed and direction of rotation of the pulley can be varied so that any desired speed relationships between the mandrel, winding head and cassette 23 can be obtained.
After the winding on of the tapes 29 and 30 and of the required number of layers of fibres 31 has been completed, two further resin-impregnated tapes are wound around the fibre winding to produce the outer layers of the pipe. The pipe is then treated in the appropriate manner to cure the resin and bond the various layers of the pipe together, and the mandrel is finally withdrawn.
In general pipes according to this invention preferably have for internal protection layers of acrylic fibre cloth and of glass cloth forming a total thickness of at least 0.05 inch. The outer protective layers should also be at least 0.05 inch in total thickness including a surface coating of resin applied as a final step The basic windings of glass fibre may have a thickness from 0.075 inch to 1 inch or more for pipes of which the internal diameter is 6 inches or more.
It will be appreciated that the internal layers 1 to 5 may, if desired, be omitted. A pipe formed only with an external protective facing of acrylic fibre and glass cloth will be useful, for example, for conveying low pressure gas under water, or as an underwater cable conduit. The external facing will be resistant to abrasion and corrosion and will remain water-tight to prevent water leaking into the pipe. If cracks are produced in the basic wound body of the pipe owing to operating strains, the glass cloth will effectively isolate the acrylic fibre from the cracks, and will thus maintain the acrylic layers intact and Water-tight. It will be appreciated moreover that this same improvement provided by the present invention can be usefully applied to other submersible hollow structures and particularly to tubular structures formed basically, as in the base fo a pipe, by a winding of resinbonded glass fibre.
1. A pipe formed by resin-bonded fiber and having, for internal protection, an inner facing layer of a resinbonded fiber of material such that the layer is more resistant to abrasion or chemical attack than would be a layer of the basic fiber which forms the body of the pipe, and a second layer lying between the facing layer and the body of the pipe and consisting of cloth formed from a fiber of material stronger than that of the fiber in the facing layer and bonded by resin.
2. A pipe according to claim 1 in which the basic fiber is of glass which is incorporated as a winding.
3. A pipe according to claim 1 in which the fiber of the facing layer is an acrylic fiber.
4. A pipe according to claim 1 in which the fiber of the second layer is of glass.
5. A pipe according to claim 1 in which the facing layer has fiber running in two or more intersecting directions.
6. A pipe according to claim 5 in which the facing layer is formed by woven tape.
7. A pipe according to claim 1 in which the cloth of the second layer is in the form of woven tape,
8. A pipe according to claim 7 in which the tape is wound helically at a pitch of which the width of the tape is substantially a multiple so that either tape or both tapes provide two or more layers by virtue of the turns overlapping.
9. A pipe according to claim 8 in which the tape forming the facing layer has a width substantially equal to three times the pitch of the turns, and the tape forming the second layer has a width substantially equal to twice the pitch of the turns, so arranged that there are around the bore two layers of the facing tape surrounded in turn by a layer of the second tape, a further layer of facing tape and then a further layer of the second tape.
10. A pipe according to claim 1 including for outside protection additional layers of resin-bonded cloth and of resin-bonded fiber material, the outermost layer being formed by resin-bonded fiber similar to that of the inner facing layer.
11. A pipe formed by a body consisting of a winding of resin-bonded glass fiber and having, for internal protection, an inner facing layer of a resin-bonded acrylic fiber cloth, and including a second layer lying between the facing layer and the body of the pipe and consisting of cloth formed from a fiber of material stronger than that of the fiber in the facing layer and bonded by resin.
12. A hollow structure formed from a basic resinbonded fiber and having for protection against abrasion or chemical attack a facing layer of resin-bonded fiber of material such that the facing layer is more resistant to abrasion or chemical attack than would be a layer of the basic fiber which forms the body of the structure, and a second layer lying between the facing layer and the body of the structure and consisting of cloth formed from a fiber of material stronger than that of the fiber in the basic layer and bonded by resin.
13. A tubular hollow structure comprising a body formed by a winding of resin-bonded glass fiber and having for protection against abrasion or chemical attack a water-tight facing layer of resin-bonded acrylic fiber cloth, and including a second layer lying between the facing layer and the body of the tubular structure and consisting of cloth formed from a fiber of material stronger than that of the fiber in the facing layer and bonded by resin.
References Cited by the Examiner UNITED STATES PATENTS 23,317 1/1951 Greenwald 138--125 2,962,050 11/1960 Ranberg et al. 138125 2,969,812 1/1961 Degenahl 138-144 X 3,062,241 11/ 1962 Brumbach 138--125 3,080,893 3/1963 Eraycraft 138141 3,172,427 3/1965 Jackson et a1. 138125 LAVERNE D. GEIGER, Primary Examiner.