US3123242A - hahn etal - Google Patents

Description

March 3, 1964 H. HAHN ET AL 3,123,242

INTERLOCKED TAPE PRESSURE VESSEL Filed Dec. 12, 1960 2 Sheets-Sheet 1 ill] F Ill Q I g Q [q t G) ""RLii? HE HERMAN H.HANINu ROGER D. LLEIYE .JCIElEPH LIJF'RET BY HAREILD LUREIEH ATTORNEY March 3, 1964 H. HAHN ETAL INTERLOCKED TAPE PRESSURE VESSEL 2 Sheets-Sheet 2 Filed Dec. 12, 1960 ATTEIRN EY United States Patent 3,123,242 INTERLOCKED TAPE PRESSURE VESSEL Henry Hahn, Fairlawn, and Herman H. Hanink, Ridgewood, N.J., Roger D. Lloyd, Cambria Heights, N.Y.,

and Joseph Loprete, Lyndhurst, and Harold Lorsch,

Dumont, N.J., assignors to Curtiss-Wright Corporation,

a corporation of Delaware Filed Dec. 12, 1960, Ser. No. 75,410 3 Claims. (Cl. 2203) This invention relates to hollow bodies and to a method of fabricating such bodies. More particularly, the invention is directed to the structure of hollow pressure vessels, such as the casing of a rocket motor, and to a method of fabricating or reinforcing such vessels.

The invention has been developed primarily for use as a rocket casing or vessel and for the fabrication of such a vessel and the invention will be described herein in connection with such use. It will become apparent, however, that the invention is not limited to this specific use and instead is of general application.

One basic Way of improving the performance of rockets is to reduce their weight. In accordance with the present invention the weight of a rocket casing is reduced by making use of 'the higher strengths which can be obtained in metallic materials by reducing their cross-sectional area, for example by cold working or drawing metallic material to elongate tape-like lengths of small cross-section. In the case of certain metals such cold working makes possible a further increase in strength by subsequent heat treatment. In accordance with the invention the tape has a cross-section such that at least one rib and groove runs longitudinally along at least one side of the tape so that adjacent lengths of the tape can be interlocked.

An object of the present invention resides in the provision of a novel hollow body structure having high strength to weight ratio and to the provision of a novel method of fabricating such a hollow body.

A further object of the invention comprises the provision of a novel structure of a hollow body in which a wall of the vessel is made up of side-by-side lengths of tape which are interlocked together.

-In accordance with a still further object of the invention the wall of the hollow body having the novel structure of the invention is made up of interlocking lengths of tape such that forces on said wall are carried by the longitudinal strength of the tape and by the transverse strength of the tape by virtue of said interlocking construction. For example, in the case of a hollow cylindrical vessel made in accordance with the invention and subject to internal fluid pressure, the radial forces on the cylindrical wall are resisted by the longitudinal strength of the tape and the axial forces on the cylindrical Wall resulting from the axial pressures against the ends of the vessel are carried by the cylindrical wall by the transverse strength of the tape by virtue of an interlocking connection between adjacent lengths of the tape.

Another object of the invention comprises the provision of a hollow body having a wall portion made up of tape wound in helical fashion from one end of the wall portion to the other with at least certain adjacent turns of said tape having an interlocked connection to prevent adjacent turns of tape from spreading apart- More particularly, the invention comprises the provision of a hollow body having a wall portion made up of a plurality of layers of tape with the tape of each layer being wound in helical fashion from one end of the wall portion to the other and with the tape turns of one layer being interlocked with the tape turns of an adjacent layer or layers.

As already stated the invention is not limited to pressure vessels such as rocket casings which have a cylindrical wall construction and instead is of general application.

3,123,242 Patented Mar. 3, 1964- "ice Thus the invention can be applied generally to vessels having a generally tubular Wall as Well as to hollow bodies having no axis of symmetry. Hence, the expression wound in helical fashion as used herein in connection with a layer of tape is intended to mean broadly wrapping tape by successive turns which are disposed in a side-byside relation.

The use of metallic tape to form the body of a rocket vessel or other pressure vessel has the further advantage that the tape can be preheat-treated and that after the tape has been wound to form the pressure vessel no machinin-g or further heat treatment of the tape wound vessel is necessary. This is an important advantage in the structure of a rocket casing since it is then readily possible to fabricate the rocket completely at the site where it is to be used.

The invention is also not limited to the use of metallic tape since for certain applications the tape obviously could be made of non-metallic materials.

Other objects of the invention will become apparent upon reading the annexed description along with the drawing in which:

FIG. 1 is a view, partly in axial section, of a rocket vessel embodying the invention;

FIG. 2 is an enlarged sectional view of a portion of FIG. 1;

FIG. 3 is a sectional view showing a further enlargement of a portion of FIG. 2;

FIG. 4 is a sectional view of a reduced scale of a collapsible mandrel useable for winding a pressure vessel embodying this invention;

FIG. 5 is a view similar to FIG. 3 but showing a slightly modified construction; and

'FIGS. 6, 7 and 8 are views generally similar to FIGS. 3 and 4 but illustrating further modifications.

Referring now to FIG. 1 of the drawing a rocket casing or vessel for solid fuel rockets is illustrated at 10. The invention will be described in connection with its application to solid fuel rockets. It will be understood, however, that the invention is not so limited. For example, the invention is also applicable to liquid fuel rocket vessels as Well as to other pressure vessels, for example pressure conduits, and to hollow bodies generally. As illustrated the rocket vessel 10 has a cylindrical construction with a closed end portion 12 at one end and a nozzle portion '14 at the other end axially spaced from the end portion 12. The cylindrical wall portion 116 of the rocket vessel between said ends has the novel construction of the invention and comprises a plurality of layers of tape which preferably has been cold worked to a small cross-sectional area and heat treated to an extent to provide the strength desired. The solid fuel (not shown) for the rocket is packed within the vessel in the usual manner and upon ignition of the fuel the resulting combustion gases discharge through the rocket nozzle 14- and produce a pressure within the vessel to provide the rocket with thrust. It is apparent, therefore, that the walls of the rocket vessel must be capable of withstanding considerable internal pressure which not only produces circumferential stresses in the cylindrical portion of the vessel but also produces axial stresses on said cylindrical portion because of the axial pressures on the two end portions 12 and 14 of the vessel.

The cylindrical wall portion 16 of the pressure vessel comprises a plurality of layers of helically wound tape. As illustrated in FIGS. 1-3, the multi-tape-layer wall portion 16 comprises three helically wound tape layers, an inner layer, an intermediate layer and an outer layer formed by tapes 18, 20 and 22 respectively. As shown the vessel end portions 12 and 14 have cylindrical extensions 24 and 26, respectively, on which the ends of the tapes 18, 20 and 22 terminate. As will become apparent, the

invention is not limited to a three-layer construction and a different plurality of layers may be provided.

In accordance with the invention, means are provided so that the multi-tape-layer wall 16 formed by the tapes lid, 2t) and 22 is capable of carrying both circumferential or hoop stresses as well as stresses in a direction axially of the vessel ltd resulting from pressures within said vessel.

For this purpose, the cross-section of the tapes 18, 2% ant. 2-2 is such that, as hereinafter described, the tape turns of adjacent layers interlock when wound as superimposed layers. As illustrated, the tape 13 forming the inner layer has a U-shaped cross-section comprising a shank portion 36 and two parallel leg or rib portions 32 disposed at right angles to and at the opposite ends of the shank portion. Thus the legs or ribs 32 run longitudinally along t ie two edges of the tape 18 and form a groove therebetween. The tape 20 forming the intermediate layer has a dumb-bell or I-beam like cross-section comprising a shank portion 34 and two leg or rib portions 36 and 37 at each end of the shank portion and projectat right angles to and in opposite directions from said shank portion. The leg or ribs as run longitudinally along the two edges of t e tape Ztl and form a groove therebetween as do the legs or ribs 37 on the other side of the tape it). The tape 22 forming the outer layer has a U-shaped cross-section and is similar to the tape 13. Thus each transverse section of the tape 22 comprises a shank portion 38 and two parallel leg or rib portions disposed at right angles to and at the opposite ends of the shank portion.

The tape 18 is wound h lically between the vessel end portions 12 and 14 to form an inner tape layer. For this purpose, a suitable collapsible mandrel 42 (hereinafter described) is supported between the cylindrical extensions 24 and 26 of the two ends 12 and 14 of the vessel. As illustrated, the external surface of the mandrel 42 is a cylindrical surface which is coaxial with and has substantially the same external diameter as that of the adjacent external surfaces of the two cylindrical extenions 24 and 26 at the two ends of the mandrel. The mandrel 52 also serves to hold the two extensions 23.4 and 26 of the vessel end portions 12 and 14 in proper axiallyspaced relation.

The tape 13 is helically wound by starting with a few turns on one cylindrical extension 24 and 26 and then winding over the mandrel 42 and finally on to the other cylindrical extension to complete the inner layer. The tape it; is wound with the legs or ribs 32 of the tape projecting outwardly and so that adjacent turns abut each other. With the tape 18 so wound, the inner surfaces of the abutting tape turns form a substantially continuous inner surface for the inner tape layer and each transverse section of the tape has an outwardly-directed channel or groove running longitudinally along the outer side of the tape between the legs or ribs 32. A few turns of the tape 13 are wound on each extension 24 and 26.

The tape Ztl is then Wound helically over the tape 18 in the same direction as the tape 18 is wound to form the second or intermediate layer. The tape 20 is started on one of the end cylindrical extensions 2 or 26 from a point beyond the tape 18 so that a few turns of tape 20 are first wound on said extension. The winding of the tape 20 is continued over the tape 18 forming the inner layer and terminates on the other end extension with a few turns beyond the tape 18.

The tape Ztl is wound so that its shank 34 is parallel to the vessel axis whereby its legs 36 and shank 34 form an inwardly facing channel or groove therebetween running longitudinally along the tape and facing the inner 'tape layer and on the other side of the tape its legs 37 and shank 34 form a similar but outwardly facing channel or groove. The tape 2th wound with the abutting legs 32 of two adjacent turns of the tape 18 received between the legs 36 of a turn of the tape 2% to provide an interlocking connection therebetween. In the free condition of the tapes the length of the shank 34 between the legs 36 of a cross-section of the tape 2% is slightly less than the combined thickness of two abutting legs 32 of adjacent turns of the tape 18 so that the tape 2% must be forced into position over the legs 32 of the tape 18 to form an interference fit between the turns of tapes 1% and 20. To facilitate this interlocking positioning of the tape 24) over the tape 18 the legs 32 of the tape 18 are tapered on their shank sides so that said legs decrease in width toward their outer ends and the legs 36 of the tape 20 are similarly tapered. This taper is indicated in FIG. 3 by the angle A which is the angle between the tapered side of a leg 32 and the direction in which the tapes 18 and 2t} are forced together. The magnitude of this taper angle A is sufficiently small so that the tape 2t) is frictionally held in position on the tape 18 when the tape as is forced over the tape 18 with the desired interference fit and at the same time the angle A is sufliciently large to facilitate said interlocking positioning of the tapes 18 and 2d. In the case of a titanium alloy, an angle A of 5-15 has been found to be satisfactory with this angle preferably being within the smaller range of lll3. The magnitude of the angle A will depend on the coefficient of friction of the material of the tapes l8 and 261.

The dimensions of the cross-section of the tape 20 are such that adjacent turns do not abut each other and instead a helical gap or passage 42 is formed between the helical turns of said tape.

The outer tape 22 is then helically wound over the tape 20 and in the same direction as the tape Ztl is wound to form the outer layer. The tape 22 is started on one of the end extensions 24 or 26 from a point beyond the tape 20 so that a few turns of tape 22 are first formed on said extension. The Winding of the tape 22 is continued over the tape 2-0 forming the intermediate layer and terminates on the other end extension with a few turns beyond the tape Ztl.

The tape 22 is wound so that unlike the tape 18, its legs or ribs it? project radially inwardly whereby each section of the tape 22 has an inwardly directed channel or groove running along the tape but like the tape 18 so that adjacent turns abut each other and so that the abutting legs 4t) of adjacent turns are forced into position with an interference fit between the outwardly directed legs 37 of a turn of the intermediate tape 2E9. Thus the length of the shank 34 between the legs 37 of a crosssection of the tape 2d is slightly less than the combined thickness of two abutting legs ll) of adjacent turns of the tape 26). To facilitate positioning of the tape 22 over the tape Ztl with said interference fit, their interlocking legs 37 and 40 are tapered in a manner similar to the aforedescribed taper of the interlocking legs 32 and 36 of the tapes 18 and 20.

The interference fit between the turns of tape 20 of the intermediate layer with the turns of the tapes l8 and 22 of the inner and outer layers stresses the shank sections 34- of the turns of the intermediate tape Z0. Thus each shank section of the tape 20 in a radial plane including the axis of the vessel 10 is prestressed in tension, by said interference fit, in a direction parallel to said axis. That is, the shank 34 of the tape 20 is prestressed in tension in a direction along the wall portion 16 and transversely of the tape 20. This interlocking interference fit between the turns of the three layers of tape 18, 20 and 22 insures that said tape layers can carry an axial load without a spreading apart of the tape turns along the wall portion 16-.

In FIGS. 1-3 the interference fit is obtained by butting the edges of adjacent turns of the inner and outer tapes l8 and 22 and by stretching the shank portion of the intermediate tape 2% so that the edge ribs 36 and 37 of each turn of the tape Ztl fit over the adjacent legs or ribs of adjacent turns of the tapes 18 and 22. Instead of this arrangement, it is obvious that the tapes 18, 2t) and 3 22 could be so dimensioned and wound that the edges of adjacent turns of the intermediate tape 20' abut each other with the U-shaped sections of the inner and outer tapes being stretched to fit over the adjacent legs or ribs of adjacent turns of the intermediate tape. With this latter arrangement, the shank portions of the inner and outer tapes l8 and 22 would be prestressed transversely in tension instead of the shank portion 34 of the tape 20.

The end extensions 24 and 26 have an enlarged diameter and helically grooved first portion 50, the outer surface of which is a continuation of the outer surface of the inner tape layer formed by the tape 18. With this arrangement a few turns of the tape 20 can readily be wound on each said enlarged diameter portion without any discontinuity in the intermediate tape layer. Said end extensions 24 and 26 also have a second enlarged outer diameter portion 52 which is helically grooved to correspond to the groove between the legs 37 of the tape 2% of the intermediate tape layer. Thus a few turns of the tape 22 can readily be wound on each said enlarged diameter portion 52 without any discontinuity in the outer tape layer.

As described, the end turns of each tape 18, 26* and 22 are wound directly around the end extensions 24 and 26 thereby providing tight frictional engagement therebetween. In addition, the two ends of each tape 18, 2t) and 22 preferaby are positively anchored to the end ex tensions 24 and 26. For example, the ends of tape 22 may be anchored to the extensions 24 and 26 by pins 54 (FIG. 1). The ends of the tapes 18 and 26 may be anchored to said extensions by similar pins (not shown).

Each of the extensions 24 and 26 preferably has a tapered end as indicated at 6t} and 62 respectively so that said ends will more readily yield or deflect outwardly in response to internal pressures. This construction avoids the sharp discontinuity of stress which would otherwise occur in the tape between the portion of the tape supported by the ends 24 and 26 and the adjacent portions not so supported.

After the multi-tape-layer wall portion 16 has been com pleted, the collapsible mandrel 42 is removed. As shown in FIG. 4 the collapsible mandrel 42 may comprise an inner shaft-like core 79 about which segments 72 are disposed to complete the mandrel. The mandrel 42 is collapsed by first pulling out the core 70 through the nozzle opening 14 whereupon the segments 72 collapse and may be removed one at a time through said opening. Obviously, other forms of collapsible mandrels may be employed.

Pressure within the rocket vessel It) will tend to helically unwind the helically wound layers of tape 18, 24B and '22. A suitable cement may be placed between adjacent layers and turns of tape to resist such unwinding. It has been found, however, that the previously described interference fit between the adjacent layers of tape provides sufficient friction to prevent any unwinding of the helically wound tape in response to internal pressures.

The wall portion 16 of the rocket vessel It) may be sealed against gas leakage through said wall by coating the inside of the vessel with a suitable liner 64, for example, of a plastic material such as Teflon or with a suitable epoxy resin. In addition, or in lieu of the plastic liner 64 a suitable sealant may be provided between adjacent turns of the layers of tape 18, 20 and 22. A metallic seal may also be provided between adjacent turns of tape for example by brazing the adjacent turns together with a suitable brazing metal.

When the three layers of tape 18, 2d and 22 are wound in the manner described the helical passage 42 is enclosed and runs from one end of the wall portion 16 to the other. This passage 42 could be used for the circulation of a liquid herethrough. If, for example, the wall portion 16 forms part of the wall of a combustion chamber or nozzle of a liquid fuel rocket then a liquid propellant of the rocket could be circulated through the passage 42 prior to combustion in the rocket. The passage 42 could also be used simply as a liquid storage space.

The wall portion 16 may include a thin metallic liner about which multi-layers of tape 13, 20 and 22 are wound. Such an arrangement is illustrated in FIG. 5 which is otherwise like the arrangement of FIGS. 13. For ease of understanding the parts of FIG. 5 have been designated by the same reference numerals as the corresponding parts of FIGS. 1-3.

In FIG. 5, a metallic liner 74 is provided for the intermediate wall portion 16. The liner 74 may be secured to the end extensions 24 and 26 as by welding or may comprise an integral part of said extension. The liner 74 may eliminate the need for a collapsible mandrel, such as the mandrel 42, to support the tape layers as they are being wound. In FIG. 5 the tape 18, 2t) and 22 is wound in helical fashion, as in FIGS. 1-3, to form a multi-layer tape wrapped wall. Instead of the wall 74 functioning only as a liner it could be made sufiiciently strong to carry a major share of the internal pressure load in which case the wire wound layers 18, 2t and 22 would serve to reinforce said wall.

The invention is not limited to the wall portion 16 comprising precisely three layers of tape wound in helical fashion. The number of tape layers depends on the strength required of the tape Wound wall portion. For example, another or additional sets of three layers obviously could be superimposed for additional strength on the three layer set shown in FIGS. 1-3 or FIG. 5.

FIG. 6 discloses a five layer arrangement in which the inner or first layer consists of tape wound in helical fashion, this tape being similar in cross-section and being wound like the tape 18 forming the inner layer 18 in FIG. 3. Likewise the outer or fifth layer consists of tape 82 wound in helical fashion, this tape being substantially like the tape 8i? and being wound in the same direction as the tape 84 to form the outer layer similar to the outer layer 22 in FIG. 3. Each of the second and fourth intermediate layers consists of similar tapes 84 and 86, respectively, also wound in helical fashion in the same direction as the tapes 8% and 82, each tape 84- and 86 having a dumb-bell like section similar to the tape 20 of FIG. 3 and being wound like said tape 26 so that an interference fit is provided between each of the tape layers 34 and 86 and the adjacent layers to prestress the shank portions of the two tapes 8d and 86 transversely in tension. The tape 88 forming the central layer also has a dumb-bell-like cross-section and has a rib and groove profile on each of its inner and outer faces similar to the rib and groove profile on one of the faces of each of the tapes 8t and 82 whereby the central tape 88 can have an interlocking interference fit with both of the tapes 84 and 86. The tapes till, 82 and 86 are wound so that their edges abut each other whereby an interference fit with the two layers of tape 84 and 86 will place the shank section of the tapes 34 and 36 transversely in tension.

FIG. 6 has the disadvantage that three different shapes and size of tape are required if certain of the layers are to be prestressed transversely in tension whereas only two different kinds are required in FIGS. 13 and in FIG. 5.

Arrangements of interlocked helically wound tape are possible in which only one type of tape is required, for example, as illustrated in FIGS. 7 and 8. In FIG. 7 the tape W has a dumb-bell-like cross-section and each layer is wound in helical fashion from end 24 and 26 to the other. As shown in FIG. 7 successive layers of tape 90 are wound to interlock with the adjacent layers.

FIG. 8 discloses a two layer construction in which the tape 92 of each layer is generally similar to the tapes 18 and 22 of FIG. 3. Thus the tape 92 has a U-shaped crosssection such that legs or ribs 94 run along its two longitudinal edges on one side of the tape to form a channel or groove 96 therebetween. The tape 92 of the inner layer has its channel or groove 96 facing outwardly while the tape 92 of the outer layer has its channel or groove 96 facing inwardly. The tape 92 is wound so that adjacent turns of each layer have their adjacent legs 94 interlockingly received within a channel or groove 96 of a turn of the other layer. The multi-layer tape-wound wall section of FIG. 8 has the advantage that like, FIGS. 1-3 and 6, the inner and outer surfaces of said wall section are smooth.

As previously stated, the invention is not limited to cylindrical vessels. Thus in FIG. S-the tape Wound section illustrated has a conical shape which could, for example, form part of the exhaust nozzle of a rocket.

If as described in connection with FIGS. 13, the hollow body 10 is to be used as a rocket casing, the tape used to form the wall portion 16 could be made of such materials as steel, aluminum, tungsten, titanium and beryllium. For reason of strength the tape preferably is of small cross-section. With a rocket casing 10 of approximately sixty inches in diameter and with tape made of a suitable titanium alloy, the tape 18 of FIG. 3 may have a cross-section such that its width is approximately 0.2 inch and its maximum height is approximately 0.025 inch. The invention, however, is not limited to any specific tape dimension. In general, tapes of larger crosssectional area will be used for larger diameter vessels. Also, where the invention is applied to a casing for a rocket using a solid propellant, the interlocked tape wall portion could be wound directly on the solid propellant.

While we have described our invention in detail in its present preferred embodiment, it will be obvious to those skilled in the art, after understanding our invention, that various changes and modifications may be made therein without departing therefrom. We aim in the appended claims to cover all such modifications.

We claim as our invention:

1. A hollow pressure vessel comprising a pair of spaced end members and an intermediate cylindrical wall interconnecting said end members; said intermediate wall consisting of at least three superimposed layers of tape wound in helical fashion from one end member to the other, the tape of the intermediate layer having a pair of internal ribs and a pair of external ribs running longitudinally along the edges of the tape to form respectively an internal longitudinal groove and an external longitudinal groove between the ribs, the tape of the inner of said layers having a pair of external ribs running longitudinally along the edges of the tape to form a longitudinal external groove therebetween and the outer of said layers having a pair of internal ribs running longitudinally along the edges of the tape to form a longitudinal internal groove therebetween, said layers being wound so that a pair of adjacent ribs on adjacent turns of each layer are received within a facing groove of a turn of an adjacent layer and the relative widths of the ribs and grooves being such that adjacent turns of both the inner and outer layers abut each other with each pair of abutting ribs of the inner layer being tightly received within the facing internal groove of the intermediate layer and with each pair of abutting ribs of the outer layer being tightly received within the facing external groove of the intermediate layer, the longitudinal groove of each of said inner and outer layers being substantially wider than the combined widths of the ribs of the intermediate layer received therein so that adjacent turns of the intermediate layer are spaced a substantial axial distance apart.

2. A hollow pressure vessel as claimed in claim 1 and in which the inner surface of said inner tape layer and the outer surface of said outer tape layer both form a substantially smooth cylindrical surface.

3. A hollow pressure vessel comprising a pair of spaced end members and an intermediate cylindrical Wall interconnecting said end members; the load carrying portion of said intermediate wall consisting substantially solely of at least three superimposed layers of tape wound in helical fashion from one end member to the other, the tape of the intermediate layer having a pair of internal ribs and a pair of external ribs running longitudinally along the edges of the tape to form respectively an internal longitudinal groove and an external longitudinal groove between the ribs, the tape of the inner of said layers having a pair of external ribs running longitudinally along the edges of the tape to form a longitudinal external groove therebetween and the outer of said layers having a pair of internal ribs running longitudinally along the edges of the tape to form a longitudinal internal groove therebetween, said layers being wound so that a pair of adjacent ribs on adjacent turns of each layer are received within a facing groove of a turn of an adjacent layer and the relative widths of the ribs and grooves being such that adjacent turns of both the inner and outer layers abut each other with each pair of abutting ribs of the inner layer being tightly received within the facing internal groove of the intermediate layer'and with each pair of abutting ribs of the outer layer being tightly received within the facing external groove of the intermediate layer, the longitudinal groove of each of said inner and outer layers being substantially wider than the combined widths of the ribs of the intermediate layer received therein so that adjacent turns of the intermediate layer are spaced a substantial axial distance apart.

References Cited in the file of this patent UNITED STATES PATENTS 417,800 Webb Dec. 24, 1889 1,004,142 Brown Sept. 26, 1911 1,962,428 Colbie June 12, 1934 2,326,176 Schierenbeck Aug. 10, 1943 2,640,501 Scott et a1. June 2, 1953 2,822,825 Enderlein et al Feb. 11, 1958 2,964,209 Eddy Dec. 13, 1960 2,984,379 Borzsei et al May 16, 1961

Claims (1)

1. A HOLLOW PRESSURE VESSEL COMPRISING A PAIR OF SPACED END MEMBERS AND AN INTERMEDIATE CYLINDRICAL WALL INTERCONNECTING SAID END MEMBERS; SAID INTERMEDIATE WALL CONSISTING OF AT LEAST THREE SUPERIMPOSED LAYERS OF TAPE WOUND IN HELICAL FASHION FROM ONE END MEMBER TO THE OTHER, THE TAPE OF THE INTERMEDIATE LAYER HAVING A PAIR OF INTERNAL RIBS AND A PAIR OF EXTERNAL RIBS RUNNING LONGITUDINALLY ALONG THE EDGES OF THE TAPE TO FORM RESPECTIVELY AN INTERNAL LONGITUDINAL GROOVE AND AN EXTERNAL LONGITUDINAL GROOVE BETWEEN THE RIBS, THE TAPE OF THE INNER OF SAID LAYERS HAVING A PAIR OF EXTERNAL RIBS RUNNING LONGITUDINALLY ALONG THE EDGES OF THE TAPE TO FORM A LONGITUDINAL EXTERNAL GROOVE THEREBETWEEN AND THE OUTER OF SAID LAYERS HAVING A PAIR OF INTERNAL RIBS RUNNING LONGITUDINALLY ALONG THE EDGES OF THE TAPE TO FORM A LONGITUDINAL INTERNAL GROOVE THEREBETWEEN, SAID LAYERS BEING WOUND SO THAT A PAIR OF ADJACENT RIBS ON ADJACENT TURNS OF EACH LAYER ARE RECEIVED WITHIN A FACING GROOVE OF A TURN OF AN ADJACENT LAYER AND THE RELATIVE WIDTHS OF THE RIBS AND GROOVES

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