GB2228771A - Refuelling surge boot - Google Patents

Abstract

A double-walled tubular bladder (82) is contained in a tubular casing (24) mounted between sections (20, 22) of a fuel line. The casing (24) has an outer shell (26), an inner shell (28) and end caps (30, 32). The inner shell (28) has a plurality of openings (80) for communicating fuel pressure to the bladder (82) which contains a compressible fluid so that the bladder (82) may be contracted by a shutoff shock in the fuel line to alleviate this shock. The bladder may be made by wrapping an inner ply on a cylindrical mandrel, inserting the inner ply and cylindrical mandrel in a tubular mandrel, wrapping an outer ply on the tubular mandrel, and joining the ends of the outer ply and the inner ply. The outer ply is cut diametrically so that the bladder can be pulled off the tubular mandrel and cut edges of the outer ply are spliced and the bladder placed in a mould for vulcanization. <IMAGE>

Description

REFUELING SURGE BOOT BACKGROUND OF THE INVENTION This invention relates to fuel surge shock alleviating apparatus and especially to apparatus which can be positioned in the fuel line of an inflight refueling system. Heretofore a fuel surge shock alleviator has been provided which is of the diaphragm type and is relatively large and heavy for aircraft. A surge suppressor has also been proposed for reducing fuel pulsation in fuel handling systems and includes a cylindrical elastic diaphragm at a radially inner wall of a tubular chamber of the suppressor. The chamber is pressurized so that when a pressure surge occurs the elastic diaphragm will be expanded against the counteracting pressure exerted by the compressed fluid in the chamber. The diaphragm is clamped at the edges along one side of the chamber in the suppressor and is stretched by the pulsations in the fuel line.These pulsations subject the material of the diaphragm to repeated stresses which results in high stress areas at the clamped edges. The life of the diaphragm is also limited due to the repeated stretching of the diaphragm in tension due to the pulsations in the fuel line.

SUMMARY OF THE INVENTION With the refueling surge boot of this invention, the compressed fluid is contained in a double-walled tubular bladder.positioned in a chamber in a tubular casing. There is no clamping of the bladder walls and accordingly the likelihood of tearing the bladder has been reduced or eliminated.

There is also no problem with sealing the space containing the compressed fluid because the fluid is fully enclosed in the bladder. The method of making the surge boot of this invention is also simplified because there is no clamping of the edges of a diaphragm to provide a fluid-tight seal. The bladder is enclosed in a cavity in the tubular casing and is inflated to a predetermined pressure during installation. Thereafter the bladder is contracted and the fluid in the bladder compressed without stretching the bladder walls and or placing high stress on clamped portions a diaphragm. This construction, therefore, need not be of a heavy construction to withstand high stresses from clamping and stretching of a diaphragm but may be of a relatively small size and a lightweight construction.A unique method of making the surge boot also contributes to the reduction in size and weight of the unit. This method of making the bladder in steps includes partially vulcanizing the bladder on a tubular core, cutting the bladder so that it can be stripped off the core and then splicing the cut edges and vulcanizing the bladder an additional amount in a mold with compressed fluid in the bladder.

BRIEF DESCRIPTION OF THE DRAWINGS Fig 1 is a schematic view showing the refueling wing pod mounted on an aircraft wing with the fuel hose and drogue extended.

Fig 2 is a side elevation of the refueling surge boot shown partly in section with parts being broken away and with the sections of fuel line and the contour of the contracted bladder wall being shown in dot-dot-dash lines.

Fig 3 is an end view taken along line 3-3 in Fig 2 with parts being broken away.

Figs 4 through 11 are schematic views reduced in size illustrating the method of making the bladder.

DETAILED DESCRIPTION Referring to Fig 1 a refueling wing pod 10 is illustrated mounted on a wing 12 shown schematically in dot-dot-dash lines with a fuel hose 14 extended and a drogue 16 in position for refueling another aircraft (not shown). Referring to Figs 2 and 3, a refueling surge boot 18 is shown which is mounted in the wing pod 10 between sections 20 and 22 shown in dot-dot-dash lines of a fuel line in the wing pod 10 connected to the fuel hose 14 and to a fuel pump (not shown).

The refueling surge boot 18 is in the form of a tubular casing 24 having a generally cylindrical outer shell member 26 and a generally cylindrical inner shell member 28 spaced radially inward from the outer shell member and cap mem-bers 30 and 32, positioned between the outer shell member 26 and inner shell member 28, are generally circular and have recessed surfaces 34 and 36 for receiving edge portions 38 and 40, respectively, of the outer shell member. Suitable fasteners such as screws 42 and 44 extend through flanges 46 and 48 of the end cap members 30 and 32 into edges 50 and 52 of the end cap members at circumferentially spaced positions around the ends 54 and 56 of the tubular casing 24.

Suitable sealing means such as O-rings 58 and 60 are positioned in grooves 62 and 64 in the edges 50 and 52 of the outer shell member 26 for engagement with the surfaces of the flanges 46 and 48.

Inner surfaces 66 and 68 of the end cap members 30 and 32 have generally the same diameter as the inner diameter of the inner shell member 28 and are recessed to provide inset portions 70 and 72 having substantially the same outer diameter as the inner shell member 28 for holding the inner shell member in a position spaced radially inward from the outer shell member 26. A cavity 74 is enclosed by the outer shell member 26, inner shell member 28 and end cap members. 30 and 32. The end cap members 30 and 32 may have flanges 76 and 78 for fastening the end cap members to the fuel line sections 20 and 22.

A plurality of spaced-apart openings such as holes 80, which may be drilled or stamped in the inner shell member 28, are provided for communication of fuel pressure between the space within the inner shell member and the cavity 74.

A tubular bladder 82 is positioned in the cavity 74 and may be of a stretch fabric 84 coated such as a knit-type nylon fabric with an elastomeric material such as nitrile rubber.

Referring to Figs 4 through 11, a preferred method of making the bladder 82 is illustrated. In Figs 4 and 5, a cylindrical mandrel 86, rotatable on a shaft 88, has a cylindrical surface 90 on which an inner ply 92 is wrapped with the edges 94 and 96 fastened together as by an overlapped splice 98.

As shown in Figs 6 and 7, the cylindrical mandrel 86, with the inner ply 92 applied to the outer surface 90 may then be inserted in a tubular mandrel 100 having an inner diameter substantially the same as the outer diameter of the inner ply 92.

The tubular mandrel 100 may then be rotated on the cylindrical mandrel 86 and an outer ply 102 of the stretch fabric 84 coated with rubber wrapped around an outer surface 104 of the tubular mandrel with edges 106 and 108 of the outer ply being overlapped to form an overlapped splice 110. Ends 112 and 114 of the inner ply 92 being are then folded radially outward and ends 116 and 118 of the outer ply 102 are folded radially inward to form overlapped end splices 120 and 122 and thereby form the tubular bladder 82.

An inlet member such as valve 124 may be mounted on the outer ply 102 for inflating the bladder 82.

Referring to Fig 8, the tubular mandrel 10Q with the bladder 82 is placed in a suitable vulcanization environment such as in an autoclave 125 shown schematically in dot-dot-dash lines for partially curing the rubber in the outer ply 102 and inner ply 92 as well as the splices 98, 110, 120 and 122 in the bladder.

After partially curing the bladder 82, the tubular mandrel 100 and bladder are removed from the autoclave 125 and the cylindrical mandrel 86 inserted inside the inner ply 92. A cutter such as a rotary knife 126 is moved into engagement with the outer ply 102 at a position 128 spaced from an edge 130 of the tubular mandrel 100. The cylindrical mandrel 86 is then rotated about the shaft 88 cutting the outer ply 102 at the position 128 extending around the tubular mandrel 100 and providing cut edges 132 and 134. The rotary knife 126 is then retracted and the tubular mandrel 100 along with the bladder 82 removed from the cylindrical mandrel 86. The bladder 82 is pulled off the tubular mandrel 100 with the edge 132 being pulled through the opening in the tubular mandrel.

The bladder 82 then has the configuration shown in Fig 10 with the cut edges 132 and 134 in close proximity. The cut edges 132 and 134 are spliced as by applying a reinforcing splicing tape 136 to the inner surface of the bladder 82 and then applying a splicing tape 138 to the outer surface of the bladder overlapping the cut edges 132 and 134 as shown in Fig 11. The bladder 82 is then placed in a mold 140 with a core 142 filling the space within the inner ply 92. The bladder 82 is inflated through the valve 124 and the mold 140 placed in a vulcanization environment, such as the autoclave 125, where the bladder is completely vulcanized along with the splice between the cut edges 132 and 134.The inflating fluid is then released from the valve 124 and the mold 140 disassembled so that the vulcanized bladder 82 can be removed from the mold and installed in the cavity 74 within the tubular casing 24 as shown in Figs 2 and 3. The valve 124 extends outwardly through an opening 144 in the outer shell member 26. Sealing means such as washers 146 may be provided to seal the opening 144 around the valve 124.

In operation, fuel is pumped from the tanks in the aircraft wing 12 through the fuel line sections 20 and 22 and through the inner shell member 28 to the fuel hose 14 and - drogue 16 which is connectable with a corresponding fuel receiving probe (not shown) of the aircraft. The bladder 82 is inflated with a suitable fluid such as air to a pressure of from about 50 psi (244 kg/cm2) to 200 psi (976.5 kg/cm2) and preferably about 150 psi (732 kg/cm2). During refueling, the aircraft being refueled may be suddenly separated from the drogue 16 by turbulence in the air causing a sudden shutting off of the fuel at the drogue resulting in a fuel shutoff shock which substantially increases the pressure in the hose 14 and fuel line sections 20 and 22 as well as other parts of the system.When this happens the bladder 82 is compressed with the inner ply 92 being deformed into the shape similar to that shown in dot-dot-dash lines in Fig 2. This deformation compresses the air in the bladder 82 and alleviates the shock protecting the system from damage.

In the embodiment shown, the surge boot 18 has an outside diameter of about 6 inches (15.24 cm) and a length of about 18 inches (45.72 cm) with a weight of about 22 pounds (9.98 kg). This replaces a shock alleviator of a much larger size and a weight of about 53 pounds (24.04 kg). The inside diameter of the inner shell member 28 is about 2 1/2 inches (6.33 cm) and the holes 80 each have a diameter of about 5/32 inch (.40 cm) with eight holes equally spaced around the inner shell member at 1 inch (2.54 cm) intervals.

While a certain representative embodiment and details have been shown for the purpose of illustrating the invention, it will be apparent to those skilled in the art that various changes and modifications may be made therein without departing from the spirit or scope of the invention.

Claims (13)

1. A refueling surge boot for alleviating fuel shutoff shock in a fuel line comprising a generally tubular casing for mounting between sections of said fuel line, said tubular casing having a generally cylindrical outer shell, a generally cylindrical inner shell spaced radially inward from said outer shell, end caps mounted on the ends of said tubular casing in sealing engagement with said outer shell forming an enclosed cavity within said tubular casing, a tubular bladder positioned in said cavity, a fluid inlet member fastened to said bladder, an opening in said tubular casing for said fluid inlet member and sealing means between said inlet member and said tubular casing, said fluid inlet member being in communication with a source of compressible fluid for inflating said bladder, a plurality of openings in said inner shell communicating fluid pressure from the space within said inner shell resulting from pressure in said fuel line to said cavity to contract said bladder and compress said compressible fluid in said bladder upon shutoff of said fuel line during refueling in flight.

2. The refueling surge boot of claim 1 wherein said bladder is of a fabric reinforced resilient rubberlike material.

3#. The refueling surge boot of claim 1 wherein said end caps have flanges for sealing engagement with with said sections of said fuel line for conveying fuel through said tubular casing between said sections of said fuel line.

4. The refueling surge boot of claim 1 wherein a sealing O-ring is clamped between each of said end caps and corresponding ends of said outer shell to prevent leakage of fuel from said tubular casing in operation.

5. The refueling surge boot of claim 1 wherein said opening in said tubular casing for said fluid inlet member is located in said outer shell.

6. The refueling surge boot of claim 1 wherein said plurality of said openings in said inner shell for communicating fluid pressure to said cavity includes a plurality of spaced-apart holes in said inner shell.

7. A method of making a refueling surge boot for alleviating shutoff shock in a fuel line comprising forming a tubular casing means from a generally cylindrical outer shell means, a generally cylindrical inner shell means spaced radially inward from said outer shell means, and end cap means mounted on the ends of said tubular casing means in sealing engagement within said outer shell means enclosing a cavity within said tubular casing, positioning a tubular bladder in said cavity during assembly of said outer shell means with said end cap means and said inner shell means, fastening an inlet member to said bladder for communication with a source of compressible fluid for inflating said bladder, forming an opening in said tubular casing for said inlet member, positioning a sealing means between said inlet member and said tubular casing, forming a plurality of openings in said inner shell means for communicating fluid pressure from the space within said inner shell means to said cavity to contract said bladder and compress said compressible fluid in said bladder upon shutoff of said fuel line during operation.

8. The method of claim 7 wherein said tubular bladder is made by: (a) wrapping an inner ply of flexible elastomeric material around a cylindrical mandrel and fastening the edges of said inner ply; (b) positioning said inner ply and said cylindrical mandrel inside a tubular mandrel; (c) wrapping an outer ply of flexible elastomeric material around an outer surface of said tubular mandrel and fastening the edges of said outer ply; (d) joining the ends of said inner ply to the ends of said outer ply by folding the ends over the edges of said tubular mandrel to form said tubular bladder; (e) partially vulcanizing said inner ply and said outer ply of said tubular bladder on said tubular mandrel; (f) cutting said outer ply at a position spaced from one of said edges of said tubular mandrel and said position extending around said tubular mandrel;; (g) pulling said partially vulcanized tubular bladder off said tubular mandrel with a portion of said outer ply being pulled through the opening in said tubular mandrel; (h) splicing cut edges of said outer ply with an overlapping splice means; (i) attaching inlet means to said tubular bladder; (j) placing said partially cured tubular bladder in a mold for confining said outer ply and said inner ply to the radii of the finished tubular bladder and inflating said bladder; (k) heating said mold to complete the vulcanization of said inner ply and said outer ply and to vulcanize said splice means; and (1) deflating said tubular bladder and removing said bladder from said mold.

9. The method of claim 8 wherein said inner ply and said outer ply include a reinforcing fabric coated with elastomeric material.

10. The method of claim 8 wherein said cutting of said outer ply includes rotating said tubular mandrel while engaging the surface of said outer ply with a cutter knife at said position spaced from one of said edges of said tubular mandrel.

11. The method of claim 8 wherein said splicing of said cut edges of said outer ply comprises overlapping the cut edges of said outer ply with reinforced splicing tape on the inside and outside of said outer ply.

12. The method of claim 8 wherein said inlet means is attached to said outer ply of tubular bladder.

13. Apparatus or method substantially as described herein and as shown in the accompanying drawings.