Self-balancing pressure bulkhead

Abstract

A pressure bulkhead for a vehicle disclosed. The pressure bulkhead is configured to separate a pressurized interior from an unpressurized interior of the vehicle. The pressure bulkhead includes a bulkhead wall having a radially inner disk and a radially outer compression ring. The radially inner disk has a surface and a first thickness and the radially outer compression ring having a second thickness that is greater than the first thickness. The radially outer compression ring defines a periphery of the bulkhead wall and the second thickness of the radially outer compression ring is effective to provide a strength to oppose meridional and hoop stresses across the surface of the radially inner disk in response to a pressure differential across the bulkhead wall. The pressure bulkhead also includes an attachment ring that is affixed to the periphery of the bulkhead wall.

Claims

1. A pressure bulkhead for a vehicle, wherein the pressure bulkhead is configured to separate a pressurized interior from an unpressurized interior of the vehicle, the pressure bulkhead comprising: a bulkhead wall having a periphery, a radially inner disk, and a radially outer compression ring having a thickness that is effective to provide a strength to oppose meridional and hoop stresses across the radially inner disk in response to a pressure differential across the bulkhead wall; and an attachment ring that is affixed to the periphery of the bulkhead wall, the attachment ring having an inner band and an outer band, wherein the outer band defines a concave surface that is configured to face towards the unpressurized interior of the vehicle.

2. The pressure bulkhead of claim 1, wherein the attachment ring is composed of at least one of carbon fiber reinforced plastic and metal.

3. The pressure bulkhead of claim 1, wherein the radially inner disk and the radially outer compression ring are composed of the same material.

4. The pressure bulkhead of claim 1, wherein the radially inner disk and the radially outer compression ring are both composed of at least one of carbon fiber reinforced plastic and metal.

5. The pressure bulkhead of claim 1, further comprising a plurality of attachment clips that are located along the concave surface of the outer band of the attachment ring.

6. The pressure bulkhead of claim 5, wherein the attachment clips are configured to affix the attachment ring to a wall of the vehicle.

7. The pressure bulkhead of claim 1, wherein the attachment ring is affixed to the bulkhead wall by mounting the periphery of the bulkhead wall on the concave surface of the attachment ring.

8. The pressure bulkhead of claim 1, wherein the attachment ring is affixed to the bulkhead wall by mounting the radially outer compression ring on the concave surface of the attachment ring.

9. A vehicle, comprising: a pressurized interior and an unpressurized interior; and a pressure bulkhead separating the pressurized interior from the unpressurized interior of the vehicle, the pressure bulkhead comprising: a bulkhead wall having a radially inner disk and a radially outer compression ring, the radially inner disk having a surface and a first thickness and the radially outer compression ring having a second thickness that is greater than the first thickness, wherein the radially outer compression ring defines a periphery of the bulkhead wall and the second thickness of the radially outer compression ring is effective to provide a strength to oppose meridional and hoop stresses across the surface of the radially inner disk in response to a pressure differential across the bulkhead wall; and an attachment ring that is affixed to the periphery of the bulkhead wall, the attachment ring having an inner band and an outer band, wherein the outer band defines a concave surface that is configured to face towards the unpressurized interior of the vehicle.

10. The vehicle of claim 9, wherein the attachment ring is composed of at least one of carbon fiber reinforced plastic and metal.

11. The vehicle of claim 9, wherein the radially inner disk and the radially outer compression ring are composed of the same material.

12. The vehicle of claim 9, wherein the radially inner disk and the radially outer compression ring are both composed of at least one of carbon fiber reinforced plastic and metal.

13. The vehicle of claim 9, further comprising a plurality of attachment clips that are located along the concave surface of the outer band of the attachment ring.

14. The vehicle of claim 13, wherein the attachment clips are configured to affix the attachment ring to a wall of the vehicle.

15. The vehicle of claim 9, wherein the attachment ring is affixed to the bulkhead wall by mounting the periphery of the bulkhead wall on the concave surface of the attachment ring.

16. The vehicle of claim 9, wherein the attachment ring is affixed to the bulkhead wall by mounting the radially outer compression ring on the concave surface of the attachment ring.

17. The vehicle of claim 9, wherein the vehicle is one of an aircraft, a spacecraft, a marine vessel, and a land vehicle.

18. A method for mounting a bulkhead wall in an aircraft, the method comprising: affixing an attachment ring to a fuselage skin of the aircraft, wherein the attachment ring includes an inner band and an outer band, the outer band defining a concave surface; directing the concave surface of the outer band towards an unpressurized interior of the aircraft; separating the unpressurized interior from a pressurized interior of the aircraft by attaching an outer periphery of the bulkhead wall to the attachment ring, wherein the bulkhead wall has a radially inner disk and a radially outer compression ring and the radially inner disk has a first thickness and the radially outer compression ring has a second thickness that is greater than the first thickness, and wherein the radially outer compression ring defines a periphery of the bulkhead wall; and in response to experiencing a pressure differential across the bulkhead wall, providing, by the radially outer compression ring, a strength to oppose meridional and hoop stresses across the surface of the radially inner disk.

19. The method of claim 18, further comprising: locating a plurality of attachment clips along the concave surface of the outer band of the attachment ring; and affixing the attachment ring to a wall of the aircraft by the attachment clips.

20. The method of claim 18, further comprising: affixing the attachment ring to the bulkhead wall by mounting the periphery of the bulkhead wall on the concave surface of the attachment ring.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a schematic, perspective view of the disclosed self-balancing pressure bulkhead, shown mounted in an aircraft;

(2) FIG. 2 is a perspective view of the self-balancing pressure bulkhead of FIG. 1, taken from the pressurized side, shown mounted in a section of aircraft fuselage;

(3) FIG. 3 is a front elevational view of the self-balancing pressure bulkhead of FIG. 1, taken from the pressurized side, shown mounted in the section of aircraft fuselage;

(4) FIG. 4 is a detail taken at line C-C of FIG. 3;

(5) FIG. 5 is a detail taken at line B-B of FIG. 3;

(6) FIG. 6 is a detail showing an exploded view in perspective of the self-balancing pressure bulkhead of FIG. 1 and an associated vehicle fuselage;

(7) FIG. 7 is a detail showing a perspective view of the self-balancing pressure bulkhead of FIG. 1, annular bracket, and clip for mounting the pressure bulkhead to the aircraft fuselage;

(8) FIG. 8 is a diagram of the forces on the self-balancing pressure bulkhead of FIG. 1 in meridional, hoop and normal directions.

(9) FIG. 9 is a front elevational view of an alternative embodiment of the disclosed self-balancing pressure bulkhead, taken from the pressurized side; and

(10) FIG. 10 is a detail taken at line D-D of FIG. 9.

DETAILED DESCRIPTION

(11) As shown in FIGS. 1 and 2, the disclosed self-balancing pressure bulkhead, generally designated 11, may be in the form of a disk or a dome, or be dome-shaped, and shaped for placement inside a vehicle, which in an embodiment may be aircraft 12, for example in the fuselage 14 of the aircraft, to separate a pressurized fuselage interior 16 (e.g., a pressurized cabin) from an unpressurized fuselage interior 18. Other types of vehicles may employ the bulkhead 11, such as spacecraft, reentry vehicles, orbiting space stations, land vehicles, and marine vehicles such as submarines. Pressure bulkhead 11 may be attached to fuselage skin 20 such that the pressure bulkhead does not shift along fuselage longitudinal axis A of the aircraft 12.

(12) The terms meridional and hoop stresses with respect to a bulkhead wall may be known to a person of ordinary skill in the art. For example, without being limited to a particular theory, in an infinitesimally small truncated conical bulkhead wall section 22, equilibrium equations for normal, meridional and hoop stresses may also be derived for an infinitesimally small conical shell element as shown in the progression of equations below with reference to FIG. 8. In FIG. 8, N.sub. and N.sub. are membrane stress resultants in the meridional and circumferential (hoop) directions (N/m), respectively, in the bulkhead 11 of FIGS. 1 and 2; N.sub. is a shear stress resultant (N/m); p.sub.n, p.sub., p.sub. are distributed surface loadings in the normal, circumferential and meridional directions (N/m.sup.2) respectively; R is radius of a theoretical barrel/cylinder (m); and is the angle of spread. (For a detailed explanation, http://www.kpq.ie/research/shelltheory.html.)

(13) From a triangle: cos =sin and sin =cos

(14) $h=\frac{z}{\sin }=\frac{z}{\cos }\mathrm{and}R=\frac{\cos }{\sin }z=\frac{\sin }{\cos }z,\mathrm{hence}R=\frac{\sin }{\cos }z\mathrm{and}Rh=zz\frac{\sin }{\cos }.$

(15) Use small angle approximation: As .fwdarw.0, cos .fwdarw.1 and sin .fwdarw., and also .sup.20, N.sub.0, N.sub.0, N.sub.0, Rh0.

(16) Normal Equilibrium:

(17) $\begin{array}{cc}{p}_n\left(R+R\right)h=N_{}h\cos p_{n}Rh+p_{n}Rh=N_{}h\cos p_{n}zz\frac{\sin }{\cos }\frac{1}{\cos }=N_{}z\frac{\cos }{\cos }{N}_{}=p_{n}z\frac{\sin }{{\cos }^2}{N}_{}=p_{n}z\sec \tan & \left(1\right)\end{array}$

(18) Circumferential Equilibrium:

(19) $N_{}R+N_{}h=\left(N_{}+N_{}\right)\left(R+R\right)+\left(N_{}+N_{}\right)h+p_{}\left(R+R\right)h+N_{}h\sin$$N_{}h+N_{}R+N_{}R+N_{}R+p_{}Rh+N_{}h\sin =0$$\frac{N_{}z}{\cos }+\frac{N_{}z\sin }{\cos }+\frac{N_{}z\sin }{\cos }+\frac{N_{}z\sin }{\cos }+\frac{p_{}zz}{\cos }+\frac{N_{}z\sin }{\cos }=0$$\frac{N_{}}{}.Math.\frac{1}{\sin }+N_{}+\frac{z{N}_{}}{z}+p_{}z\frac{1}{\cos }+N_{}=0$

(20) But from equation,

(21) $\begin{array}{cc}{N}_{}=p_{n}z\frac{\sin }{{\cos }^2}\mathrm{hence}\frac{N_{}}{}=\frac{z{p}_n}{}\frac{\sin }{{\cos }^2}2N_{}+\frac{z{N}_{}}{z}=-z\frac{1}{\cos }\left(p_{}+\frac{1}{\cos }z\frac{p_n}{}\right)2N_{}+\frac{z{N}_{}}{z}=-z\sec \left(p_{}+\sec z\frac{p_n}{}\right)& \left(2\right)\end{array}$

(22) Meridional Equilibrium:

(23) $N_{}R+N_{}h+N_{}h\sin =p_{}\left(R+R\right)h+\left(N_{}+N_{}\right)\left(R+R\right)+\left(N_{}+N_{}\right)h$$N_{}h\sin =p_{}Rh+N_{}R+N_{}R+N_{}R+N_{}h$$\frac{N_{}h\sin }{\cos }=\frac{p_{}zz\sin }{{\cos }^2}+\frac{N_{}z\sin }{\cos }+\frac{N_{}z\sin }{\cos }+\frac{N_{}z\sin }{\cos }+\frac{N_{}z}{\cos }$$N_{}=p_{}z\frac{1}{\cos }+N_{}+\frac{z{N}_{}}{z}+N_{}+\frac{N_{}}{}\frac{1}{\sin }$$N_{}+\frac{z{N}_{}}{z}=-\frac{N_{}}{}\frac{1}{\sin }+N_{}-p_{}z\frac{1}{\cos }-N_{}$

(24) But from Equation 1,

(25) $\begin{array}{cc}{N}_{}=p_{n}z\frac{\sin }{{\cos }^2}{N}_{}+\frac{z{N}_{}}{z}=-\frac{1}{\sin }\frac{N_{}}{}+z\frac{1}{\cos }\left(p_n\frac{\sin }{\cos }-p_{}\right)N_{}+\frac{z{N}_{}}{z}=-\mathrm{cosec}\frac{N_{}}{}+z\sec \left(p_n\tan -p_{}\right)& \left(3\right)\end{array}$

(26) In an embodiment, as shown in FIG. 3, the pressure bulkhead 11 may include a bulkhead wall 24 having a radially inner disk 26 and a radially outer compression ring 28, the outer compression ring being reinforced to balance meridional and hoop stresses sustained by the bulkhead wall in response to a pressure differential across the pressure bulkhead. The radially inner disk 26 may be unitary with the outer compression ring 28 and made of the same material as the outer compression ring.

(27) In an embodiment, as shown in FIGS. 3, 4, and 5, the radially inner disk 26 may have a first thickness y, and the outer compression ring 28 may have a second thickness z greater than the first thickness y. In an embodiment, the thickness of the radially inner disk 26 tapers from an outer periphery 30 adjacent the outer compression ring 28 to a center 32 of the pressure bulkhead 11.

(28) In an embodiment, the taper:distance ramp may be from about 1:5 to about 1:100. In an embodiment, the bulkhead wall 24, that is, the radially inner disk 26 and the outer compression ring 28, may be made of carbon fiber reinforced plastic (CFRP). In an embodiment, the taper:distance ramp for a CFRP bulkhead wall may be from about 1:10 to about 1:100.

(29) In an embodiment, the bulkhead wall 24, that is, the radially inner disk 26 and the outer compression ring 28, may be made of a metal, for example, aluminum or an aluminum alloy. In an embodiment, the taper:distance ramp for a metal bulkhead wall may be from about 1:5 to about 1:10. In an embodiment, the ramp may be from a step function to a ramp from 1:1 to 1:100.

(30) In an embodiment, the pressure bulkhead 11 further may include a plurality of stiffeners 34 attached to the bulkhead wall 26 and extending in a radial direction, for example, a meridional direction, from center 32 toward the outer compression ring 28. The stiffeners 34 may be evenly spaced about the bulkhead wall 26 in a spoke-like fashion as shown in FIG. 3, or in embodiments may be unevenly spaced. The plurality of stiffeners 34 may include a shorter stiffener 36 and/or a longer stiffener 38.

(31) In an embodiment, the bulkhead 11 may include one or more tear straps and/or reinforcement regions, for example, annular tear straps 40 attached to the bulkhead wall 24 (see FIG. 2). Stiffeners 34 and annular tear strips 40 may form a plurality of tear regions 42. In an embodiment, the reinforcement regions may be of any configuration, dimension and/or orientation along the bulkhead wall, for example, those known to one of skill in the art as polar or Cartesian regions,

(32) With reference to FIGS. 4, 6, and 7, in an embodiment, the pressure bulkhead 11 may include an attachment mechanism in the form of an attachment ring 44 attached to the outer compression ring 28. In another embodiment, the attachment of the bulkhead wall 24 to the attachment ring 44 may be by means such as by an adhesive, by a plurality of screws (not shown) spaced about the periphery of the bulkhead wall 24, or by rivets (not shown) spaced about the periphery of the bulkhead wall, and the like.

(33) With reference to FIGS. 1, 4, 6, and 7, in an embodiment, the bulkhead 10 may further comprise a plurality of clips 46 configured to attach the attachment ring 44 to a wall 48 of, for example, an aircraft fuselage 14. In an embodiment, the wall 48 may be the skin 20 of an aircraft. The clips 46 may be attached to the skin 20 of the aircraft by, for example, bolting the clips to the skin.

(34) With reference to FIGS. 1, 4, 5, 6, and 7, in an embodiment, the pressure bulkhead 10 may include a bulkhead wall 24 having a radially inner disk 26 made of an isotropic carbon fiber reinforced plastic laminate, and an outer compression ring 28 made of an orthotropic carbon fiber reinforced plastic laminate attached to and extending about a periphery 30 of the radially inner disk 26. In an embodiment, the outer compression ring 28 may be selected to be of sufficient strength to balance meridional and hoop stresses sustained by the dome-shaped bulkhead wall 24 in response to a pressure load applied to the bulkhead wall, such as a pressure differential across the bulkhead wall. In an embodiment, a taper region 56 of radially inner disk 26 extending from periphery 30 toward center 32 may include isotropic carbon fiber reinforced plastic laminate and/or orthotropic carbon fiber reinforced plastic laminate.

(35) The terms isotropic carbon reinforced plastic laminate and orthotropic carbon reinforced plastic laminate may be known to a person of ordinary skill in the art and such laminates may be constructed according to known methods. In an embodiment, an orthotropic carbon reinforced plastic laminate may include laminates preferentially oriented along a circumferential, or hoop, stress resultant to balance such pressure-load stresses. With reference to FIG. 8, normal, circumferential (hoop), and meridional resultants calculated from p.sub.n, p.sub., p.sub. are used to determine sufficient laminate strengths to react or oppose such resultants across the entire bulkhead 10. Such calculations may be known to a person of skill in the art of mechanical stress modeling.

(36) With reference to FIGS. 1, 4, 6, and 7, in an embodiment, a pressure bulkhead 10 may include a bulkhead wall 24 having a radially inner disk 26 made of metal and having a first thickness y, and a compression ring 28 made of metal attached to and extending about a periphery 30 of the inner disk. The compression ring may have a second thickness z greater than the first thickness y and sufficient to balance meridional and hoop stresses sustained by the bulkhead wall 24 in response to a pressure load applied to the bulkhead wall. In an embodiment, the metal may be aluminum, titanium, a mixture thereof,or an alloy of either or both aluminum and titanium.

(37) With reference to FIGS. 1-7, in an embodiment, there may be provided a vehicle 12 having a fuselage 14 enclosed by a skin 20; and a pressure bulkhead 10 attached to the skin, about a periphery 30 of the outer compression ring 28. In embodiments, the vehicle 12 may be one of an aircraft, a spacecraft, a marine vessel, and a land vehicle.

(38) With reference to FIGS. 1-7, in an embodiment, the periphery 30 of the bulkhead wall 24 may comprise an attachment ring 44 having a radially inner band 50 and a radially outer band 52. The attachment ring 44 may be shaped to form a concave surface 54 oriented toward a non-pressurized section 18 of the vehicle fuselage 14. The radially outer band 52 may be attached to the skin 20 of the vehicle fuselage 14. The radially inner band 50 may be attached to the compression ring 28.

(39) With reference to FIGS. 1-7, in an embodiment, a method of mounting a pressure bulkhead 10 in a vehicle, for example, an aircraft, includes affixing to a fuselage skin 20 of the aircraft an attachment ring 44 having an inner band 50 and an outer band 52 defining a concave surface 54 such that the concave surface 54 is directed toward a non-pressurized section 18 of the aircraft when the aircraft fuselage is under a pressure load; and attaching a periphery 30 of a bulkhead wall 24 to the attachment ring 44, the bulkhead wall 24 having a radially inner disk 26 and a radially outer compression ring 28, the inner disk 26 and outer compression ring 28 being made of the same material, the material being one of carbon fiber reinforced plastic and/or metal, the outer compression ring 28 being of sufficient strength to balance meridional and hoop stresses sustained by the bulkhead wall 24 in response to a pressure load applied to the bulkhead wall 24.

(40) In an embodiment, the attachment ring 44 and/or the clip 46 is made of one of carbon fiber reinforced plastic and/or metal. In another embodiment the installing may further comprise a plurality of clips 46 on the concave surface 54 which clips '46 are configured to fix the attachment ring 44 to the skin 48.

(41) In an alternative embodiment the bulkhead wall 24 may be attached to the attachment ring 44 by mounting the periphery 30 and/or the compression ring 28 on the concave surface 54, that is, between the attachment ring 44 and the clip 46.

(42) The bulkhead 10 described herein provides a lightweight alternative to conventional pressure bulkheads. By providing a relatively strong compression ring 28 that is connected to a relatively weaker, and in some embodiments thinner, radially inner disk 26, the compression ring provides resistance to the hoop stress imposed by pressure differential across the surface of the radially inner disk. In some embodiments, the outer compression ring 28 may be made of the same material as the radially inner disk 26, such as CFRP, in which case the outer compression ring may be relatively thick and the radially inner disk may taper in thickness radially inward to the center of the radially inner disk.

(43) With reference to FIG. 9 and FIG. 10, in an alternative embodiment, the pressure bulkhead 11 may include bulkhead wall 56 of substantially uniform thickness from center 58 to periphery 60. The pressure bulkhead 11 further may include a plurality of stiffeners 62 attached to the bulkhead wall 56 in a Cartesian configuration. From periphery 60 to the edge 64, an attachment mechanism in the form of one or more doubler rings 66, 68 may be in contact with bulkhead wall 56 and a structure to join the bulkhead wall to the skin. In an embodiment, the one or more doubler rings 66, 68 may contact the bulkhead wall on either side of bulkhead wall 56 or on one side of the bulkhead wall 56. In an embodiment, the one or more doubler rings 66, 68 may be of the same or of different size. In an embodiment, two or more doubler rings may be placed on both sides of the bulkhead wall 56. The bulkhead wall may be made of any suitable material, for example, CFRP and/or metal. The doubler ring may be made of any suitable material, for example CFRP and/or metal.

(44) In another alternative embodiment, the one or more doubler rings 66, 68 may be attached to attachment ring 70. Attachment ring 70 may be shaped to form a concave surface oriented toward a non-pressurized section 18 of the vehicle fuselage 14 and the attachment ring 70 may be attached to the wall 48.

(45) The bulkhead 11 may further comprise a plurality of clips 72 configured to attach the attachment ring 70 to wall 48 of, for example, an aircraft fuselage 14. In an embodiment, the wall 48 may be the skin 20 of an aircraft. The clips 72 may be attached to the skin 20 of the aircraft by, for example, bolting the clips to the skin.

(46) While the forms of apparatus and methods disclosed herein constitute preferred embodiments of the invention, it is to be understood that the invention is not limited to these precise forms of apparatus, and that changes may be made therein without departing from the scope of the invention.