US3616075A - Fuselage jig - Google Patents

Abstract

Briefly, the invention relates to jigs for placing aircraft component parts in assembled relationship and providing the pressure to bond them into a stressed skin construction.

Description

111111em1 Mates Patent 1 1 3,616,075

[72] Inventors Richard L. Jarvis 56 Referen e cited g i g b th m UNITED STATES PATENTS m 2,391,426 12/1945 Kramer et a1. 144/281 [21] Appll No. 777,362

. 2,944,504 7/1960 Herman etal. 113/99 [22] Flled Nov. 20, 1968 3,330,550 7/1967 Brownlee 156/580 X [45} Patented 0ct.26, 1971 3,376,184 4/1968 Ritchey et a1 156/580 [73] Asslgnee American Aviation Corporation 2 563 218 @1951 D t l 244 123 Cleveland, Ohio arracott e a Primary Examiner-Benjamin A. Borchelt Assistant Examiner-J. J. Devitt FUSELAGE Attorney-Fay, Sharpe and Mulholland 5 Claims, 34 Drawing Figs.

[52] 1.1.5. C1 .1 156/479, 156/285,156/214 [51] 111111.181 B32b 3/04,

B29c 17/04 ABSTRACT: Briefly, the invention relates to jigs for placing [50] Field of Search 156/479, aircraft component parts in assembled relationship and 285, 286, 287, 288,583, 211, 214; 269/22, 37, 40; providing the pressure to bond them into a stressed skin con- 244/117,119, 123,132 struction.

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SHEET 05 0F 17 INVENTORS RlGHARID L. JARVIS WALTER KULLY PATENTEDUU 26 Ian 3,616,075

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SHEET 17 0F 17 I l G. 34 INVENTORS RICHARD L. JARVIS WALTER KULLY Jay, 5W i WYLLU Ha/ML ATTO R N EYS FUSELAGE 1G A generic concept to the invention is the use of selectively actuated pressure applying surfaces over the areas to be bonded while the parts are held in their proper relative locations.

One portion of the invention relates to the bonding of an upper aft fuselage section comprising flanged bulkhead sections and stringers and a stressed skin thereover in a singlestage jig having a fluid expansible diaphragm over each of the areas to be joined, the fluid expansible diaphragms being in one half of a jig which is pinned together to hold each of the bulkhead, stringer and skin components in proper relation while providing a reaction force upon the application of the bonding pressure by means of the introduction of pressure into the diaphragrns.

A second portion of the invention relates to the construction of a skeleton of a wing having a main tubular spar and a trailing edge spar with flanged ribs of stamped metal, a jig including supports for the ribs and spars and individual resistance heating means for applying heat and pressure at each of the joints of the wing skeleton. The second-stage jig for bonding the skin to the wing skeleton includes a means for tensioning the skin over the skeleton as well as fluid pressure expansible means to provide the bonding pressure in all areas where the skin is bonded to the ribs and spars. The ribs of the wings have flanges into which transitory reinforcing means closely fit to prevent deflection of the flanges under the bonding pressure applied thereto, a transitory reinforcing means being segmented such that they may be pulled out through cutouts in the ribs of the wings after the bonding operation is completed.

A further portion of the invention relates to bonding of a plurality of ribs and a torque tube of an aircraft control element in assembled relation by means of a liquid epoxy resin in a tube cradle and rib clamping jig which maintains the parallel relationship of the ribs at a fixed angular and lateral position with respect to the tube.

The invention provides, in the second stage in the creation of a bonded aircraft control element, a jig which has pivoted contoured arms to clampingly engage the skin in areas in register over the ribs and trailing edge such that the areas to be bonded receive the proper bonding pressure. This pressure is supplied by means of a fluid pressure expansible means and manifold system connected thereto.

In addition to the air frame, wing and control element jigs, the invention includes ajig for bonding a frame member for an airplane cutout to the periphery of the cutout which is a transitory self-supporting jig having opposing members which may be moved into and out of clamping engagement with the margin of the skin defining the cutout by means of screw means connecting the two opposing members. The opposing pressure applying surfaces of the two members include at least one fluid pressure expansible means for application of the proper bonding pressure and a brief description.

BACKGROUND OF THE INVENTION This invention relates to light airplane tooling and its use. Heretofore, small aircraft structures have been constructed using monocoque and semimonocoque construction and a multitude of rivets to fasten the skins and bulkheads together. The bonded stressed'skin-type of construction has been used for fuselage, wing and control element construction of larger airplanes; but, because of the difficulty and expense of providing the necessary tooling for properly locating the assembled parts and applying the required bonding pressures at the multitudes of joint locations therebetween, it has not been widely adopted in light airplane manufacture. As a consequence, most light airplanes of recent years have been of riveted or mechanical construction.

The present invention is a breakthrough in the economic use of bonded stressed-skin construction for the manufacture of light airplanes on a production basis. It is because of the novel tooling of this invention and its method of use that a light airplane of bonded stressed-skin construction can now be economically produced. Such an airplane is clearly superior to those having a riveted skin both because of its smooth rivetfree appearance and its reduced drag.

Briefly, one type of airplane to be constructed by the novel tooling and method of the invention is of a construction in which the lower portion of the fuselage is made up of a bonded honeycomb sandwich structure reinforced by thin metal strips and angles. The particular design of this type of aircraft includes the use of a "turtle-back" or unitary upper aft fuselage section having a stressed-skin construction bonded over a framework of thin metal bulkheads held in place by a central stringer.

The jig for the turtle-back" portion of the fuselage has been provided such that two overlapped thin metal bulkhead sections are located and held firmly in place for bonding at a plurality of intermediate stations along the length of the jig. The aft bulkhead is of one piece. These are then tied together with a central upper stringer and the whole structure is uniformly bonded together with the metal skin stressed thereover in a single bonding operation.

A novel manner of providing a uniform bonding pressure and stressing the skin evenly over the bulkheads and stringer is provided. A thermosetting structural adhesive bonds the structural elements into a single rigid structure as they are held in proper assembled relationship by the novel tooling of the invention.

A tubular section projects entirely through the lower fuselage in such a manner that it provides for the connection and support of the wings at a proper dihedral angle. Each wing has a primary tubular spar which fits on the tubular section.

The wings and control surfaces of the airplane are also made of a bonded stressedskin structure. The wing structure is primarily of a tubular spar construction having flanged thin transverse ribs with the stressed skin bonded thereto. A secondary channel-shaped spar joins the ends of the ribs adjacent the trailing edge. The control surfaces are similarly constructed utilizing single tubular spars and ribs. In the case of the wings, the ribs are made of flanged thin metal stampings, and in the case of the control surfaces, either stampings or honeycomb sandwich ribs of appropriate shape may be utilized.

Each of the airfoil structures is constructed in two stages: First, the skeleton is formed by assembling the ribs and the spars in an appropriate jig to accurately align and locate them. Then they are fixed in this assembled relation either by adhesive or mechanical fastening means. The skin is then stressed and bonded to the skeleton in a second jig designed to apply localized bonding pressures to the joints between the skin and ribs during the curing of the adhesive. These jigs have, over the areas of skin bonding to the skeleton, expansible pressure diaphragms which, after the two parts of the jig are clamped together, are inflated by fluid pressure: to apply the necessary bonding pressure for the structural adhesive material being used. Special transitory reinforcing members to provide reaction forces and prevent distortion of the flanges during application of bonding pressures are utilized. Provision is made in the wing jig for thermal expansion and contraction during the bonding operation. Examples of suitable adhesives for use are the types manufactured by Narmco Materials Division of Whittaker Corporation under the trademarks "Metlbond 22S" and Metlbond 328." Before bonding, all parts are surface prepared by treatment in a sulfuric acid sodium dichromate bath with an appropriate rinsing operation. These operations are performed prior to the assembly of the parts in the jig, and the parts are then carefully handled with cloth gloves to avoid contamination. The entire operation is performed in a controlled environment to further insure that the parts remain uncontaminated.

The turtle-back bulkhead sections and stringer are set in a special single stage bonding fixture which is clamped with the skin laid thereover with all bonding points having 10 to 20 p.s.i. applied thereto. Thermocouples are attached to the structure at appropriate points and the jig is placed in the oven at a temperature of from 245 to 265 F. until all bonded joints are cured at 245 F. for 60 minutes. After the removal from the oven and a cooling down period, a complete inspection, including ultrasonic testing and mechanical testing of bonded specimens made simultaneously with the structure in the fixture, is performed. The control surface bonding operations are performed at the same temperature and pressure but, as stated before, in two stages, the first stage bonded rib and torque tube units being secured by means of an adhesive produced by the Minnesota Mining and Manufacturing Co. under the trademark 3M 2214." This adhesive requires no pressure to perfect its bond.

The cutouts for the windows in the turtle-back portion are provided by means of a novel workpiece supported clamping fixture. In order to provide the frames about the window cutouts, the angular frame members of I." -shaped cross section are bonded to the periphery of the cutouts. The clamping fixture for this purpose has force-applying surfaces on the opposing faces of two separate jaw portions which are bolted in clamping engagement through the cutout with the marginal portion of the skin and the frame therebetween. At least one force-applying surface of the clamping fixture has a pressure expansible diaphragm member mounted in a groove thereof so that, after the fixture parts are bolted into place, air pressure may be introduced into the expansible diaphragm. This applies a uniform bonding pressure to all points of the adhesive joint between the skin and the frame.

BRIEF DESCRIPTION OF THE INVENTION Briefly, the invention relates to jigs for placing aircraft component parts in assembled relationship and providing the pressure to bond them into a stressed skin construction.

A generic concept to the invention is the use of selectively actuated pressure applying surfaces over the areas to be bonded while the parts are held in their proper relative locations.

One portion of the invention relates to the bonding of an upper aft fuselage section comprising flanged bulkhead sections and stringers and a stressed skin thereover in a singlestage jig having fluid expansible diaphragm over each of the areas to be joined, the fluid expansible diaphragms being in one half of a jig which is pinned together to hold each of the bulkhead, stringer and skin components in proper relation while providing a reaction force upon the application of the bonding pressure by means of the introduction of pressure into the diaphragms.

A second portion of the invention relates to the construction of a skeleton of a wing having a main tubular spar and a trailing edge spar with flanged ribs of stamped metal, the jig including supports for the ribs and spars and individual resistance heating means for applying heat and pressure at each of the joints of the wing skeleton. The second-stage jig for bonding the skin to the wing skeleton includes a means for tensioning the skin over the skeleton as well as fluid pressure expansible means to provide the bonding pressure in all areas where the skin is bonded to the ribs and spars. The ribs of the wings have flanges into which transitory reinforcing means closely fit to prevent deflection of the flanges under the bonding pressure applied thereto, a transitory reinforcing means being segmented such that they may be pulled out through cutouts in the ribs of the wings after the bonding operation is completed.

A further portion of the invention relates to bonding of a plurality oi ribs and a torque tube of an aircraft control element in assembled relation by means of a liquid epoxy resin in a tube cradle and rib clamping jig which maintains the parallel relationship of the ribs at a fixed angular and lateral position with respect to the tube.

The invention provides, in the second stage In the creation of a bonded aircraft control element. a jig which has pivoted contoured arms clampingly to engage the skin in areas in register over the ribs and trailing edge such that the areas to be bonded receive the proper bonding pressure. This pressure is supplied by means of a fluid pressure expansible means and manifold system connectedthereto.

In addition to the air frame, wing and control element jigs, the invention includes a jig for bonding a frame member for an airplane cutout to the periphery of the cutout which is a transitory self-supporting jig having opposing members which may be moved into and out of clamping engagement with the margin of the skin defining the cutout by means of screw means connecting the two opposing members. The opposing pressure applying surfaces of the two members include at least one fluid pressure expansible means for application of the proper bonding pressure.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 represents a plan view of the upper aft fuselage assembly or turtle-back" of a light airplane constructed using the tooling and method of this invention.

FIG. 2 represents a side elevation view of the turtle-back" of FIG. 1.

FIG. 3 represents a front elevation of the turtle-back of FIG. 1.

FIG. 4 represents a fragmentary view taken along the line 4-4 of FIG. 3 with portions of the parts broken away for clarity.

FIG. 5 represents a cross-sectional side elevation view of the lower portion of the "turtle-back" jig with the bulkhead sections and channel in place thereon.

FIG. 6 is an enlarged detailed view of a portion of FIG. 5.

FIG. 7 is a schematic side elevation view of the turtleback" jig with the top portion assembled to the bottom portion and the skin and bulkheads in place for bonding showing the manifolding for the fluid expansible pressure diaphragms.

FIG. 8 is an enlarged detailed cross-sectional elevation view ofthe assembled turtIe-back"jig of FIG. 7.

FIG. 9 is a cross-sectional view taken along the line 9-9 of FIG. 8 during the application of fluid pressure.

FIG. 10 is a cross-sectional view taken along the line 10- I0 of FIG. 8.

FIG. 11 is a side elevation view of the first stage bonding jig for the wing showing the spars and ribs in place.

FIG. 12 is a cross-sectional elevation view taken along the line l2-l2 ofFIG. 11.

FIG. 13 is a detailed side elevation view taken along the line 13-13 of FIG. 12.

FIG. 14 is a fragmentary cross-sectional view taken along line 14l4 of FIG. 13.

FIG. 15 is a detailed cross-sectional elevation view of a portion of FIG. 13 with certain other portions shown in FIG. I4 omitted for clarity.

FIG. 16 is a schematic view of the fluid actuated heating clamps ofthe jig of FIGS. 11 to 15.

FIG. 17 is a side elevation view of the second stage jig for bonding the wing with the skin and transitory reinforcing members in place.

FIG. 18 is a cross-sectional elevation view of the monocoque wing structure of the invention prior to insertion in the jig of FIG. 17.

FIG. 19 is a cross-sectional elevation view taken along the line 19-19 ofFlG. 17.

FIG. 20 is a plan view of a typical control surface.

FIG. 21 is a cross-sectional view taken along the line 2I-2I of FIG. 20.

FIG. 22 is a detailed cross-sectional view of the trailing edge of the control surface taken along the lines 22-22 of FIG. 20.

FIG. 23 is a plan view of the spar and ribs of the control surface of FIG. 20 in its first-stage bonded jig.

FIG. 24 is an end elevation view of the structure of FIG. 23.

FIG. 25 is a top plan view of the second-stage bonding jig for the control element illustrated in FIG. 20.

FIG. 26 is an end elevation view of the structure shown in FIG. 25.

Claims (4)

1. 2. A jig for assembling and bonding a semimonocoque fuselage structure of a light airplane which includes, in combination; a frame having parallel horizontal support members; a plurality of upstanding parallel bulkhead support members mounted on said horizontal support members; clamps on said bulkhead support members for clamping flanged bulkheads in spaced aligned arrangement; a fixed plate holding said upstanding support members in aligned relationship; fixed tapered portions mounted in spaced relation along said fixed plate at the top edge thereof; movable members alternated between said fixed tapered portions with complimentarily tapered surfaces in aligned engagement with said fixed tapered portions such that a stringer may be placed over and in engagement with all of said tapered portions and all of said bulkheads; a top frame structure having pressure applying surfaces disposed in a contoured frame over each of said bulkheads and over said stringer; said top frame having means to hold it in clamping engagement with a metal skin to clamp together said skin and the skeleton defined by said stringer and bulkheads between said top frame and said bulkhead support members and movable tapered members; whereby all of the skin, bulkhead and stringer joints receive pressure for adhesive bonding over all areas of contact therebetween.
2. 3. The jig of claim 2 in which the top frame is defined by contoured channel-shaped members and said pressure applying surfaces are fluid-expansible diaphragm members.
3. 4. The jig of claim 3 in which the fluid-expansible diaphragm members are silicon rubber hoses.
4. 5. The jig of claim 3 wherein a manifold system is mounted on the exterior of said top frame to supply air under pressure to said fluid-expansible diaphragm members.

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