AU7398398A - Laminate structural bulkhead - Google Patents

Description

Regulilion 3.2(2)

AUSTRALIA

Patents Act 1990

ORIGINAL

COMPLETE

SPECIFICATION

STANDARD PATENT Application Number: Lodged: Invention Title: LAMINATE STRUCTURAL BULKHEAD The following statement is a full description of this invention, including the best method of performing it known to us '2-

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LAMINATE STRUCTURALJ BULKIEN2q CrosRefeelet This application is based oni,-prdOVZs:5olal app..~tOlSra No. 60/051 f118, filed- July .18. 1997.

ParticularlJ in automotive-appliatio0fs, box SeqtiOns such as main frame rails arYe s ubje cted t o considerable 5t-r ss forces where cross M~erber are bolted to the rails. For example, when engine cradles are bolted to main frame rails they produce joints that are susceptible to durability cracking over time. In addition, the bolts which hold sach componentS in place may loosen due to vibration at the joint. Moreover, conventional structures create a "noise path" which extends from the vehicle wheels and engine through the frame and int o the passenger compartment.

As will be appreciated by those skillead in the. art,. in order to bolt a heavy component to the side of a rail section it,- is nrecessary to create a reinforced region or support structure at the site of attachment of the bolt- On pproachr which is used i~n.

the art is to provide a stamped bulkhead which supports a metal bus~hing. The bulkhead gener-ally has three flange Portionls which ae s pot welded to the rail C-sectiOn. MoreLSpeC4f~l~ h stamped bulkhead has a wall portionl that extends froma one wall of the rail section to the opposite 4all or cap.. Thus, the bulkhead forms a partition in the channel or cavity defined by the rail.

In order to secure this wall portion in place, the bulkhead has three surfaces or flanges that are perpendicular to the bulkhead wall portion; that is, the bulkhead is in essence a shallow rectangular box that is open on one side. These three surfaces mate with the inner surfaces of the rail and are spot welded in place.

S In order to utilize the bulkhead as a support for the cross structure which is attached thereto, it is designed to position a metal bushing that is spot welded to the bulkhead stamping. A bolt theinpasses through the bushing and secures the cross structure to the rail at the bulkhead-reinforced region. This convetional approach will be more fully illustrated hereinafter.

While the conventional bulkhead design does serve to reinforce the rail section at the attachment site of the cross.

member, it generally requires large gauge bushings and stampings and can actually increase unwanted vibration and noise.

Moreover, the through-bolt, bushing, metal stamping and rail section essentially perform as discrete elements more than a unitary, integral reinforcement structure. This results not only in the above-mentioned increase in vibration and noise, but also fails to provide full reinforcement of the rail, resulting in metal fatigue at the joint and, in particular, at weld locations.

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7; fI, The present inventor has developed a number of approaches to the reinforcement-of hollow metal parts such as: a reinforcing beam for a vehicle door which comprises an open channel-shaped metal member having a longitudinal cavity which is filled with a thermoset or thermoplastic resin-based material; a hollow torsion -bar cut to length and charged with a resin-based material; a precast reinforcement insert for structural'members which is formed of a plurality of pellets containing a thermoset '"esin with a blowing agent, the-precast member being expanded and cured in place in the structural member; a composite door beam which has a resin-based core that occupies not more than one-third of the bore of a metal tube; a hollow laminate beam characterized .by high stiffness-to-mass ratio and having an outer portion which is S. separated from an inner tube by a thin layer of structural foam; an.i-beam reinforcement member which comprises a preformed structural insert having an external foam which is then inserted into a hollow structural member; and a metal w-shaped bracket which serves as a carrier for an expandable resin which is foamed in place in a hollow section.

None of these prior approaches, however, deal specifically with solving the problems associated with conventional reinforcing bulkheads in rail sections' at cross member attachment -sites. The present invention solves many of the problemsinherent in the prior art.

It is an object of the present invention, o provide a reinforced hollow metal structure which incorporates a bushing and a stamping in a bulkhead structure in a manner in which the components of the bulkhead work together as an integral unit with the reinforced structure.

It is a further object of the invention to provide a reinforced metal box section which pro-ides greater strength to the section without significantly increasing vibration and noise transmission levels.

It is a further object of the present invention to proyidea reinforced frame rail section at the attachment of a cross member such as an engine cradle in a manner in which stress forces are distributed over a region of the reinforced railrather than at the.discrete welds and in which noise and vibration are dampened.

These and other objects and advantages of the invention will S be more fully appreciated in accordance with the detailed S description of the preferred embodiments of the invention and the drawings.

*i Summary of the Invention In one aspect the present invention provides a reinforced structure. The reinforced structure includes a hollow structural member and a reinforcing member disposed therein. The reinforcing member has a pair of opposed walls. A layer of S thermally expanded polymer is disposed between and is bonded to the opposed walls. This layer of polymer is also bonded directly to the structural member. A sleeve extends through the polymer parallel with and between the opposed walls. The polymer is bonded to the sleeve and the sleeve defines a passage through the polymer. The reinforced structure has holes that are in alignment with the ends of the sleeve. A bolt is then used to secure a component to the structural member. Thus, the hollow structural member.is reinforced locally in the present invention at-that position by virtue of the reinforcing member. The polymer is expanded in place by heating the entire structure Safter assembly, where it expands to fill gaps betweenthe reinforcing structure and the structural member and bonds the t reinforcing structure to the structural member.

In another aspect the reinforced structure of the present invention is a motor vehicle rail such as a front rail where local reinforcement for the attachment of components such as an l. engine cradle is required. In this aspect, the invention reduces vibration and noise transmission as well as increases the S strength of the part at the site of the reinforcement.

In still another aspect the sleeve is a thin wall metal bushing, the opposed walls are metal stampings with flang.s which are welded to the structural member and the polymer is a thermally expanded epoxy resin which contains hollow microspheres for density reduction.

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In still another asoect the presen rnven _Qfl Drovides method of reinforcing a structural mempber having a 1 ong qitt d ial ,channel. In this aspect a laminated structurejnavifg- two.-opposed walls separated by a layer. ot thermall-y expnrdable P6lymer .is placed in the channel of a rail section or the li 1ke. The laminated structure has a sleeve disposed in the layer, or thermally expandable polymer. The sleeve defies._a passage perpendicular to the opposed walls.. The lami nated: structure also has a-;pair of end flanges. The laminated structure is pl aized in the longitudinal channel such that said sleeve passage is perpendicular to the longitudina'l channel. The laminated structure is then welded to the structural mebrat the *Flanges.

The entire structure is then heated to a temper-ature ef ecti-ve to activate, the blowing agent of the polymer and therby thermally expand the-polymer such that it bonds -'ne laminated 5tructure- to the structural member.

Brief Dscription of the Drawinas Figure 1 is a dl a g r a m at ic excloded perspective view c conventidonal prior art 'bulkheaa reinrorcement structure;- Figure 2 is a diagrammatic front elevational view of the~ structure of Figure 1 with the cap plate removed; Figure_ 3- is a di agra.-Lmatic exploded perspective view off the reinrforced rail, sect~lon oZ.the oreSenc. a.-venrion illustratl na tn-e constructionhf the- reinforci-ng Iaminrate !bulkhead; *iFigure 4 i~s a diagraThrnt2.c front elevat2ional vieW of the Structure sh o wn i n Fioure 3 with the cap clate remfoved; and Figure 5 is a. diaogran'atic back view or m-e oulkhead portion or Fiaure5s 3ad4.

Detailed Des.ri-Pti-Qa Reerng now to Figures 1 and 2 of the drawi-es, prior art front rail section 20 is shown having c-section 22 that defines channel -23 and which receives cap p-late 24.. Bulkhe=ad stamoina- 26 is seen having vertical wall 28 and flanges,30. Bushing 32 is welded to wall 28 at an arcuace bend 33 in wall 28. Flanges are welded to section 22 to hold bulkhead 26 i place.Bot3 extends through cap 24, bushing 32 and ver-tical wall 37 of Section 22 and then through a componen~t 38 which is t5o attached to rail 20. Nut 40 is then attached to bolt 36 to secure component 38 in place. This is representative of the o rior art and suffers -from the drawbacks described above, i.e. inadauate reinforcement, inadequate sound dampeniing and vibration problem.

Turning now to F aure 3 of the drawinus,.C erore d structure 50 JIs Show-.r one erooorr-aenz as a r-norced on ralofa utmtVerCand includes fae rai C -s5e ctzi oa -2 which is closed by capn 'a t 54 such that- channel or cavity 56 is defined i n r e iZ'o r c ed structure 50 Tn other words :n-e fri-me rai isholow C-secto. fcldes verticaml WaI7 nort~on ze, and oppiosed w' IDortionaS 60 a nd 62 E a ch oroed wa± I rortlon 60.62 has a flange portion 64 of the attacniament of can plate 54 by welding or the like at the =Lianue areas. Reinforciina miezber or bul, khead 68 is seen disposed in channel, 56 of C-section 52 and has a first wall or side 70 and a second wall or side 72. Walls and 72 are parallel to one another and are separated by polymer laver 74; that is, polymer laver -74 is disposed between walls 70 and 72- As bes t seen in Eicures 4 and 5 of the drawings, each wall 70,72 has an associat-ed arcuate portion r,76 for wail- 72 and 78 for wall 70) which is designed to accoramodate sleeve 81 in a manner to be more fuly described hereinafter. Each arcuate nortion 76,718 is approximately midway along the lenigth of each wall '70,72 and can be view,,ed as a curved inner surface. Sleeve 81 is a metal 'bushing or the like and, as best seen in Figure 4 of the drawings is spot welded to wails 70 and 72 at weld points 83 and 85. Polymer layer 74 essentially envelopes sleeve 8l as shown in IFigure 4 Bulkhead 68 is secured in place in cnannel 56 bv virtue of attachment flanges 80 and 82 which extend from walls 70 and 72 at 790 degree anglies. That is, eacn wall 70, 72 has at each, end a bent portion that, mates with a similar cortizon on the oco-osec wall to form an attaclurent flange 20,32 t-har.IS welded on, side wall1 60,62, resnecti-lv-.y The width of" walls 70 and 72 (distance be tWieen verZIcal Wall 58 and cap plate 54) is such that bul'khead 63 is in contact with vertical wall 58 anid cap plate 54. Accordingly, bol-t 84 extends throgh cp oate 54 at hole 66, throughseee8 andt- uf correspondinlg hole in vertical wall 58 (not shown) BoElt 84 then, extends through a hole in a cross memb-Oersc as enginecrde8 which is shown in phantom, as fragment 86. Nut 88 is5 then secured ol bolt 84 to secure engine cradle 8E onto reiforced structure Bulhea 68is reatielyligc eia!ht structure for the amount of strength added to the f rame. rail I al 1s 70 and 72 can be formed of th-i steel stamnpings, for examplSi m 0 o bu .08 inch in thickness. Mild to mediun trnt stel i particularly preferred- Aslso, sleeve 81 which is preferably a metal bushing may b a thi4n wall tube having a wall thickness of from about .08,to about .2 inch- and i s oreferablv maild steel. Of .PI course, these dim~ensionls are merelyill iustrative and are not intended to limit the full scope o r th-ne in-vienicn as defined in the claims. Each attachme.nt fianae 80,82 is generall-y from about erettabout 30pret of the lengthl Of Wallis .70,72. The outer diameter of sleeve 31 will- typicallyr be -from about 'i to about -I inch. The width of Dolyiner laver 74 wrill oe a function of the distance between wa-11S or Diates 70 and 72 and willgenerallv be between about .1 and about .4 inc~- t is to De understood that the en-tire depth. of IVlkead 68 ISfildwt polymer layer 74; that is, as shown in Figure 5 of the drawings polymer layer 74 extends from the front of bulkhead 68 to the back.

The polymer used to form polymer layer 74 is a resin based material which is thermally expandable. A number of resin-based compositions can be utilized to form thermally expanded layer 74 .1 the present invention. The preferred compositions impart excellent strength and stiffness characteristics while adding only marginally to the weight. With specific reference now to the composition of layer 74, the density of the material should preferably be from about 20 pounds per cubic feet to about pounds per cubic feet to minimize weight. The melting point, heat distortion temperature and the temperature at which chemical breakdown occurs must also be sufficiently high such that layer 74 maintains its structure at high temperatures typically encountered in paint ovens and the like. Therefore, layer 74 should be able to withstand temperatures in excess of 320 degrees F. and preferably 350 degrees F. for short times. Also, layer 74 should be able to withstand heats of about 90 degrees F. to 200 degrees F. for extended periods without exhibiting substantial heat-induced distortion or degradation.

The foam 74 may be initially applied to one or both walls 70,72 and then expand into intimate contact with both walls and with sleeve 81. Advantageously heat from the paint oven may be used to expand foam 74 when it is heat expandable.

In more detail, in one particularly preferred embodiment thermally expanded structural foam for layer 74 includes a synthetic resin, a cell-forming agent, and a filler. A synthetic resin comprises from about 40 percent to about 80 percent by weight, preferably from about 45 percent to about 75 percent by weight, and most preferably from about 50 percent to about percent by weight of layer 74. Most preferably, a portion of the resin includes a flexible epoxy. As used herein, the term "cellforming agent" refers generally to agents which produce bubbles, pores, or cavities in layer 74. That is, layer 74 has a cellular S structure, having numerous cells disposed throughout its mass.

This cellular structure provides a low-density, high-strength :material, which provides a strong, yet lightweight structure.

Cell-forming agents which are compatible with the present invention include reinforcing "hollow" microspheres or .microbubbles which may be formed of either glass or plastic.

Also, the cell-forming agent may comprise a blowing agent which may be either a chemical blowing agent or a physical blowing agent. Glass microspheres are particularly preferred. Where the cell-forming agent comprises microspheres or macrospheres, it.

constitutes from about 10 percent to about 50 percent by weight, preferably from about 15 percent to about 45 percent by weight, and most preferably from 20 percent to about 40 percent by weight -11of the material which forms layer 74. Where the cell-forming agent comprises a blowing agent, it constitutes from about percent to about 5.0 percent by weight, preferably from about 1 percent to about 4.0 percent by weight, and most preferably from about 1 percent to about 2 percent by weight of thermally expanded structural foam layer 74. Suitable fillers include glass or plastic microspheres, fumed silica, calcium carbonate, milled glass fiber, and chopped glass strand. A:thixotropic filler is particularly preferred. Other materials may be suitable. A filler comprises from about 1 percent to about percent by weight, preferably from about 2 percent to about S percent by weight and most preferably from about 3 percent to about 8 percent by weight of layer 74.

Preferred synthetic resins for use in the present invention include thermosets such as epoxy resins, vinyl ester resins, thermoset polyester resins, and urethane resins. It is not intended that the scope of the present invention be limited by molecular weight of the resin and suitable weights will be understood by those skilled in the art based on the present disclosure. Where the resin component of the liquid filler material is a thermoset resin, various accelerators, such as imidizoles and curing agent, preferably dicyandiamide may also be included to enhance the cure rate. A functional amount of accelerator is typically from'about 0.5 percent to about -12percent of the resin weight with corresponding reduction in one of the three components, resin, cell-forming agent or filler.

Similarly, the amount of curing agent used is typically from about 1 percent to about 8 percent of the resin weight with a corresponding reduction in one of the three components, resin, cell-forming agent or filler. Effective amounts of processing aids, stabilizers, colorants, UV absorbers and the like may also be included in layer. Thermoplastics may also be suitable.

In the following table, a preferred formulation for layer 74 is set forth. It has been found that this formulation provides a material which full expands and cures at about 320 degrees F. and provides excellent structural properties. All percentages in the present disclosure are percent by weight unless otherwise S specifically designated.

INGREDIENT PERCENTAGE BY WEIGHT EPON 828 (epoxy resin) 37.0 DER 331 (flexible epoxy 18.0 DI-CY (dicyandiamide curing agent) IMIDIZOLE (accelerator) 0.8 FUMED SILICA (thixotropic filler) 1.1 CELOGEN AZ199 (asodicarbonamide blowing 1.2 83 MICROS (glass microspheres) 37.0 WINNOFIL CALCIUM CARBONATE (CaCO3 filler) 0.9 While the invention has been described primarily in connection with vehicle parts, it is to be understood that the invention may be practiced as part of other products, such as aircrafts, ships;, bicycles or virtually anything that requires energy for movement. Similarly, the invention may be used with stationary or static structures, such as buildings, to provide a rigid support when subjected to vibration such as from an earthquake or simply to provide a lightweight support for structures subjected to loads. Additionally, while the invention has been described primarily with respect to heat expandable foams and with respect to metal parts such as the inner tubes 16, 58 and 76, other materials can be used. For example, the foam could be any suitable known expandable foam which is chemically activated into expansion and forms a rigid structural foam. The bulkhead walls 70,70 and sleeve 81 could be made of materials other than metal such as various plastics or polymeric materials or various wood type fibrous materials having sufficient rigidity to function as a back drop or support for the foam. Where a heat expandable foam is used the bulkhead walls and sleeve should be able to withstand the heat encountered during the heat curing.

Where other types of foam materials are used, however, it is not necessary that the bulkhead walls and sleeve be able to withstand high temperatures. Instead, the basic requirement for the bulkhead walls and sleeve is that it have sufficient rigidity to function in its intended manner. It is also possible, for 1 1: I i sLI~-~' ~i

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example, to use as the bulkhead walls and sleeve materials which in themselves become rigid upon curing or further treatment. The invention may also be practiced where the bulkhead walls and, sleeve are made of materials other than metal. It is preferred, however, that materials be selected so that the thin unexpanded foam upon expansion forms a strong bond with the bulkhead walls and sleeve so that a structural composition will result.

While particular embodiments of this invention are shown and described herein, it will be understood, of course, that the invention is not to be limited thereto since many modifications may be made, particularly by those skilled in this art, in light of this disclosure. It is contemplated, therefore, by the appended claims, to cover any such modifications as fall within the true spirit and scope of this invention.

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Claims (19)

1. 2. The reinforced structure recited in claim 1, further including a bolt which extends through said structural member and which extends through said sleeve.
2. 3. The reinforced structure recited in claim 1, wherein said reinforced structure is an automotive rail section.
3. 4. The reinforced structure recited in claim 3, wherein said automotive rail section is a front rail. The reinforced structure recited in claim 4, wherein said rail section is U-shaped with outwardly extending flanges, and a cap plate secured-to said flanges.
4. 6. The reinforced structure recited in claim 1, wherein said opposed walls are welded to said structural member.
5. 7. The reinforced structure recited in claim 1, wherein said sleeve is welded to at least one of said first and second walls.
6. 8. The reinforced structure recited in claim 1, wherein Ssaid reinforced structural member has a pair of through holes in alignment with said bolt-receiving passage of S: said sleeve.
7. 9. The reinforced structure recited in claim 1, wherein said layer of expanded polymer is epoxy. S 10. The reinforced structure recited in claim 1, wherein said sleeve is substantially parallel with said first and second opposed walls.
8. 11. The reinforced structure recited in claim 1, wherein said layer of expanded polymer is thermally expanded formed from, in percentage by weight, from about 40% to about 60% resin; from about 10% to about microspheres; from about 0.5% to about 5% blowing agent; from about 1% to about 15% filler; from about to about 2.0% accelerator and from about 1% to about 8% curing agent. i:e :ij -I i- ii ;i i:. 4 4 Ii.
9. 12. A reinforced structural member, comprising: a rail having opposed side walls and defining a longitudinal channel, said longitudinal channel lying along a longitudinal axis; a laminate reinforcement member disposed in said channel perpendicular to said longitudinal channel, said laminated reinforcement member having two opposed retaining walls separated by a layer of expanded polymer; a sleeve disposed between said opposed retaining walls and defining a passage; said layer of expanded polymer being bonded to said opposed walls of said rail, and said sleeve; and a bolt extending throughsaid rail and said sleve.
10. 13. The reinforced structural member of claim 12, wherein said rail is made of steel, and said walls having flanges welded to said steel rail.
11. 14. The reinforced structural member recited in claim 12, wherein said opposed retaining walls each include ani inner convex surface at the position of said sleeve The reinforced structure recited in claim 12, wherein said sleeve is welded to at least one of said opposed retaining walls.
12. 16. The reinforced structure recited in claim 12, wherein said layer of expanded polymer is epoxy. -iF -1: rir_ 1,, -iC7: Lp-R~i-rara~~~CCC----Li~C*~X-
13. 17. The reinforced structure recited in claim 16, wherein said epoxy is thermally expanded and further contains microspheres which reduces the density of said epoxy.
14. 18. The reinforced structural member recited in claim 12, wherein said laminated reinforcement member has a flange portion at each end thereof.
15. 19. ,A method of reinforcing a structural member having a longitudinal channel there through, comprising the steps of: providing a structural member which defines a longitudinal channel; providing a laminated structure having two opposed walls separated by a layer of expandable polymer; said laminated structure having a sleeve disposed in said layer of expandable polymer, said sleeve defining a passage between said opposed walls; placing said laminated structure in said longitudinal channel such that said sleeve passage is substantially perpendicular to said longitudinal channel; welding said laminated structure to said_ structural member; and actuating said polymer to expand into intimate contact with said walls and said sleeve. The method recited in claim 19, wherein the polymer is thermally expandable, and heating said structural member to a temperature sufficient to thermally expand said layer of thermally expandable polymer such that said polymer bonds said laminated structure to said structural member.
16. 21. The method recited in claim 19, wherein said structural member is an automotive rail.
17. 22. The reinforced structure recited in claim 20, wherein said epoxy further includes microspheres which reduce the density of said epoxy.
18. 23. A reinforced structural member formed by the process of claim 19.
19. 24. A reinforced structure, comprising a structural member defining a space; a reintorcing-member disposed in said space, said reinforcing member having first and second opposed walls; a layer of thermally expandable polymer disposed between and bonded to said first and seconc Sopposed walls, said thermally expandable polymer also being bonded to said structural member; wherein said layer of thermally expandable polymer includes, in percentage by weight, 37%.epoxy resin, 18% flexible epoxy resin, 4% dicyandiamide curing agent, 0.8% imidizole accelerator, 1.1% fumed silica, 1.2% azodiarbonamide blowing agent, 37% glass microspheres, and.0. 9 calcium carbonate; a sleeve extending through said thermally expandable polymer, said sleeve being disposed between lsaid first and second opposed walls, said thermally expandable polymer being bonded to said sleeve; and said sleeve defining a passage adapted to receive a bolt. DATLED this 1st day of July 1998. F: \DOCS\wLY-\PATNASEB\ 392 HENKEL CORPORATION WATER4ARK PATE'fl TRADENARK ATIORNEYS 290 BURW(YJD ROAD HAWJTHOR. VIC. 3122- -21- F