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Патент USA US3074167

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Jan. 22, 1963
Filed March 4, 1959
* Br {4/6. W
United States Patent 0 " 1C@
Gilbert L. Wolfe, 9440 Balltown Road, Schenectady, FLY.
Filed Mar. 4, 1959, Ser. No. 797,141
2 Claims. (Cl. 29-469)
This invention relates to an improved monocoque panel
for a prefabricated building structure, and more particu
larly it relates to a manufacturing process for economical
Patented Jan. 22, 1963
to resist bending in directions opposite to its compound
curvature and such that it is ideally suited for securing
to adjacent panels formed in the same manner to give an
extremely rigid and e?icient building structure.
The subject matter which I regard as my invention is
particularly pointed out and distinctly claimed in the
concluding portion of this speci?cation. My invention,
however, both as to organization and method of opera
tion, together with further objects and advantages thereof,
ly producing a stressed skin work-hardened self-sustaining 10 may best be understood by reference to the following
panel which effectively combines load-bearing and shelter
description taken in connection with the accompanying
ing functions in a single member using a minimum of
drawing, in which:
FIG. 1 is a horizontal elevation drawing showing the
The load-bearing properties of a complex curved sur
preferred methd of fabrication on a stretch-forming ma
face such as that found in an eggshell have long been 15 chine and showing an edge view of the panel as it is
recognized. It is also recognized that the yield strength
formed over the complex die;
of a metal may be appreciably increased by ‘*cold work
FIG. 2 is a cross-section view taken along line 2—-—2
ing” the metal in the plastic region beyond its elastic
of P16. 1;
limit. Uses have been made in the past of the superior
FIG. 3 is perspective view of an assembled building
load-bearing characteristics of complex or multi—direction 20 structure using a number of my improved monocoque
al curved surfaces in building structures. These have gen
building panels;
erally been produced in their already complex shape,
PEG. 4 is a detailed view of the joint between panels
however, such as by casting or pouring a hardenable
in FIG. 3, showing one method of securing adjacent
liquid into a mold as in the case of concrete, or by simply
panels; and
building the complex structure up from a number of in 25
FIG. 5 is a detailed view of a modi?ed panel joint.
dividually shaped members having good structural char
The desire to achieve such a complex surface eco
nomically with sheet metal, because of its desirability as
Referring now to PEG. 1 of the drawing, a stretch
former 1 is shown in the process of stretch-forming a
metal sheet 2 over a die 3. Stretch-forming has found
some popularity in the aluminum industries due to the
a building material, has led to many suggestions, such as 30 relative ductility of the metal. One of the principal ad
corrugating the metal in a plane transverse to the plane of
vantages in using stretch-forming is that the trouble
bending so as to give the overall effect of bending in two
some problem of “spring-back” is practically eliminated,
directions at one time. Although this has been partially
since all areas of the metal are stressed in tension beyond
successful, it will ‘be appreciated that this is only an ap
the elastic range.
proximation of a true compound-curved smooth surface, 35
The stretch-former 1, by which this process is accom
and the presence of the corrugations makes the structure
plished, is shown in simple diagrammatic form in FIG. 1
inherently non-rigid in at least one plane. Moreover, the
as comprising a vertically movable die table 4 which is
ethod of corrugating the metal sheets is wasteful of ma
caused to be raised by hydraulic cylinders 5 disposed
terial and involves intricate bending or roll-forming ap
beneath the die table. A pair of jaws 6, '7, which are
paratus which may not bring about the full bene?ts of
adapted to tightly grip the metal sheet 2 by means of hy
work hardening in the ?nal structure.
draulically operated clamps 6a, 7a, are supported by head
The obvious desirability of a monocoque or single skin
assemblies 8, 9 respectively. laws 6, 7 are individually
panel which would be self-supporting and which could
be manufactured out of a relatively light gage piece of
sheet metal, led to the conception of a method for pro
ducing such a monocoque panel in a shape which makes
use of the superior load-bearing characteristics of a com
plex surface and which at the same time effectively utilizes
cold working and intentionally induced “cold set” internal
forces to provide a structure of unusual strength.
Accordingly, an object of the present invention is to
provide an improved monocoque self-sustaining panel
which can be used in connection with similar panels to
movable in the head assemblies 8, h by virtue of being
mounted on the ends of hydraulic pistons 11.1, 12 respec
tively. The head assemblies 8, 9 are supported by hori
zontally movable slides 13, M, and are arranged so that
they can pivot in a vertical plane about the pinned connec
tions 15, 16 when actuated by gears 17, 18 in a manner
which will be obvious from the drawing.
It will be appreciated that the stretc -former 1 may
be adjusted to the position as shown in FIG. 1 so that the
die table 4 will exert an upward force on die 3 against the
surface of the metal sheet 2, while at the same time, the
form a light-weight prefabricated building structure.
jaws 6, 7 acting at the proper angle as shown, will grip
Another object of the invention is to disclose a process 55 the opposite ends of the sheet 2 to provide a reaction
for forming the monocoque panel in a novel con?guration
force resisting the upward movement. The stretch-former
which combines the utilization of “cold set” internal
l is constructed to exert a powerful force on the work
forces with the utilization of a complex surface to greatly
piece which may be in the nature of 60 tons to 300 tons
increase the strength of the panel.
or more and which causes the metal to be stressed in
A still further object is to provide a prefabricated build 60 tension beyond the elastic range. It is understood, of
ing structure which is simple to erect, economical to pro
course, that this forming operation takes place at normal
duce and transport, which has a high strength-weight
temperatures rather than elevated temperatures. Upon
ratio, which needs no beams or internal supporting mem
bers, and which has relatively few parts to assemble.
exceeding the elastic range the sheet will undergo plastic
deformation to stretch or elongate in the longitudinal di
rection. The metal will slide over the smooth working
surface of the die 3 and attempt to attain the con?gura
tion of the die surface.
FIG. 2 shows a transverse section through the metal
the tensile strength and to produce “locked-in” tensile 70 sheet 2 and a portion of the die 3 which will illustrate the
forces in grain structure of the metal sheet. The con~
novel manner in which the stretch-forming process is
?guration of the resulting panel is such that it is adapted
utilized to provide “locked-in” tensile forces in the mono
Generally stated, the invention is practiced by utilizing
the process of “stretch-forming” to form a sheet of fair
ly ductile metal, such as aluminum, into a shape of com
plex curvature so as to cold work the metal to increase
coque'panel, the purpose of'which will 'be later described.
There it will be seen that, in addition to the “primary
arch” de?ned by the die and extending from jaw 6 to
jaw 7 ‘in FIG. 1, the die is transversely arched to form a
would ordinarily place the'?bers in the convex‘v surface
in compression, act ?rst to relieve the internal tensile
stress thus reducing the wrinkling tendency of a thin
walled member under compressive stresses.
generous curvature or “secondary arch” in the transverse
direction which spans the distance between the sidewalls
3a of the die. As the sheet 2 is stretched in the longi
tudinal direction to form the primary arch illustrated in
FIG. 1, the tendency of the metal to contract transversely
as it elongates, coupled with the inwardly directed com
ponent of the stretching force and the outward pressure
in the middle of the sheet, causes the outer edge portions
211 of the sheet to “curl” inwardly toward the radial
portions 3a of the die. This causes the secondary arch
to be formed in a plane transverse to the curvature of
A preferred use of my improved
novel monocoque
building panel may be illustrated by reference to FIG. 3
of the drawing. There may be seen a partially assembled
the primary arch. The resulting panel exhibits great
strength and rigidity in resistance to bending ‘from all
structure comprising adjacent panels 2’, 2'', etc, which
have been manufactured to the desired dimensions by
the process illustrated in FIGS. 1 and 2. The assembled
panels may be used to form a simple roof structure by
securing them to the tops of opposite walls by some suit
able means.
As shown in FIG. 3, however, it consists of
a complete wall~and~roof structure, in order to achieve
the most economical enclosure possible. it may be noted
from the drawings in ‘FIGS. 1 and 3 that the “feet” of
the primary arch are closer together than the sides of the
outward directions.
arch at its widest point. The purpose of this is twofold.
As mentioned previously, the use of stretch-forming
First, the con?guration results in a better utilization of
stresses all areas of the metal in tension beyond its elastic 20 space, since the “headroom” is not diminished, as it would
limit, while at the same time it produces the bidirectional
be if the arch curved inward immediately. Of perhaps
arches. The cold working, or stretching, of the metal into
greater importance is the fact that the outward thrust on
this shape produces a piece which has been work hardened
the foundation walls due to deformation of the panel
to increase the tensile strength, i.e. the shaping and cold
under a load is counteracted by the inwardly directed
Working occur simultaneously. Such a shape, if it could 25 components produced by the converging of the panel feet,
be produced by roll-forming or bending techniques, where
which will reduce, it not entirely eliminate the net out
the metal is not formed while held in tension but is merely
ward thrust on the foundation walls. The bottom edges
bent 'angularly, would require very costly tooling in a
29 of the panels are secured to a ground-level support
complicated series of operations; and furthermore, in
such as a concrete footing 2.1 by a suitable means, for
such a series of operations the metal cannot be uniformly
shaped and simultaneously stressed or work hardened to
example, anchor bolts and angle brackets properly shaped
produce the relatively high tensile strengths desired in
the ?nished con?guration.
Thus, the shape I have achieved is one which, in itself,
and drilled for this purpose (not shown).
Reference to FIG. 4 will disclose a suitable method of
connecting adjacent panels. The extending ?ange por
tions, 2a’, 2a" of adjoining panels 2’, 2" perform a dual
on account of its bi-directional curvature, has great re
35 function in keeping with the simplicity of the novel struc
sistance to inward pressure from all directions. In addi
ture illustrated. In addition to providing an extending
tion to achieving this desirable shape, ‘moreover, cold
?ange surface in the radial direction which acts as a
working the entire area of the original sheet in the varying
strengthening girder to improve the resistance to bending,
directions desired produces a tensile strength which would
these ?ange portions also provide convenient relatively
be difficult to achieve by other methods. For example, 40 flat abutting surfaces for fastening the panels together.
while metal stamping in a conventional press could also
This is illustrated by the use of expandable pin fasteners
produce a high tensile strength, the punch could not
of a suitable material such as nylon, one of which is
easily be withdrawn from a continuously arched single
shown at 22. These are spaced at intervals around the
panel such as illustrated in the preferred shape of FIG. 1,
primary arch and serve to hold the structure rigidly to
due to the fact that the primary arch extends more than
gether. It will be appreciated that the expandable fas
180° in order to increase the useful space inside the ' tener 22 is shown ‘for purposes of illustration only, and
structure and in order to reduce side thrust on the founda
that many other methods of fastening, such as welding,
tion Walls.
bolting or riveting, could be used to hold the panels
As mentioned previously, the use of stretch-forming
?rmly together.
stresses all areas of the metal in tension. In addition to
In order to deaden the sound transmission between
the cold working effect, it is felt that the strength of
panels, and to provide a seal, a ?exible gasket 23 of some
the panel may vbe increased still further by the following
compressible material such as neoprene sponge rubber
ere the stretching is elfected in the
may be employed, although the use of a gasket is by no
curved plane of the primary ‘arch, the outer ?bers on the
means mandatory. A putty or mastic 24» in the joint be
convex surface 2b will be elongated more than the outer
most ?bers on the concave surface 2c since the total
distance is greater due to the thickness of the metal. By
use of a die which has a generous curvature in the trans
verse dircction as well as in the primary longitudinal
direction, the outer edges 2a, as they curl in around the
die under the action of the stretching force, will also
stress the outermost ?bers in the transverse direction.
Thus it can be seen that the convex surface 2b of the
sheet will be subjected to increased elongation over that
of concave surface 20, and that this increased elongation
will exist both in the longitudinal direction along the
primary arch and in the transverse direction along the
secondary arch. Upon relaxing the force on sheet 2 and
disengaging jaws 6, 7, this bi-directional curvature will
manifest itself by constituting convex surface 2b much
as a stretched membrane whereby “locked-in” tensile
forces will exist in the convex surface 2b of the sheet.
The bi-directional curvature of the sheet will prevent the
sheet from ?exing in order to relieve itself of these in
ternal forces. When the panel is loaded, any forces which
tween panels completes the assembly by acting to provide
a watertight seal.
There are many other commercial
methods of sealing and fastening which also may be used.
The erection and operation of my improved building
structure should now be apparent. The stressed skin
monocoque panels are simply placed as they will stand in
the ?nal structure. Due to their unique con?guration
and method of forming, they are completely self-support
ing. They need only be fastened together from the in
side with the fasteners 22 using gasket 23 between panels
or by assembling without gaskets. The holes for the
fasteners can either be prepunched or drilled at the build
ing site.
Other modi?cations of the preferred structure will
occur to those skilled in the art. For example, in order
to produce very wide spans, it may be desirable to manu
facture panels in two sections, joining them together
along the ridge of the building by a suitable method such
as overlapping the half-panels end-to-end and securing
them ?rmly or by riveting or by butting, capping, and
Likewise, the half-panels mentioned above could easily
be made wider at the bottom of the building than at the
top, still retaining the bi-directional curvature, of course,
sheets of ductile metal in its longitudinal direction over
said die to simultaneously stretch the sheet in a major arc
and form the opposite transverse edges of said sheet into
in order to form an end for the building shown in FIG. 3
substantially parallel ?anges, arranging the sheets side-by
or in order to construct a circular enclosure.
side with adjacent ?ange portions extending in the same
FIG. 5 shows a modi?cation or" the joint described in
FIG. 4. Instead of allowing the side edges to be directed
direction, securing the ?ange portions of adjacent sheets
face-to-face substantially along the entire length thereof,
toward the inside of the enclosure as in FIG. 4, they are
and sealing between the ?anges of adjacent sheets to pre
vformed with a reverse curve as at 26 during stretch
vent leakage.
forming. This adds to the girder eifect of the panel edges 10
2. The method of constructing a self-supporting build
in resisting bending. Since the panel edges are disposed
ing structure comprising the steps of: providing a plu
at a greater radius from the center of curvature of the
rality of ?at sheets of ductile work-hardenable metal of
primary arch than portions Z6, they will receive a greater
su?icient length to provide at least part of the sidewall
amount of cold working when the panel is stretched and
and roof of said structure, providing a bi-directionally
therefore will have greater ultimate strength. It also 15 convex die, exerting tension on opposite ends of said
locates the joining members outside the structure which
sheets of metal over said die to are the sheet in its longi
may be preferable for inside appearance. A compres
tudinal direct-ion and to form the transverse edges of the
sible gasket 27 similar to that of FIG. 4 may be used, if
sheet into opposite parallel ?anges, providing each of
desired, in order to deaden sound transmission between
said ?anges with longitudinally spaced holes, arranging
panels which are fastened together by rivets 28. A 20 said sheets side-by-side with adjacent ?ange portions ex
U-shaped cap 29 which is preferably of a ?exible mate
tending in the same direction, attaching the ?anges of the
rial such as an extruded vinyl composition may be used
sheets face-to-face with pin fastening means in said holes
to prevent leakage.
along substantially the entire ?ange length, and sealing
It only remains to note that the shape of the panel
between said ?anges to prevent leakage.
adapts it to nesting several panels together, whether manu 25
References Cited in the ?le of this patent
factured as a complete span or in two sections to be
joined at the ridge. Also the simplicity of the structure
and the need of relatively few parts for erection makes it
Sykes _______________ __ Apr. 11, 1933
Longren ______________ __ July 2, 1935
use such as emergency disaster area housing, barracks or
Schmidt _____________ __ Oct. 12, 1937
other shelters.
While there has been described what is at present con
sidered to be the preferred embodiment of the invention,
it will be understood that various modi?cations may be 35
made therein, and it is intended to cover in the appended
claims all such modi?cations which fall within the scope
of this invention.
Braglio ______________ __ Sept. 24,
Berliner et al. ________ __ Apr. 14,
Stolz et a1. ___________ __ May 4,
Cowin ______________ __ Aug. 31,
Drew _______________ __ Oct. 24,
Lermont et a1. _______ __ June 19,
Bentley ______________ __ Mar. 8,
Bath ________________ __ July 19,
K-raybill _____________ __ Sept. 2,
Pine _______________ __ Sept. 16,
Messmore ____________ __ Feb. 3, 1959
Martin ______________ __ Apr. 19, 1960
an ideal structure for summer camps, farm buildings,
boat houses, machinery storage, garages, or for temporary 30
What I claim as new and desire to secure by Letters
Patent of the United States is:
1. The method of constructing a self-supporting build
ing structure comprising the steps of: providing a plu
rality of ?at ductile metal sheets each of a length su?i
cient for forming both a wall and roof portion of said
structure, providing a bi-directionally convex male die ‘15
de?ning a gradual major arc with secondary arcs normal
thereto, exerting tension at opposite ends of each of said
Principles of Stretch-Wrap Forming—Hutford Machine
‘Works Inc, ?rst edition (1950), pages 58-611, 75, 76.
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