Note: Descriptions are shown in the official language in which they were submitted.
3~02
WO 94/04766 PCT/DE93/00725
Framework with Hollow Members, Process for Producing the Same and
Its Use
The invention relates to frameworks with hollow members of
nodes and bars, a process for producing them and their use.
Frameworks are known as supporting and bearing elements in
the most varied fields - for instance for structures, in
particular bridges or even houses - or also for the construction
of air, land and marine vehicles, shelf systems and the like.
They have the advantage, among other things, of making
possible light construction which nevertheless is resistant to
stresses.
Tube frames were already employed in automobiles, in
particular the old "gull-wing Mercedes SL" to make possible a
particularly light, sturdy and torsion-proof construction. The
framework construction was also often employed in aircraft, where
weight savings are an essential aspect in construction.
The known frameworks lent themselves to further improvement
in that weak points could occur in the nodes of the framework in
the course of attachment of the framework components. The
individual elements were usually fastened there, for example
welded, on top of or flush with each other. Corrosions did easily
appear at the weld seams, glued spots or the like, as well as at
the en~s of the hollow elements to be connected - the application
of corrosion protection there was extremely difficult and often
not satisfactory.
These weld spots or fastening places of cross members on
the longitudinal element were always points of weakness and also
resulted in elaborate operations being necessary during
manufacture.
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It was furthermore disadvantageous that, for reasons of the
need to fasten further transverse hollow elements on the
longitudinal hollow element, it was necessary to employ relatively
large wall thicknesses in the hollow elements for producing a
satisfactory connection, which led to undesirably great weight of
this part.
In contrast thereto it is the object of the invention to
produce frameworks as well as individual components for them which
are easier to manipulate and are more corrosion-resistant than the--
known individual components.
This object is attained in accordance with the invention in
connection with a framework, in particularly an at least partially
hollow framework with nodes and rods, by nodes formed by at least
one pro~ection on the hollow framework element and at least one
further hollow element placed thereon and fastened.
In this connection it is advantageous if the run of the
fibers extends essentially parallel with the exterior contours of
the hollow element.
It can be of advantage if at least the framework elements
having nodes have several layers of the same or different
materials which extend parallel to each other and are placed on
top of each other and the run of whose fibers is parallel in
respect to each other.
In connection with a preferred embodiment at least the
node/rod elements are made of steel, having a wall thickness
between 0.1 to 1.5 cm, preferably between 0.2 and 0.5 cm.
For saving weight in particular, the framework can
essentially be made of a light metal.
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For example, the light metal can be aluminum or an alloy
thereof, which can also include advantageous corrosion res-istance.
It is possible, and desired in many applications, for the
framework to have reinforced-fiber materials which have a high
mechanical load-bearing capacity along with light weight.
The framework of nodes and rods has different longitudinal
sections and also different cross sections.
It can be advantageous for the individual components-of the
framework to consist of different materials.
It can be favorable for at least one hollow element to have
depressions and/or openings formed therein.
An advantageous process for producing frameworks in
accordance with one of the preceding claims consists in that the
framework nodes are produced from a shapable hollow material by
means of a shaping process.
The shaping process preferably is an internal high-pressure
shaping process.
A preferred embodiment of the production process for a
framework node element has the following steps:
Provision of a hollow profiled section, if required with
different diameters;
Placement of a hollow profiled section into a mold with a
widening in the shaping area;
Application of internal high pressure to the tube, so that
the tube wall is widened in the area of the mold widening;
Removal of the shaped hollow element with a node area with
widenings and, if necessary,
Fastening of framework elements on the widenings.
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The internal high-pressure process, also called IHV-
process, is understood here to be the process as described, for
example, in the Industrieanzeiger [Industrial Gazette] No. 20 of
03/09/1984, or also in "Metallumformtechnik" [Metal Shaping
Technology], volume lD/91, pp. 16 et. seq.: A. Ebbinghaus:
Prazisionswerkstucke in Leichtbauweise, hergestellt durch
Innenhochdruckumformen" [Precision Workpieces of Light
Construction, Produced by Internal High-Pressure Shaping], or in
Werkstoff und Betrieb [Materials and Factory] 123 (1990), 3, page ---
241 to 243: A. Ebbinghaus: "Wirtschaftliches Konstruieren mit
innenhochdruckgeformten Prazisionswerkstucken" [Economical
Construction with Precision Workpieces Made by Internal High-
Pressure Shaping], or Werkstoff und Betrieb 122, (1991), 11,
(1989), page 933 to 938. Full reference is made below to their
disclosures to avoid repetitions. This method had been used up to
now for producing flanges, for example to produce manufactured
camshafts for fastening cams on a tube for producing hollow
camshafts.
In a surprising manner it is now possible by means of this
internal high-pressure process to form a completely novel
framework piece in which the node or the "intersection" has
already been formed in one piece and the run of the fibers in the
area of the intersection as well of the walls essentially extends
parallel with the outer contour without there being sharp bends or
other weak spots. Thus, because of the great wall strength ~aused
by the advantageous run of the fibers, the framework in accordance
with the invention can be embodied in a lighter form than was
possible up to now and therefore makes possible considerable
weight savings. It is also possible to employ laminated materials
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as long as they can be shaped together. Through proper material
selection, laminates can be lighter than solid materials-and have
the additional advantage of acting in a vibration-damping manner,
so that such an element additionally has advantageous oscillation
damping properties - i.e. connecting points are less stressed by
oscillations.
It is also possible to select a multi-layered metal tube as
the initial part, depending on the requirements made on the
material. In this case multi-layered embodiments have the --
advantage of having different capacities of the surfaces of the
hollow element to withstand stress, and also the advantage of
transmitting oscillations of every type less, which decisively
improves the vibration behavior of the hollow element.
Advantageous uses for the frameworks in accordance with the
invention occur in connection with land, air and marine vehicles,
frames for bicycles, motorcycles and automobiles, structural and
civil engineering, scaffolding, shelf systems, furniture.
Because in accordance with the invention hollow elements
which are closed-off to a large extent are used for producing the
framework, it is possible to allow the simplest connection of
further framework elements in the areas of the nodes of the
framework. The connection in the area where one projection of a
hollow element overlaps the end section of a further hollow
element of the framework can be made by welding, gluing, riveting,
screwing as well as other fastening methods known to one skilled
in the art, wherein it is also possible to make releasable
connections, such as are desired for scaffolding, by running
screws through, or the like.
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Because an internal high-pressure shaping process is
employed it is possible to produce projections and recesses,
openings and the like already in one shaping process. In this way
it is possible to reduce finishing steps.
The most varied hollow profiled sections, such as square
profiled sections, angled profiled sections, tubes, etc. can be
employed as hollow elements.
In this way an element is produced which has a reduced
weight in respect to conventional elements with the same load- --
bearing capacity, or even higher load-bearing capacity at the same
weight; which in addition can be produced with a high production
accuracy and with a reduced re~ection rate.
The hollow element of the invention can preferably be
produced in accordance with the internal high-pressure process.
In a surprising manner it is now possible by means of this
internal high-pressure process to form a completely novel
framework piece in which the node has already been formed in one
piece and the run of the fibers in the area of the intersection as
well of the walls essentially extends parallel with the outer
contour without there being sharp bends or other weak spots.
Thus, because of the great wall strength caused by the
advantageous run of the fibers, the framework in accordance with
the invention can be embodied in a lighter form than was possible
up to now and therefore makes possible considerable weight
savings. It is also possible to employ laminated materials as
long as they can be shaped together. Laminates have the
additional advantage of acting in a vibration-damping manner, so
that such an element also has advantageous oscillation damping
properties.
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The production of the hollow element in accordance-with the
invention takes place as follows: A tube element with different
diameters is produced (for example by circular kneading), wherein
the node area is subsequently pressed against an external mold
under internal pressure to obtain a cross-shaped element with two
closed ends.
In the course of shaping it is desirable to feed material
in the direction of the longitudinal tube axis to prevent the
creation of thin spots in the material in the area of the --
intersection.
The invention will be described in detail below by means of
the attached drawings, in
Fig. 1 a schematic perspective view of a section of a
framework ;
Fig. 2 a longitudinal section of the hollow framework made
of solid material with several node areas;
Fig. 3 a longitudinal view of a portion of the framework
made of a laminate with a node area;
Fig. 4 a detailed view of a node of solid material shaped
by internal high pressure;
Fig. 5 a cross section through a node area of a hollow
element with a square profile;
Fig. 6 a cross section through the node area of a round
tube as the hollow element; and
Fig. 7 a cross section through the node area of a polygonal
tube.
AS can be seen in Fig. 1, which shows a section of a
framework in accordance with the invention, the framework consists
of node/rod parts 12 and further node/rod parts 12 or rod parts
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18. Projections 30 have been formed on the node-rod parts 12 in
the node area 14, on which rod parts 18, but also node/rod parts
12 can be placed, for example, which the can be connected
releasably or solidly with the projection 30.
As shown in Fig. 2, the nodes can extend spatially
depending on the requirements, so that a three-dimensional
framework of high solidity can be attained.
Care must be taken that predetermined compression places
can be formed by directly cut-in grooves in the framework elements -
produced by the shaping process - for example for absorbing energy
by directed deformation in vehicles in case of an accident - or
that profiled reinforcement sections can be worked in - for
example by forming linear ribs (passenger compartment).
In the process, the hollow profiled sections of the
framework can have varying diameters over their linear extension,
as well as varying cross sections.
The embodiment of a node is shown in detail in longitudinal
section in Fig. 3. In this case an embodiment was selected
wherein a node/rod element 12 made of several layers was combined
with a rod element made of one material - for example this can be
a portion of a ladder-like element with laminated longitudinal
stringers and steps of another material.
Fig. 4 shows an embodiment of the connection between the
node/rod element 12 and the rod element 18 in section, wherein
both elements are made of a single-layer material.
In both cases the fastening of the rod parts 18 or even
further node/rod parts 12 on the node/rod part 12 is only
schematically represented and can take place in actuality by
gluing, welding or also screwing, riveting or the like.
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Varied shapes can be employed as hollow profiled sections,
as can be seen from Figs. 5 to 7.
Depending on the form of application it can useful to
provide a rectangular profiled section 22 with a projection 30.
In the same way it is possible to embody a round or oval
profiled section 24 with a projection 30 for connecting it with a
rod element, as can be seen from Fig. 6. As shown in Fig. 7, such
projections can also be embodied on rectangular hollow profiled
sections 26 for simplifying the fastening of rods on nodes.
In the process the hollow profiled sections can be made of
a single material, for example steel or a light metal alloy,
however, depending on the method of use it is also possible to
shape laminated material, also plastic-layered or coated tubes,
depending on the purpose of use.
By providing appropriate layers it is possible to achieve
corrosion resistance or coloration without the necessity for
further operational steps.
As known, the node area can be "pushed", so to speak, out
of the hollow element precursor by means of the internal high-
pressure process, so that several projections 30 are created in
the hollow element, as shown in the figures. By feeding material
along the longitudinal tube axis during shaping, for example by
movable mold elements, it is possible to attain an essentially
uniform wall thickness, so that weak spots in the wall thickness
because of the formation of such projections can be compensated at
least partially, so that the forming of the intersection area
takes place without weakening. This element is light and has no
welded places or the like in the intersection area because of the
advantageous run of the fibers.
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In this way a more resistant, lighter framework than was
possible up to now is created by means of the embodiment-, in
particular of the node areas of a framework, in accordance with
the invention.
Further embodiments and developments are obvious to one
skilled in the art within the framework of the scope of protection
of the claims, and the scope of protection is in no way limited to
the embodiments shown here by way of example, which are merely
intended for explanation.
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