Aeronautics and astronautics – Aircraft sustentation – Sustaining airfoils
Reexamination Certificate
1998-09-25
2001-02-06
Poon, Peter M. (Department: 3644)
Aeronautics and astronautics
Aircraft sustentation
Sustaining airfoils
C244S075100, C416S13200B
Reexamination Certificate
active
06182929
ABSTRACT:
PRIORITY CLAIM
This application is based on and claims the priority under 35 U.S.C. §119 of German Patent Application 197 42 314.0, filed on Sep. 25, 1997, the entire disclosure of which is incorporated herein by reference.
FIELD OF THE INVENTION
The invention relates to a load carrying structure that has a variable flexibility, i.e. that can be selectively adjusted or actuated to be relatively rigid or relatively flexible or deformable, as needed at any time.
BACKGROUND INFORMATION
According to the state of the art, structural components that are to be connected together in a manner that is selectively rigid or flexibly movable are typically connected by a joint or hinge structure that is, in itself, flexible. In order to provide the necessary rigidity in addition to the necessary flexibility, the known structures further include a locking device that can be selectively locked or released, so as to selectively lock the flexible joint in one or more desired fixed positions, or alternatively release the joint to allow it to be flexibly bendable. The selective operation of the locking device further requires the use of a control unit for actuating the locking device. As a result, known load carrying structures that are selectively adjustable to be rigid or flexible thus require complicated joint members and locking devices, and a rather great total number of components interacting in rather complicated ways. This is especially disadvantageous in structures that are to be built according to lightweight construction techniques, for which the primary goal is naturally a minimization of the overall weight together with a reduction of the number of components.
SUMMARY OF THE INVENTION
In view of the above, it is an object of the invention to provide a simply constructed, lightweight, load carrying structure that can be selectively adjusted, set, or actuated to be either rigid or flexible as needed at any time. The invention further aims to avoid or overcome the disadvantages of the prior art, and to achieve additional advantages, as apparent from the present description.
The above objects have been achieved in a load carrying structure that can be selectively actuated to be rigid or flexible, according to the invention, comprising a thermoplastic material having a softening temperature above the operating temperature range of the load carrying structure, and a heating arrangement adapted to heat the thermoplastic material to a temperature at or above the softening temperature. Thereby, when the load carrying structure is being used under its normal operating conditions, the thermoplastic material is rigid, and when the heating arrangement is actuated to heat the thermoplastic material to at least its softening temperature, the rigid condition is released and the thermoplastic material becomes flexible. As a result, the load carrying structure can be made selectively rigid or flexible. Throughout this specification, the term “rigid” refers to a non-softened solid state of the material, in which the material has its normal rigidity and strength adequate for withstanding the loads expected to arise during its operation without yielding or permanently deflecting or deforming. The term “rigid” is not intended to be limited to absolute rigidity and is intended to allow for some elastic strain of the material and the structure.
According to the invention, the load carrying structure is at least partially made of the thermoplastic material. If the overall load carrying structure essentially consists of the thermoplastic material and the heating arrangement, then the overall load carrying structure can be made selectively rigid or flexible as described above. On the other hand, the thermoplastic material member may be a joint member that interconnects two other rigid components of the overall load carrying structure. In this manner, the thermoplastic material member simply acts as a selectively flexible joint.
The invention provides a variably flexible structure with an integrated selective releasing and locking function, in a very simple manner. When the heating arrangement heats the thermoplastic material to a temperature at or above the softening temperature, the rigid condition is released or overcome, so that the thermoplastic material element and the overall load carrying structure becomes flexibly movable into a new position or configuration. After the heating arrangement is switched off and the thermoplastic material cools down to the normal operating temperature below the softening temperature, the thermoplastic material again becomes rigid, whereby the new position or configuration is rigidly fixed. The invention achieves this without requiring any additional locking mechanism.
The invention thus deviates from the previously known concepts that require selectively rigid or movably adjustable load carrying structures to have a complicated multi-component construction. In comparison, the load carrying structure according to the invention is characterized by a functional integration and component integration that is enabled by the selectively actuatable stiffness of the thermoplastic material. Moreover, the load carrying structure according to the invention requires only a small adjusting or deflecting force for achieving a change in configuration once the thermoplastic material has been softened.
The thermoplastic material used according to the invention is preferably a thermoplastic synthetic polymer or plastic. In this context, high-melting synthetic thermoplastics such as polyether ether ketones (PEEK) or polyether sulfones (PES) are generally preferred, because these materials have a relatively high softening temperature and thus make it possible for the load carrying structure incorporating such materials to operate at a corresponding high operating temperature.
The load carrying structure according to the invention can be particularly constructed in various ways. For example, the load carrying structure may be made entirely of the thermoplastic material along with the heating arrangement. In other words, according to this alternative, the load carrying structure essentially consists of a thermoplastic material element together with the heating arrangement. On the other hand, the load carrying structure according to the invention may, for example, comprise two or more components that are interconnected by the thermoplastic material element. In this case, the other components that are to be joined preferably have a softening temperature that lies above the softening temperature of the thermoplastic material, so that the components do not undergo softening. In this context, the other components can be made of metal, and particularly a light metal or alloy, or may be made of a synthetic plastic and especially a fiber-reinforced synthetic composite material that has a higher softening temperature than the thermoplastic material that connects or joins these other components.
In the second case, namely in which the load carrying structure comprises a plurality of components that are interconnected by a thermoplastic material element, the thermoplastic element provides a rigid connection or joining of the components at normal operating temperatures below the softening temperature of the thermoplastic material. Then, when it is desired to release the rigid connection of the components, it is simply necessary to heat the thermoplastic material up to the softening temperature using the heating arrangement, whereupon the joint becomes flexible.
Since the thermoplastic material can be deformed in any desired manner after it is heated to at least its softening temperature, the flexibility or reconfigurability of the load carrying structure can be carried out in many very different embodiments. For example, in an embodiment in which the load carrying structure comprises a plurality of rigid components that are connected together by the thermoplastic material, after heating the thermoplastic material to the softening temperature the thermoplastic material can be subjected to a thrust load, i.e
Himmel Norbert
Kuhn Marcel
Martin Willi
Siegling Hans-Friedrich
Daimler-Chrysler AG
Fasse W. F.
Fasse W. G.
Palo Francis T.
Poon Peter M.
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