Stock material or miscellaneous articles – Structurally defined web or sheet – Honeycomb-like
Reexamination Certificate
1999-07-22
2001-08-14
Lorin, Francis J. (Department: 1775)
Stock material or miscellaneous articles
Structurally defined web or sheet
Honeycomb-like
C156S197000
Reexamination Certificate
active
06274216
ABSTRACT:
The present invention is directed at an improved honeycomb structure mainly suitable for the construction of soundproofing panels, as well as to its production process.
A known soundproofing structure is in the form of a panel constituted by honeycomb cells intercalated between a solid plate and a perforated plate by which the cells open towards the noisy medium. Sound waves propagate in the cells passing through the perforations and are absorbed there by successive reflections on the walls without really being able to pass out of the same. This structure is known as a Helmholtz resonator.
It is possible to stack two layers of such cells by intercalating a perforated plate or sheet in order to separate them and whilst maintaining the communication between them. A continuous plate is then placed at the rear of the stack and a perforated plate at the front. Thus, the sound waves enter the first layer of cells and then the second, which improves the absorption of sound. This structure is known as a Helmholtz resonator with two degrees of freedom. As a variant, the perforated separating plate or sheet can be replaced by a wire gauze, which is bonded between the layers of cells or a perforated sheet separating them.
A disadvantage of such more complex structures is that the assemblies of the layers of cells and sheets or gauze are generally fragile and sometimes difficult to implement in a satisfactory manner. As it is often also necessary to bend or deform in a random manner the panels before being able to use them in equipment, shear stresses appear, which are higher in the interior of the panel than on the surface thereof, which explains why it readily tears at its interfaces between layers of cells. This situation is further aggravated if bending is accompanied by tension or compression and if it occurs around two length and width directions, or if the interface of the layers is not at the mid-thickness of the structure, because the neutral line of the stresses is spaced from the interface, which is then more greatly loaded.
It is possible to obviate these disadvantages by separately deforming the layers of cells and then assembling them, which eliminates the shear stresses at the interfaces, but the adjustment of the layers of cells is even more complicated and it is necessary to ensure that forming takes place with adequate precision to permit such an adjustment.
The essential feature of the invention is that the metal plate by which the layers of cells are conventionally separated is replaced by initially folded sheets, which make it possible to obtain successive layers of cells with a much greater ease of manufacture without greatly stiffening the structure, so that high stresses neither appear, nor are received. Thus, the separating sheets of the cells can be much thinner than the plates or gauzes conventionally used, because they are not exposed to breaking risks either at the time of manufacture or subsequently and also has no function in the assembly of the structure.
Thus, in its most general form, the invention relates to a structure formed from main sheets, of a sinuous nature and alternatively joined by straight edges to two neighbouring, opposite, main sheets, whilst defining cells having a hexagonal cross-section, characterized in that it comprises sheets intermediate with respect to the main sheets, which are folded and joined to straight edges of two neighbouring, main sheets, whilst forming broken fold membranes in the cells. The broken fold introduced here is an initially formed fold, but which decreases or disappears during the manufacture of the structure.
The intermediate sheets can be porous, perforated, continuous, flexible, semi-rigid, or in composite form, thin sheet, gauze, etc. Several examples appropriate for the construction of Helmholtz resonators will be given.
The invention also relates to a process for the production of such a structure, characterized in that it consists of longitudinally folding the intermediate sheets in order to form there two lips separated by a fold, alternately stacking the main and intermediate sheets, whilst joining first faces of the main sheets alternately to two neighbouring, main sheets, at locations intended to give straight edges, and second faces, opposite to the first faces, of main sheets to intermediate sheet portions, said portions belonging to a single lip among the two lips and being spaced from the fold.
REFERENCES:
patent: 4265955 (1981-05-01), Harp et al.
patent: 5785919 (1998-07-01), Wilson
patent: 2 261 872 (1975-09-01), None
patent: 2 660 787 (1991-10-01), None
patent: 52-141010 (1977-11-01), None
patent: WO 92/12856 (1992-08-01), None
Gonidec Patrick
Treger Jean Adam Roger
Hispano Suiza Aerostructures
Lorin Francis J.
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
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