Resilient tires and wheels – Spring wheels – Deformable ground engaging part
Reexamination Certificate
1998-11-25
2001-01-09
Stormer, Russell D. (Department: 3617)
Resilient tires and wheels
Spring wheels
Deformable ground engaging part
C152S005000, C301S055000, C301S104000
Reexamination Certificate
active
06170544
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention concerns nonpneumatic wheels, notably, those capable of being used in substitution for tires on vehicles.
It has been tried for a long time to design such nonpneumatic wheels, that is, operating without compressed air, in order to overcome every problem raised by flats or reduction of inflation pressure of tires.
Among very numerous proposals, the one described in U.S. Pat. No. 3,234,988 can be cited. That patent describes a nonpneumatic deformable wheel containing a disk, an internal element fastened to the disk, an annular external element, flexible and appreciably inextensible, intended to come in contact with the road, and a plurality of spokes arranged between the internal and external elements. The external element has a length such that it stresses the spokes under radial compression. In other words, they are prestressed (that is, preloaded). Beyond a certain stress threshold, since the spokes are stressed on end, the radially oriented reaction force that each of those spokes can develop remains constant. The wheel also contains means of stabilization of the relative positions of the external and internal elements. The spokes bend in a meridian plane and the means of stabilization limit the relative axial displacements of the internal and external elements.
This deformable wheel uses as connection between the internal and external elements spokes prestressed beyond their buckling load. Thus, in case of increase of the load supported by the wheel, that increase is compensated only by an increase in number of spokes actually supporting the load. This results in an increase of length of the contact between the wheel and the road. Such behavior is very close to that of a tire.
This wheel presents, however, one major disadvantage. The different spokes buckle in their meridian planes, but have practically no possibility of circumferential deformation, for their section presents great inertia in the circumferential direction. Now, on rolling, considerable longitudinal forces are undergone by the external element in contact with the road, notably, in the area of contact, which leads to rapid deterioration of the previous nonpneumatic wheel.
SUMMARY OF THE INVENTION
The object of the invention is a deformable structure designed to constitute, with a disk, for example, a nonpneumatic wheel presenting the same advantages of comfort and performance, while solving the preceding problem.
The deformable structure for a vehicle, according to the invention, designed to roll on an axis of rotation, comprises an annular internal element centered on the axis, an annular external element, flexible and appreciably inextensible, forming a tread, radially arranged externally relative to the internal element, a plurality of spokes arranged between the internal and external elements, each spoke being capable of opposing an appreciably constant force under a radial compressive stress beyond a given threshold, the annular external element having a length such that the spokes are prestressed in radial compression, as well as means for stabilizing the relative positions of the internal and external elements. This rolling structure is characterized in that the spokes are formed and arranged between the internal element and external element, in such a way that their flexibility in a meridian plane is well below their flexibility in a circumferential plane, and in that the means for stabilizing limit the amplitude of a circumferential relative rotation between the internal and external elements.
The wheel obtained from the deformable structure according to the invention presents the following advantage: each spoke can be deformed in a circumferential direction, in particular during rolling, when it is in the zone of contact between the external element and the road.
The spokes are preferably prestressed beyond their buckling load. The means of stabilization can also include elastic connections nonradially joining the internal and external elements, such as cables or slender beams. The means of stabilization are prestressed in extension in state of rest in order to exert a return force immediately upon a relative rotation displacement between the internal and external elements. The ends of the spokes can be fastened by embedding or by joints in the internal element and/or external element. The means of stabilization can also be a thin shell prestressed in radial extension.
The deformable structure according to the invention can also constitute a safety insert designed to be mounted in an assembly consisting of a tire and a rim.
REFERENCES:
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patent: 1424101 (1922-07-01), Johnson
patent: 1692001 (1928-11-01), Stenberg
patent: 3234988 (1966-02-01), Cummings
patent: 4729605 (1988-03-01), Imao et al.
patent: 4858297 (1989-08-01), Longcamp
patent: 4867217 (1989-09-01), Laurent
patent: 5110190 (1992-05-01), Johnson
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patent: 190968 (1986-08-01), None
patent: 379090 (1907-10-01), None
patent: 553969 (1923-06-01), None
patent: 1064851 (1954-05-01), None
patent: 1005 (1911-01-01), None
patent: 4-221201 (1992-08-01), None
Baker & Botts L.L.P.
Compagnie Generale des Etablissements Michelin - Michelin & Cie
Stormer Russell D.
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