Land vehicles: wheels and axles – Wheel – Skate wheel
Reexamination Certificate
2000-11-01
2003-10-07
Stormer, Russell D. (Department: 3617)
Land vehicles: wheels and axles
Wheel
Skate wheel
C301S005301, C301S005309
Reexamination Certificate
active
06629735
ABSTRACT:
The instant application is based upon French Patent Application No. 99 13965, filed Nov. 2, 1999, the disclosure of which is hereby incorporated by reference thereto in its entirety, and the priority of which is hereby claimed under 35 U.S.C. §119.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a wheel primarily for a roller skate, especially for a skate whose wheels are aligned.
2. Description of Background and Relevant Information
Skate wheels are generally constituted of a hub made of a very rigid plastic material, such as polyamide, for example, on which a tread, made of one or several materials having a lower modulus of traction than that of the hub, such as polyurethane, for example, is duplicate, molded.
The characteristics which a good wheel must have are numerous. Initially, the tread must have good adherence qualities, which is particularly true for the portions thereof that are in contact with the ground in curves, i;e., when the wheel is inclined. The tread adherence depends mainly on the properties of its constituent material, i.e., on its chemical constitution, and on its macro-molecular properties.
Second, the wheel should not be overly flexible. Indeed, too much flexibility in the wheel causes a substantial deformation thereof, which negatively. affects performance, especially in terms of speed and stability.
Third, the wheel must be as resilient as possible. The resiliency of a wheel is translated into its capacity to return the maximum of the energy that is transmitted to it. This is easily appreciated by the rebounding effect of the wheel. A highly resilient wheel therefore promotes speed, because it is capable of returning a substantial portion of the energy during the expansion that follows the compression of the wheel. A non-resilient wheel absorbs much of this energy and dissipates it as heat.
Fourth, an in-line roller skate wheel must be such that the hub should not come in contact with the ground at any time during use. Indeed, in a curve and at very high speed, i.e., when the wheel is very inclined, the zone of the hub that interfaces with the tread, i.e., the peripheral zone of the hub, runs the risk of coming in contact with the ground. As a result, there is an automatic, definitive. loss of adherence.
Fifth the wheel, axle and frame assembly must be stable and should not permit any deformation, especially when the wheel is biased along a direction that is not in its median plane.
Finally, a wheel must be lightweight, and especially inexpensive to manufacture.
The document WO 96/20030 proposes to construct a skate wheel in which the lateral zones of the tread are not as hard as the central zone. Such a wheel remains heavy and especially very expensive to make.
Another document, U.S. Pat. No. 5,924,705, proposes to modify the deformability of the lateral zones of the tread by providing annular grooves on the sides thereof. Depending on the dimensions of the grooves, the use of such a wheel generates a weight gain. However, such a solution is not applicable to all wheel-profiles. Indeed, to avoid a substantial modification of the wheel behavior in curves, these annular grooves located in the tread cannot open up in a zone that comes in contact with the ground when the wheel is inclined. This is one of the reasons why a particular wheel profile was selected in this document, namely, a wheel having a substantially flat tread surface framed by substantially vertical flanks. This particular profile provides a relatively large contact surface in a straight line, which limits speed performance.
In another embodiment described in this same document, a skate wheel is provided whose rigidity can be modified by adding disks in cavities that have been especially adapted to receive them. The disks are removable and fixed on the hub by means of screws. The choice of versatility in this embodiment has led the designer to envision only one particular form of cavity, namely, a shallow cavity. Indeed, it is necessary to ensure that the residual width of the hub, in the area of the cavities, is sufficiently large to enable the positioning of the means for fixing the disks. Furthermore, such a wheel is not economical to manufacture because it requires assembling various parts, especially with screws.
The patent U.S. Pat. No. 5,938,214 proposes to reduce the lateral inclination angle of the frame/wheel assembly. To this end, two solutions are proposed.
In the first solution, an enlarged tread is duplicate molded on a conventional hub, i.e., a hub whose width enables the arrangement of two bearings and a spacer. Such an arrangement makes it possible to reduce the lateral inclination angle of the frame/wheel subassembly.
Furthermore, due to such an arrangement, the risk of contact of the hub with the ground is practically avoided. However, the necessity to enlarge the tread causes an increase in the weight of the wheels, and therefore of the skate, which is contrary to a search for performance. Moreover, such a wheel requires a specific frame, i.e., a frame including several independent pairs of wings serving to fix the axles of the wheels. The stability of the frame is reduced due to the independence of the four pairs of wings.
The second solution uses a tread having a conventional profile that is fixed to a hub that has only one bearing. In this solution, the weight gain occurs at the expense of the holding stability of the wheel on its axle.
The document U.S. Pat. No. 5,655,784 describes a skate wheel provided to be fixed on an axle by means of a single bearing, and which is equipped with a tire whose width is reduced with respect to that of the hub. Furthermore, the hardness of the material used for the tire is higher than 85 durometers on the A scale. In fact, it is comprised between 60 and 85 durometers on the D scale. Such a hardness provides the wheel with a very low resiliency and only offers very little adherence to the user of this wheel. Furthermore, the presence of a single bearing requires the use of a bearing having a very large outer diameter, and does not offer an optimum stability to the skate, especially when the latter is biased along a direction that is not in the longitudinal plane of the skate.
The standard wheels that are commonly used on the in-line roller skates have a hub about 24 millimeters (mm) wide, and whose outer diameter varies generally between 38 and 45 mm. This is a diameter that does not take into account the interlock that is embedded in the tread. This value is to be applied to the total outer diameter of a wheel that varies approximately between 72 mm and 82 mm. Indeed, it is estimated that to eliminate the risk of contact of the hub with the ground, the outer diameter of the hub should not exceed 60% of the value of the total outer diameter of the wheel, and preferably should not exceed 55%. The wheels that have a hub larger than 45 mm and whose diameter does not exceed 82 mm put the user at a great risk of hub/ground contact.
Furthermore, the standard wheels are mounted on an axle by means of two roller bearings whose diameter is less than or equal to 22 millimeters. The two bearings are arranged at a distance from one another at both ends of the inner surface of the hub.
For economical reasons, the manufacture of the largest portion of the skate wheels calls for the techniques of duplicate molding of plastic materials. The hub is first obtained by plastic molding or injection; the tread is then duplicate molded. Gravity molding along a feed bush is then used. After demolding, a sprue remains, which is located on one of the flanks of the wheel, in the area of the hub/tread interface. This sprue is then cut along a direction perpendicular to the axle of the wheel. Manufacturing the skate wheels by duplicate molding makes it possible to produce wheels that have satisfactory performances at low cost. However, it does not make it possible to obtain wheels having a particular profile, especially because of the cutting of the sprue that is perpendicular to the axle of the wheel.
SUMMARY OF THE IN
Greenblum & Bernstein P.L.C.
Salomon S.A.
Stormer Russell D.
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