Wheel with dual density

• US 20050269862A1
• Filed: 06/04/2004
• Published: 12/08/2005
• Est. Priority Date: 06/04/2004
• Status: Active Grant

• Current Assignee: NHS, Inc.
• Original Assignee: NHS, Inc.
• Inventors: Piumarta, Timothy, Fox, Jeremy
• Granted Patent: US 7,125,083 B2
• Time in Patent Office: Days
• US Class Current: 301/5.230
• CPC Class Codes: A63C 17/223 Wheel hubs

Abstract

A wheel is provided for coupling to a bearing case at an outer cylindrical surface and a lateral annular surface of the bearing case. The wheel includes an inner wheel portion with an annular body defining a central hole with an inner cylindrical surface and a lateral annular surface for engaging the bearing case. The inner wheel portion may substantially comprise a thermoset, polyurethane material having a density and have a surface exhibiting a hardness. The wheel also may include an outer wheel portion bonded to the inner wheel portion. The outer wheel portion may be substantially comprised of the same thermoset, polyurethane material as the inner wheel portion. The outer wheel surface may exhibit a hardness substantially the same as that of the inner wheel surface. The inner wheel material may have a lesser density than that of the outer wheel material. The lesser density of the inner wheel portion may be provided by gas bubbles included in the material of the inner wheel portion, which bubbles may be provided by hollow plastic spheres.

Claims

1. A wheel for coupling to a bearing case at an outer cylindrical surface and a lateral annular surface of the bearing case, the wheel comprising:

an inner wheel portion with an annular body defining a central hole, the inner wheel portion having a surface including an inner cylindrical surface in the central hole for engaging the outer cylindrical surface of the bearing case, the central hole further including a lateral annular surface for engaging the lateral annular surface of the bearing case, the inner wheel portion substantially comprised of a thermoset, polyurethane material having a density, the inner wheel surface exhibiting a hardness;

an outer wheel portion having a surface, the outer wheel portion bonded to the inner wheel portion, the outer wheel substantially comprised of the same thermoset, polyurethane material as the inner wheel portion, the outer wheel surface exhibiting a hardness substantially the same as the inner wheel surface,

wherein the inner wheel material has a lesser density than that of the outer wheel material.

2. The wheel of claim 1 wherein the lesser density of the inner wheel portion is provided by gas bubbles included in the material of the inner wheel portion.

3. The wheel of claim 2 wherein the gas bubbles are provided by hollow plastic spheres in the inner wheel portion.

4. The wheel of claim 3 wherein the spheres are added to the inner wheel material in an un-expanded state and are expanded during a molding of the inner wheel portion.

5. The wheel of claim 3 wherein the spheres are added to the inner wheel material in a pre-expanded state.

6. The wheel of claim 2 wherein the gas bubbles are added with a blowing agent.

7. The wheel of claim 1 wherein the density of the inner wheel material is between about 0.60 grams per 1 cubic centimeter and about 0.90 grams per cubic centimeter.

8. The wheel of claim 1 wherein the density of the outer wheel material is between about 1.1 grams per 1 cubic centimeter and about 1.3 grams per 1 cubic centimeter.

9. The wheel of claim 1 wherein a ratio of the density of the inner wheel material to the density of the outer wheel material is between about 0.6 and about 0.95.

10. The wheel of claim 1 wherein the hardnesses of the inner and outer wheel portions are between about 97 and about 100 on Shore scale A.

11. The wheel of claim 1 wherein the hardnesses of the inner and outer wheel portions are between about 50 and about 60 on Shore scale D.

12. The wheel of claim 1 wherein the inner wheel includes a beveled outer surface and at least a portion of the outer wheel portion is bonded to the beveled outer surface.

13. A bearing-mounted wheel for affixing to an axle, the wheel comprising:

a bearing case having an outer cylindrical surface and a lateral annular surface.

an inner wheel portion with an annular body defining a central hole, the inner wheel portion having a surface including an inner cylindrical surface in the central hole for engaging the outer cylindrical surface of the bearing, the central hole further including a lateral annular surface for engaging the lateral annular surface of the bearing case, the inner wheel portion substantially comprised of a thermoset, polyurethane material having a density, the inner wheel surface exhibiting a harness; and

an outer wheel portion having a surface, the outer wheel portion bonded to the inner wheel portion, the outer wheel substantially comprised of the same thermoset, polyurethane material as the inner wheel portion, the outer wheel surface exhibiting a hardness substantially the same as the inner wheel surface, the outer wheel material having a lesser density than that of the inner wheel material.

14. The wheel of claim 13 further comprising a second bearing case having an outer cylindrical surface and a lateral annular surface.

15. The wheel of claim 14 wherein the inner wheel includes an opposed pair of inner cylindrical and lateral annular surfaces for engaging the mating surfaces of the first and second bearing cases.

16. The wheel of claim 15 wherein the bearing cases each include a pair of opposed lateral annular surfaces, the surfaces of each pair in freely rotatable relation to one another, a first one of each pair engaging the inner wheel portion, a second one of each pair configured to be fixedly engaged to the axle.

17. A method for constructing a wheel for coupling to a bearing ring, the method comprising:

providing a polyurethane material prepared to be cured to a thermoset condition, the material when thermoset having a measurable hardness;

providing a first mold for molding an inner wheel portion;

filling the inner wheel mold with the polyurethane material;

producing gas bubbles in the polyurethane material in the inner wheel mold;

releasing the inner wheel portion from the mold;

providing a second mold for molding an outer wheel portion;

inserting the inner wheel portion in the outer wheel mold;

filling the outer wheel mold with the polyurethane material to create the outer wheel portion and to bond the wheel portions together;

releasing the bonded inner and outer wheel portions from the outer wheel mold.

18. The method of claim 17 further including a step after releasing the inner wheel from the mold of beveling an outer surface of the inner wheel.

19. The method of claim 17 wherein the step of producing gas bubbles in the inner wheel portion includes adding hollow plastic spheres to the polyurethane material contemporaneously with filling the inner wheel mold with the material.

20. The method of claim 19 wherein the hollow plastic spheres are unexpanded when added to the polyurethane material.

21. The method of claim 19 wherein the hollow plastic spheres are pre-expanded before adding to the polyurethane material.

22. The method of claim 17 wherein the step of producing gas bubbles in the inner wheel portion includes introducing a blowing agent into the polyurethane material contemporaneously with filling the inner wheel mold with the material.

23. The method of claim 17 wherein the inner wheel portion and the outer wheel portion have substantially the same hardness.