Belt over mid-rollers

1. A wheel structure for a track-propelled vehicle driven by a first belt, made of a polymer, tensioned around a drive wheel, an idler wheel and a plurality of supporting mid-roller wheels between the drive wheel and the idler wheel, wherein

a second track belt is tensioned around said plurality of supporting mid-roller wheels, between an inner surface of the first belt and support surfaces of the supporting mid-rollers, in contact with said inner surface of the first belt, and is driven by friction, said second belt protecting the first belt and said supporting mid-roller wheels against wear by protecting said supporting mid-rollers against flowable debris ingested between the inner surface of the first belt and the support surfaces of the supporting mid-rollers.

2. The wheel structure according to claim 1 , wherein said second track belt comprises guide lugs on an inner surface thereof.

3. The wheel structure according to claim 1 , wherein said inner surface of the first belt comprises a series of longitudinally spaced guide lug members.

4. The wheel structure according to claim 1 , wherein said first belt has a reinforced core.

5. The wheel structure according to claim 1 , wherein said first belt comprises guide lugs on said inner surface thereof, a relative speed between said second track belt and the guide lugs of the first belt remaining constant.

6. The wheel structure according to claim 3 , wherein a relative speed between said second track belt and the guide lug members of the first belt remaining constant.

7. The wheel structure according to claim 1 , wherein the first belt and the second belt are made in a polymeric material.

8. The wheel structure according to claim 1 , wherein the first belt and the second belt are made in one of rubber and composite.