Patent ID: 7748422

Claim:
A tire assembly comprising: a wheel configured to rotate about a rotational axis above a contact surface; a tire mounted to the wheel and configured to deflect when in contact with the contact surface, the tire at least partially defining a tire chamber configured to hold air pressurized relative to the ambient air; and an air pump carried by the wheel and comprising: first and second elements coupled together for relative reciprocation between an intake stroke, during which the first and second elements are reciprocally collapsed, and a compression stroke, during which the first and second elements are reciprocally extended; a variable volume chamber defined by the first and second elements and selectively fluidly coupled to the ambient air and to the tire chamber, and the variable volume chamber is configured to increase in volume during the intake stroke to draw ambient air into the variable voluble chamber and decrease in volume during the compression stroke to force the ambient air in the variable volume chamber into the tire chamber; and a portion of one of the first and second elements fluidly separating the variable volume chamber from the tire chamber such that one side of the portion is exposed to the air in the variable volume chamber and another side of the portion, opposite the one side, is exposed to the air in the tire chamber, and defines a pressure differential across the portion based on the air pressure in the tire chamber and the air pressure in the variable volume chamber; wherein as the wheel rotates, one of the first and second elements responds to the deflection of the tire to effect the intake stroke and draw ambient air into the variable volume chamber, and the continued rotation of the wheel frees the one of the first and second elements from the deflection of the tire and the pressure differential provides the force to reciprocate the first and second elements to effect the compression stroke and force the ambient air from the variable volume chamber into the tire chamber to pump up the tire.