Coupling unit

A Coupling unit for coupling a tire to a rim, comprising:

• an upper surface, a lower surface, and side surfaces,
• wherein a maximum length of the Coupling unit is larger than a distance between both hooks of the rim,
• wherein the side surfaces include sliding areas that are slidable with respect to the hooks of the rim such that the Coupling unit is easily inserted into the rim while the Coupling unit is being inserted into the rim,
• wherein in a state in which the Coupling unit is completely inserted into the rim, at least a part of the upper surface is in surface contact with lower surfaces of the hooks to prevent the Coupling unit from being separated from the rim, and
• wherein satisfies the following equations 1 to equations 3;
• L
• ≥
• (
• L
• R
• +
• P
• -
• 1
• 2
• 
• h
• )
• 2
• +
• (
• H
• R
• +
• R
• )
• 2
• [
• equations
• 
• 
• 1
• ]
• wherein, L denotes the maximum length of the Coupling unit, LR denotes a length between the hooks of the rim, P denotes a maximum length by which the hooks protrude from inner walls of a flange, R denotes ½ of the thickness of the hooks, h denotes a maximum height from the upper surface to the lower surface of the Coupling unit, and HR denotes a height of the inner walls of the flange;
• h≤HR [equations 2]
• wherein, h denotes the maximum height from the upper surface to the lower surface of the Coupling unit, and HR denotes the height of the inner walls of the flange,
• l≤√{square root over ((LR+P−b)2+(HR+R)2)} [equations 3]
• wherein, l denotes a minimum length between the side surfaces, LR denotes the length between the hooks of the rim, P denotes the maximum length by which the hooks protrude from the inner walls of the flange, R denotes ½ of the thickness of the hooks, and b denotes a larger one of the maximum height from the upper surface to the lower surface of the Coupling unit and 0.5* (the maximum length of the Coupling unit—the minimum length between the side surfaces).