Conventional pneumatic tires for wheeled vehicles, such as automobiles and the like, rely on a single air chamber inflated at uniform pressure for absorbing road shocks and bumps. However, shock absorbing is accomplished most effectively with relatively low pressure tires, whereas ease and precision of steering, durability of the tires and fuel economy are more aptly to be achieved with relatively high pressure tires. Therefore, conventional single chamber tires are a compromise between inherently conflicting requirements.
The present invention relates to pneumatic tires for wheeled vehicles, and more particularly to an improved tubeless pneumatic tire provided with a pair of concentric annular air chambers inflated preferably at different air pressures, the pressure in the outermost chamber being higher than the pressure in the innermost chamber.
Attempts have been made in the past to design pneumatic tires with a multiplicity of air chambers, as disclosed for example in U.S. Pat. Nos. 2,196,814, 2,525,752, 2,735,471 and 2,925,845, and in British patent specification No. 347,690 and German Patent Publication No. 2,517,895. Such designs of multi-chamber pneumatic tires are complicated, and therefore require complex and costly molds for manufacturing, resulting in heavy structures using a large volume of solid rubber material or casing material as compared to the volume of air contained in the air chambers, with the resulting inconvenience of high cost of raw materials, lack of flexibility of the pneumatic tire, heavy masses in rotation, and substantial constant friction and deformation of elastomeric material causing considerable heating.
Other designs have been proposed for pneumatic tires such as disclosed in U.S Pat. Nos. 2,780,266, 2,508,596, 2,560,609 and 2,680,463, and in the aforementioned German Patent Publication, for example, which are, for all practical purposes, directed to concentrically mounting a pair of pneumatic tires, one within the other, with the added complication of rendering such compound pneumatic tires incapable of being mounted on conventional wheel rims.
Further efforts in designing multi-chamber pneumatic tires are represented by structures such as disclosed in U.S. Pat. No. 1,989,402 wherein a pneumatic tire having much analogy with a conventional tire is provided with an auxiliary thread mounted thereon by rivets, or other fasteners, such auxiliary thread being provided with a built-in air chamber, and in U.S. Pat. No. 2,850,069 teaching a multi-chamber inner tube for pneumatic tires requiring special rims or special retaining flaps mounted within the inner tube.