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This paper presents a novel device that propagates through small pipes, named the twisted bundled tube locomotive device. The device consists of three elastic silicone rubber tubes that are twisted and bonded. When any tube is pressurized, it inflates, and the device deforms into a helix. If these tubes are sequentially pressurized, the device exhibits helical rotation, that is, it rotates about its body axis while retaining its helical shape. Thus, the device moves along the pipe axis. Since helical rotation is generated by bending motion alone, the device is highly airtight, and thus strongly resistant to the environment. Helical rotating motion does not scratch the inner wall of the pipe or block the flow in the pipe. The device can be made sufficiently small to travel through thin pipes, because of its simple structure. The device is very flexible and can pass through an elbow-pipe without requiring complicated control. Therefore, the device could be adopted in endoscopes used for pipe inspection. The propulsion principle and the theoretical velocity of the device are discussed and confirmed in prototypes. The manufacturing method for the prototype is also presented. The small prototype (approximate diameter 6 mm) travels at 45 mm/s in a 20-mm diameter pipe, and it passes through the elbow. Moreover, a prototype equipped with a camera can send images of the camera view as it moves the pipe.
Takayama et al. (Wed,) studied this question.