Abstract: A multiple-stage positioning structure of dual shafts includes a dual shaft assembly, which includes first and second rotary shafts that are connected to each other with coupling members for being rotated synchronously. The first rotary shaft has a curved section and a planar section. Positioning sleeves are fit over the first and the second rotary shafts. Bearing members bear a positioning bar in such a way to have the planar section of the first rotary shaft in contact engagement with a lateral planar section of the positioning bar. When the first rotary shaft is rotated to have the curved section engage the lateral planar section of the positioning bar, an effect of outward expanding and stretching the positioning sleeves is induced. When the first rotary shaft is rotated to have the planar section re-engage the lateral planar section of the positioning bar, an effect of positioning is induced.

Abstract: A dual-axle hinge structure includes a dual axle assembly, at least one sleeve, and a contactor. The dual axle assembly includes first and second axles that are connected by and mutually push/pull each other through connection members for synchronous rotation. The sleeve is fit over and houses the first and axles. The contactor is arranged between the first and second axles and has two opposite sides respectively in contact engagement with surfaces of the first and second axles. By means of the tight retention achieved with the sleeve and the abutting engagement achieved with the two sides of the contactor, tight engagement is established among the sleeve, the first and second axles, and the contactor to allow for synchronous rotation, in a step-less manner, and positioning of the first axle and the second axle in a tightly retained condition.

Abstract: A synchronized multiple-angle rotatable dual-pivot structure includes a first pivot, a second pivot, a plurality of connection members, and a support frame. The first pivot and the second pivot are each provided with an installation slot. The connection members are of the same length and each has two ends respectively and movably mounted in the installation slots of the first pivot and the second pivot. The support frame has two ends respectively coupled to the first pivot and the second pivot. The connection members are connected between the first pivot and the second pivot so that when one of the first pivot and the second pivot is rotated, forces are induced between the first pivot and the second pivot to mutually pull and push each other so that synchronized rotation can be achieved in an easy and effortless manner and the rotation angle can reach at least 180 degrees.