| CPC F16H 19/0618 (2013.01) | 1 Claim |
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1. An extension-retraction device comprising:
an extendable and retractable cylindrical structure; and
an inner guide member disposed inside the cylindrical structure, wherein:
the cylindrical structure includes an outer belt and an inner belt disposed on an inner side of the outer belt;
the outer belt is provided with a plurality of outer belt protrusions and a plurality of outer belt holes, each outer belt protrusions of the plurality of the outer belt protrusions corresponding to an outer belt hole of the plurality of the outer belt holes, the plurality of the outer belt protrusion and respective outer belt holes being provided in two rows in a longitudinal direction of the outer belt;
the inner belt is provided with a plurality of inner belt protrusions and a plurality of inner belt holes, each inner belt protrusions of the plurality of the inner belt protrusions corresponding to an inner belt hole of the plurality of the inner belt holes, the plurality of the inner belt protrusion and respective inner belt holes being provided in two rows in a longitudinal direction of the inner belt;
the inner guide member includes a first spiral groove extending along the inner belt protrusions provided in a first row of the two rows, and a second spiral groove extending along the inner belt protrusions provided on a second row of the two rows, the first row being different from the second row;
when the inner guide member rotates counterclockwise around a central axis of the cylindrical structure, the outer belt and the inner belt are sent out to be spirally wound while engaging with each other, and the cylindrical structure extends;
when the inner guide member rotates clockwise around the central axis, the outer belt and the inner belt that have been engaged and wound are drawn in to be unwound, and the cylindrical structure retracts;
the first spiral groove includes a fitting portion in which one or more of the protrusions of the inner belt are fitted in the first spiral groove;
when the cylindrical structure is viewed, in a direction in which the central axis is aligned vertically and the inner belt wound spirally around the inner guide member appears to rise to right, the first row is vertically above the adjacent second row;
a first plane is parallel to the central axis, and includes the central axis and a vertical lower end portion of the fitting portion;
a second plane is parallel to the central axis, and includes the central axis and a vertical lower terminal end of the second spiral groove; and
an angle made by intersecting the first plane and the second plane is less than 180 degrees.
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