Geometrical instruments – Straightedge type – Cord type
Patent
1989-11-27
1991-08-27
Will, Thomas B.
Geometrical instruments
Straightedge type
Cord type
33756, B44D 338
Patent
active
050421590
ABSTRACT:
A chalk line retraction device is formed of a hollow casing defining a chalk line aperture therethrough. A chalk line reel carrying a chalk line is mounted for rotation within the casing and is keyed to a spur gear. The spur gear is engaged with a ring gear of much larger pitch diameter. The ring gear is coupled to a movable end of a spirally wound band spring. The other end of the band spring is anchored to the casing. The gearing arrangement provides a mechanical advantage such that a relatively long movement of the chalk line produces a corresponding short movement of the movable end of the band spring, thereby allowing a chalk line of considerable length to be taken up on the chalk line reel.
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Thomas Charles H.
Will Thomas B.
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