Tape measure with compact retraction system
A tool, such as a tape measure, including a spring-based retraction system is shown. Various spring-based retraction system embodiments are configured to decrease the size occupied by the spring within the tape measure housing, which consequently reduces tape measure housing size providing a more compact tape measure. Various spring-based retraction system embodiments are configured to control retraction of the tape measure in a manner that reduces whip or otherwise controls tape blade retraction. Some retraction system embodiments utilize a reduction gear train, and others utilize a compression spring and a transmission system that converts rotational movement of the tape reel to axial movement, which compresses the spring.
1. A tape measure comprising:
a housing;
a tape reel rotatably mounted within the housing, the tape reel comprising a radially outward facing surface and a radially inward facing surface defining an interior reel cavity; and
an elongate tape blade wound around the radially outward facing surface of the tape reel;
wherein the tape reel comprises a diameter, D, measured across the radially outward facing surface of the tape reel, wherein the elongate tape blade has a total maximum extended length of TL, wherein TL/D is greater than 237.
2. The tape measure of claim 1 , wherein TL/D is greater than 240.
3. The tape measure of claim 1 , wherein TL/D is less than 250.
4. The tape measure of claim 1 , wherein TL is between 6 feet and 50 feet.
5. The tape measure of claim 1 , wherein TL is less than 29 feet.
6. The tape measure of claim 1 , wherein TL is less than 27 feet.
7. The tape measure of claim 1 , wherein the tape reel comprises a reel area, RA, located within the radially outward facing surface of the tape reel, wherein TL/RA is greater than 6.6.
8. The tape measure of claim 7 , wherein TL/RA is greater than 6.7.
9. The tape measure of claim 7 , wherein TL/RA is greater than 7.
10. The tape measure of claim 7 , wherein TL/RA is less than 7.5.
11. The tape measure of claim 1 , further comprising:
a shaft;
a spiral spring coupled between the tape reel and the shaft such that, when the elongate tape blade is unwound from the tape reel to extend from the housing, the spiral spring stores energy and the spiral spring releases energy driving rewinding of the elongate tape blade on to the tape reel; and
a turn reduction mechanism rotatably coupling the spiral spring to the tape reel such that, during extension of the elongate tape blade from the housing, each full rotation of the tape reel is translated into less than a full rotation of the spring.
12. The tape measure of claim 11 , wherein the turn reduction mechanism comprises a gear train.
13. The tape measure of claim 12 , wherein the gear train is a planetary gear train comprising:
a sun gear;
a ring gear surrounding the sun gear; and
a planetary gear located between the sun gear and the ring gear.
14. The tape measure of claim 13 , wherein at least one of the sun gear and the ring gear rotates in a path around the shaft.
15. The tape measure of claim 14 , wherein the planetary gear rotates about an axis at a fixed location relative to the shaft.
16. The tape measure of claim 15 , wherein an inner end of the spiral spring is coupled to the shaft.
17. The tape measure of claim 12 , wherein the gear train provides a gear reduction such that a full turn of the spiral spring about the shaft results in at least 1.5 rotations of the tape reel about the shaft.
18. The tape measure of claim 17 , wherein there is only one spiral spring located within interior reel cavity.
19. The tape measure of claim 12 , wherein the gear train provides a gear reduction such that a full turn of the spiral spring about the shaft results in between 1.8 and 3.5 rotations of the tape reel about the shaft.
20. The tape measure of claim 12 , wherein the elongate tape blade comprises a metal core and a coating layer, and the metal core has an average thickness, TT, and the spiral spring has an average thickness, ST, wherein TT/ST is between 0.1 and 0.7.