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, wherein the tape reel comprises a reel area, RA, located within the radially outward facing surface of the tape reel; and
an elongate tape blade wound around the radially outward facing surface of the tape reel, wherein the elongate tape blade has a maximum extended length, TL;
wherein TL/RA is greater than 6.6.
2. The tape measure of claim 1 , further comprising:
a shaft located within the housing;
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 spring stores energy and the spiral spring releases energy driving rewinding of the elongate tape blade on to the tape reel; and
a turn differential 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.
3. The tape measure of claim 2 , wherein the turn differential mechanism comprises a gear train.
4. The tape measure of claim 2 , wherein the turn differential mechanism is a planetary gear train comprising a ring gear, a sun gear, and at least two planetary gears.
5. The tape measure of claim 2 , wherein the spiral spring is at least partially located within the interior reel cavity and at least partially surrounded by the elongate tape blade in the radial direction, wherein the turn differential mechanism is a reduction gear train, wherein at least one gear of the reduction gear train is at least partially surrounded by the elongate tape blade in the radial direction.
6. The tape measure of claim 1 , wherein TL/RA is greater than 6.7.
7. The tape measure of claim 1 , wherein TL/RA is greater than 7.
8. The tape measure of claim 1 , wherein TL/RA is less than 7.5.
9. The tape measure of claim 1 , wherein TL is between 6 feet and 50 feet.
10. The tape measure of claim 1 , wherein the tape measure has only one spiral spring located within the interior reel cavity.
11. The tape measure of claim 1 , wherein the elongate tape blade comprises a metal core and a coating layer, and the metal core has an average cross-sectional area, TA, wherein the spring has an average cross-sectional area, SA, and wherein TA/SA is less than 0.9.
12. The tape measure of claim 11 , wherein TA/SA is less than 0.98.
13. The tape measure of claim 11 , wherein TA/SA is less than 0.7.
14. The tape measure of claim 11 , wherein TA/SA is less than 0.6.
15. The tape measure of claim 11 , wherein TA/SA is less than 0.5.
16. The tape measure of claim 1 , further comprising a total spring length, SL, wherein TL/SL is greater than 2.52.
17. The tape measure of claim 16 , wherein TL/SL is greater than 3.0.
18. The tape measure of claim 16 , wherein TL/SL is greater than 3.6.
19. The tape measure of claim 16 , wherein TL/SL is greater than 3.7.
20. The tape measure of claim 16 , wherein TL/SL is greater than 4.0.
21. The tape measure of claim 16 , wherein TL/SL is between 3 and 5.
22. The tape measure of claim 1 , wherein there is only one spiral spring located within interior reel cavity.