US 6,981,428 B2 | ||
Linear actuators | ||
Alistair Ross Donald, North Somerset (United Kingdom); and Paul John Dursley, Bristol (United Kingdom) | ||
Assigned to Vetco Gray Controls Limited, Bristol (United Kingdom) | ||
Filed on Jan. 28, 2003, as Appl. No. 10/352,442. | ||
Claims priority of application No. 0202405 (GB), filed on Feb. 01, 2002; and application No. 0209047 (GB), filed on Apr. 19, 2002. | ||
Prior Publication US 2003/0145667 A1, Aug. 07, 2003 | ||
Int. Cl. F16H 25/20 (2006.01) |
U.S. Cl. 74—89.26 | 12 Claims |
1. A linear actuator comprising:
rotary motion producing means;
linear motion producing means coupled with said rotary motion producing means for converting said rotary motion to linear
motion, said linear motion producing means comprising a threaded shaft and nut arrangement;
a driven member movable linearly by said linear motion producing means between a first position and a second position, said
driven member being coupled to one of said shaft and nut arrangement; and
back-drive means for returning said driven member to said first position in the event of a fault; characterized in that:said linear motion producing means includes torque reaction means which, in normal operation, is in an activated condition
and provides a torque reaction path to enable the driven member to be reversibly moved between said first and said second
positions, the driven member being restrained from rotating, but which, in the event of a fault, is in a de-activated condition
so that it no longer provides said torque reaction path and said back-drive means can move the driven member to said first
position, without disengaging the rotary motion producing means; whereinthe nut arrangement is rotated by a worm and wheel arrangement to move said shaft linearly and said shaft is coupled to said
driven member; andwherein said torque reaction means includes a first gear wheel on said shaft, coupled to a further gear wheel and means which
prevents rotation of the further gear wheel during normal operation so that said gear wheels and said shaft cannot rotate
but which allows said further gear wheel and thereby said first gear wheel and said shaft to rotate in the event of a fault.
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