Drive apparatus with primary and secondary no-back features
AssigneeSundstrand Corporation
InventorDavid E. Russ
Life of this patent
Estimating the term…
Abstract
A linear ballscrew type actuator including a bi-directional no-back device having both primary and secondary no-back features is provided. The secondary no-back features only become active following a failure of the primary no-back features, thereby ensuring maximum reliability by precluding wear or fatigue of the secondary no-back components during normal operation of the actuator. The secondary no-back features are provided by secondary pawl mechanisms mounted at the distal end of an articulated eccentric arm. The angular position of the eccentric arm is utilized to annunciate the operational condition of the no-back device. Angular motion of the eccentric arm is utilized to trigger engagement of a secondary locking device, upon failure of the primary no-back features.
Claims22
In a drive apparatus operatively connecting a prime mover to a load moved thereby, a no-back mechanism including:
- a shaft, rotatable about an axis, and operably connected within said drive apparatus to be rotated by said prime mover or by movement of said load;
- and
- first brake means for resisting rotation of said shaft in one direction about said axis;
- said first brake means including both a primary and a secondary no-back means for resisting said rotation of said shaft in said one direction, with said secondary no-back means only resisting said rotation in said one direction following a failure of said primary no-back means to resist said rotation in said one direction.
A no-back mechanism including:
- a housing;
- a shaft mounted within said housing for rotation about an axis in either a clockwise or a counterclockwise direction;
- first brake means for resisting rotation of said shaft in said clockwise direction about said axis;
- second brake means for resisting rotation of said shaft in a counterclockwise direction about said axis;
- each of said first and second brake means including:
- a ratchet wheel, having ratchet teeth attached thereto, mounted for rotation independently of said shaft about said axis;
- primary pawl means operatively connected between said housing and said ratchet wheel in a manner allowing said ratchet wheel to rotate freely in one direction but to engage said ratchet teeth and prevent further rotation of said ratchet wheel in an opposite direction;
- secondary pawl means including:
- an eccentric arm having one end thereof pivotably mounted to allow angular rotation of the arm between a first and a second angular position, within a plane parallel to said plane of rotation of said ratchet wheel, about a pivot point located along a line extending generally perpendicularly and radially through said axis;
- a secondary pawl having a first end thereof pivotably attached to a distal end of said eccentric arm;
- said secondary pawl having a distal end thereof configured to engage said ratchet teeth when said ratchet wheel is rotating in said opposite direction, and to ride across said first ratchet teeth without engagement with said first ratchet teeth when said first ratchet wheel is rotated in said one direction;
- and
- stop means for preventing angular rotation of said eccentric arm past said second angular position by reacting forces transferred to said arm as a result of the engagement of said secondary pawl with said ratchet wheel, into said housing, thereby locking said ratchet wheel against further rotation in said opposite direction.
In an aircraft having a movable control surface, and an actuator operatively connected to move said control surface, said actuator including:
- first brake means for resisting movement of said control surface in one direction with respect to said aircraft;
- said first brake means including both a primary and a secondary no-back means for resisting said movement of said control surface in said one direction, with said secondary no-back means only resisting said movement in said one direction following a failure of said primary no-back means to resist said movement in said one direction;
- and
- second brake means for resisting movement of said control surface in an opposite direction with respect to said aircraft;
- said second brake means including both a primary and a secondary no-back means for resisting said movement of said control surface in said opposite direction, with said secondary no-back means of said second brake means only resisting said movement in said opposite direction following a failure of said primary no-back means of said second brake means to resist said movement in said opposite direction.
In a drive apparatus operatively connecting a prime mover to a load moved thereby along a path, a no-back mechanism including:
- first brake means for resisting movement of said load in one direction along said path;
- said first brake means including both a primary and secondary no-back means for resisting said movement of said load in said one direction along said path, with said secondary no-back means only resisting said movement in said one direction following a failure of said primary no-back means to resist said movement in said one direction along said path.
Dependencies are inferred from the claim text.