Patent ID: 6109415
Filing Date: 2000-08-29
Classification: B64C,F16D,F16H

Abstract:
A no-back device comprising;a ballscrew rotatable in opposite directions and having a ballscrew flange with radial surfaces at opposite sides thereof and rotatable with the ballscrew, the ballscrew receiving and transferring a bi-directional axial and torque load from an external source;a housing receiving a section of the ballscrew including the ballscrew flange and permitting limited axial movement of the ballscrew in the housing; anda multi-stage brake mounted in the housing and including:first and second ratchet wheels rotatable relative to the ballscrew and mounted at opposite sides of the ballscrew flange, each of the ratchet wheels having flat radial surfaces at opposite sides thereof parallel to the radial surfaces of the ballscrew flange;a first skewed roller brake ring sandwiched between the ballscrew flange and the first ratchet wheel;a second skewed roller brake ring sandwiched between the ballscrew flange and the second ratchet wheel;first and second thrust plate assemblies disposed, respectively, at opposite sides of the first and second ratchet wheels and having flat radial surfaces facing the ballscrew flange and parallel to the radial surfaces of the ballscrew flange, said thrust plate assemblies being mounted for rotation with the ballscrew;a third skewed roller brake ring disposed between the first ratchet wheel and the first thrust plate assembly;a fourth skewed roller brake ring disposed between the second ratchet wheel and the second thrust plate assembly;the first and second thrust plate assemblies being moveable axially of the ballscrew in the housing for transfer of compressive loads exerted on the ballscrew in one direction and tensile loads exerted on the ballscrew in the other direction for maintaining the first and third skewed roller brake rings in tight frictional engagement with the ballscrew flange, first ratchet wheel and first thrust plate assembly or the second and fourth skewed roller brake rings in tight frictional engagement with the ballscrew flange second ratchet wheel and second thrust plate assembly depending on the direction of the external force applied to the ballscrew; andfirst and second pawl assemblies mounted on the housing and cooperating with the first and second ratchet wheels to permit freewheeling of the first ratchet wheel in a first direction and freewheeling of the second ratchet wheel in the opposite direction, for controlling the effective brake torque applied by the multi-stage brakes.