Actuator with no-back mechanism

Claim 2

In an actuator, a first member having longitudinal screw threads and a second member having corresponding longitudinal screw threads with the members positioned such that a rotation of one member effects an axial longitudinal translation of the other, and a no-back braking device comprising an annular flange means attached to the rotated one of said two members an annular member positioned adjacent to but normally longitudinally spaced from the flange means, said flange means being longitudinally movable into and out of engagement with said annular member, wall means encircling the annular member, and unidirectional braking means positioned between the annular member and the wall means to permit relative rotation in one direction but prevent it in the other, the unidirectional braking means comprising an overrunning clutch, and means operable upon longitudinal displacement of said flange means relative to said annular member to effect engagement of said flange means and said annular member so as to drivingly interconnect said unidirectional braking means with said rotated member.

Claim 3

In an actuator, as described in claim 1, wherein the overrunning clutch is a roller clutch.

Claim 4

In an actuator, as described in claim 2, wherein the roller clutch comprises a plurality of ramplike indentations in an outer surface of thE annular member, roller means in each indentation, and means urging each roller means to wedge between the ramplike indentation and the wall means.

Claim 5

In an actuator, as described in claim 2, wherein the roller clutch comprises a plurality of ramplike indentations in an inner surface of the wall means, roller means in each indentation, and means urging each roller means to wedge between the ramplike indentation and a radially outer surface of the annular member.

Claim 6

In an actuator, as described in claim 1, wherein an annular friction disc is attached to the flange means adjacent to the annular member.

Claim 7

The actuator of claim 5, wherein the coefficient of friction Mu between the friction disc and the adjacent annular member is equal to or greater than the lead L of the screw threads divided by (Rm the mean radius of the friction disc times 2 pi ) or, expressed in formula form, the coefficient of friction Mu L/Rm2 pi .

Claim 8

In an actuator, as defined in claim 2, wherein the no-back braking device comprises a plurality of annular flange means.

Claim 9

In an actuator comprising a lead screw means and a corresponding nut means wherein an axial motion of the nut is effected by a rotation of the screw, and a no-back brake means comprising an annular flange means attached to the screw and having front and rear surfaces, a first unidirectional braking means cooperating with the front surface of the flange means to resist rotation of the screw means in one direction, and a second unidirectional braking means cooperating with the rear surface of the flange means to resist rotation of the screw means in the opposite direction, the improvement wherein: the unidirectional braking means comprise, respectively, first and second friction discs connected to the front and rear surfaces of the flange means, first and second freely rotating annular members adjacent to each friction disc housing means surrounding the annular members, and left- and right-handed roller clutch means, respectively, mounted between each annular member and the surrounding housing.

Claim 10

In an actuator comprising a lead screw means and a corresponding nut means wherein an axial motion of the nut is effected by a rotation of the screw, and a no-back brake means comprising an annular flange means attached to the screw and having front and rear surfaces, a first unidirectional braking means cooperating with the front surface of the flange means to resist rotation of the screw means in one direction, and a second unidirectional braking means cooperating with the rear surface of the flange means to resist rotation of the screw means in the opposite direction, the improvement wherein: the unidirectional braking means comprise, respectively, first and second friction discs connected to the front and rear surfaces of the flange means, first and second freely rotating annular members adjacent to each friction disc housing means surrounding the annular members, and left- and right-handed roller clutch means, respectively, mounted between each annular member and the surrounding housing.

Claim 11

In an actuator, as described in claim 8, wherein the roller clutch means comprise a plurality of indented ramps in a radially outer surface of each annular member, roller means in each indented ramp, and means urging each roller means to wedge between the ramp and the surrounding housing.

Claim 12

In an actuator, as described in claim 8, wherein the roller clutch means comprises a plurality of indented ramps in a radially inner surface of the surrounding housing, roller means in each indented ramp, and means urging each roller means to wedge between the ramp and a radially outer surface of each annular member.

Claim 13

In an actuator, as described in claim 9, wherein the means urging each roller means comprise spring means.

Claim 14

In an actuator, as described in claim 10, wherein the means urging each roller means, comprise spring means.

Claim 15

A linear actuator comprising: housing means, a low-friction lead screw within the housing means, a corresponding nut attached to a part to be actuated, and cooperating with the screw such that a rotary motion of the screw causes an axial movement of the nut, a no-back braking means comprising: an annular flange on the screw, first and second friction discs on the opposite surfaces of the flange, first and second annular members having radially outer surfaces and being rotatably positioned within the housing means adjacent to the friction discs, a plurality of camming depressions sloping radially inwardly from the radially outer surface of the first annular member in a clockwise direction, and a plurality of camming depressions sloping radially inwardly from the radially outer surface of the second annular member in a counterclockwise direction, roller means in the depressions between the annular members and the housing, means associated with each roller means to urge each roller means to wedge bEtween the housing means and the camming depression, whereby the first annular member resists rotation in one direction but permits it in the other, and the second annular member resists and permits relative rotation in respectively different directions than the first annular member.

Claim 16

A linear actuator comprising: housing means, a low-friction lead screw within the housing means, a corresponding nut attached to a part to be actuated, and cooperating with the screw such that a rotary motion of the screw causes an axial movement of the nut, a no-back braking means comprising: an annular flange on the screw, first and second friction discs on the opposite surfaces of the flange, first and second annular members having radially outer surfaces and being rotatably positioned within the housing means adjacent to the friction discs, a plurality of camming depressions sloping radially inwardly from the radially outer surface of the first annular member in a clockwise direction, and a plurality of camming depressions sloping radially inwardly from the radially outer surface of the second annular member in a counterclockwise direction, roller means in the depressions between the annular members and the housing, means associated with each roller means to urge each roller means to wedge bEtween the housing means and the camming depression, whereby the first annular member resists rotation in one direction but permits it in the other, and the second annular member resists and permits relative rotation in respectively different directions than the first annular member.

Claim 17

A linear actuator, as described in claim 13, wherein the means associated with each roller means comprise spring means.

Claim 18

A linear actuator, as described in claim 13, wherein the friction discs and their respective adjacent annular member are not in contact.

Claim 19

An actuator comprising a screw member having external longitudinal screw threads and a nut member having corresponding longitudinal screw threads with the members positioned such that rotation of one member effects an axial longitudinal displacement of the other and a no-back braking device comprising a peripheral radial flange attached to the screw, an annular member surrounding said screw and having one radial face positioned adjacent to a radial face of the flange of said screw, said screw being longitudinally movable relative to said annular member so as to move said radial face of said flange into and out of engagement with said radial face of said annular member, wall means encircling the annular member, and unidirectional braking means positioned between the annular member and the wall means to permit rotation of the annular member in one direction but prevent it in the other, and means operable upon longitudinal displacement of said screw in one direction to effect rotational driving engagement of said radial face of said flange and said radial face of said annular member so as to interconnect said unidirectional braking means with said screw member.

Claim 20

An actuator comprising a screw member having external longitudinal screw threads and a nut member having corresponding longitudinal screw threads with the members positioned such that rotation of one member effects an axial longitudinal displacement of the other and a no-back braking device comprising a peripheral radial flange attached to the screw, an annular member surrounding said screw and having one radial face positioned adjacent to a radial face of the flange of said screw, said screw being longitudinally movable relative to said annular member so as to move said radial face of said flange into and out of engagement with said radial face of said annular member, wall means encircling the annular member, and unidirectional braking means positioned between the annular member and the wall means to permit rotation of the annular member in one direction but prevent it in the other, and means operable upon longitudinal displacement of said screw in one direction to effect rotational driving engagement of said radial face of said flange and said radial face of said annular member so as to interconnect said unidirectional braking means with said screw member.

Claim 21

The actuator of claim 16, wherein the unidirectional braking means comprises a plurality of ramplike indentations in an outer surface of the annular member, a plurality of roller means, and means urging each roller means to wedge between the ramplike indentations, and the wall means.

Claim 22

The actuator of claim 16, wherein a friction disc is fixedly attached to said radial face of said flange and said radial face of said annular member.

Claim 23

The actuator of claim 18, wherein the coefficient of friction Mu between the friction disc and the annular member is equal to or greater than the lead L of the screw threads divided by (Rm the means radius of the friction disc times 2 pi ) or, expressed in formula form, the coefficient of friction Mu L/Rm 2 pi .