Friction drive differential screw

Claim 2

A mechanism for converting rotary motion into linear motion comprising: a first threaded member, a second threaded member having threads adapted for continuous engagement with said first threaded member at least at one point of contact, means for allowing said second member to rotate freely, means for restricting the displacement of said second member along a single path between greater and lesser thread engagement with said first threaded member, and bias means for pressing said second member toward full threaded engagement with said first member.

Claim 3

A mechanism for converting rotary motion into linear motion as set forth in claim 1 comprising further: means for precompressing said elements of said mechanism whereby backlash is avoided

Claim 4

A mechanism for converting rotary motion into linear motion as set forth in claim 1 in which said first threaded member comprises, a threaded shaft.

Claim 5

A mechanism for converting rotary motion into linear motion as set forth in claim 3 in which said second threaded member comprises, a nut surrounding said shaft and having internal threads of a greater pitch diameter than the threads of said shaft.

Claim 6

A mechanism for converting rotary motion into linear motion as set forth in claim 1 in which said means for allowing said second member to rotate freely comprises, first anti-friction bearing means disposed around said nut for allowing said nut to rotate freely about said shaft.

Claim 7

A mechanism for converting rotary motion into linear motion as set forth in claim 5 in which said anti-friction bearing means comprises, a first external ring having a first internal raceway, and a second raceway on the external surface of said nut for cooperating with said first internal raceway.

Claim 8

A mechanism for converting rotary motion into linear motion as set forth in claim 6 in which said means for restricting the displacement of said second member comprises, guide means to each side of said external ring for restricting the displacement of said nut to a single path between a position toward the first threaded member to a position away from the first threaded member.

Claim 9

A mechanism for converting rotary motion into linear motion as set forth in claim 7 further comprising: second bearing means mounted for rotational support of said shaft.

Claim 10

A mechanism for converting rotary motion into linear motion as set forth in claim 7 further comprising: third and fourth bearing means mounted above and below said first external ring for rotational support of said nut, a first and a second nut centering crescent mounted opposed to said third and fourth bearing means for bringing the longitudinal axis of said nut into alignment with the longitudinal axis of said shaft, a braking surface on said nut, brake means adapted for pushing said nut from full engagement with said threaded shaft toward said nut centering means and for stopping rotation of said nut when said nut is pressed against said first and second nut centering crescent, and the internal pitch diameter of said nut is less than the external pitch diameter of said threaded shaft.

Claim 11

A mechanism for converting rotary motion into linear Motion as set forth in claim 1 in which said second threaded member comprises, a thread extending spirally along the interior of said threaded member and at least one flank of the thread has a profile different from that of the flank of the thread of said first member.

Claim 12

A mechanism for converting rotary motion into linear motion as set forth in claim 1 in which said first threaded member comprises, a thread extending spirally along the exterior of said threaded member and each flank of the thread has a convex profile.

Claim 13

A mechanism for converting rotary motion into linear motion as set forth in claim 11 in which said second threaded member comprises, a nut having threads extending spirally along the interior of said nut and each flank of the thread has a flat profile.

Claim 14

A mechanism for converting rotary motion into linear motion as set forth in claim 11 in which said second threaded member comprises, a nut having threads extending spirally along the interior of said nut and each flank of the thread has a convex profile.

Claim 15

A mechanism for converting rotary motion into linear motion as set forth in claim 11 in which said second threaded member comprises, a nut having threads extending spirally along the interior of said nut and each flank of the thread has a concave flank of a radius of curvature greater than that of said convex profile of said first threaded member.

Claim 16

A mechanism for converting rotary motion into linear motion as set forth in claim 14 in which said second bias means comprises, a spring which exerts greater force than said first bias means.

Claim 17

A mechanism for converting rotary motion into linear motion as set forth in claim 1 further comprising: a second bias means for resisting motion of said second member when said second member has moved a predetermined distance against said first bias means along said single path away from full engagement with said first member.

Claim 18

A mechanism for converting rotary motion into linear motion as set forth in claim 1 in which said second threaded member comprises, a compound nut having a first and a second nut element, each having internal threads of a greater pitch diameter than said first member and being adapted for relative movement only along the longitudinal axis of said compound nut.

Claim 19

A mechanism for converting rotary motion into linear motion as set forth in claim 17 comprising further, means for moving said second nut element axially with respect to said first nut element whereby the axial position of said first and second nut elements in respect to each other is varied to cause the ratio of rotary motion to linear motion of said first threaded member to vary with the different axial positions of said first and second nut elements.

Claim 20

A mechanism for converting rotary motion into linear motion as set forth in claim 1 in which, said first threaded member has a lead which is an integral multiple of the lead of said second threaded member.

Claim 21

A mechanism for converting rotary motion into linear motion as set forth in claim 19 in which, said first threaded member is a nut, and said second threaded member is a shaft.

Claim 22

A mechanism for converting rotary motion into linear motion at an infinitely variable rate comprising: a first threaded member, a compound threaded member having a first and a second threaded element, each having threads adapted for continuous engagement with said first threaded member on at least one point of contact, means for allowing said compound threaded member to rotate freely, bias means for pressing said compound threaded member toward full engagement with said first threaded member, means for restricting the displacement of said compound threaded member along a single path between greater and lesser thread engagement with said first threaded member, means for moving one of said first and second threaded elements axially relative to said first threaded membEr whereby the position of said first and second threaded element is varied relative to said first threaded member and the direction of linear motion of said first threaded member may be reversed as well as infinitely varied.

Claim 23

A mechanism for converting rotary motion into linear motion at an infinitely variable rate comprising: a first threaded member, a compound threaded member having a first and a second threaded element, each having threads adapted for continuous engagement with said first threaded member on at least one point of contact, means for allowing said compound threaded member to rotate freely, bias means for pressing said compound threaded member toward full engagement with said first threaded member, means for restricting the displacement of said compound threaded member along a single path between greater and lesser thread engagement with said first threaded member, means for moving one of said first and second threaded elements axially relative to said first threaded membEr whereby the position of said first and second threaded element is varied relative to said first threaded member and the direction of linear motion of said first threaded member may be reversed as well as infinitely varied.

Claim 24

A mechanism for converting rotary motion into rectilinear motion as set forth in claim 21 in which said compound nut comprises, a first and a second nut element each having an internal diameter which is about equal to an integral multiple of the diameter of said shaft and is at least twice the diameter of said shaft, and at least a double thread having the same pitch as the threads on said shaft and extending around the interior of each said nut.

Claim 25

A mechanism for converting rotary motion into linear motion at an infinitely variable rate comprising, a rotatable lead screw having external threads of a given diameter, a compound nut having a first and a second nut element, each having internal threads of a greater diameter than the threads of said lead screw, a first race formed on the exterior of said first nut element, means for connecting said nut elements to allow relative axial motion but hold said nut elements from relative rotational motion, a first anti-friction bearing means mounted for rotational support of said lead screw, a second anti-friction bearing means mounted for rotational support of said nut and having its center line coincident with the center line of said nut and parallel to the center line of said shaft and comprising, a first race on the exterior of said first nut element, a second race formed on the interior of an external ring, means for pressing said nut toward said rotatable lead screw and for restricting the movement of said nut to a direction normal to the center line of said lead screw, and means for moving said second nut axially with respect to said first nut whereby the position of said first and second nut, in respect to said lead screw, is varied to cause the ratio of rotary motion to linear motion of said lead screw to vary with the varying position of said second nut.

Claim 26

A mechanism for converting rotary motion into linear motion at an infinitely variable rate comprising, a rotatable lead screw having external threads of a given diameter, a compound nut having a first and a second nut element, each having internal threads of a greater diameter than the threads of said lead screw, a first race formed on the exterior of said first nut element, means for connecting said nut elements to allow relative axial motion but hold said nut elements from relative rotational motion, a first anti-friction bearing means mounted for rotational support of said lead screw, a second anti-friction bearing means mounted for rotational support of said nut and having its center line coincident with the center line of said nut and parallel to the center line of said shaft and comprising, a first race on the exterior of said first nut element, a second race formed on the interior of an external ring, means for pressing said nut toward said rotatable lead screw and for restricting the movement of said nut to a direction normal to the center line of said lead screw, and means for moving said second nut axially with respect to said first nut whereby the position of said first and second nut, in respect to said lead screw, is varied to cause the ratio of rotary motion to linear motion of said lead screw to vary with the varying position of said second nut.

Claim 27

A mechanism for converting rotary motion into linear motion at an infinitely variable rate as set forth in claim 23 in which said pressing and restricting means comprises, means for restricting the movement of said second anti-friction bearing means to a direction normal to the centerline of said screw, and bias means for pressing the external ring of said second anti-friction bearing means toward said slidable means.

Claim 28

A mechanism for converting rotary motion into linear motion comprising: a first threaded member, a second threaded member having threads adapted for continuous engagement with said first threaded member at least at one point of contact, bearing means for allowing said second threaded member to rotate freely, and bias means for pressing said second threaded member toward full engagement with said first threaded member.

Claim 29

A mechanism for converting rotary motion into linear motion comprising: a first threaded member, a second threaded member having threads adapted for continuous engagement with said first threaded member at least at one point of contact, bearing means for allowing said second threaded member to rotate freely, and bias means for pressing said second threaded member toward full engagement with said first threaded member.

Claim 30

A mechanism for converting rotary motion into linear motion as set forth in claim 25 in which said second threaded member comprises, a roller having external threads.

Claim 31

A mechanism for converting rotary motion into linear motion as set forth in claim 25 in which said second threaded member comprises, a member having a cylindrical surface, and at least one thread extending around said surface and each said thread having zero lead angle whereby the threads of said first and second members mesh to cause the mechanism to operate like a simple anti-friction screw.

Claim 34

A method of conVerting rotary motion into linear motion as set forth in claim 28 comprising the further steps of, shaping the flank profile of the threads of at least one member to be other than flat.

Claim 35

A method of converting rotary motion into linear motion as set forth in claim 29 comprising the further step of, applying a force to the first threaded member along its longitudinal axis whereby the threads of said first threaded member are urged along the direction of the longitudinal axis of said first member and a lateral force is applied to the threads of said second member.

Claim 36

A method of converting rotary motion into linear motion as set forth in claim 30 further comprising the step of, moving said second threaded member to a position where its longitudinal axis is coincident with the longitudinal axis of said first threaded member and the threads are in contact along their length, and stopping the rotation of said second threaded member whereby said first and second threaded members operate like a conventional nut and bolt.

Claim 37

A method of converting rotary motion into linear motion as set forth in claim 29 comprising the further steps of, placing a third threaded member having the same pitch diameter as said second threaded member to rotate with said second threaded member, and moving the longitudinal position of said third threaded member in relation to said second threaded member whereby the amount of engagement of the threads of said first threaded member with said second and third threaded member is changed to vary the effective pitch diameter of the members.

Claim 38

A mechanism for converting rotary motion into linear motion comprising: a first threaded member; a second threaded member having a different pitch diameter from said first member; means for allowing said second member to rotate freely; means for restricting the displacement of said second member along a single path generally lateral to the longitudinal axes of said first and second threaded members to give greater and lesser thread engagement with said first threaded member; and bias means for pressing said second member toward full threaded engagement with said first member.

Claim 39

A mechanism for converting rotary motion into linear motion comprising: a first threaded member; a second threaded member having a different pitch diameter from said first member; means for allowing said second member to rotate freely; means for restricting the displacement of said second member along a single path generally lateral to the longitudinal axes of said first and second threaded members to give greater and lesser thread engagement with said first threaded member; and bias means for pressing said second member toward full threaded engagement with said first member.