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US-12624747-B2 - Annular pulley system

US12624747B2US 12624747 B2US12624747 B2US 12624747B2US-12624747-B2

Abstract

In general, this disclosure involves a pulley system that includes a plurality of fixed sheaves arranged in a first annulus and a plurality of traveling sheaves arranged in a second annulus. The plurality of traveling sheaves are configured to travel along an axis of travel and are coupled to an output shaft configured to pass through the first annulus and translate along the axis of travel. The plurality of traveling sheaves are aligned with the plurality of fixed sheaves such that at least half of a plurality of spans between the plurality of traveling sheaves and the plurality of fixed sheaves are parallel spans that are parallel with the axis of travel. A flat belt extends between and around the plurality of fixed sheaves and the plurality of traveling sheaves, the flat belt including a plurality of twists along the parallel spans to form a plurality of twisted spans.

Inventors

  • BLAKE SESSIONS

Assignees

  • Liftwave, Inc.

Dates

Publication Date
20260512
Application Date
20241223

Claims (7)

  1. 1 . A belt driven linear actuator comprising: a support structure; an output shaft; a first pulley system comprising: a first plurality of sheaves coupled to the support structure; a second plurality of sheaves coupled to the output shaft; and a flat belt extending between and around the first plurality of sheaves and the second plurality of sheaves with a predetermined number of free spans between them, and out of the first pulley system, wherein the first pulley system is configured such that removing belt from the first pulley system causes the second plurality of sheaves to translate the output shaft along an axis of travel in a contracting direction; a second pulley system comprising: a third plurality of sheaves arranged in an annular configuration and coupled to the support structure, wherein the third plurality of sheaves at least partially surround the output shaft; a fourth plurality of sheaves arranged in an annular configuration and coupled to the output shaft, wherein the fourth plurality of sheaves at least partially surround the output shaft; the flat belt extending between and around the third plurality of sheaves and the fourth plurality of sheaves with the predetermined number of free spans between them, wherein the second pulley system is configured such that removing belt from the second pulley system causes the fourth plurality of sheaves to translate the output shaft along the axis of travel in an expanding direction; and a belt drive mechanism configured to transfer belt between the first pulley system and the second pulley system.
  2. 2 . The linear actuator of claim 1 , wherein the third plurality of sheaves comprises four sheaves, and wherein the fourth plurality of sheaves comprises five sheaves.
  3. 3 . The linear actuator of claim 1 , wherein the flat belt passing between the third plurality of sheaves and the fourth plurality of sheaves forms a plurality of spans, wherein at least half of the plurality of spans are parallel spans aligned in parallel with the axis of travel, and wherein a subset of the plurality spans are alignment spans, aligned in paired sets with symmetric angles with respect to the axis of travel to minimize torque applied to the output shaft generated by belt tension.
  4. 4 . The linear actuator of claim 3 , wherein at least two of the alignment spans are redirected to be parallel with the axis of travel by at least two redirection sheaves.
  5. 5 . The linear actuator of claim 4 , wherein each parallel span comprises a twist of 72±10 degrees.
  6. 6 . The linear actuator of claim 1 , wherein the belt drive mechanism comprises a capstan, and wherein the flat belt extends from a first anchor point, through the first pulley system, about the capstan, through the second pulley system, and to a second anchor point.
  7. 7 . The linear actuator of claim 6 , wherein the capstan is operated by an electric motor.

Description

CROSS REFERENCE TO RELATED APPLICATION This application is a divisional of U.S. patent application Ser. No. 18/196,019 filed May 11, 2023, the entire content of which application is hereby incorporated by reference in its entirety. TECHNICAL FIELD This disclosure generally relates to a pulley system arranged in an annular configuration. This pulley system can be used in electric linear actuators. BACKGROUND Modern belts have many desirable characteristics. They can be lightweight, low-maintenance, and have high strength under tension. Many new and old applications of modern belts are currently being adapted. SUMMARY In general, the disclosure involves a pulley system that includes a plurality of fixed sheaves arranged in a first annulus and a plurality of traveling sheaves arranged in a second annulus. The plurality of traveling sheaves are configured to travel along an axis of travel and are coupled to an output shaft configured to pass through the first annulus and translate along the axis of travel. The plurality of traveling sheaves are aligned with the plurality of fixed sheaves such that at least half of a plurality of spans between the plurality of traveling sheaves and the plurality of fixed sheaves are parallel spans that are parallel with the axis of travel. A flat belt extends between and around the plurality of fixed sheaves and the plurality of traveling sheaves, the flat belt including a plurality of twists along the parallel spans to form a plurality of twisted spans. Implementations can optionally include one or more of the following features. In some instances, the plurality of fixed sheaves includes four sheaves and the plurality of traveling sheaves includes five sheaves. In some instances, each twisted span of the plurality of twisted spans is twisted by 72±10 degrees. In some instances, the plurality of spans between the plurality of traveling sheaves and the plurality of fixed sheaves comprises eight spans. In some instances, the plurality of fixed sheaves are coupled to a common structure that is a component of a linear actuator. In some instances, a subset of the plurality of spans between the plurality of traveling sheaves and the plurality of fixed sheaves are alignment spans, aligned in paired sets with symmetric angles with respect to the axis of travel to minimize torque applied to the output shaft generated by belt tension. In some instances, the plurality of spans includes four parallel spans and four alignment spans. The four alignment spans include two alignment spans that oppose rotation in a first direction about the axis of travel and two alignment spans that oppose rotation in a second direction about the axis of travel. This disclosure further describes a belt driven linear actuator that includes a support structure, and output shaft, a first pulley system, a second pulley system, and a belt drive mechanism. The first pulley system includes a first plurality of sheaves coupled to the support structure, a second plurality of sheaves coupled to the output shaft, and a flat belt extending between and around the first plurality of sheaves and the second plurality of sheaves with a predetermined number of free spans between them, and out of the first pulley system. The first pulley system is configured such that removing belt from the first pulley system causes the second plurality of sheaves to translate the output shaft along an axis of travel in a contracting direction. The second pulley system includes a third plurality of sheaves arranged in an annular configuration and coupled to the support structure, the third plurality of sheaves at least partially surrounding the output shaft. The second pulley system includes a fourth plurality of sheaves arranged in an annular configuration and coupled to the output shaft, the fourth plurality of sheaves a least partially surrounding the output shaft. The flat belt extends between and around the third plurality of sheaves and the fourth plurality of sheaves with the predetermined number of free spans between them. The second pulley system is configured such that removing belt from the second pulley system causes the fourth plurality of sheaves to translate the output shaft along the axis of travel in an expanding direction. The belt drive mechanism is configured to transfer belt between the first pulley system and the second pulley system. In some instances, the third plurality of sheaves includes four sheaves and the fourth plurality of sheaves includes five sheaves. In some instances, the flat belt passing between the third plurality of sheaves and the fourth plurality of sheaves forms a plurality of spans, and at least half of the plurality of spans are parallel spans aligned in parallel with the axis of travel, and a subset of the plurality spans are alignment spans, aligned to oppose rotation about the axis of travel. In some instances, the plurality of spans includes four parallel spans and four spans alignment spans, and t