US-12624748-B2 - Expanding force electric linear actuator

US12624748B2US 12624748 B2US12624748 B2US 12624748B2US-12624748-B2

Abstract

In general, this disclosure involves a pulley system that includes a plurality of fixed sheaves arranged to at least partially encircle an output shaft, a plurality of traveling sheaves coupled to the output shaft. The output shaft can be configured to pass through the fixed sheaves and translate along an axis of travel and the plurality of traveling sheaves can be arranged such that a geometric average of belt tension created by spans of belt between the plurality of traveling sheaves and the plurality of fixed sheaves is approximately coincident with a centerline of the output shaft. The system further includes a belt extending between and around the plurality of fixed sheaves and the plurality of traveling sheaves such that the belt flexes toward a single surface of the belt.

Inventors

BLAKE SESSIONS
Toomas Sepp

Assignees

Liftwave, Inc.

Dates

Publication Date: 20260512
Application Date: 20241007

Claims (20)

1 . A pulley system comprising: a plurality of fixed sheaves arranged to at least partially encircle an output shaft; a plurality of traveling sheaves coupled to the output shaft, the output shaft configured to pass through the fixed sheaves and translate along an axis of travel, wherein the plurality of traveling sheaves are arranged such that a geometric average of belt tension created by spans of belt between the plurality of traveling sheaves and the plurality of fixed sheaves is located within the output shaft; and a belt extending between and around the plurality of fixed sheaves and the plurality of traveling sheaves.
2 . The system of claim 1 , wherein the plurality of fixed sheaves comprises six sheaves arranged in pairs on three axles that are mounted to a device casing, wherein one pair of sheaves is arranged such that the sheave positioned farther from the output shaft is smaller in diameter than the sheave positioned closer to the output shaft, and wherein two pairs of sheaves are arranged such that the sheaves positioned farther from the output shaft are larger in diameter than the sheaves positioned closer to the output shaft.
3 . The system of claim 2 , wherein the plurality of fixed sheaves are retained on the three axles by a set of flanged end caps that are each bolted to the device casing through a center of their respective axle.
4 . The system of claim 2 , wherein two belt spans each exiting the larger of the sheaves on the two pairs of sheaves arranged such that the larger diameter sheave positioned farther from the output shaft are positioned externally to a casing that encompasses belt spans between the fixed sheaves and the traveling sheaves.
5 . The system of claim 1 , wherein the plurality of traveling sheaves comprises five sheaves coupled to an end of the output shaft.
6 . The system of claim 1 , wherein the belt forms at least ten spans between the plurality of traveling sheaves and the plurality of fixed sheaves.
7 . The system of claim 1 , wherein the device casing at least partially encloses the pulley system, and wherein a device casing is cylindrical.
8 . A belt driven linear actuator comprising: a support structure; an output shaft; a pulley system comprising: a plurality of fixed sheaves arranged to at least partially encircle the output shaft; a plurality of traveling sheaves coupled to the output shaft, the output shaft configured to pass through fixed sheaves and translate along an axis of travel, wherein the plurality of traveling sheaves are arranged such that a geometric average of belt tension created by spans of belt between the plurality of traveling sheaves and the plurality of fixed sheaves is located within the output shaft; and a belt extending between and around the plurality of fixed sheaves; and a belt drive mechanism configured to withdraw belt from the pulley system and pay out belt to the pulley system.
9 . The actuator of claim 8 , wherein the plurality of fixed sheaves comprises six sheaves arranged in pairs on three axles, and wherein the three axles are mounted to the support structure, wherein one pair of sheaves is arranged such that the sheave positioned farther from the output shaft is smaller in diameter than the sheave positioned closer to the output shaft, and wherein two pairs of sheaves are arranged such that the sheaves positioned farther from the output shaft are larger in diameter than the sheaves positioned closer to the output shaft.
10 . The actuator of claim 9 , wherein the plurality of fixed sheaves are retained on the three axles by a set of flanged end caps that are each bolted to the support structure through a center of their respective axle.
11 . The actuator of claim 9 , wherein the belt drive mechanism comprises an electric motor and a capstan.
12 . The actuator of claim 8 , wherein the plurality of traveling sheaves comprises five sheaves coupled to an end of the output shaft.
13 . The actuator of claim 8 , wherein the belt forms at least ten spans between the plurality of traveling sheaves and the plurality of fixed sheaves.
14 . The actuator of claim 8 , wherein the pulley system is at least partially enclosed by a cylindrical casing.
15 . A method of operating a linear actuator, the method comprising: removing a portion of belt from a pulley system using a belt drive mechanism, wherein the pulley system comprises: a plurality of fixed sheaves arranged in to at least partially encircle an output shaft; a plurality of traveling sheaves coupled to an output shaft, the output shaft configured to pass through the fixed sheaves and translate along an axis of travel, wherein the plurality of traveling sheaves are arranged such that a geometric average of belt tension created by spans of belt between the plurality of traveling sheaves and the plurality of fixed sheaves is located within the output shaft; and the belt extending between and around the plurality of fixed sheaves and the plurality of traveling sheaves.
16 . The method of claim 15 , wherein removing the portion of the belt from the pulley system causes the plurality of traveling sheaves and the output shaft to translate along the axis of travel in an expanding direction.
17 . The method of claim 15 , comprising: paying out a portion of the belt to the pulley system to enable the output shaft to translate along the axis of travel in a contracting direction.
18 . The method of claim 15 , wherein the plurality of traveling sheaves comprises five sheaves coupled to an end of the output shaft.
19 . The method of claim 15 , wherein the belt drive mechanism comprises a capstan, and wherein the belt extends from a first anchor point, through the pulley system, about the capstan, and to a stowage reel.
20 . The method of claim 19 , wherein the capstan is operated by an electric motor.

Description

CROSS REFERENCE TO RELATED APPLICATION This application is a continuation of U.S. patent application Ser. No. 18/436,624, filed Feb. 8, 2024, the contents of which are hereby incorporated by reference in its entirety. TECHNICAL FIELD This disclosure generally relates to a pulley system arranged to enable expansion of an electrically driven linear actuator. 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 and method of use that includes a plurality of fixed sheaves arranged to at least partially encircle an output shaft, a plurality of traveling sheaves coupled to the output shaft. The output shaft can be configured to pass through the fixed sheaves and translate along an axis of travel and the plurality of traveling sheaves can be arranged such that a geometric average of belt tension created by spans of belt between the plurality of traveling sheaves and the plurality of fixed sheaves is approximately coincident with a centerline of the output shaft. The system further includes a belt extending between and around the plurality of fixed sheaves and the plurality of traveling sheaves such that the belt flexes toward a single surface of the belt. Implementations can optionally include one or more of the following features. In some instances, the plurality of fixed sheaves includes six sheaves arranged in pairs on three axles that are mounted to a device casing, one pair of sheaves is arranged such that the sheave positioned farther from the output shaft is smaller in diameter than the sheave positioned closer to the output shaft. Two pairs of sheaves are arranged such that the sheaves positioned farther from the output shaft are larger in diameter than the sheaves positioned closer to the output shaft. In some instances, the plurality of fixed sheaves are retained on the three axles by a set of flanged end caps that are each bolted to the device casing through a center of their respective axle. In some instances, two additional belt spans each exit the larger sheaves on the two pairs of sheaves arranged such that the larger diameter sheave is positioned farther from the output shaft and are positioned externally to the device casing. In some instances, the plurality of traveling sheaves includes five sheaves coupled to an end of the output shaft. In some instances, the belt forms at least ten spans between the plurality of traveling sheaves and the plurality of fixed sheaves. In some instances the pulley system is at least partially enclosed by the device casing, and the device casing is cylindrical. This disclosure describes a pulley system that enables extension and contraction of a linear actuator under an expanding force and is configured to fit around the output shaft of that linear actuator. Belt driven systems can have many advantages over other similar systems. For example, a belt driven linear actuator can require less maintenance, be lighter weight, and be capable of more cycles than a similar hydraulic linear actuator. Further the belt driven system, when operated by an electric motor is capable of recouping energy during some movement events (e.g., lowering a load). Many belt drive mechanisms include a capstan, which can receive one or more turns or partial turns of a belt and provide rotational force to draw/take in or pay out the belt. The capstan can be powered by, for example, an electric motor via a set of reduction gears or a hydraulic motor, among other things. The belt can be drawn/taken in or payed out to and from various pulley systems within the linear actuator. To improve durability and maximum capacity of a belt-driven actuator, the internal pulley system can be designed with certain parameters. In general, belt wear and stress will be a limiting factor, and can be reduced by reducing (e.g., minimizing) the amount of bend the belt is subjected to. At the same time, the overall size and shape of the actuator can be similar to the form factor of conventional actuators such as hydraulic pistons. Therefore, this disclosure describes a pulley system that is capable of handling large loads while maintaining an approximately cylindrical form factor. Bending a belt causes non-uniform internal stresses within the belt that can cause accelerated degradation. Thus, minimizing the amount of bend in the belt increases maximum load capacity and service life. To minimize the amount of bend, the device can include relatively large sheaves, and can include only bends in a single direction, that is, avoiding “back bending” or contra-flexion of the belt. The disclosed pulley configuration is designed to allow for large sheaves contained within a relatively small cross-section and does not contra-flex the belt. The details of one or more implementations of the subject matter of thi