How Exoskeletons Use Screws and Cables to Move Joints
This patent describes a mechanical system for exoskeletons that uses a rotating screw to push a nut, which then pulls cables to make a joint bend or straighten.
Original patent title: “Ball screw and tensile member exoskeleton joint actuation device”
This patent describes a mechanical system for exoskeletons that uses a rotating screw to push a nut, which then pulls cables to make a joint bend or straighten. Granted to Ekso Bionics in 2020 with 23 claims and 6 forward citations, and it is expected to expire in 2037.
Coverage
What does this patent actually cover?
The patent describes an exoskeleton joint actuator that connects a first support (like a torso brace) to a second support (like an upper leg support) via a joint (such as a hip joint, claimclaimA numbered sentence at the end of a patent that legally defines what the inventor owns. The most important section.Read more → 10). The actuator includes a "ball screw" and a "ball nut assembly" that moves along the screw (claim 1). This ball nut assembly is connected to "at least two tensile members," which are like strong cables. When the ball nut assembly moves in one direction along the screw, it pulls on these tensile members. This pulling action causes the second support to rotate in a specific direction relative to the first support around the joint. Moving the ball nut assembly in the opposite direction makes the joint rotate the other way, allowing for controlled bending and straightening of the exoskeleton's limb.
The gap
What does this patent NOT cover?
- Exoskeletons that use hydraulic or pneumatic cylinders for joint movement instead of a ball screw and tensile members.
- Joint actuation systems that use rigid linkages or gears directly to move the supports, rather than flexible tensile members.
- Actuators that rely on only a single tensile member to create bidirectional joint rotation.
- Systems where the tensile members are not routed with portions extending in opposite directions from the ball nut assembly, or not on opposite sides of the ball screw (claimclaimA numbered sentence at the end of a patent that legally defines what the inventor owns. The most important section.Read more → 1).
- Exoskeletons where the joint does not include a joint pulley connected to the tensile members (claimclaimA numbered sentence at the end of a patent that legally defines what the inventor owns. The most important section.Read more → 2).
These exclusions are unique to PatentBrief — derived from the actual claim language, not patent-office boilerplate.
Key facts
What made this novel
The noveltynoveltyThe requirement that an invention be different from anything publicly known before its priority date.Read more → lies in efficiently converting the linear motion of a ball nut along a screw into powerful, bidirectional rotational motion at a joint using a specific arrangement of multiple tensile members. This allows for a compact and robust design for controlling exoskeleton joints.
The Patent Drawing
Schematic visualization of the patent's claim structure. Hand-drawn diagrams in progress for each landmark patent.
Where you've seen this
Real-world examples
Ekso Bionics EksoNR exoskeleton
Industrial exoskeletons for lifting assistance
Rehabilitation exoskeletons for gait training
Why it matters
The bigger picture
This type of actuation is important for exoskeletons because it allows for precise and powerful control of movement. Exoskeletons, like those made by Ekso Bionics, help people with mobility challenges or assist workers in physically demanding jobs. A reliable and strong joint mechanism is crucial for safety and effective assistance, enabling users to walk or lift with support.
Filed
April 27, 2017
Granted
July 7, 2020
Market context
Who's building on this
Companies in this space
Ekso Bionics Inc., the assigneeassigneeThe entity that owns the patent — usually the inventor's employer or a company.Read more →, continues to develop and market exoskeletons for medical and industrial use. Other companies in the powered exoskeleton space, such as Sarcos Technology and Robotics Corporation and Cyberdyne, also work on advanced joint actuation systems.
Market impact
This type of precise and powerful actuation system has enabled the development of more capable and reliable powered exoskeletons. It helps create devices that can safely assist in rehabilitation or augment human strength in industrial settings, contributing to the growth of the assistive robotics market.
Claim 1 — Plain English
What this patent covers
The patent describes an exoskeleton joint actuator that connects a first support (like a torso brace) to a second support (like an upper leg support) via a joint (such as a hip joint, claim 10). The actuator includes a "ball screw" and a "ball nut assembly" that moves along the screw (claim 1). This ball nut assembly is connected to "at least two tensile members," which are like strong cables. When the ball nut assembly moves in one direction along the screw, it pulls on these tensile members. This pulling action causes the second support to rotate in a specific direction relative to the first support around the joint. Moving the ball nut assembly in the opposite direction makes the joint rotate the other way, allowing for controlled bending and straightening of the exoskeleton's limb.
The clever bit
The novelty lies in efficiently converting the linear motion of a ball nut along a screw into powerful, bidirectional rotational motion at a joint using a specific arrangement of multiple tensile members. This allows for a compact and robust design for controlling exoskeleton joints.
What it does not cover
- Exoskeletons that use hydraulic or pneumatic cylinders for joint movement instead of a ball screw and tensile members.
- Joint actuation systems that use rigid linkages or gears directly to move the supports, rather than flexible tensile members.
- Actuators that rely on only a single tensile member to create bidirectional joint rotation.
- Systems where the tensile members are not routed with portions extending in opposite directions from the ball nut assembly, or not on opposite sides of the ball screw (claim 1).
- Exoskeletons where the joint does not include a joint pulley connected to the tensile members (claim 2).
Patent timeline
Application submitted to the patent office
Application published, typically 18 months after filing
Patent officially issued
Patent enters public domain
PatentBrief Score
Impact Score
Moderate
Citation count
17/40
Early citations
Claim breadth
15/20
Broad claimsclaimsThe numbered statements at the end of a patent that legally define what the inventor owns.Read more →
Recency
10/20
Granted 5–10 years ago
Assignee scale
0/20
Independent or smaller assigneeassigneeThe entity that owns the patent — usually the inventor's employer or a company.Read more →
PatentBrief Impact Score — based on citation count, claim breadth, recency, and assignee scale. Not a legal assessment.
Heuristic Value Estimate
What this patent might be worth
$137K – $439K
Midpoint $275K · 10.5 yr remaining · industry ×2.2
Heuristic only — blends forward/backward citation counts, claim scope, time remaining, litigation history, and CPC-derived industry baseline. Real valuations need a professional appraisal.
Claim text not yet imported for this patent
The original legal language
Original claims
23 claims as filed with the patent office.
Concepts involved
Citations
Patent lineage
Cite this patent
Hughes, M., & JULIN, A. (2020). How Exoskeletons Use Screws and Cables to Move Joints (U.S. Patent No. 10,702,441). U.S. Patent and Trademark Office. https://patentbrief.org/patent/us/10702441/ball-screw-and-tensile-member-exoskeleton-joint-actuation-device
Auto-generated from the patent record. Double-check author order and the issue date against the official USPTO document before submitting.
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Common Questions
Frequently Asked Questions
What does How Exoskeletons Use Screws and Cables to Move Joints cover?
This patent describes a mechanical system for exoskeletons that uses a rotating screw to push a nut, which then pulls cables to make a joint bend or straighten.
Who owns patent US 10702441?
Ekso Bionics owns this patent, granted in 2020.
When does this patent expire?
This patent is expected to expire on April 27, 2037, when the invention enters the public domain.
What is patent US 10702441 cited by?
This patent has been cited by 6 later patents that build on its ideas.
What problem does this patent solve?
This type of actuation is important for exoskeletons because it allows for precise and powerful control of movement. Exoskeletons, like those made by Ekso Bionics, help people with mobility challenges or assist workers in physically demanding jobs. A reliable and strong joint mechanism is crucial for safety and effective assistance, enabling users to walk or lift with support.
What does this patent NOT cover?
Exoskeletons that use hydraulic or pneumatic cylinders for joint movement instead of a ball screw and tensile members.
Same assignee
More from Ekso Bionics
Patent monitoring