# 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. - **Patent:** US 10702441 - **Original title:** Ball screw and tensile member exoskeleton joint actuation device - **Owner:** Ekso Bionics - **Granted:** 2020 - **Status:** Active - **Times cited:** 6 - **Field:** mechanical, consumer_electronics, healthcare ## What it does 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. ## 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). ## 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. ## Real-world examples 1. Ekso Bionics EksoNR exoskeleton 2. Industrial exoskeletons for lifting assistance 3. Rehabilitation exoskeletons for gait training ## Why it matters 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. ## 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. **Full plain-English explainer:** https://patentbrief.org/patent/us/10702441/ball-screw-and-tensile-member-exoskeleton-joint-actuation-device **Original patent:** https://patents.google.com/patent/US10702441 --- _Source: PatentBrief — https://patentbrief.org. Patent facts are from public records; the plain-English explanation is PatentBrief's._ ## Related patents Semantically similar inventions in the PatentBrief corpus: - [How an Exoskeleton Joint Moves with a Motor, Screw, and Linkage](https://patentbrief.org/patent/us/11673253/actuator-devices-for-human-exoskeleton-joints) — This patent describes a compact and efficient way to make an exoskeleton joint bend and straighten using a motor, a special screw, and a clever set of levers. - [How a Robotic Exoskeleton Helps Your Shoulder Move](https://patentbrief.org/patent/us/10800031/spherical-parallel-manipulator-architecture-for-shoulder-robotic-exoskeleton) — This patent describes a robotic shoulder exoskeleton using multiple straight-moving actuators arranged in a "spherical parallel manipulator" to assist or rehabilitate arm movements while preventing joint misalignment. - [Flexible Footplate for Robotic Walking Assistance](https://patentbrief.org/patent/us/11304827/unidirectional-actuated-exoskeleton-device) — This patent describes a specialized composite footplate for footwear that includes a mechanical joint to help users with natural foot movements like pointing toes up or down, and rolling their ankles, especially when connected to an exoskeleton. - [Exoskeleton Shoulder Joint That Adapts to Your Arm's Movement](https://patentbrief.org/patent/us/10814473/mechanism-for-alleviating-the-effects-of-joint-misalignment-between-users-and-we) — This patent describes a shoulder exoskeleton that uses a special slip mechanism to prevent the robot's joints from getting out of sync with a user's natural arm movements, making it more comfortable and effective. - [How Humanoid Robot Actuators Connect with a Smart Wire Assembly](https://patentbrief.org/patent/us/12734717/humanoid-robot-with-advanced-wiring-assembly) — This patent describes a specific way to connect two moving parts (actuators) in a humanoid robot using a wire bundle that routes through openings and connects to circuit boards with different numbers of pins.