# US 11,309,769 B2 · Method and system for generating electricity from footsteps > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,309,769 B2 - Document ID: US11309769B2 - Status: Granted - Kind: B2 - Application number: 16/300,505 - Filed: 2017-05-10 - Published: 2019-08-01 - Granted: 2022-04-19 - Earliest claimed: 2016-05-10 - Assignees: Pavegen Systems Limited - Applicants: Pavegen Systems Limited - Inventors: Craig Webster; Ben Gordon - Web page: https://patentgrep.com/patent/US11309769B2 ## CPC - H02K 7/1853: {driven by intermittent forces} - H02K 7/025: {for power storage} - H02K 7/06: Means for converting reciprocating motion into rotary motion or vice versa - Y02E 60/16: Mechanical energy storage, e.g. flywheels or pressurised fluids - H02K: DYNAMO-ELECTRIC MACHINES (dynamo-electric relays H01H53/00; conversion of DC or AC input power into surge output power {H03K3/53}) - Y02E: REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION ## Abstract A disclosed electrical generator includes a housing, an actuator, a rotatable member, a stator, a rotor, an electrical circuit, and a current controller. The actuator is movable relative to the housing and the rotatable member is also rotatable relative to the housing. The rotatable member cooperates with the actuator such that movement of the actuator causes rotation of the rotatable member. The stator is fixed relative to the housing and the rotor receives rotational kinetic energy from the rotatable member. Movement of the rotor relative to the stator generates electromagnetic induction in the rotor and/or the stator which produces a three-phase alternating current. The electrical circuit includes a rectifier that converts the alternating current to a direct current. The current controller regulates the direct current to thereby generate a fixed constant direct current. ## Claims ### Claim 1 An electrical generator configured to convert axial kinetic energy into electrical energy, the electrical generator comprising: a housing; an actuator configured to be movable axially relative to the housing by an axial distance of between approximately 5 mm and approximately 10 mm; a rotatable member configured to be rotatable relative to the housing and configured to cooperate with the actuator such that axial movement of the actuator causes rotation of the rotatable member; a stator fixedly attached to the housing; a rotor configured to receive rotational kinetic energy from the rotatable member, wherein the rotor and the stator are configured to interact such that rotation of the rotor relative to the stator generates electromagnetic induction in the rotor and/or the stator which produces a three-phase alternating current; an electronic circuit including a rectifier, the electronic circuit configured to convert the alternating current to a direct current; and a current controller configured to regulate the direct current to generate a fixed constant current of between approximately 150 mA and approximately 500 mA. ### Claim 2 (depends on 1) The electrical generator of claim 1 wherein the electronic circuit includes a flyback converter. ### Claim 3 (depends on 1) The electrical generator of claim 1, wherein the electronic circuit includes a battery and a diode. ### Claim 4 (depends on 1) The electrical generator of claim 1, wherein the fixed constant current has a value in a range from approximately 350 mA to approximately 400 mA. ### Claim 5 (depends on 1) The electrical generator of claim 1, wherein the fixed constant current has a value that is approximately 350 mA. ### Claim 6 (depends on 1) The electrical generator of claim 1, wherein: the actuator is biased in a first direction and the rotatable member is configured to be rotatable relative to the housing on a rotation axis parallel to the first direction, and the rotatable member is configured to cooperate with the actuator such that movement of the actuator in a second direction opposite the first direction causes the rotatable member to rotate about the rotation axis. ### Claim 7 (depends on 6) The electrical generator of claim 6, wherein the first direction is a first axial direction and the second direction is a second axial direction opposite the first axial direction. ### Claim 8 (depends on 1) The electrical generator of claim 1, further comprising a flywheel between the rotatable member and the rotor. ### Claim 9 (depends on 1) The electrical generator of claim 1, wherein a first one of the actuator and the rotatable member includes a ball screw, and a second one of the actuator and the rotatable member includes a ball nut, and wherein the electrical generator includes a plurality of balls between the actuator and the rotatable member. ### Claim 10 (depends on 9) The electrical generator of claim 9, wherein the rotatable member includes a first helical groove and the actuator includes a second helical groove that complements the first helical groove such that the first and second helical grooves together form a helical channel having a circular cross section that is configured to accommodate the plurality of balls. ### Claim 11 (depends on 10) The electrical generator of claim 10, wherein each of the plurality of balls has a diameter that corresponds to a diameter of a circular cross section of the helical channel. ### Claim 12 (depends on 10) The electrical generator of claim 10, wherein the diameter of each of the plurality of balls is selected to minimize friction and to maximize conversion of axial to rotational movement. ### Claim 13 (depends on 10) The electrical generator of claim 10, further comprising a clutch arrangement between the rotatable member and the rotor. ### Claim 14 (depends on 13) The electrical generator of claim 13, wherein the clutch arrangement includes an overrunning clutch that allows continued rotation of the rotor by inertia after rotation of the rotatable member concludes. ### Claim 15 (depends on 13) The electrical generator of claim 13, wherein the clutch arrangement includes a sprag clutch: that allows transmission of torque from the rotatable member to the rotor when the rotatable member rotates in a first direction of rotation, and that prevents transmission of torque from the rotatable member to the rotor when the rotatable member rotates in a second direction of rotation opposite the first direction of rotation. ### Claim 16 (depends on 15) The electrical generator of claim 15, wherein: the actuator is biased in a first direction and the rotatable member is configured to be rotatable relative to the housing on a rotation axis that is parallel to the first direction, the rotatable member is configured to cooperate with the actuator such that movement of the actuator in a second direction, opposite the first direction, causes the rotatable member to rotate about the rotation axis, the first direction is a first axial direction and the second direction is a second axial direction opposite the first axial direction, and the first direction of rotation results from movement of the actuator in the second axial direction and the second direction of rotation results from movement of the actuator in the first axial direction. ### Claim 17 (depends on 13) The electrical generator of claim 13, wherein the clutch arrangement includes both an overrunning clutch and a sprag clutch either separately or as a single clutch.