# US 10,864,887 B2 · Retractor pretensioner with piston rest area > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,864,887 B2 - Document ID: US10864887B2 - Status: Granted - Kind: B2 - Application number: 16/238,914 - Filed: 2019-01-03 - Published: 2019-07-18 - Granted: 2020-12-15 - Earliest claimed: 2018-01-12 - Assignees: Autoliv Development AB - Applicants: Autoliv Development AB - Inventors: Christian Fischer; Markus Furchert - Web page: https://patentgrep.com/patent/US10864887B2 ## CPC - B60R 22/4633: {Linear actuators, e.g. comprising a piston moving along reel axis and rotating along its own axis} - B60R 22/1954: {characterised by fluid actuators, e.g. pyrotechnic gas generators (actuating a cable B60R22/1952)} - B60R 22/4628: {characterised by fluid actuators, e.g. pyrotechnic gas generators (actuating a cable B60R22/4619)} - B60R 2022/4642: {the gas directly propelling a flexible driving means, e.g. a plurality of successive masses, in a tubular chamber} - B60R: VEHICLES, VEHICLE FITTINGS, OR VEHICLE PARTS, NOT OTHERWISE PROVIDED FOR ## Abstract A seatbelt tensioner for a seat belt retractor, having a pipe (1) with a tensioner drive wheel, a gas generator (10), a piston (3), and at least one mass body (4). The mass body (4) is drivable by gas from the gas generator (10) acting on the piston (3) between the gas generator (10) and a mass body (4). The mass body drives the tensioner drive wheel. The pipe (1) has a receiving section (5) with a first inner diameter (2), in which the piston (3) in its initial state is arranged with an initial-state outer diameter (8). The pipe (1) has a guide section (6) which adjoins the receiving section (5) and which has a second inner diameter (7). The second inner diameter (7) is smaller than the first inner diameter (2) and smaller than the initial-state outer diameter (8) of the piston (3). ## Claims ### Claim 1 A seatbelt tensioner for a seatbelt retractor, comprising, a pipe with a tensioner drive wheel, wherein a pyrotechnical gas generator, a piston, and at least one mass body are arranged in the pipe, wherein the at least one mass body is drivable by a pressure generable by the gas generator and acting on the piston arranged between the gas generator and the at least one mass body, and which can be made to mesh in a force-transmitting manner with the tensioner drive wheel, when exiting the pipe, thus driving a belt shaft of the seatbelt retractor in a tensioning direction that retracts a seatbelt, further comprising, the pipe has a receiving section with a first inner diameter, in which the piston having an initial-state outer diameter before installation into the receiving section is arranged in the receiving section prior to an ignition of the gas generator, the pipe has a guide section which adjoins the receiving section and which has a second inner diameter, within which the piston is driven after the ignition of the gas generator, wherein the second inner diameter is smaller than the first inner diameter and smaller than the initial-state outer diameter of the piston. ### Claim 2 (depends on 1) The seatbelt tensioner according to claim 1 further comprising, a run-up slope is formed on the inner side of the pipe as a transition section between the receiving section and the guide section. ### Claim 3 (depends on 1) The seatbelt tensioner according to claim 1 further comprising, the piston in an initial state bears against a spring. ### Claim 4 (depends on 1) The seatbelt tensioner according to claim 1 further comprising, the second inner diameter is 2% smaller than the first inner diameter. ### Claim 5 (depends on 1) The seatbelt tensioner according to claim 1 further comprising, the second inner diameter is 3% smaller than the first inner diameter. ### Claim 6 (depends on 1) The seatbelt tensioner according to claim 1 further comprising, the second inner diameter is at least 0.2 mm smaller than the first inner diameter. ### Claim 7 (depends on 1) The seatbelt tensioner according to claim 1 further comprising, the second inner diameter is at least 0.4 mm smaller than the first inner diameter. ### Claim 8 (depends on 1) The seatbelt tensioner according to claim 1 further comprising, the second inner diameter is at least 0.6 mm smaller than the first inner diameter. ### Claim 9 (depends on 1) The seatbelt tensioner according to claim 1 further comprising, the first inner diameter is no more than 0.2 mm smaller than the initial-state outer diameter of the piston. ### Claim 10 (depends on 1) The seatbelt tensioner according to claim 1 further comprising, the first inner diameter is no more than 0.4 mm smaller than the initial-state outer diameter of the piston. ### Claim 11 (depends on 2) The seatbelt tensioner according to claim 2 further comprising, the transition section has a length of 10 mm or less. ### Claim 12 (depends on 2) The seatbelt tensioner according to claim 2 further comprising, the transition section has a length of 5 mm or less.