# US 11,078,910 B2 · Pumping unit and use > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,078,910 B2 - Document ID: US11078910B2 - Status: Granted - Kind: B2 - Application number: 16/500,847 - Filed: 2018-03-21 - Published: 2020-06-18 - Granted: 2021-08-03 - Earliest claimed: 2017-04-07 - Assignees: Pfeiffer Vacuum GmbH - Applicants: Pfeiffer Vacuum - Inventors: Philippe D'Harboulle - Web page: https://patentgrep.com/patent/US11078910B2 ## CPC - F04C 23/001: {of similar working principle} - F04C 18/126: {with radially from the rotor body extending elements, not necessarily co-operating with corresponding recesses in the other rotor, e.g. lobes, Roots type} - F04C 25/02: for producing high vacuum (sealing arrangements F04C27/00; silencing F04C29/06) - F04C 2220/10: Vacuum - F04C 2220/12: Dry running - F04C 2220/30: Use in a chemical vapor deposition [CVD] process or in a similar process - F04C 2270/185: Controlled or regulated - F04C 2270/21: Pressure difference - F04C: ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS (engines F03C); ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS ## Abstract A pumping unit is provided, including a primary vacuum pump of a multistage dry type, including at least four pumping stages fitted in series; and a two-stage Roots vacuum pump, including a first pumping stage and a second pumping stage fitted in series, the second pumping stage being fitted in series with and upstream of a first pumping stage of the primary vacuum pump in a direction of flow of gases to be pumped, in which a ratio of a volume displacement of the first pumping stage of the two-stage Roots vacuum pump to a volume displacement of the second pumping stage of the two-stage Roots vacuum pump is less than six, and in which a ratio of a volume displacement of the second pumping stage of the two-stage Roots vacuum pump to a volume displacement of the first pumping stage of the primary vacuum pump is less than six. ## Claims ### Claim 1 A pumping unit, comprising: a primary vacuum pump of a multistage dry type, comprising at least four pumping stages fitted in series; and a two-stage Roots vacuum pump, comprising a first pumping stage and a second pumping stage fitted in series, the second pumping stage being fitted in series with and upstream of a first pumping stage of the primary vacuum pump in a direction of flow of gases to be pumped, wherein a ratio of a volume displacement of the first pumping stage of the two-stage Roots vacuum pump to a volume displacement of the second pumping stage of the two-stage Roots vacuum pump being less than six, and wherein a ratio of a volume displacement of the second pumping stage of the two-stage Roots vacuum pump to a volume displacement of the first pumping stage of the primary vacuum pump being less than six. ### Claim 2 (depends on 1) The pumping unit according to claim 1, wherein the volume displacement of the first pumping stage of the two-stage Roots vacuum pump is greater than or equal to 3000 m3/h. ### Claim 3 (depends on 1) The pumping unit according to claim 1, wherein the volume displacement of the first pumping stage of the two-stage Roots vacuum pump is between 3500 m3/h and 5000 m3/h. ### Claim 4 (depends on 1) The pumping unit according to claim 1, wherein the volume displacement of the second pumping stage of the two-stage Roots vacuum pump is greater than or equal to 500 m3/h. ### Claim 5 (depends on 1) The pumping unit according to claim 1, wherein the volume displacement of the second pumping stage of the two-stage Roots vacuum pump is between 500 m3/h and 1000 m3/h. ### Claim 6 (depends on 1) The pumping unit according to claim 1, wherein the ratio of the volume displacement of the first pumping stage of the two-stage Roots vacuum pump to the volume displacement of the second pumping stage of the two-stage Roots vacuum pump is less than 5.5. ### Claim 7 (depends on 1) The pumping unit according to claim 1, wherein the ratio of the volume displacement of the second pumping stage of the two-stage Roots vacuum pump to the volume displacement of the first pumping stage of the primary vacuum pump is less than or equal to five. ### Claim 8 (depends on 1) The pumping unit according to claim 1, wherein the volume displacement of the first pumping stage of the primary vacuum pump is greater than or equal to 100 m3/h. ### Claim 9 (depends on 1) The pumping unit according to claim 1, wherein the volume displacement of the first pumping stage of the primary vacuum pump is between 100 m3/h and 400 m3/h. ### Claim 10 (depends on 1) The pumping unit according to claim 1, wherein the ratio of the volume displacement of the first pumping stage of the primary vacuum pump to the volume displacement of the second pumping stage of the primary vacuum pump is less than or equal to three. ### Claim 11 (depends on 1) The pumping unit according to claim 1, wherein the ratio of the volume displacement of the first pumping stage of the two-stage Roots vacuum pump to the volume displacement of the third pumping stage of the primary vacuum pump is less than or equal to 120. ### Claim 12 (depends on 1) The pumping unit according to claim 1, wherein the primary vacuum pump comprises at least five pumping stages fitted in series. ### Claim 13 (depends on 1) The pumping unit according to claim 1, further comprising a passage connecting an intake of the two-stage Roots vacuum pump to an inlet of the second pumping stage of the two-stage Roots vacuum pump, the passage comprising a relief module configured to open as soon as a pressure difference between the intake and a delivery end of the first pumping stage exceeds a predefined value. ### Claim 14 (depends on 1) The pumping unit according to claim 1, wherein the pumping unit is configured to: pump out an enclosure of a semiconductor manufacturing installation, and control a pressure inside the enclosure at levels of between 53 Pa and 266 Pa, for pumped gas flows in the enclosure of between 50 Pa·m3·s−1 and 170 Pa·m3·s−1.