Vacuum pump with plural labyrinth seal portions

• US 4,734,018 A
• Filed: 12/29/1986
• Issued: 03/29/1988
• Est. Priority Date: 12/27/1985
• Status: Expired due to Fees

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Taniyama, Minoru, Nagaoka, Takashi, Mase, Masahiro
• Primary Examiner(s): NOT, DEFINED
• Assistant Examiner(s): NOT, DEFINED
• Application Number:
  US06/947,282
• Time in Patent Office: 456 Days
• Field of Search: 417/423 C, 417/423 M, 417/424 A, 417/366, 417/407, 415/90, 415/110, 415/111, 415/112, 415/175, 277/3, 277/53, 277/70, 277/71, 277/79
• US Class Current: 417/423.4
• CPC Class Codes: F04D 19/04 specially adapted to the production of a high vacuum, e.g. molecular pumps
• CPC Class Codes: F04D 29/104 the sealing fluid being other than the working fluid or being the working fluid treated
• CPC Class Codes: F16J 15/406 by at least one pump

Abstract

A vacuum pump with a seal structure for a pump unit of the vacuum pump and a driving mechanism for rotating a rotor in the pump stages of the pump is disclosed. The seal structure is provided with a narrow gap sealing arrangement formed by a stationary member which is opposed to the portion of a shaft of the driving mechanism which is between the pump unit and an upper bearing supporting the same shaft, which narrow gap sealing arrangement comprises first, second and third seal portions; a mechanism for supplying a discharge gas to the first seal portion; and a mechanism for supplying a purge gas to the second and third seal portions. Owing to these parts, the feed rate of the purge gas can be minimized, and the entry of the oil mist, which occurs during the lubrication of the bearing, into the interior of the pump unit can be prevented. This enables the interior of the pump unit to be kept clean.

Claims

1. A vacuum pump having a casing provided with an inlet port and an outlet port, a plurality of pump stages provided in said casing, a driving means connected to a shaft of said pump stages, bearings supporting said shaft, and a means for supplying a lubricating oil to said bearings, a gas sucked from said inlet port being discharged from said outlet port, comprising a narrow gap sealing means formed by the portion of said shaft which is between said pump stages and the upper bearing and a stationary member opposed to said portion of said shaft, and comprising a first seal portion for circulating a part of a discharge gas from said pump stages to the rear surface of said pump final impeller, a second seal portion for supplying a purge gas to said first seal portion, and a third seal portion for supplying said purge gas toward said bearing;

a means for supplying a part of said discharge gas to said first seal portion; and

a means for supplying said purge gas to said second and third seal portions, and wherein said means for supplying a part of said discharge gas to said first seal portion comprises an annular groove for discharge gas, which is provided in said stationary member, and a discharge gas passage formed in said stationary member and communicated with said annular groove so that said discharge gas flows circularly from the first seal portion to the discharge gas passage via said rear surface of said pump final impeller, said means for supplying said purge gas to said second and third seal portions comprising an annular groove for purge gas, which is provided in said stationary member, and a purge gas passage communicated with said annular groove for purge gas and used to supply said purge gas from the ouside to the same annular groove.

2. A vacuum pump according to claim 1, wherein said first, second and third seal portions constituting said narrow gap sealing means consists of labyrinth seals.

3. A vacuum pump according to claim 1, wherein said first and second seal portions constituting a part of said narrow gap sealing means comprise labyrinth seals, said third seal portion which constitutes the remaining part of said narrow gap sealing means comprising a threaded seal.

4. A vacuum pump according to claim 1, wherein said first seal portion constituting a part of said narrow gap sealing means comprises a threaded seal, said second and third seal portions which constitutes the remaining part of said narrow gap sealing means comprising labyrinth seals.

5. A vacuum pump according to claim 1, wherein said first and third seal portions constituting a part of said narrow gap sealing means comprise threaded seals, said second seal portion which constitutes the remaining part of said narrow gap sealing means comprising a labyrinth seal.