US3677664A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Rotary mechanical pumps of the screw type
Assignee: Edwards High Vacuum International Ltd
•
Filing: 1970-06-29
•
Granted: 1972-07-18
•
Expires: 1990-06-29
Abstract
Abstract An oil-sealed screw rotor mechanical vacuum pump which may be used as a backing pump, together with a rotary dry-running fine pump, in a high vacuum pumping unit. The screw rotor pump has one or more non-return valves between the chambers being limited by the screw rotor action and the atmosphere. The sealing oil also acts as a ''''liquid piston'''' to sweep pumped medium out of the chambers via the non-return valve(s).
Inventors
- 👤 Henryk Wycliffe
- 👤 Basil Dixon Power
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-27 10:03
CPC Classifications
F; F04; F04C; F04C28/00; F04C28/28; F04C18/00; F04C18/08; F04C18/12; F04C18/14; F04C18/16; F04C23/00; F04C23/001; F04C29/00; F04C29/02
Claims Analysis
Total Claims: 7
Claim 1
Independent Claim
180 words
A rotary mechanical vacuum pump apparatus of the screw type comprising in combination: a. a housing; b. a low pressure inlet region in said housing; c. a high pressure outlet region in said housing; d. two intermeshing screw rotors accommodated in said housing, said rotors being rotatable in opposite directions to produce a pumping and compressing action between said low pressure inlet region and said high pressure outlet region by limiting working chambers formed between said rotors and said housing; e. an outlet port, provided with a non-return outlet valve, in said outlet region; f. a plurality of additional ports communicating directly with said working chambers and the said outlet region, each of said additional ports being provided with a pressure relief valve whereby said working chambers are vented to said outlet region when a predetermined excess pressure exists between said working chambers and said outlet region; and g. means for introducing a sealing liquid into said working chambers, said sealing liquid providing a ''''liquid piston'''' which sweeps pumped medium out of said working chambers via said non-return outlet valve.
Claim 2
Dependent Claim
180 words
A rotary mechanical vacuum pump apparatus of the screw type comprising in combination: a. a housing; b. a low pressure inlet region in said housing; c. a high pressure outlet region in said housing; d. two intermeshing screw rotors accommodated in said housing, said rotors being rotatable in opposite directions to produce a pumping and compressing action between said low pressure inlet region and said high pressure outlet region by limiting working chambers formed between said rotors and said housing; e. an outlet port, provided with a non-return outlet valve, in said outlet region; f. a plurality of additional ports communicating directly with said working chambers and the said outlet region, each of said additional ports being provided with a pressure relief valve whereby said working chambers are vented to said outlet region when a predetermined excess pressure exists between said working chambers and said outlet region; and g. means for introducing a sealing liquid into said working chambers, said sealing liquid providing a ''''liquid piston'''' which sweeps pumped medium out of said working chambers via said non-return outlet valve.
Claim 3
Dependent Claim
36 words
A pump apparatus according to claim 1, in which said sealing liquid introduction means introduces sealing liquid into said working chambers when said working chambers are no lOnger in communication with said low pressure inlet region.
Claim 4
Dependent Claim
36 words
A pump apparatus according to claim 1, further including gas introduction means whereby gas ballast is introduced into said working chambers when said working chambers are no longer in communication with said low pressure inlet region.
Claim 5
Dependent Claim
43 words
A pump apparatus according to claim 1, in which each of said rotors is formed with a central bore which is closed at said low pressure inlet region and is rotatably mounted on a cantilever shaft supported at said high pressure outlet region.
Claim 6
Dependent Claim
26 words
A pump apparatus comprising an oil sealed pump according to claim 1 further including a dry running high vacuum screw type pump in flow series therewith.
Claim 7
Dependent Claim
69 words
A pump apparatus according to claim 5, in which said dry running pump and said oil sealed pump have a common housing with two axially displaced pairs of dry and oil sealed rotors therein, e. the corresponding rotors of said two pairs are provided with a common shaft, and f. said common shafts have and are rotatably mounted in bearings located at the respective ends of said oil-sealed rotor.
References Cited (Backward Citations)
US2519913A
Cited
US3129877A
Cited
US3122308A
Cited
US3241744A
Cited
US3084851A
Cited
US3093300A
Cited
GB992141A
Cited
US3279682A
Cited
US3237524A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1975-07-18 | 1976-01-17 | 1976-07-18 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1979-07-18 | 1980-01-17 | 1980-07-18 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1983-07-18 | 1984-01-17 | 1984-07-18 | $7700.00 | Window Closed / Lapsed |