Seal for a joint or juncture – Seal between relatively movable parts – Circumferential contact seal for other than piston
Reexamination Certificate
1999-11-29
2001-09-25
Knight, Anthony (Department: 3626)
Seal for a joint or juncture
Seal between relatively movable parts
Circumferential contact seal for other than piston
C217S074000, C217S074000, C217S074000
Reexamination Certificate
active
06293558
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to gaskets for rotating shafts and to the devices incorporating such gaskets.
More specifically, the invention relates to a gasket designed to be inserted between:
a housing with an interior volume filled with liquid lubricant and subjected to a certain level of pressure,
and a shaft projecting out from said housing and rotating at a certain rotation speed about a longitudinal axis, this gasket comprising a first annular sealing lip which is designed to be joined to the housing and placed in sliding rotary contact with the shaft, the first sealing lip being designed to withstand a first lubricant threshold pressure below
1
bar and to permit shaft rotation speeds in excess of 5000 rpm (revolutions per minute).
BACKGROUND OF THE INVENTION
Document EP-A-0 189 723 describes an example of such a gasket which is perfectly adequate, provided the lubricant contained in the housing is at low pressure.
However, this gasket is no longer suitable when this lubricant is at a relatively high pressure, higher than 5 bar and generally 10 to 20 bar, for example, which will occur in particular if the gasket is fitted on a lubricated bearing subjected to pressure, in particular a bearing of an automatic gearbox for a motor vehicle.
The invention is intended more specifically to overcome this disadvantage.
To this end, the invention proposes a gasket of the type outlined above, in which:
it also has a second annular sealing lip which is also designed to be joined to the housing and to be in sliding contact with the shaft, the second sealing lip being designed to permit shaft rotation speeds in excess of 5000 rpm and to withstand a second threshold pressure, in excess of 5 bar, prevailing in the interior volume of the housing, this second sealing lip being designed so that it can be inserted between the interior volume of the housing and the first sealing lip,
the second sealing lip delimits, in conjunction with the first sealing lip, a lubricant collecting chamber provided with a discharge passage for the lubricant, the gasket also has a calibrated nozzle bypassing the second sealing lip so as to provide direct communication between the interior volume of the housing and the collecting chamber,
the calibrated nozzle, the second sealing lip and the lubricant discharge passage are so dimensioned that a lubricant pressure prevailing in the collecting chamber is at most equal to said first threshold pressure when the lubricant contained in the interior volume of the housing is at a pressure at most equal to the second threshold pressure.
As a result of these features, it is possible to provide a gasket that is suitable for fitting on shafts rotating at relatively high speeds operating with lubricants which are also at high pressures.
In preferred embodiments of the gasket proposed by the invention, one and/or the other of the following features may also be incorporated:
the second sealing lip is made from PTFE;
the first sealing lip is made from elastomer;
the gasket also has a third anti-dust sealing lip which is joined to the housing and which is in sliding rotary contact with the shaft, this third sealing lip being arranged opposite the collecting chamber relative to the first sealing lip in order to protect said first sealing lip;
the calibrated nozzle and the second sealing lip are so dimensioned that lubricant flows at a rate ranging between 7 and 100 l/h from the interior volume of the housing to the collecting chamber if a pressure ranging between 10 and 20 bar prevails in said interior volume;
the second threshold pressure is between 10 and 20 bar;
the first and second sealing lips are joined respectively to first and second rigid frames which are fixed one to the other in a clamped fit, at least one of these frames having at least one recess which forms the discharge passage for the lubricant.
The invention also relates to a device comprising:
a housing with an interior volume filled with liquid lubricant which is subjected to a certain level of pressure,
a shaft projecting out from said housing and rotating at a certain rotation speed about a longitudinal axis,
and a gasket as defined above, inserted between the shaft and the housing, the first and second sealing lips of the gasket being joined to the housing and in sliding rotary contact with the shaft, the second sealing lip being disposed axially between the interior volume of the housing and the first sealing lip and the calibrated nozzle providing direct communication between the interior volume of the housing and the collecting chamber.
In preferred embodiments of this device, one and/or the other of the following features may also be incorporated:
the second sealing lip has an L-shaped cross section, with a first arm joined to a rigid frame substantially perpendicular to the longitudinal axis of the shaft and having a second arm which extends towards the interior volume of the housing substantially parallel with the longitudinal axis of the shaft;
the first and second sealing lips being joined respectively to first and second rigid frames which are fixed one to the other in a clamp fit, the second frame having at least one recess which forms the lubricant discharge passage, the first and second frames each having a cylindrical wall covered with elastomer which co-operates to provide a fitting on the housing to close off respectively the interior volume of the housing and the collecting chamber, and the first frame also having an external extension which is joined directly to the housing;
the first and second sealing lips are joined respectively to first and second rigid frames which are fixed one to the other in a clamp fit, the second frame having at least one recess which forms the lubricant discharge passage, the first frame having a cylindrical wall covered with elastomer which co-operates to form a fitting on the housing to provide a sealed closure of the collecting chamber, this cylindrical wall being extended by a rigid, enlarged cylindrical collet which is in direct contact with the housing and which co-operates with said housing by means of a force-fit, the second frame being joined to an additional sealing lip which cooperates with the housing to seal off the interior volume of said housing;
the first and second sealing lips are joined respectively to first and second rigid frames, which are fixed one to the other by a clamp fit with a layer of elastomer seal inserted between them, the second frame having at least one recess which forms the lubricant discharge passage, the first frame being joined to a first additional elastomer sealing lip which co-operates with the housing to seal off the collecting chamber, the second frame being joined to a second additional sealing lip which co-operates with the housing to seal off the interior volume of said housing, the first frame being joined directly to the housing and being axially supported against the second frame at local points.
REFERENCES:
patent: 3682488 (1972-08-01), Matsushima
patent: 4428630 (1984-01-01), Folger et al.
patent: 4433846 (1984-02-01), Romero et al.
patent: 4550920 (1985-11-01), Matsushima
patent: 5421591 (1995-06-01), Katzensteiner
patent: 5522600 (1996-06-01), Duckwall
patent: 41 05 746 (1991-08-01), None
patent: 0 189 723 (1986-08-01), None
patent: 1 437 899 (1966-07-01), None
patent: 2 408 081 (1979-06-01), None
patent: 1 202 061 (1970-08-01), None
patent: 2 106 196 (1983-04-01), None
French Preliminary Search Report dated Jul. 27, 1999, Int'l. Appl. No. FR 9815128.
Hutchinson
Knight Anthony
Marshall Gerstein & Borun
Peavey Enoch E.
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