Valves and valve actuation – Mechanical movement actuator – Particularly packed or sealed
Patent
1994-04-25
1996-04-02
Walton, George L.
Valves and valve actuation
Mechanical movement actuator
Particularly packed or sealed
251305, 277 3, 277 29, 277 71, 277173, F16K 4100, F16J 1530
Patent
active
055033679
DESCRIPTION:
BRIEF SUMMARY
This invention relates to an improved seal for the spindle of a butterfly valve, particularly a butterfly valve used as an obturator in the exhaust of an internal combustion engine.
Exhaust obturators, for I.C. engines, have been known for many years and often comprise a butterfly valve located close to the engine and operable to close the exhaust duct. With the butterfly valve in the open condition, pressure in the exhaust system is normal, but when the valve is closed, pressure upstream of the valve rises very quickly, and the resultant back pressure on the engine acts as a brake.
The maximum pressure upstream of the valve when the butterfly is closed is directly related to the retarding effect of the engine, but is however limited by the condition of the engine and the maximum back pressure that the engine valves and gaskets are designed to withstand. Design back pressures up to 5 bar (75 p.s.i.) are typical.
Exhaust obturators have uses other than as an exhaust brake. An obturator may be designed to divert flow from one exhaust stack to another, thereby permitting incineration of unburnt hydrocarbons in a non-working stack. Alternatively, or in addition, an obturator may be used to impose a low back pressure on an engine, thereby to make the engine work harder and reduce warm-up time from cold start; such an arrangement has the particular advantage of reducing cab warm-up time in cold weather.
The fit of the butterfly valve in the exhaust duct is not critical (unless used as a diverter valve) and a small leakage can be tolerated. Sealing of the butterfly spindle where it passes through the wall of the exhaust duct to an operating lever is, however, more important, because when the butterfly is closed, the high upstream pressure may cause a jet of very hot raw exhaust gas to issue, often at pedestrian level. This problem is compounded by the need for reasonable large spindle/bearing clearance to cater for heat expansion, and exacerbated by the fact that, when the butterfly is closed, the spindle is pushed in the low pressure direction, thus maximising the spindle clearance on the high pressure side.
Hitherto, the problem of spindle sealing has usually been solved by the use of a strong spring to bias an annular face of the spindle against an annular face of the butterfly valve body. The metal/metal seal is not very satisfactory and results in a high operating load, high drag forces and very high hysteresis. The arrangement is nevertheless acceptable for directly operated single function obturators.
In recent times it has been proposed to provide reactive butterfly obturators, in which the butterfly itself reacts to changes in back pressure. Such a reactive butterfly valve is described in WO-A-9208887. In this arrangement axial loading of the spindle to form a gas seal is unacceptable because the high hysteresis and drag would prevent reaction of the butterfly to small changes in back pressure; reaction would also be inconsistent.
It is essential to provide a spindle seal which ensures that raw exhaust gases do not leak to the exterior of the obturator; small leakage past the butterfly to the low pressure side can be tolerated without detriment to operation of an exhaust brake or cab heater.
The present invention provides a spindle seal which is more effective than in prior art arrangements, and which exerts no axial load on the butterfly spindle.
According to the invention there is provided an exhaust obturator comprising a tubular housing, a spindle crossing said housing and journalled in the wall thereof, and a butterfly attached to said spindle and arcuately movable with the spindle to open and close the obturator, the wall of the housing defining a chamber through which said spindle passes, the chamber defining an annular space around said spindle and having a sealing face substantially perpendicular to the axis of said spindle, and said spindle having an annular sealing ring slidable thereon and movable into sealing engagement with said sealing face under the action of a biasing force.
Preferably s
REFERENCES:
patent: 3179422 (1965-04-01), Phillips
patent: 3746301 (1973-07-01), Budzich et al.
patent: 3988000 (1976-10-01), Reese
patent: 4022424 (1977-05-01), Davis et al.
patent: 4291863 (1981-09-01), Gachot
patent: 4328974 (1982-05-01), White et al.
patent: 4353388 (1982-10-01), Isoyama et al.
patent: 4398727 (1983-08-01), Rylander
patent: 4447062 (1984-05-01), Leicht
patent: 4541612 (1985-09-01), Yohner
patent: 4640305 (1987-02-01), Johnson
patent: 4721313 (1988-01-01), Pennick
patent: 4773440 (1988-09-01), Yanagawa et al.
patent: 5037065 (1991-08-01), Hirz et al.
patent: 5078175 (1992-01-01), Martin et al.
patent: 5251874 (1993-10-01), Coleman et al.
Flett Magnus E.
Thompson Derek
Wabco Automotive U.K. Limited
Walton George L.
LandOfFree
Butterfly valve seal does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Butterfly valve seal, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Butterfly valve seal will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2012194