Valves and valve actuation – Rotary valves – Butterfly
Reexamination Certificate
1998-10-01
2001-02-27
Fox, John (Department: 3753)
Valves and valve actuation
Rotary valves
Butterfly
C123S323000
Reexamination Certificate
active
06193214
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to a shut-off or throttle valve comprising a housing encircling a flow passage and a valve flap pivotally arranged about an axis of rotation extending across the flow cross-section of the valve, in particular for flow passages of combustion engines arranged for loading or discharging exhaust gases, the surface of the valve flap being subdivided into a pair of sections by said axis of rotation.
A valve flap has been known which is inclined with respect to the direction of fluid flow when it is in its closed position in order to avoid jamming caused by thermal expansions and which therefore has an inclined cylinder section so that its peripheral surface sealingly engages the tube wall and, respectively, the wall of the cylindrical valve housing. This measure for preventing jamming is effective only at the peripheral portions which are furthest from the axis of rotation; it is ineffective in the area of the peripheral portions intersecting the axis of rotation because there is no inclination with respect to the tube axis in the direction of the axis. At this location it is necessary to provide a gap to compensate for thermal expansions, and as a result the valve is not sealed there. For providing the complicate shape of the valve flap, the flap has to be ground or milled at its periphery, which on the one hand will cause high machining costs and on the other hand cannot prevent leakage losses through the valve which increase with higher pressures.
Furthermore, it has become known to provide recesses in the internal wall of the valve housing which are engaged by the valve flap portions remote from the axis of rotation when being in the closed position inclined to the direction of fluid flow, further including abutment surfaces facing said valve flap portions, which abutment surfaces are engaged by the valve flap when it is in its closed position. Also with this arrangement, milling operations of the valve housing are required, and the above mentioned leakage losses in the area of the valve flap peripheral portions intersecting the valve axis are also true for this type of valve.
When such a valve is used in the exhaust conduit of a combustion engine provided with an exhaust gas heat exchanger and a catalytic converter in order to conduct the exhaust gas either through the heat exchanger or through a bypass, with the valve being used for closing the bypass, energy is lost by leakage through the bypass valve. Leakage losses of more than 50% are possible.
The problem to be solved by the invention is to design a valve of the above identified type such that it reliably operates at varying temperatures, that it can be manufactured in a simple and cost effective manner and that it can be relatively easily assembled even under limited space conditions. In particular, it should be able to generate a ram pressure of 5 bar in the exhaust conduit of a combustion engine during idling, i.e. at about 500 rpm. Furthermore, the valve should be suited for a flow control, in particular for controlling the ram pressure in a conduit while remaining in a stable position even at small opening angles and under the influence of flow turbulence, or it should be suited to be used as a check valve, having an opening pressure which may be adjusted if desired.
For solving this problem the valve of the above identified type has been designed such that said valve flap when being in the closed position is located in a closing plane which contains said axis of rotation and extends transversely to the flow direction, and further the valve flap is spaced at its edge in all positions along all sides in the plane of the valve flap from the housing at a distance such that this distance cannot be overcome by thermal expansions to be expected in operation, and further that the peripheral portions of the housing include an abutment edge each extending towards the axis of rotation, and that said abutment edges are disposed on different sides of the valve flap and are associated to said valve sections so as to form a face seal.
Such structure does not require any expensive machining of the valve flap or the valve housing; rather a stamped flap and a simple tube material for forming the housing can be used. The spacing between the flap rim and internal wall of the housing all around allows to compensate for thermal expansions without any risk of jamming. Since the flap engages the abutment edges all around without any gaps, excellent sealing thereof is ensured.
In an embodiment which may be used, for example, as a shut-off valve the axis of rotation subdivides the flap surface into a pair of sections having the same size.
When a pivotal flap valve is used, the desired opening position thereof may be set by a servo motor. This type of valve is instable at small opening angles due to flow turbulances. A valve which enables to set the desired ram pressure by a biasing force would be preferable. To this end a preferred embodiment of the valve of the invention is designed such that the axis of rotation subdivides the flap surface into a pair of sections of different sizes and that the greatest dimension of the flap parallel to the axis of rotation is smaller than the width of the flow passage as measured in the same direction.
When the valve is assembled such that the ram pressure acts upon the larger flap section and a biasing force dependent on the flap stroke acts upon the flap in the closing direction, a stable position of the flap may be obtained any time, with the flap in such position maintaining a ram pressure according to the characteristic of the biasing force.
A particularly advantageous embodiment consists in that said housing comprises a tubular sleeve through which said axis of rotation extends, and a pair of tube portions enclosed by said tubular sleeve, the edges of said tube portions facing the valve flap on opposite sides of said axis of rotation serving as abutment edges for the valve flap when it is in its closed position and extending towards the axis of rotation so as to be spaced from the center of rotation for at least half of the wall thickness of the valve flap and extending therebehind outside of the area of pivotal movements of the valve flap. A simple design thereof consists in that the edges of the tube portions facing said valve flap are subdivided by a stepped portion extending parallel to the axis of rotation into a pair of portions offset with respect to each other in the flow direction of the valve, which offset portions each extend in parallel to the plane of the valve flap in its closed position.
This results in a particularly simple and cost effective structure which may be assembled relatively easily even under difficult space conditions because the valve housing may be assembled in situ and the essential part of the valve consists of the tubular sleeve with the valve flap mounted therein. When the adjacent conduit portions have been prepared by respective machining of their ends to be connected to the valve, the only thing necessary is to align these conduit portions for being inserted into the tubular sleeve and fixed thereto.
When the space conditions are particularly limited, a preferred alternative consists in that the abutment edges extend to the axis of rotation so as to be spaced therefrom for half the diameter the axis of rotation, and that the wall thickness of the valve does not exceed the diameter of the axis of rotation. This allows, when the valve flap is in its opening position, to displace the tubular sleeve with the valve flap onto a first tube end until the offset edge portion engages the axis of rotation so that a tube end continuing the conduit on the other side of the valve can be aligned with respect to the sleeve and thereafter the sleeve can be mounted onto such tube end until both tube ends are properly positioned in the sleeve and the sleeve can be connected to the tube ends. In this manner it is possible to mount the valve, without having been disassembled before, into conduits from which a portion has been cut away for
Fox John
Harness Dickey & Pierce PLC
Schatz Thermo System GmbH
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