Fluid handling – With repair – tapping – assembly – or disassembly means – Tool for applying or removing valve or valve member
Reexamination Certificate
1999-11-22
2001-02-13
Lee, Kevin (Department: 3753)
Fluid handling
With repair, tapping, assembly, or disassembly means
Tool for applying or removing valve or valve member
C137S315170, C137S315250, C029S213100, C029S221600
Reexamination Certificate
active
06186164
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates to a rotary valve which comprises a housing surrounding a housing bore open at at least one end, thus forming an opening. This opening is normally closed by at least one removable bearing cover on one side while the other end of the housing bore may be closed either by another bearing cover or some other wall. The bearing cover includes a first bearing. Within the housing bore, a cellular wheel is supported by the first bearing and is, thus, rotatable about an axis of rotation. The cellular wheel includes series of web plates arranged to extend radially in a star-shape on a hub. This cellular wheel can be dismantled and drawn out of the housing bore in axial direction so that the orientation of the axis of rotation defines a dismantling direction. A drawing device is mounted on the side of the removable bearing cover for aiding in dismantling the cellular wheel and comprises a guiding device which extends in a dismantling direction and, thus enables guided dismantling of the cellular wheel in an axial direction out of the housing bore.
BACKGROUND INFORMATION
Rotary valves of this kind are usually used for conveying or metering bulk material from a supply bin into a pneumatic conveying conduit. At the occasion of periodic maintenance and repair as well as for the purpose of cleaning the valve, for example when changing the type of bulk material to be conveyed, it may be necessary to remove the cellular wheel from the housing bore. However, there is only a small and narrow gap between the cellular wheel and the inner surface of the housing bore in order to achieve good sealing properties in radial direction. Therefore, removal and re-insertion of the cellular wheel require much care so that the inner wall of the housing bore is not damaged by the web plates of the cellular wheel.
In the case of small rotary valves, the cellular wheel can, in some cases, be removed manually. Rotary valves which comprise heavy cellular wheels, however, are often provided with a drawing device which facilitates drawing the cellular wheel out of the housing bore.
Such a rotary valve is disclosed in German Patent No. DE 38 18 145. The cellular wheel has shaft ends or stub shafts at the opposite front surfaces and is supported by bearing covers closing the housing bore. On one side of the housing, a guidance is provided which extends in an axial direction and comprises a pair of guide columns connected to the housing and a carriage displaceable on and along them, the carriage being screwed together with that one of the bearing covers which is arranged at the side of the guide columns.
Thus, the cellular wheel can be displaced together with the bearing cover including the fast bearing at the side of the guide columns along its middle axis of rotation in the direction of the guide columns or dismantling direction thereby drawing that stub shaft which is opposite the side of the guide columns, out of the slip-on bearing provided in an opposite bearing cover.
Such a rotary valve is able to prevent any undesirable canting of the cellular wheel up to a certain weight of it. With very heavy cellular wheels, however, a single fast bearing is not able to bear the weight of the cellular wheel. Of course, the same would apply, if the cellular wheel were provided with a rim for supporting it on the outer circumference of the rim instead of providing stub shafts or any shaft.
In order to avoid canting, German Patent Application DE 41 35 395 A1 suggests to arrange a pair of spaced bearings in each one of the bearing covers so that a cellular wheel may be supported in a “flying” manner by two bearings when drawn out of the bearings of the opposite bearing cover.
This measure, however, due to redundancy in determination, leads in operation of the valve to permanent bending stress of the cellular wheel's shaft if there is only a small deviation from precise alignment, thus resulting in an increased drive moment, and to fatigue fracture.
SUMMARY OF THE INVENTION
It is an object of the present invention to develop the design according to the prior art further in such a way that any overstrain of the components of a rotary valve are reliably prevented both in operation and when cleaning or repairing it.
This object is achieved in that the guidance includes an additional supporting arrangement which engages and supports the cellular wheel at least temporarily during dismantling. This supporting arrangement can be formed by a simple fork or other surface by which the cellular wheel is supported during dismantling either by the rim mentioned above or, by at least one shaft having two ends (or a pair of opposite stub shafts). In the latter case, it is preferred if one end of the shaft engages the bearing on the side of the guidance, while the additional support may be connected to this shaft end.
Of course, particularly when using a single shaft that extends over the whole axial length of the cellular wheel, it would be possible to shift the shaft through or over the support device or the bearing forming it. However, it is preferred if the support device is displaceable in dismantling direction relative to the bearing cover. In this way, both the support device and the cellular wheel can be moved together without causing too much relative movement between them.
It has been mentioned above that canting of the cellular wheel is to be avoided. As long as the cellular wheel's opposite shaft end has not yet been drawn out of the slip-on bearing while the shaft end or the cellular wheel engages the additional support provided according to the present invention, there is again some redundancy which can cause the risk of canting during dismantling. In order to adapt the additional support to the level of the cellular wheel, and the shaft end to be supported, it is desirable if there is some arrangement which enables displacing the additional support transversely to the dismantling direction in order to vary and match the position or level of the cellular wheel when the latter is to engage the additional support.
Since the risk of canting exists especially in a vertical direction due to the weight of the cellular wheel whose axis of rotation will normally extend in a horizontal direction, the additional support is preferably displaceable in a vertical direction by the respective displacing device.
Such displacing device can be formed by a positive drive, such as a screwed spindle, to vary the position of the additional support. However, it is simpler in construction and handling if the displacing device comprises resilient means, such as a pressure spring.
REFERENCES:
patent: 4875523 (1989-10-01), Thornburrow
patent: 4917141 (1990-04-01), Brunnel et al.
patent: 5129417 (1992-07-01), Dupont et al.
patent: 5529087 (1996-06-01), Berry et al.
patent: 5975104 (1999-11-01), Wilkins
patent: 3818145 (1989-11-01), None
patent: 4135395 (1993-04-01), None
Hemmelmann Klaus
Könlg Ewald
Pfeifer Kurt
Burns Doane , Swecker, Mathis LLP
Lee Kevin
Waeschle GmbH
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