Conveyors: fluid current – Load flow diverter – divider – or combiner – Movable conduit section
Reexamination Certificate
1998-08-13
2001-06-19
Ellis, Christopher P. (Department: 3615)
Conveyors: fluid current
Load flow diverter, divider, or combiner
Movable conduit section
C137S876000
Reexamination Certificate
active
06247877
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to a pipe switch for use in a conveying unit for pneumatically conveying bulk material.
German Pat. No. 41 14 949 C1 describes a pipe switch including a housing which has an inlet port and two outlet ports, and accommodates a plug for selectively connecting the inlet port with either one of the two outlet ports. The plug exhibits a circumferential perimeter, which is at least partially spherically arched, and is formed therein with a channel. The plug is rotatably supported in the housing about a pivot axis which extends perpendicular to a great circle of a sphere containing the circumferential perimeter. The housing is provided with an inner surface which complements the circumferential perimeter of the plug, with the inlet port and the outlet ports of the housing being connectable via the channel in a substantially smooth manner. The circumferential surface of the plug is a freely-shaped surface area (a random surface area which is characterized by varying radii of curvature), which constitutes only by approximation and sacrifice of an accurate coincidence of the ports of the channel in the plug with corresponding ports in the housing an area of a spherical segment which is bounded by two parallel planes oriented in symmetry to a center plane extending perpendicular to the pivot axis of the plug. The axis of the channel is offset with respect to the pivot axis of the plug while the channel itself is in symmetric disposition to the center plane. In order to allow assembly and dismantling of the plug, the housing is split in the center plane. Thus, the joint lies on a great circle in the rotational area of the plug and must be made with particular care. Even then, the seals typically used in this area are subject to increased wear during rotation of the plug.
SUMMARY OF THE INVENTION
It is thus an object of the present invention to provide an improved pipe switch, obviating the afore-stated drawbacks.
In particular, it is an object of the present invention to provide an improved pipe switch which is so constructed as to reduce the complexity of manufacturing the housing while avoiding an increased wear on the seals.
These objects, and others which will become apparent hereinafter, are attained in accordance with the present invention by a housing having an inlet port and at least two outlet ports, and a plug formed with a channel having opposite ports for connecting in a substantially smooth manner the inlet port with either one of the outlet ports, with the plug being supported in the housing for rotation about a pivot axis which extends perpendicular to a great circle of a sphere containing the circumferential perimeter, with the housing having an inner perimeter corresponding to the circumferential surface of the plug, wherein the plug is formed by a spherical segment within a spherical volume bounded by the great circle, with the ports of the channel being bounded at least approximately by substantially coincidental ellipses in the spherical segment of the plug in a projection along an imaginary line connecting the centers of the ports, with the imaginary line extending offset with respect to the pivot axis of the plug, wherein the ellipses are defined by major axes describing in a projection in the direction of the imaginary line with the pivot axis of the plug an angle which increases with increasing distance of the imaginary line from the great circle, whereby the offset of the imaginary line with respect to the pivot axis of the plug increases with increasing angle.
It will be understood by persons skilled in the art that the term “spherical segment” will denote a volume that is bounded by a sphere and two parallel planes which intersect the sphere in parallel disposition to a particular great circle of the sphere.
The present invention is based on the surprising recognition that, contrary to conventional teaching, a smooth transition between the inlet and outlet ports of the housing and the respective ports of the channel of the plug can be accomplished even when the channel or at least its ports are situated outside the great circle, and one departs from conventional wisdom that the respective cross section needs to be point-symmetric, i.e. circular, square or rectangular. Based on this recognition, a pipe switch constructed in accordance with the present invention is particularly advantageous because the housing partition plane can now be shifted away from the spherical volume into the plane of a great circle or a plane parallel thereto. As a consequence, the housing may be made by a plug-receiving housing portion and a flange-mounted cover which is substantially flat and closes the housing portion. Thus, the seals will neither be contacted by the plug between the flange-mounted cover and the housing portion nor will seals, which optionally circumscribe the ports of the channel of the plug, pass over a joint or a partition line in the housing portion.
There is no need to provide plug-forming spherical segment and the complementary inner surface of the housing of full shape. Rather, it is sufficient to construct the circumferential perimeter zones of the plug and the corresponding inner surface zones of the housing, arranged co-extensively in the respective rotational positions of the plug, as spherical segments in the area of the respective ports. Thus, the plug can be reduced in size to achieve a substantial weight reduction. Naturally, the formation of dead spaces between plug and inner housing surface should be avoided as bulk material (granular and/or pulverized material) may collect there.
A pipe switch according to the present invention can be designed in various ways and the construction depends on the respective application. This is true for the cross sectional areas of the channel ports and the inlet and outlet ports of the housing as well as to the shape and pattern of the channel and the extent of the offset of the imaginary line, which connects the centers of the port areas, with respect to the pivot axis of the plug. There is no requirement to design a straight channel. It is even conceivable to design the channel with a section arranged outside of the spherical segment of the plug.
REFERENCES:
patent: 4952100 (1990-08-01), Heep et al.
patent: 5269638 (1993-12-01), Sindermann et al.
patent: 5727595 (1998-03-01), Eminger
patent: 41 14 949 C1 (1992-10-01), None
Day Ursula B.
Dillon, Jr. Joe
Ellis Christopher P.
Feiereisen Henry M.
Waeschle GmbH
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