The present invention relates to pumping elements having static seals, and in particular centrifugal water pumps.
Many pumps include a static seal that is in contact with a rotating seal. These two seals co-act to minimize leakage out of the housing of the pump. However, since there is a frictional interface of the rotating seal sliding on the static seal, these seals can also coact to create heat from sliding friction. This heat can provide several deleterious effects including increased seal wear and also formation of vapor bubbles.
To overcome these adverse affects, some pumps incorporate secondary cooling passages that provide a cooling medium to the seal interface to reduce the temperature. For example, in a centrifugal pump, the cooling passage may connect the high pressure fluid exiting the pump with a region of lower pressure near the inner diameter of the pump.
However, some pumps include fluid passageways of simple shape which do not provide optimum protection for the pump seals. Further, some newer pumps are required to work in hotter applications where the removal of heat from the frictional seal interface is critical. Sometimes the simply shaped fluid passageways provide inadequate cooling flow such that reasonable operating temperatures cannot be achieved. In yet other applications the pressure of the cooling fluid in the vicinity of the seal is too low to prevent the formation of vapor bubbles and damage by cavitation. In yet other applications, the fluid passageway is directed toward the centerline of the rotor, such that there is no tangentially-directed fluid to flush debris away from the seal interface.
The present invention provides solutions to these problems in novel and unobvious ways.
The present invention includes multiple embodiments that relate to various methods and apparatus for cooling a seal within a pump which includes a rotating member.
In one embodiment, the present invention includes at least one fluid passageway that directs fluid toward a seal element, with the fluid flow including a component that is generally tangential to the seal element.
In yet another embodiment, the pump includes a passageway providing fluid directed at a seal, the passageway having at least a portion thereof with a decreasing cross sectional area such that the fluid accelerates toward the seal area.
Yet another aspect of the invention concerns a curving, open-channel fluid passageway that is arranged and configured such that rotation of the pump rotor over the fluid passageway increases the velocity of the fluid flowing in the passageway. Yet other aspects of the invention concern closed-channel fluid passageways.
These and other objects and advantages of the present invention will be apparent from the drawings, description, and claims to follow.
For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiments illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations and further modifications in the illustrated devices, and such further applications of the principles of the invention as illustrated therein being contemplated as would normally occur to one skilled in the art to which the invention relates.
The present invention relates to method and apparatus for cooling and flushing a seal of a pump assembly which includes a rotating member.
In one embodiment, the assembly includes a rotating centrifugal element rotating within a pump housing. The pump housing includes one or more grooves for channels which direct the flow of fluid toward a static seal member or the housing thereof. In one embodiment, the grooves or fluid passageways have at least a portion thereof curved in shape. As a portion of the pump rotor, such as the backplate, travels across the curved fluid passageway, fluid drag from the rotating member imparts energy into the fluid within the passageway and increases the velocity and/or pressure of the fluid flowing in the curved passageway. In yet another embodiment, the fluid passageway includes at least a portion thereof with a cross-sectional area that decreases in the direction toward the static seal. This decrease in cross-sectional area causes a subsequent increase in the velocity of the fluid flowing within the passageway.
In various embodiments of the present invention, the fluid directed at the static seal has increased velocity. This higher fluid velocity results in increased convective heat transfer away from the static seal and into the cooling fluid. This reduces the temperature of the seal. Further, the increased velocity of the fluid in the fluid passageway results in a higher pressure within the chamber surrounding the static seal. In some embodiments, this increase in seal cooling and increase in seal chamber pressure results in an overall reduction in the formation of vapor bubbles within the seal chamber and a subsequent reduction in damage from cavitation. In some embodiments, the higher flow end near the seal provides lubrication of the sliding interface and also provides flow to flush debris away from the seal.
Housing 38 rotatably supports centrifugal rotor assembly 40 along shaft 42 thereof preferably by a pair of ball bearings 50, although the present invention also contemplates those embodiments with single bearings and also those embodiments with plain bearings and roller bearings. Housing 38 includes a generally flat surface 62 which is spaced apart from and faces a generally flat surface 63 of backplate 46 of rotor assembly 40. As rotor assembly 40 rotates within housing 38, surface 63 rotates over static surface 62. As best seen in
Pump 30 includes a first rotating seal member 70 and a second static seal member 72 which prevent and/or reduce leakage of fluid from pump 30. Seal members 70 and 72 act together to prevent and/or reduce leakage. In one embodiment, neither seal member 70 nor seal member 72 prevent or reduce leakage by themselves, without the benefit of co-action with the other member. However, the present invention contemplates other types of seal members which can independently prevent and/or reduce leakage of fluid from pump 30. First rotating seal member 70 is coupled to and rotates with hub 44 of centrifugal rotor assembly 40. As examples, the present invention contemplates embodiments in which seal member 70 is a press-fit on hub 44, and also those embodiments in which seal member 70 is a press-fit onto other rotating portions of rotor assembly 40. Further, the present invention contemplates methods of coupling seal member 72 rotor assembly 40 without a press-fit. Second static seal member 72 is statically held within a seal housing 58 of pump housing 38. Seal members 70 and 72 each include a surface in contact with the other seal member. Therefore, rotation of rotor assembly 40 within housing 38 creates friction at the contact between seal members 70 and 72. Any fluid leaking past seal number 72 exits pump 30 through drainage port 69.
In some embodiments, housing surface 62 includes one or more grooves or fluid passageways that permit flow of higher pressure fluid from rotor outer diameter 41 toward hub 44, seal members 70 and 72, and seal housing 58. Preferably, these fluid passageways are open channels placed within housing surface 62. Referring to
Although what has been shown and described are passageways which include centerlines, walls, and boundaries, which can be described with a single radius acting about a central point, the present invention also contemplates those embodiments in which the various centerlines, walls, and boundaries of the passageway include one or more piecewise linear segments which approximate circular arcs. Further, the present invention contemplates those passageways where the centerlines, walls, and boundaries which are curved and/or piecewise linearly approximated along parabolic paths and curved paths of higher mathematical order, as examples.
Fluid passageways 60 and 61 have been depicted and described with a cross-sectional area that decreases in a direction from rotor outer diameter 41 to seal housing 58. As shown in
Because of fluid drag effects from backplate surface 63 acting on any fluid adjacent the backplate and also because of the shape of the fluid passageways, the fluid within passageways 60 and 61 are induced by rotor rotation to flow in a direction from the rotor outer diameter 41 toward rotor inner diameter 39. Drag from backplate surface 63 imparts energy in the rotational direction to any fluid in passageway 60 and 61. Because passageways 60 and 61 have pathways with directional components that are directed radially inward, any fluid influenced by the drag of backplate surface 63 is turned by the walls of the passageways to move along the passageways and thus inward toward the seal interface.
Referring to
Pump assembly 130 is the same as pump 30, except for differences in the fluid passageways which will be described. Surface 162 of housing 138 includes fluid passageways 160, 161, and 161.5. Fluid passageway 160 includes a first, generally linear section from the passageway inlet toward a central position along surface 162. Fluid passageway 160 includes a second, curved portion extending from the interior end of the linear portion toward seal housing 158. Fluid passageway 161 includes a first curved portion extending from a position near the outer diameter 141 of the rotor toward a point along the interior portion of surface 162. Fluid pathway 161 further includes a linear portion extending from the end of the curved portion and proceeding in a linear path toward seal housing 158. In some embodiments, the linear end portion of passageway 161 is tangential to seal housing 158. Further, pump assembly 130 includes a third fluid passageway 161.5 which is generally linearly along its entire length from a position near rotor outer diameter 141 to seal housing 158. The centerline of fluid passageway 161.5 is preferably tangential to seal housing 158. Fluid passageways 160, 161, and 161.5 each have a direction that preferably includes a directional component that is parallel to rotational direction 174.
While the invention has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that only the preferred embodiments have been shown and described and that all changes and modifications that come within the spirit of the invention are desired to be protected.
This application claims the benefit of priority to U.S. provisional patent application Ser. No. 60/426,149, filed Nov. 14, 2002, which is incorporated herein by reference.
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Number | Date | Country | |
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20040136826 A1 | Jul 2004 | US |
Number | Date | Country | |
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60426149 | Nov 2002 | US |