The present invention relates generally to rotary, mechanical shaft seals and in particular to an improved cartridge seal.
Pumps and similar equipment which include rotating shafts have been provided with seals of various types to prevent leakage along their shafts. One conventional type of seal is known as a face seal and typically comprises a rotating portion fixed to the shaft defining a radial sealing face and a fixed portion secured to the housing also defining a radial sealing face, the two sealing faces disposed in abutting, sealing contact. Normally, the seal faces are maintained in engagement by a spring forming part of the seal assembly.
Examples of this type of seal can be found in U.S. Pat. No. 3,447,810 and U.S. Pat. No. 4,342,538, both owned by the assignee of the present application.
U.S. Pat. No. 4,815,747 discloses a cartridge form of a pump seal that is used to seal the pump shaft of a centrifugal pump. All the seals disclosed in the above-referenced U.S. patents, include non-rotating seal sections mounted in a pump cavity and a rotating seal section mounted to the shaft. The rotating seal section includes a coil spring surrounding the shaft for spring loading a rotating seal ring towards engagement with a non-rotating seal ring forming part of the fixed seal section. Both seal rings define radial faces which during pump operation sealingly engage.
In the seal construction disclosed in the '810 and '538 patents, the rotating and non-rotating seal sections are separately installed into the pump. In the '747 patent, the non-rotating and rotating seal sections are in a cartridge form prior to installation. During installation, a frangible element separates so that the rotating section can rotate with a pump shaft whereas the non-rotating section is fixed to the pump housing. The cartridge seal disclosed in the '747 patent has enjoyed great commercial success.
The present invention provides a new and improved seal cartridge for sealing the interface between a rotating shaft and a stationary housing such as that found in a centrifugal pump. The cartridge seal of the present invention represents an improvement in the cartridge seal disclosed in U.S. Pat. No. 4,815,747, which is hereby incorporated by reference. According to the invention, the seal cartridge is constructed as a unitary assembly having interconnected rotating and non-rotating portions. During installation of the seal cartridge, the coupling between the rotating and non-rotating portions is disconnected or separated so that after installation, the rotating portion is operatively connected to the shaft and the non-rotating portion is fixed to the housing. A rotating, sealing interface is defined between the non-rotating and rotating portions.
To facilitate the explanation of the invention, it will be described in connection with its use in a centrifugal pump. It should be understood, however, that the invention can be used in any application that requires a rotary seal for sealing a shaft/housing interface.
In the preferred embodiment, the seal cartridge includes a support member which prior to installation supports both the non-rotating and rotating portions of the seal. According to the invention, a frangible member couples the non-rotating portion of the seal to the support member.
The rotating seal portion is the same or similar to the rotating seal portion disclosed in the '747 patent. The non-rotating portion of the seal includes a seal holder or seal seat which supports a stationary seal ring. The holder is sealingly received by pump housing structure. In the preferred and illustrated embodiment, a peripheral seal surrounds the stationary seal ring and sealingly engages an axial inside surface of the holder. The O-ring may be carried by a groove in the stationary seal ring located intermediate inside and outside end faces of the seal ring. Alternately, the groove may be an end groove located on the inside face of the seal ring. In still another alternative, the O-ring may be carried by an internal groove formed in the holder or stationary seat.
The non-rotating portion of the seal includes a seal seat or holder which supports the stationary seal ring and which is secured to housing structure. According to a feature of the invention, the stationary seal ring includes an inside end face which confrontingly engages a radial surface or radial face of the stationary holder. The abutting engagement between the seal ring and the holder promotes heat transfer from the seal ring to the holder from where it is transferred to the pump housing. With the present invention, cooling of the seal is promoted resulting in increased seal life.
According to the invention, the seal cartridge is installed into the mechanism i.e. pump, by placing the assembly onto the shaft. The support member is pushed or advanced until the seal seat reaches its installed position. Further advancement of the support member causes the frangible coupling to separate so that the non-rotating portion of the seal is decoupled from the support member enabling the rotating portion to rotate relative to the non-rotating portion.
In the preferred embodiment, the support sleeve is advanced onto the shaft until an end surface abuts a shoulder formed on the shaft. The sleeve is locked or clamped in position by a locking element which locks the support sleeve and hence the rotating portion of the seal to the shaft.
In the disclosed embodiment, the seal cartridge is used to seal the rotating shaft of a centrifugal pump. In this embodiment, the seal is located in a seal cavity defined by a cup-shaped seal plate. The pump shaft includes a threaded end adapted to threadedly receive an impeller. In the preferred installation method, the seal cartridge is placed on the end of the impeller shaft and the impeller is then threaded onto the shaft end. An inner end-face of the impeller abuts an end of the seal cartridge and advances the support sleeve axially along the pump shaft as the impeller is threaded onto the shaft end. The support sleeve is sized such that when fully installed, it is clamped between the inner end-face of the impeller and a shoulder formed on the pump shaft and is rigidly held thereto.
According to additional features of the invention, the stationary seal ring and/or seal ring holder includes a plurality of slots for receiving lubricating fluid from inside the pump housing. The slots may be formed on an inside end face of the seal ring so that when the seal ring abuttingly engages the radial surface on the holder, cooling oil is received in the region where heat transfer between the seal ring and the holder occurs. Alternately, the slots may be formed in the radial heat exchange surface of the holder.
Additional features of the invention will become apparent and a fuller understanding obtained by reading the following detailed description made in connection with the accompanying drawings.
The foregoing and other features of the present invention will become apparent to one skilled in the art to which the present invention relates upon consideration of the following description of the invention with reference to the accompanying drawings, wherein:
Turning first to
The housing 14 defines a cup-shaped seal cavity 18 including a machined recess 18a which receives a non-rotating portion 10a of the cartridge seal 10. The remainder of the seal cavity 18 shrouds a rotating part 10b of the cartridge seal and at least partially protects seal components from-material being pumped through an impeller chamber (not specifically shown, but indicated generally by the reference character 20.
According to the invention, the seal cartridge 10 is constructed as a unitary assembly with the rotating portion 10b and the non-rotating portion 10a coupled together so that both portions of the seal are installed concurrently during an installation process.
With the illustrated construction, the entire seal 10 including both the rotating and non-rotating portions 10a, 10b are installed concurrently. The alignment of the parts are maintained throughout the installation process.
The present invention represents an improvement over a cartridge seal disclosed in U.S. Pat. No. 4,815,747, owned by the Assignee of the present application, and is hereby incorporated by reference. The seal cartridge disclosed in the '747 patent illustrates and provides additional details regarding a cartridge seal having rotating and non-rotation portions that are coupled together prior to installation so that both portions of the seal are installed concurrently. During the installation process, and as more fully described in the '747 patent, the coupling between the rotating and non-rotating portion is broken.
Referring also to
The non-rotating seal ring seat 40 includes an O-ring seal 42 which sealing engages the recess 18a to inhibit fluid leakage between itself and the housing 14. The stationary seal ring holder 40 carries a seal ring or face seal element 22b in a way that inhibits relative rotation between itself and the seal ring 22b and also carries an O-ring seal 44 for inhibiting fluid leakage between the seat 40 and the seal ring 22b.
According to the invention, the circumferential, O-ring seal 44, seals the periphery of the seal ring 22b to an inside, axial surface 40a of the holder 40. In the embodiment illustrated in
As seen best in
It should also be noted here that in the illustrated embodiment, the frictional engagement of the O-ring seal 42 with the housing recess 18a and the holder 40 inhibits relative rotation between these components. Similarly, the O-ring seal 44 inhibits relative rotation between the holder 40 and the face seal 22b. Mechanical engagement structure such as splines, lugs, pins, etc. between the holder 40 and the housing 14 and/or the holder 40 and the sealing element 22b are also contemplated by the invention.
As is conventional, the rotating portion 10b of the seal cartridge 10 includes a bellows member 46 clamped at its left end to the support member 30 (as viewed in
As indicated above, at the commencement of the installation process, the rotating and non-rotating portions 10b, 10a of the seal cartridge 10 are interconnected so that both portions are installed concurrently. In particular, the stationary seal ring seat 40 is coupled to the support member 30 by the frangible ring-like element 38. For purposes of explanation the element 38 will be termed a “shear ring”. As seen best in
In the preferred installation method and referring in particular to
After the seal ring seat 40 bottoms in the recess 18a i.e. once an outer radial end face 40c of the seat abuts a radial end surface 90 defined by the recess 18a, continued advancement of the support member 30 (by rotating the impeller further onto the pump shaft 12) causes tab portions 38a of the shear ring 38 to separate from an annular band-like portion 38b as seen in
The support member 30 is locked to the pump shaft 12 by virtue of being clamped between the radial face 16a of the impeller 16 and the shoulder 92 on the pump shaft 12. After installation, the non-rotating and rotating portions 10a, 10b of the seal are relatively rotatable. The fluid seal is established by the abutting contact between the radial seal faces 50, 52 defined by the rotating and non-rotating seal rings 22a, 22b, respectively (shown in
The term “O-ring” used above is intended to serve as a generic description for an annular type seal. This invention is not limited to an “O-ring” having a circular cross section. “O-rings” with rectangular (often termed quad rings), oblong and other cross sections are contemplated by the present invention.
As viewed in
The stationary seat 40″ including the radial slots 90 can also be used in the alternate construction shown in
Although the invention has been described with a certain degree of particularity, it should be understood that those skilled in the art can make various changes to it without departing from the spirit or scope of the invention as hereinafter claimed.
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/US06/40163 | 10/12/2006 | WO | 00 | 4/10/2009 |