Seal for a joint or juncture – Seal between relatively movable parts – Relatively rotatable radially extending sealing face member
Patent
1997-12-30
2000-09-05
Knight, Anthony
Seal for a joint or juncture
Seal between relatively movable parts
Relatively rotatable radially extending sealing face member
F16J 1516
Patent
active
061131040
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a device for sealing a rotary shaft extending into a container, in which overpressure is maintained. More particularly, the present invention relates to such a device which can be used, for example, in a pressurized screen for the screening of pulp suspensions, in which case the container is the airtight housing of the pressurized screen.
BACKGROUND OF THE INVENTION
A pressurized screen for the screening of pulp suspensions comprises an airtight housing, in which a screening member is located. The housing has an inlet for the pulp suspension and outlets for accept and rejection portions, respectively. In order to promote the screening process, the pulp suspension is caused to flow along the screening member, and the accept portion passes through the screening member, which can be rotary or stationary. In the latter case, the rotor is located in the housing for generating the flow along the screening member.
The rotor of the rotary screening member in such devices is mounted on a shaft, which is driven by a motor located outside the housing. The shaft is supported in bearings and extends into the housing. The housing is pressurized and, therefore, a seal is provided where the shaft enters the housing. In order to provide stability for the shaft, an internal axial bearing is located in an airtight casing, which extends into the housing. The seal is mounted in a seal holder between the casing and the interior of the housing inside the internal bearing.
This structural design has the disadvantage that the external (atmospheric) side of the shaft seal is accessible only after the entire shaft with its bearings has been dismounted. This results in the fact that conventional shaft seals of the mechanical seal type, for example a so-called cartridge seal, cannot be applied. In many cases this is a considerable disadvantage, because it requires complicated structures and lengthy dismantling work at the time of seal exchange.
The present invention has the object of eliminating the aforesaid problems. The device according to the present invention, therefore, renders it possible for the shaft seal side located outside the container, i.e. in the casing, to be made accessible during seal exchange in a simple manner.
SUMMARY OF THE INVENTION
In accordance with the present invention, these and other objects have now been accomplished by the discovery of apparatus for sealing a rotary shaft supported by bearings within an airtight casing and extending from the airtight casing into a housing maintained at an overpressure, which comprises a mechanical shaft seal for sealing the shaft as it passes into the housing, seal mounting means mounted on the casing for mounting the mechanical shaft seal, the casing including at least one opening for providing access to the mechanical shaft seal within the casing, and a removable airtight cover for sealing the at least one opening in the casing during operation of the apparatus. Preferably, the mechanical shaft seal comprises a mechanical cartridge seal.
In accordance with a preferred embodiment of the apparatus of the present invention, the apparatus includes O-ring means for sealing the removable cover to the casing. In a preferred embodiment, the casing is mounted within a pressurized screen for the screening of a pulp suspension.
BRIEF DESCRIPTION OF THE DRAWINGS
The present invention may be more fully appreciated with reference to the following detailed description, which, in turn, refers to the drawing which is a side, elevational, partially sectional view of the apparatus of the present invention used in connection with a pressurized screen for the screening of a pulp suspension.
DETAILED DESCRIPTION
Referring to the drawings, a pressurized screen for screening pulp suspensions comprises an airtight housing 10, in which a stationary screening member 11 is located. The housing has an inlet 12 for the suspension and outlets 13 and 14 for accept and reject portions, respectively. A rotor 15 is located outside the
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Bergdahl Anders
Forslund Kjell
Kristrom Klas
Knight Anthony
Pickard Alison K.
Valmet Fibertech Aktiebolag
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