Valves and valve actuation – With means to increase head and seat contact pressure – Gate valve
Reexamination Certificate
2000-02-18
2001-05-29
Kaufman, Joseph A. (Department: 3754)
Valves and valve actuation
With means to increase head and seat contact pressure
Gate valve
C251S193000
Reexamination Certificate
active
06237892
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a gate valve and more particularly to a gate valve for use in a processing device for processing a semiconductor wafer or the like.
2. Description of the Prior Art
In a processing device for processing a semiconductor wafer, a liquid crystal substrate or the like, the wafer or the substrate is inserted into or taken out from one of many kinds of processing rooms through passages each having a gate valve. It is necessary to prevent as much as possible foreign matters from entering into the processing room.
Such gate valve is described in the Japanese Patent Laid-Open No. 156781/83. In such gate valve, a valve disc is moved up and down while separating from a valve seat, and the valve disc is brought into contact with the valve seat by urging the side surface of the valve disc toward the valve seat when the valve disc is positioned to face to the valve seat.
In said gate valve heretofore in use, a valve rod for supporting the valve disc and a valve housing are connected by a cylindrical bellows which is extensible, contractible and inclinable in order to cut off the vacuum space in the valve housing from the atmosphere outside of the housing.
However, a large pressure difference is generated between the outside and inside of the cylindrical bellows in the conventional gate valve, and accordingly, when the cylindrical bellows are curved according to the inclination of the valve rod for driving the valve disc an abnormal stress is applied on each portion of the cylindrical bellows, so that the service life of the cylindrical bellows becomes short.
The inventor found out by experiments that the above defect could be obviated by arranging the cylindrical bellows so as to project from the valve housing outwardly so that the outer surface of the cylindrical bellows is subjected to the atmosphere and arranging a pivotal point of the valve rod at a center of the axial length of the cylindrical bellows in the compressed state.
The present invention can be obtained by the above results of the experiments.
SUMMARY OF THE INVENTION
The invention can be summarized as follows.
A gate valve of the present invention comprises a valve housing, a valve disc disposed in said valve housing so that it is selectively brought into contact with a valve seat provided inside of said valve housing, a valve rod sealingly projected from the inside of said valve housing to the outside of said valve housing, said valve rod being capable of moving up and down and inclining, a cylindrical bellows provided at the outside of said valve housing, one end of said cylindrical bellows being sealingly secured to said valve housing and the other end of said cylindrical bellows being sealingly secured to said valve rod, and a driving means provided at the outside of said valve housing for (1) driving said valve rod to move said valve disc between a position where said valve disc is faced with a gap to said valve seat and a position where said valve disc is not faced to said valve seat, and for (2) inclining said valve rod so that said valve disc is brought into contact under pressure with said valve seat when said valve disc is moved to the position where it is faced to said valve seat, wherein said driving means comprises a piston cylinder means having a piston cylinder and a piston rod, a roller formed on one of said piston rod and said valve rod, an elongated obligue hole formed on the other of said piston rod and said valve rod, said roller being passed through said hole to connect said piston rod with said valve rod, a spring for separating axially said piston rod and said valve rod from each other, a guide formed on a side surface of said piston cylinder for guiding said valve rod so as to move up and down, and means for inclining said valve rod at a center of the axial direction of said cylindrical bellows in the compressed state thereof, and wherein when said piston rod is urged toward said valve rod, said valve rod is inclined centering around said center and said disc is brought into contact under pressure with said valve seat.
A gate valve of the present invention comprises a valve housing, a valve disc disposed in said valve housing so that it is selectively brought into contact with a valve seat provided inside of said valve housing, a valve rod sealingly projected from the inside of said valve housing to the outside of said valve housing, said valve rod being capable of moving up and down and inclining, a cylindrical bellows provided at the outside of said valve housing, one end of said cylindrical bellows being sealingly secured to said valve housing and the other end of said cylindrical bellows being sealingly secured to said valve rod, and a driving means provided at the outside of said valve housing for (1) driving said valve rod to move said valve disc between a position where said valve disc is faced with a gap to said valve seat and a position where said valve disc in not faced to said valve seat, and for (2) inclining said valve rod so that said valve disc is brought into contact under pressure with said valve seat when said valve disc is moved to the position where it is faced to said valve seat, wherein said driving means comprises a piston cylinder means having a piston cylinder and a piston rod, an inclined link with both ends pivotally connected to said piston rod and said valve rod, respectively, so as to connect said piston rod with said valve rod, a spring for separating axially said piston rod and said valve rod from each other, a guide formed on a side surface of said piston cylinder for guiding said valve rod so as to move up and down, and means for inclining said valve rod at a center of the axial direction of said cylindrical bellows in the compressed state thereof, and wherein when said piston rod is urged toward said valve rod, said valve rod is inclined centering around said center and said disc is brought into contact under pressure with said valve seat.
Said valve rod has a pivotal shaft which is guided by said guide, and wherein said pivotal shaft and said guide are located on or near a line passing through the surface of the valve seat facing the valve disc.
Other objects and advantages will become apparent from the following description of the preferred embodiments taken in conjunction with the accompanying drawings.
REFERENCES:
patent: 3120944 (1964-02-01), Cogez et al.
patent: 4560141 (1985-12-01), Bösch
patent: 4721282 (1988-01-01), Shawver et al.
patent: 5002255 (1991-03-01), Sawa et al.
patent: 5120019 (1992-06-01), Davis, Jr.
patent: 5415376 (1995-05-01), Ito
patent: 5641149 (1997-06-01), Ito
patent: 5755255 (1998-05-01), Iwabuchi
patent: 6095780 (2000-08-01), Ishigaki et al.
Bonderer D. Austin
Kaufman Joseph A.
Nilles & Nilles SC
V Tex Corporation
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