Fluid handling – With heating or cooling of the system – With electric heating element
Reexamination Certificate
2000-06-15
2001-11-27
Lee, Kevin (Department: 3753)
Fluid handling
With heating or cooling of the system
With electric heating element
C251S251000, C251S321000, C251S356000
Reexamination Certificate
active
06321780
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a valve for controlling a flow rate of gas, and more particularly to a control valve proper for using in a discharge system and a supply system in a system for manufacturing semiconductors, liquid crystals and others.
In the discharge system of the semiconductor manufacturing system, a needle control valve is used for controlling the flow rate of gas. The needle valve is linearly operated by a diaphragm under the condition of a positioning device, or by a screw rotated by a motor.
In the discharge system of the semiconductor manufacturing system, it is required to control the process pressure of several torrs and cleaning pressure of several hundred torrs. The controllable range of the needle control valve is determined by the control characteristic of the needle and the range-ability (the ratio between a controllable maximum capacity coefficient and a controllable minimum capacity coefficient) of the needle. However, the range-ability of the needle valve is about 15-30 in the linear characteristic and about 50-100 in the equal percentage characteristic when the needle valve is controlled in linear proportion relation. Namely, the control range is narrow, so that a high pressure range can not be controlled by the needle valve.
On the other hand, it is required to shut the passage at a high speed smaller than 2 seconds in an emergency. However, if the needle valve is controlled at such a high speed, hunting occurs. As a result, the pressure fluctuation becomes large, which renders the needle valve impossible to control a minimum range.
The above described problems are not trouble for the needle valve only, other valves, for example the shut off valve, has the same problem.
In addition, since the conventional needle valve can not be used to shut off the passage, a shut off valve must be parallelly used.
SUMMARY OF THE INVENTION
Accordingly, a first object of the present invention is to provide a flow rate control valve in which a valve body can be operated at a high speed, the controllability of the valve body can be increased, increasing the solving power thereof, thereby satisfying the requirements for both of the high speed operation and the controllability in a high pressure range.
A second object of the present invention is to provide a flow rate control valve having a flow rate control function and a shut off function, and possible to control the pressure in a wide range such as the process pressure and cleaning pressure in the discharge system of the semiconductor manufacturing system, thereby providing an economical control valve.
A third object of the present invention is to provide a flow rate control valve which keeps a valve thrust even if the electric power is cut off, thereby preventing the gas from leaking.
According to the present invention there is provided a valve comprising, a valve body having a passage including a hole in which gas flows, a valve seat surrounding a port of the hole, a valve disc for closing the port of the hole, an actuator for operating the valve disc in a sine curve motion.
The valve disc has a closing portion engaged with the valve seat and a needle portion inserted in the hole in the passage.
The valve according to claim
1
further comprising an inside heater for heating the valve disc.
An outside heater is provided for heating parts of the valve body surrounding the valve seat and the valve disc.
A seal ring made of elastic material is provided on the closing portion so as to be pressed against the valve seat.
The actuator comprises a motor, a horizontal drive shaft as a driving shaft of the motor, an eccentric cam secured to the driving shaft, a slider connected to the valve disc and vertically moved by the eccentric cam.
These and other objects and features of the present invention will become more apparent from the following detailed description with reference to the accompanying drawings.
REFERENCES:
patent: 4610423 (1986-09-01), Morino
patent: 5636652 (1997-06-01), Toschi et al.
patent: 5915410 (1999-06-01), Zajac
Benkan Corporation
Birch & Stewart Kolasch & Birch, LLP
Lee Kevin
LandOfFree
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