Fluid handling – Line condition change responsive valves – Direct response valves
Reexamination Certificate
2002-08-28
2004-12-14
Krishnamurthy, Ramesh (Department: 3753)
Fluid handling
Line condition change responsive valves
Direct response valves
C137S513700, C137S515500, C137S529000, C137S541000
Reexamination Certificate
active
06830064
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates to a leak control valve, and more particularly to a check valve for protecting the vacuum chamber and neighboring instruments in case of the abrupt vacuum leakage by accident.
DESCRIPTION OF THE RELATED ART
Recently, a check valve has been used for protecting the vacuum chamber, for instance, in the manufacturing lines of semiconductors and plasma display panels.
Since the conventional check valve, however, shuts off the leak in a unidirectional manner, it is technically difficult to apply the conventional check valve to the vacuum control system between a vacuum pump and a vacuum tube.
In
FIG. 1
is shown a cross-sectional view of a traditional check valve. Referring to
FIG. 1
, the internal spring
100
exerts a restoring force against the flow through the inlet
110
so that the inlet
110
is closed.
Now, it may happen by accident that an abnormally high pressure is formed at the inlet
110
. If the pressure at the inlet
110
is higher than the resisting force of the spring
100
, the control valve is opened and the flow of high pressure is by-passed through the pathway
130
.
As another approach in accordance with the prior art, an automatic control valve can be employed. However, the automatic control valve has an inherent problem in a sense that the response time of the automatic control valve is relatively slower than the propagation time of the pressure flow from the inlet to the outlet.
In other words, the prior art needs an instrument that senses the leak of flow and sends a control signal to the valve. However, the shortcomings of the prior art is that since the response time of the vacuum sensor or the leak detector is generally slow, the automatic control valve does not respond to the diffusion speed of the pressure flow.
Therefore, the vacuum control valve of the prior art can not promptly respond to the sudden leak of the flow by accident.
FIG. 2
is a schematic diagram illustrating the vacuum control valve in accordance with the prior art Referring to
FIG. 2
, pressure sensors
210
and
220
detect any leakage and report the leak to the controller
230
in case when the leak, for instance, due to breakage of the vacuum tube
200
happens by accident.
Then, the controller
230
blocks the vacuum tube
200
from the vacuum pump
250
through closing the vacuum valve
240
. In this case, the fact is that the propagation speed of electrical signal of the pressure sensors
210
and
220
, as well as the controller
230
is relatively faster than the propagation speed of the pressure from the vacuum tube.
However, the vacuum valve
240
of the prior art has shortcomings because the sensing speed of the instruments like the pressure sensor
210
and
220
is slower than the propagation speed of the pressure.
Furthermore, in case when one of the vacuum tubes
260
in production lines such as in semiconductor manufacturing industry or in plasma display panel (PDP) manufacturing lines is broken, the adjacent vacuum tubes
270
,
280
,
290
and
300
are simultaneously damaged due to the leak from the broken tube
260
.
SUMMARY OF THE INVENTION
In view of these problems, there is a need in the art for a vacuum control valve effectively and promptly blocking the propagation of flow due to pressure difference in case of the accidental leak between the vacuum tube and the vacuum pump.
Accordingly, it is an object of the present invention to provide a vacuum control value that can promptly block the propagation of the pressure flow in case when the leak occurs between the vacuum tube and the vacuum pump by accident.
It is further an object of the present invention to provide a vacuum control valve that can protect the adjacent instruments such as the other vacuum tubes or the sensors when abrupt alteration of pressure is caused by the accidental leak between the vacuum tube and the vacuum pump.
Yet it is another object of the present invention to provide a vacuum control valve that prevents the breakage of the vacuum tubes due to the reverse flow in case when the vacuum pump malfunctions by accident.
REFERENCES:
patent: 701754 (1902-06-01), Moran
patent: 2541282 (1951-02-01), Powers
patent: 2929399 (1960-03-01), Magowan, Jr.
patent: 3403697 (1968-10-01), Fenton
patent: 3561471 (1971-02-01), Sands
patent: 3756270 (1973-09-01), Fonseca et al.
patent: 3850195 (1974-11-01), Olsson
patent: 4172470 (1979-10-01), Walker
patent: 4190075 (1980-02-01), Kayser
patent: 4562861 (1986-01-01), Payton
patent: 4706705 (1987-11-01), Lee, II
patent: 4811756 (1989-03-01), Hall
patent: 6513545 (2003-02-01), Rhone et al.
PCT International Search Report from Korean Intellectual Office dated Mar. 28, 2002.
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