Fluid handling – Line condition change responsive valves – Pilot or servo controlled
Reexamination Certificate
2000-04-26
2001-05-15
Lee, Kevin (Department: 3753)
Fluid handling
Line condition change responsive valves
Pilot or servo controlled
C137S129000, C137S129000
Reexamination Certificate
active
06230738
ABSTRACT:
CROSS-REFERENCE TO RELATED APPLICATIONS
This application is based upon and claims the benefit of priority from the prior Japanese Patent Applications No. 11-125208, filed Apr. 30, 1999; and No. 11-340499, filed Nov. 30, 1999, the entire contents of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
The present invention relates to a flow rate control valve and a flow rate control system for precisely controlling the flow rate of a target fluid to be measured.
A stepping motor or a differential transformer is used in a driver for actuating a valve body of a flow rate control valve. In a flow rate control valve in which a stepping motor is used in the driver, the stepping motor looses its holding torque for holding the rotating position of the rotary shaft if the power supply to the stepping motor is stopped. As a result, the valve body is moved by the pressure of the fluid to be measured. It follows that, in order to maintain constant the opening degree of the valve hole, it is necessary to continue to supply power to the stepping motor, leading to an increased power consumption. In addition, the heat generated by the power supply causes the temperature of the fluid to be measured to be elevated. Further, since the stepping motor is relatively large in size, it is difficult to miniaturize the apparatus.
What should also be noted is that, since the accuracy (resolution) of the rotating position control of the stepping motor is determined by the number of teeth of the stator, it is necessary for the stepping motor to include a costly stator having a large number of teeth or a large stator in order to improve the accuracy. It follows that the driver using a stepping motor is not adapted for controlling a low flow rate requiring control of a high precision.
In addition, since the stepping motor generates a magnetic field, the electronic devices arranged around the flow rate control valve tend to be adversely affected to cause, for example, malfunction.
The driver using a differential transformer also gives rise to problems similar to those produced by the driver using a stepping motor. In addition, the differential transformer is caused to incur malfunction in the presence of magnetism.
BRIEF SUMMARY OF THE INVENTION
An object of the present invention is to provide a flow rate control valve and a flow rate control system capable of maintaining the opening degree of the valve body at a high accuracy even if the power supply to the driver is stopped so as to perform the flow rate control at a high precision and not generating magnetism giving adverse effects such as malfunction to the electronic devices arranged around the flow rate control valve and the flow rate control system.
According to one embodiment of the present invention, there is provided a flow rate control valve for controlling the flow rate of a target fluid to be measured, comprising:
an apparatus body having a valve hole;
a valve body for opening/closing the valve hole; and
a driver consisting of an ultrasonic motor having a rotary shaft for driving the valve body to adjust the opening degree of the valve hole so as to control the flow rate of the target fluid flowing through the valve hole.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.
REFERENCES:
patent: 4909212 (1990-03-01), Minowa et al.
patent: 4915074 (1990-04-01), Arai
Fujita Hiroshi
Hayamizu Naoya
Hirabayashi Hideaki
Senda Keiichiro
Watanabe Yasushi
Lee Kevin
Scully Scott Murphy & Presser
Tokyo Keiso Co., Ltd.
LandOfFree
Flow rate control valve and flow rate control system does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Flow rate control valve and flow rate control system, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Flow rate control valve and flow rate control system will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2509067