Power plants – Pressure fluid source and motor – Ram driven by fluid pumped from reservoir
Patent
1982-03-15
1984-07-10
Croyle, Carlton R.
Power plants
Pressure fluid source and motor
Ram driven by fluid pumped from reservoir
60494, F16D 3102
Patent
active
044584873
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE TECHNIQUE
This invention relates to an electromagnetic actuator which controls a load such as a valve by use of a fluid pressure established by the operation of an electromagnetic pump.
BACKGROUND OF THE INVENTION
Various actuators have been heretofore used for controlling a load such as a valve in accordance with an electric signal. Among these actuators, those of a construction having a driven member secured to a plunger driven by an electromagnetic force created by an electromagnetic coil are used most widely. However, in an actuator of such a conventional construction, when it is desired to drive a member to be driven in a large stroke, the axial length of the electromagnetic coil inevitably increases, thus increasing the size of the actuator and reducing the stability of the same. Furthermore, servomotors widely used for a proportional control of a driven member are formed disadvantageous when a large driving force is required, and it is difficult to maintain the driven member stably at a predetermined position by use of the servomotor.
On the other hand, the fluid pressure obtained by an electromagnetic pump is required to be maintained at a constant value, and it has been a conventional practice to detect the delivery side pressure of the electromagnetic pump, and to vary the pulse width of a pulse current based on the detected pressure for maintaining a constant pressure at the delivery side of the electromagnetic pump.
For realizing such a feature, the driving device of the electromagnetic pump has been so constructed that it comprises a monostable multivibrator driven under the control of a pulse signal generated from a self-running multivibrator, and that the time-constant of the monostable multivibrator is controlled so as to vary the pulse width of the pulse current delivered the monostable multivibrator.
However, the resistance of the coil of the electromagnetic pump is varied in accordance with the temperature rise of the coil, and therefore the current flowing through the coil is varied regardless of the constant pulse width of the pulse current supplied from the driving device so as to vary the delivery of the electromagnetic pump, such a feature constituting a drawback of the conventional construction.
SUMMARY OF THE INVENTION
An object of the present invention is to provide an electromagnetic actuator which is capable of not only driving a driven member in a large stroke, but also capable of maintaining the driven member at a predetermined position.
Another object of the present invention is to provide an electromagnetic actuator which can displace a valve member at a predetermined velocity in response to an electric signal, and also can prevent the valve member from being held at an opening position even in a case of a fault occurring in the actuator.
Still another object of the invention is to provide an electromagnetic actuator which can proportionally control a load according to an electric proportional control signal, and the operation of which is extremely stable.
Still another object of the invention is to provide an electromagnetic actuator which can control a damper of a damper device with a high reliability.
A further object of the present invention is to provide an electromagnetic actuator which can assure a stable delivery of an electromagnetic pump.
According to an embodiment of the present invention, there is provided an electromagnetic actuator which comprises an electromagnetic pump for supplying a fluid from a first chamber to a second chamber in accordance with an output of a driving device; a passage interconnecting the first and second chambers; a responsive load means comprising a responsive member responsive to a pressure in the second chamber, and a load driven by the responsive member, and operable for controlling the mechanical displacement of the load; and a flow-rate control means provided in the passage for maintaining the pressure in the second chamber at a predetermined value.
According to another embodiment of the present invention there
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patent: 3415487 (1968-12-01), Robarge
patent: 3516332 (1970-06-01), Ray
patent: 3842601 (1974-10-01), Borst
patent: 3871176 (1975-03-01), Schukei
patent: 4241644 (1980-12-01), Schertler
Ichida Shunji
Inoue Kentaro
Kojima Tadashi
Morio Shyuji
Morozumi Eiichi
Croyle Carlton R.
Feldman Alfred N.
Honeywell Inc.
Stout Donald E.
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