Power plants – Pressure fluid source and motor – Pump means moves motive fluid from one chamber to an...
Patent
1983-12-13
1987-02-17
Look, Edward K.
Power plants
Pressure fluid source and motor
Pump means moves motive fluid from one chamber to an...
60473, 91459, 91462, F16D 3102
Patent
active
046429867
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a hydraulic servomotor in which movement is provided by the direct transfer of the liquid.
Developments in data processing have led to digital systems adapted to controlling industrial processes and capable of controlling a considerable number of analog control loops in order to control industrial production units of the boiler type, chemical or oil units, paper machines, cement works and so on.
This is done by replacing conventional control loops with improved optimization, but necessitates digital/analog conversion for positioning the control valves, which are actuated by pneumatic servomotors and thus necessitate another electro-pneumatic conversion.
As compared with the prior art systems, the present invention relates to a hydraulic servomotor comprising a jack or actuator adapted to be connected by its rod to a movable component which is required to be accurately moved and positioned, the jack being completely filled with liquid, the servomotor being characterized in that the piston movement is provided by the direct transfer of liquid from one chamber of the actuator to the other via at least one electric vibrator pump powered by an a.c. supply and a safety solenoid valve, which is open in the inoperative state, is connected to connect the two chambers of the actuator.
According to another feature of the invention, the jack is a double-acting and double-rod jack.
According to another feature of the invention, a spring is disposed between the cylinder and the piston of the jack in order to tend to return the piston always towards one end of the cylinder.
According to another feature of the invention, a solenoid valve for reversing the direction of the movement is connected to connect the two chambers of the jack.
The invention is illustrated by way of example without any limiting force in the accompanying drawings wherein:
FIG. 1 is a diagram of a servomotor according to the invention having a single vibrator pump and a double-acting double-rod jack.
FIG. 2 is a variant of FIG. 1, the servomotor comprising two vibrator pumps.
FIG. 3 is a servomotor in which the energization circuit is in the form of a closed bridge.
FIG. 4 is a servomotor with a single-acting jack.
The object of this invention is to provide a hydraulic servomotor providing a direct response to the orders from a process computer, without analog conversion or ancillary equipment, without the need for a pressure liquid supply system and with a low electrical power consumption, the time of which is limited to the duration of the servomotor control pulses.
Another object of the servomotor according to the invention is high accuracy of movement or positioning while the speed of the movement or the power is readily adjustable.
The reversal of the direction of the movement is also instantaneous without any dead zone and this results in the effect obtained being proportional to the control command.
The movement obtained is also perfectly linear while the available thrust is very considerable.
The servomotor is also of reduced size, weight and cost and highly reliable.
The servomotor according to the invention will be applied to the accurate and powerful movement or positioning of any controlled component, e.g. control valves, the tools of machine tools, and so on. According to the examplified embodiment shown in FIG. 1, the servomotor comprises a double-acting double-rod jack 1, the piston 2 being provided with two rods, 3.sub.1, 3.sub.2 of the same section intended for connection to the component which is to be controlled.
Since the rods 3.sub.1 and 3.sub.2 have identical sections, the chambers 1.sub.1 and 1.sub.2 defined by the piston 2 also have the same section and give an identical movement of the piston 2 in either direction for a given volume of fluid introduced via the end ports 4.sub.1, 4.sub.2 of the cylinder 1.
The ports 4.sub.1, 4.sub.2 are connected by the conduits 5 of a hydraulic circuit comprising in parallel: a vibrator pump 6, a solenoid valve 7 which is in the open position when no voltage is applie
REFERENCES:
patent: 2948118 (1960-08-01), Carlson, Jr. et al.
patent: 3954046 (1976-05-01), Stillhard
patent: 4416187 (1983-11-01), Nystrom Per H. G.
patent: 4437385 (1984-03-01), Kramer et al.
Look Edward K.
Orenbuch Louis
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