Motors: expansible chamber type – Constantly applied motive fluid with controlled venting – Motive fluid constantly applied to and vented from opposed...
Patent
1985-09-16
1987-06-02
Croyle, Carlton R.
Motors: expansible chamber type
Constantly applied motive fluid with controlled venting
Motive fluid constantly applied to and vented from opposed...
91461, 91464, 91465, 13759616, F15B 1302
Patent
active
046693580
DESCRIPTION:
BRIEF SUMMARY
Shifting means, e.g. servo motors, are often used for manipulation of heavy devices within the industry and other technical fields, such as heating plants, water treatment plants, lifting equipment and so on. The manipulation work is affected by means of a pressure fluid, or pressure gas, which acts e.g. on a piston axially slideable within a cylinder, or on a rotatably mounted wing.
The governing of the pressure medium to and from the cylinder is affected by means of a governing valve or, as it is often called a pilot valve, or servo valve. In lifting or escavating machines for instance the controlling motion of such valves is made manually, but may alternatively also be governed by a signal impulse to an internal servo system within the valve, so to say servo on servo.
The most common type of servo valve is the well known, so called sliding piston, comprising a cylinder with radial ports and corresponding piston portions arranged axially on a common shaft.
This sliding piston will require comparatively large impulse energy for its movement, in spite of its often small diameter (5-10 mm.). The axial movement for the opening and closing of the ports tends to be long, because the pistons need a certain overlap to ensure acceptable sealing.
It is an object of the present invention to eliminate the above mentioned problems. The demand for better servo valves has increased through the present computerisation of industrial processes.
The invention relates to a pneumatic servo valve, which by means of electric signals can be brought to distribute compressed air to or from a double acting servo motor, whereby the compressed air is introduced into the valve through a hole in the middle of a cylinder, which is incorporated in the device and further from this through a circular groove in the centre of a piston in the cylinder and thereafter on through a drilling from the groove, radially towards the centre of a piston shaft having a central, lengthwise drilled channel, rigidly connected to and axially protruding from each side of the piston. The servo valve comprises channels for the connection of lines to said servo motor. The invention is characterized in that the distribution of pressure air is supplied by two double mushroom valves, having the point ends in the same direction, said valves being arranged coaxially in relationship to the piston shaft, so that these, towards the middle directed cones can be brought to seal against the centrally drilled channel in the piston shaft. Decompression seats are arranged coaxially with the valves and adjustably against their outer cones. The valves are loaded by one or two springs in such way that it is possible to adjust said decompression seats so that the piston can be displaced via the valves to a middle position, when it is not in any other way biased to move axially. The valves seal in this position with both cones against their respective valve seats, and the cylinder is so short in relation to the piston that the piston and the rigidly connected shaft can not move axially more than necessary for the valves to open fully and close for the distribution of pressure air. The space around the valves, between the ends of the shaft and the adjustable valve seats, communicate with channels for connection of lines to the servo motor, further the piston can be influenced to slide axially because both of its sides are connected to two independent flapper-nozzle systems. The flappers are forced by springs against the nozzles, and electromagnets are arranged for lifting of the flappers from the nozzles. The magnets being designed to receive electric signals from a computer located outside the servo valve.
The invention will now be described with reference to the accompanying drawings, in which
FIG. 1 show a servo valve according to the invention, which is connected to a schematically depicted control system,
FIG. 2 is an end view of the servo valve,
FIG. 3 shows the servo valve in one end position, and
FIG. 4 shows an alternative arrangement of the mushroom valves.
The servo va
REFERENCES:
patent: 2729242 (1956-01-01), Olson
patent: 2924200 (1960-02-01), Hanna et al.
patent: 3318332 (1967-05-01), Lansky et al.
patent: 4513782 (1985-04-01), Contartese et al.
Aspervall Roland
Jareke Bo
Aspervall Instrument AB
Computer Instrument AB
Croyle Carlton R.
Neils Paul F.
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