Motors: expansible chamber type – With motive fluid valve – To provide unequal inlet and exhaust flow rates to single...
Patent
1985-06-27
1988-05-24
Hart, Douglas
Motors: expansible chamber type
With motive fluid valve
To provide unequal inlet and exhaust flow rates to single...
91420, 91444, 91463, F15B 1108, F15B 1304
Patent
active
047458453
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to an improvement in compressed air flow regulating devices which are placed between a conventional distributor of compressed air and a pneumatic jack.
To reduce the speed of pneumatic jacks, it is known to use flow regulating devices which comprise an adjustable reduced passage for regulating the flow in one direction, and shunted on said reduced passage, a valve which, being closed by the pressure in that direction, opens in the other to allow the full flow. Flow regulating devices are used either to regulate the admission flow into the driving chamber of the jack, or to regulate the flow discharged into the atmosphere from the other exhaust chamber. The admission flow being the only one regulated, the triggering of the jack is instantaneous, said exhaust chamber emptying very rapidly. This solution has the disadvantage, when the jack loads tend to drive the latter, to reduce the control of the speed which increases considerably. When pressure drop sensors are used, they can issue their end-of-stroke signals well before the actual end of the stroke, due to the rapid disappearance of the exhaust counter-pressure. The exhaust flow being the only one regulated, trigerring of the jacks is slow, due to the important volume of air to be evacuated through the constriction and it can be accompanied by jerks. Pressure drop sensors tend to deliver end-of-stroke signals which are all the more delayed that the passage constriction is great. The device for regulating the speed of a double acting jack is therefore constituted of at least two flow regulators either of the admission flow or of the exhaust flow.
However, in order to derive all the advantages inherent in each of these two methods, it is often necessary to fit four regulating devices and the adjustments become very complicated. Hydraulic distributors are also known in which the slide valve is auto-piloted and subjected on its two faces to the action of springs. But this device, being used with incompressible liquids, has passages which supply flows and and do not permit, as in the present invention where compressible gases are involved, to limit the speed of a jack by controlling the air flow.
Moreover, the low viscosity of the air could generate vibration phenomena which are unacceptable to the balance between the two springs.
Finally, said known device does not enable a ready adjustment of the position of the slide valve by means of movable abutments. The device according to the present invention enables to eliminate the drawbacks related to the use of the known regulators and devices for regulating the speed of pneumatic actuating means such as pressure cylinders or jacks.
According to the present invention, the air flow regulator comprises a body having a cylindrical housing limited by two bottoms and in which is mounted for axial sliding a movable revolving member of which the stroke is limited at each end of the housing by an adjustable abutting member, said body being traversed, perpendicularly to said cylindrical housing, by two passageways supplying the jack, each of which passageways issues into a chamber defined by the bottom, the cylindrical housing and the movable member, said movable member comprising central tightness means isolating the two chambers defined at the two ends of the bistable housing, regulating the opening of the passageways in relation to the position of the abutting members situated at the two ends of the housing, in such a way as to cause a regulation of the air supplying and draining flows of the two volumes of air of the double-acting jack, and this in every moving direction of the cylinder piston.
The device according to the invention enables to regulate, in both ways of the stroke, the admission flow as well as the exhaust flow, using the same regulation for the two directions. Said flow regulator which is placed between a compressed air distributor and a pneumatic jack enables to adjust the speed of the piston of a jack in every direction.
It comprises no return valve. For a given value of
REFERENCES:
patent: 3093159 (1963-06-01), Royle
patent: 3119306 (1964-01-01), Colonius
patent: 3473571 (1969-10-01), Dugay
patent: 3509968 (1970-05-01), Gregory
patent: 3532119 (1970-10-01), Lind
patent: 3974742 (1976-08-01), Johnson
Legris Andre
Levenez Yves
Hart Douglas
Societe Anonyme Styled LEGRIS
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