Power plants – Pressure fluid source and motor – Valve means reverses flow from pump to reversible rotary motor
Patent
1980-05-02
1982-09-14
Vrablik, John J.
Power plants
Pressure fluid source and motor
Valve means reverses flow from pump to reversible rotary motor
60494, 417440, 418201, F16D 3104, F04B 4902, F01C 116, F04C 1816
Patent
active
043488650
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a gear machine comprising at least two helical gears or screw gears running in mesh with each other, a first sealing body coming against one end surface of the gear pair, and a fluid port in the first sealing body.
BACKGROUND ART
Gear machines for use as hydraulic pumps have been well-known for a long time. A permanent disadvantage with known such machines, is however, that it has so far not been possible to regulate their capacity without loosing driving energy.
OBJECT OF THE INVENTION
One object of the invention is therefore to provide a gear machine of the type mentioned in the introduction with a controllable capacity. A further object is to provide a machine of the type mentioned in the introduction, which can be utilized as a gear compressor with simply variable supercharging.
SUMMARY OF THE INVENTION
In a gear machine of the type mentioned in the introduction these objects are in accordance with the invention achieved in that a second sealing body comes against the outside circles of the gears at one gear nip, that the tooth tops of the gears are arranged to seal against the tooth bottoms in the axis plane of the gears, that the port includes a plurality of holes which at one end open out to said end surface of the gear pair in a zone comprising an area substantially including the union of the surfaces, each defined by the top and bottom circles of the respective gear between the axis plane and a gear radius forming an angle to the axis plane attaining at most (B tan .beta.)/R, where B is the width of the gear pair, R is the outside circle radius of the respective gear, and .beta. is the helix angle of the gears, that the other ends of the holes open out in a duct at axially spaced places in the duct in the same order as they open out, in the circumferential direction of the gears, to said end surface in that a sealing piston is displaceably arranged in the duct, and that one end of the duct communicates with the fluid outlet of the machine, whereby the machine can be controlled at constant revolutions by displacing the piston in the duct.
For the case where the machine is to be utilized as a gear compressor, the piston is suitably adapted to close the holes in a direction inwards towards the axis plane, whereby the axial length of the piston in the duct determines the supercharging of the machine.
The helical teeth of the inventive machine are also to be regarded as including screws such as those utilized in conventional screw pumps or screw compressors, since the inventive concept is applicable to such apparatus also.
Screw pumps have previously been modified into supercharging screw compressors (so-called Lysholm compressors) e.g. by reducing the pitch of the screws in a direction towards the outlet. This results in high screw manufacturing costs. Conventional screw pumps can now be modified into supercharging pumps with the aid of the invention, by arranging an end wall at the outlet end of the screws, provided with a port arrangement in accordance with the present invention. The inventive idea is thus also applicable to screw machines, the "teeth" of which extend more than one revolution round the "gear wheels".
For practical reasons, the angle between the axis plane and the radius should be less than 90.degree. and preferably about 60.degree., and the expression B.times.(1/R).times.tan .beta. should be supplemented by the factor n.times.2.pi. for the case where the inventive idea is to be utilized in screw machines proper (n being a positive whole number corresponding to the number of complete revolutions a "tooth" extends round the screw).
It is however possible to connect each of the upper branches of the Y-shaped port to a duct (possibly a straight duct) which is directed as far as possible along the respective branch portion. Two such ducts, each with its control piston, can then substantially replace the upper part of the previously mentioned duct.
In the case where the inventive machine is to be utilized as a hydraulic pump, the
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patent: 2016040 (1935-10-01), Kennedy
patent: 2266820 (1941-12-01), Smith
patent: 2515301 (1950-07-01), Hughey
patent: 2623469 (1952-12-01), Gray
patent: 2656972 (1953-10-01), Rathman
patent: 3451614 (1969-06-01), Tosh
patent: 3527548 (1970-09-01), Kocher et al.
patent: 3773444 (1973-11-01), Koch
patent: 4042310 (1977-08-01), Schibbye et al.
AB Bonnierforetagen
Vrablik John J.
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