Pumps – With condition responsive pumped fluid control – Pressure responsive relief or bypass valve
Patent
1990-10-23
1991-10-01
Smith, Leonard E.
Pumps
With condition responsive pumped fluid control
Pressure responsive relief or bypass valve
417440, 417418, 4182012, F04B 4900, F04B 1704, F04B 2300, F01C 116
Patent
active
050529013
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a pressure actuated lift valve in a machine of the rotary screw type mounted in one of the end walls of the machine and containing a valve member being displaceable in an axial boring, one end of the boring facing the working space of the machine.
A machine of the rotary screw type contains two rotors mounted in a working space, which is limited by two end walls and a barrel wall extending therebetween. The barrel wall has the shape of two intersecting cylinders, each housing one of the rotors. Each rotor is provided with helically extending lobes and grooves, being in intermesh to form chevron-shaped compression or expansion chambers. In these a gaseous fluid is displaced and, when working as a compressor, compressed from an inlet channel to an outlet channel. Each compression chamber during a filling phase communicates with the inlet, during a compression phase undergoes a continuous reduction in volume and during a discharge phase communicates with the outlet.
Machines of this kind often are provided with valve means for regulating the built-in volume ratio or the capacity or for other purposes. When continuous regulation is required usually slide valves are used whereas at simpler regulation needs it might be sufficient to use lift valves. Such a valve is mounted in the barrel wall of the machine or in one of the end walls, normally the high pressure end wall. An example thereof is disclosed in U.S. Pat. No. 2,519,913.
In a pressure actuated lift valve of the specified kind using the outlet pressure for actuating, it is necessary that the surface exposed to the actuating pressure is larger than the surface facing the working chamber in order to attain a sufficient actuating force. In the embodiment in U.S. Pat. No. 2,519,913 where the lift valve solely is actuated by pressure (see FIG. 9) the valve member therefore has the form of two discs of different diameters rigidly connected by a rod. The disc of the smaller diameter constitutes the active valve member and is exposed to the working space of the compressor whereas the disc of the larger diameter is affected by actuating pressure. In the Swedish published Patent Application 8600427-2 a lift valve is disclosed, in this case mounted in the barrel wall, where the valve member in a similar way has two sections of different diameters in order to attain a surface large enough for the actuating pressure to act on.
The way to attain a sufficient surface for the actuating pressure to act on, used in the referred publications entails manufacturing problems, as it requires a precise centering of the two sections of valve member to the respective surrounding borings or cylinders. This problem is particularly accentuated if the two sections of the valve member are eccentric relative each other, since the eccentricity of these sections in this case has to correspond precisely to the relative eccentricity of the two borings.
Th object of the present invention therefore is to attain a valve of the kind in question where this problem is overcome.
This has according to the invention been achieved in that the valve member in a valve of the introductionally specified kind is cylindrical and is controlled by a separate actuating piston being displaceable in a cylinder (14), which actuating piston (12) is not joined to the valve member (11) and acts upon the valve member (11) by contact forces.
Thanks to the departure from the conventional technique where the valve member has sections of different diameters and instead make the valve member as a cylindrical piece of uniform shape the manufacturing complications discussed above are avoided, and by means of the separately made actuating piston a sufficient surface for the actuating pressure to act on is attained.
The assembly of the valve thus is considerably facilitated as it only requires to insert the valve member into the boring made therefor and then the actuating piston into its boring. Since each of the valve member and the actuating piston is made as a plain cylindrical part the ma
REFERENCES:
patent: 3869227 (1975-03-01), Kocher et al.
patent: 3877846 (1975-04-01), Lundberg
patent: 4575323 (1986-03-01), Yoshimura
patent: 4946362 (1990-08-01), Soderlund et al.
Basichas Alfred
Smith Leonard E.
Svenska Rotor Maskiner AB
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