Fluid handling – Line condition change responsive valves – With separate connected fluid reactor surface
Patent
1987-05-01
1989-05-09
Hepperle, Stephen
Fluid handling
Line condition change responsive valves
With separate connected fluid reactor surface
137504, F16K 31365, G05D 701
Patent
active
048279714
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION:
The present invention concerns a constant air flow rate valve where, in a flow passage confined by a passage section, has been disposed a throttling member presenting a throttling part which changes shape.
A constant air flow rate valve of this type has been disclosed e.g. in the EP Pat. No. 0027068. Constant air flow rate valves of prior art have an elastic throttling member which has been placed in the interior space of the air passage. When the differential pressure acting across the throttling member increases, the throttling member changes shape so that the flow aperture is reduced. The higher the differential pressure becomes, the smaller becomes the flow aperture similarly, decrease of the differential pressure causes the flow aperture to grow larger. In this way the air flow passing through the constant air flow rate valve is kept approximately constant.
SUMMARY OF THE INVENTION
The object of the invention is to provide an improved constant air flow rate valve in which the known drawbacks of the above-mentioned constant air flow rate valves are avoided, that is, in which within a wide enough differential pressure range is achieved a large enough through-flow in relation to the passage size, and wherein even at high flow velocities the noise level is low, and in said valve the passing air flow rate is controllable to equal a given air flow rate set-point value, and said valve being advantageous in manufacturing.
The constant air flow rate valve of the invention is mainly characterized in that the substantially circular projection of the valve's throttling member on a plane perpendicular against the central axis, has been disposed to grow on its periphery when the differential pressure increases, or to diminish on its periphery when the differential pressure grows less.
The above-mentioned changing of the projection is understood to mean that the throttling portion of the throttling part has been arranged, depending on the differential pressure across the valve, to move radially with its entire mantle surface cross section towards the passage section constituting the flow aperture.
The constant air flow rate valve of the invention is advantageously so designed that said valve passage is a conical structure of which the cross section area decreases linearly in the direction of the longitudinal axis. Now when the throttling member is moved in relation to said valve passage, the distance of the throttling member from the valve passage will be changed at the same time. The substantially circular configuration of the elastic throttling member in the constant air flow rate valve of the invention enables the throttling to take place uniformly over the entire flow cross section area.
The invention also concerns a procedure for controlling the constant air flow rate valve.
The procedure of the invention is in its main parts characterized in that the air flow rate set-point value is input to the constant air flow rate valve by changing the position relative to each other of the elastic throttling part of the constant air flow rate valve's throttling member and the preferably conical passage section of the passage section with variable flow cross section area.
In accordance with the invention a novel constant air flow rate valve controlling method has been implemented wherein set-point adjustment is substantially stepless within a wide flow rate range in such manner that one limit of the flow rate is the fully closed position of the valve, or zero flow condition. The structural design of the constant air flow rate valve of the invention is also very simple and advantageous in view of manufacturing technology. As taught by the invention, adjustment of the set-point value of the constant air flow rate valve is advantageously accomplished in that the throttling member with substantially circular cross section and made of an elastic material is moved in relation to the valve passage in the direction of the longitudinal axis of the valve passage.
BRIEF DESCRIPTION OF THE DRAWINGS
REFERENCES:
patent: 2740418 (1956-04-01), Pankratz
patent: 2925826 (1960-02-01), Streeter
patent: 3022977 (1962-02-01), Jones
patent: 3255963 (1966-06-01), Gorchev et al.
patent: 3718160 (1973-02-01), Jardinier et al.
patent: 3958605 (1976-05-01), Nishizu et al.
Halton Oy
Hepperle Stephen
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