Fluid handling – Line condition change responsive valves – Direct response valves
Patent
1991-09-06
1993-08-10
Nilson, Robert G.
Fluid handling
Line condition change responsive valves
Direct response valves
F16K 1706
Patent
active
052340287
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD OF THE INVENTION
This invention relates to a variable pressure control valve arranged to enable the pressure of hydraulic fluid flowing thereinto from a pressurized fluid inlet port to be variably set by introducing a pilot fluid pressure.
BACKGROUND ART OF THE INVENTION
As a variable pressure control valve, a valve constructed as shown, for example, in FIG. 1 is known.
Stated briefly, a variable pressure control valve is known wherein a spool 2 is kept in pressure contact with a valve seat of a pressurized fluid inlet port 1 by the resilient force of a compression spring 3, and a pilot fluid pressure Pp is introduced into a pilot piston 4 which supports the spring 3. The arrangement is made such that the force exerted on the spool 2 to keep it in pressure contact with the valve seat of the pressurized fluid inlet port 1 is increased or decreased by varying the pilot pressure Pp so that pressure of hydraulic fluid flowing thereinto from the pressurized fluid inlet port 1 can be variably set.
In such a variable pressure control valve, since the compression spring 3 is directly compressed by the pilot piston 4, it is necessary for the pilot piston 4 to have a large pressure receiving area. This results in a larger overall size of the valve, the valve cannot be made compact.
Stated more specifically, since in such a variable pressure control valve, the compression spring 3 having a high compression spring load is compressed directly by the pilot piston 4 and the pilot pressure Pp exerted on the pilot piston 4 is generally 30 kg/cm.sup.2, the pressure receiving area of the pilot piston 4 needs to be increased in order to increase the urging force thereof. Thus, the diameter of the pilot piston 4 becomes larger, thus unavoidably making the overall size of the valve larger.
Stating concretely, if the diameter of the pressurized fluid inlet port 1 is designated by d, and the diameter of the pilot piston 4 by D.sub.1, then the spring load W.sub.1 set by the compression spring 3 is given by the following formula ##EQU1## wherein P denotes the pressure within the pressurized fluid inlet port.
To increase the pressure P set in this condition by P, it is required to set the spring load W.sub.1 at .pi./4d.sup.2 (P+.DELTA.P).
Further, the urging or pushing force F given by the pilot piston 4 will be .pi./4D.sub.1.sup.2 X Pp.
Therefore, the diameter D.sub.1 of the pilot piston 4 needs to be set at such a value which enables the valve to support the above-mentioned spring load W.sub.1.
SUMMARY OF THE INVENTION
The present invention has been made in view of the above-mentioned circumstances in the prior art and has for its object to provide a variable pressure control valve constructed to enable a pilot piston having a comparatively small diameter to be used thereby making the whole body of the valve compact to solve the above-mentioned problem in the prior art.
To achieve the above-mentioned object, according to the present invention, there is provided a variable pressure control valve comprising: a spool kept into pressure contact with the valve seat of a pressurized fluid inlet port by the resilient force of a compression spring; a stationary spring shoe fixed so as to support the base end of the compression spring; and an auxiliary compression spring which urges the above-mentioned spool to the side of the valve seat on one side thereof and is urged by a pilot piston on the other side thereof.
According to the present invention having the above-mentioned aspect, since it is only necessary that the auxiliary compression spring is urged by a force which corresponds in magnitude to an increment in pressure to be set by the pilot piston, the urging force of the pilot piston can be reduced so that the pressure receiving area of the pilot piston can be reduced correspondingly.
Accordingly, the diameter of the pilot piston can be made comparatively small so that the whole body of the variable pressure control valve can be made compact.
The above-mentioned and other objects, aspects and advantages of the
REFERENCES:
patent: 2944564 (1960-07-01), Pettey
patent: 3017897 (1962-01-01), Seguenot
patent: 3442502 (1969-05-01), Fischer et al.
patent: 4648423 (1987-03-01), Henken
Ishizaki Naoki
Nunotani Sadao
Takano Toshiro
Kabushiki Kaisho Komatsu Seisakusho
Kananen Ronald P.
Nilson Robert G.
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