Pressure limiting valve with stable spring pad

Details Pressure limiting valve with stable spring pad Pressure limiting valve with stable spring pad

1992-09-17

1994-02-15

Rivell, John

Fluid handling

Line condition change responsive valves

With separate connected fluid reactor surface

1375123, 137538, 251337, F16K 1506, F16K 1704

Patent

active

052858138

DESCRIPTION:

BRIEF SUMMARY
The invention relates to a pressure limiting valve.
Such pressure limiting valves are used especially in underground mining to effectively protect hydraulic systems from sudden overloads, e.g. due to a sudden sagging or rock burst. The sudden bursts may overload the individual prop or even the entire system in such a way that permanent damage or even destruction occurs. The pressure limiting valves prevent this by opening and releasing pressure fluid in response to a sudden overload.
German OLS 28 30 891 proposes a safety valve where excess pressures may be reduced in the system via a valve spring suspended between a screw plug and valve piston. Hereby a cone-shaped closing element which is lifted from the valve seat if an overload occurs is connected to the valve plate. A throttle cylinder which limits the flow-through opening is connected to the valve closure piston. Such valve closures do not have the necessary closing safety. In addition, a different design of the spring may result in a different function of such pressure limiting valves.
The pressure limiting valve proposed in German 33 14 837 has a valve case which is closed with a cover and which holds the valve spring itself. The valve spring loads the valve piston which is guided in a sliding manner in the piston guiding portion inside the piston bore constructed there. The bore holding the valve piston has a groove holding an O-ring which ensures the necessary seal. The radial bores must move completely past the O-ring in the valve piston in order to ensure flawless opening of the valve and to attain long life spans for the O-ring seal. At the level of the valve plate are exit bores through which the pressure medium is discharged when the valve responds. A disadvantage here is that the pressure medium must be deflected several times to make it exit from the pressure limiting valve. For this reason, and also because of uneven support of the spring plate, the valve plate flutters and the valve spring rests against the inside wall of the spring sleeve.
German Patent 35 08 986 describes a valve where proficient guidance of the pressure medium inside the pressure limiting valve results in a protection of internal parts and greater flow-through volume. The spring plate is angled on its underside and there are channels in the inside wall of the spring sleeve through which the pressure medium may be guided past the valve spring, whereupon it then is passed after all through the spring into the flow-through opening of the adjusting screw and from there is discharged into the atmosphere. The disadvantage here is that the pressure medium still must flow past the spring plate, influence it, and possibly contribute to an angling of the spring plate so that the valve spring is loaded unevenly.


SUMMARY OF THE INVENTION

The invention is based on the task of creating a pressure limiting valve which is constructed so as to maintain a favorable flow and to enable a high flow-through volume. According to the invention this task is solved.
In a pressure limiting valve constructed in this manner, the pressure medium may be passed advantageously near or finally even through the spring plate when the valve responds, without being deflected too much. In addition, the piston is positioned so far in the spring plate, i.e. in the blind bore constructed there, that a much more stable position of the system is achieved and the force application is therefore improved. Angling of the spring and even bulging may be safely prevented in this way. Finally, by constructing the spring sleeve with a corresponding funnel-shaped recess, a path which promotes an advantageous flow is provided for the pressure medium when the O-ring is passed over. This funnel-shaped recess starts right above the O-ring so that the pressure medium then still may exit in the correct direction, i.e. radially, in order to be passed along the funnel walls in the direction of the internal chamber of the spring sleeve.
According to a useful construction of the invention, provisions are made that the spring pl

REFERENCES:
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patent: 4716928 (1988-01-01), Kussel et al.
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